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Biomedical subjects

I H Chaudry

Publications and source records attributed to I H Chaudry.

At least 91 records · Page 5Linked to original sources
PubMed1999

Proteasome participates in the alteration of signal transduction in T and B lymphocytes following trauma-hemorrhage.

Proteasomes are essential components of the cellular protein degradation machinery. They are nonlysosomal and their participation is critical for (1) the removal of short lived proteins involved in metabolic regulation and cell proliferation, (2) the control of the activities of regulators involved in gene transcription, such as nuclear factor-kappa B (NF-kappa B) and signal transducer and activator of transcription (STAT1), and (3) processing of antigenic peptides for MHC class I presentation. Trauma-hemorrhage induces profound immunosuppression which is characterized by reduced splenocyte proliferation, interleukin (IL)-2 and interferon (IFN)-gamma productive capacity, increased activation of transcription factors NF-kappa B and STAT1 in splenic T lymphocytes, reduced macrophage antigen presentation capacity and inordinate release of proinflammatory cytokines, such as IL-6 and tumor necrosis factor-alpha. Furthermore, it appears that the activity of several regulatory proteins involved in immune function is altered by trauma-hemorrhage. Since proteasomes are involved in regulation and removal of regulatory proteins, we hypothesized that trauma-hemorrhage alters proteasomal activity in splenic lymphocytes. The data showed that activities of 26s proteasome from CD3+CD4+ and CD3+CD8+ splenic T lymphocytes were enhanced following trauma-hemorrhage which was associated with increased expression of NF-kappa B and STAT1. On the other hand, trauma-hemorrhage attenuated the activity of 26s proteasome from splenic B lymphocytes which was restored upon IFN-gamma stimulation and correlated with increased expression of NF-kappa B. These studies indicate a potential role for proteasomes in the regulation of signal transduction in splenic T and B lymphocytes following trauma-hemorrhage, and also suggest them as potential therapeutic targets for attenuation of immune suppression associated with this form of injury.

Animals↗
PubMed1999

Does uninjured skin release proinflammatory cytokines following trauma and hemorrhage?

HYPOTHESIS: Uninjured skin contributes to the elevation in circulating levels of proinflammatory cytokines seen following severe injury. DESIGN: Male C3H/HeN mice underwent trauma, trauma-hemorrhage and resuscitation, or closed long-bone fracture. Serum, skin, and liver samples were harvested at designated times after experimental treatment. MAIN OUTCOME MEASURES: Levels of interleukin (IL) 1beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) were determined in serum and skin cultures at 1, 8, and 24 hours after trauma-hemorrhage. The RNA was isolated from liver and skin samples at 1, 2, 4, 8, and 24 hours from all 3 experimental groups, and gene expression of the cytokines was determined. RESULTS: Remote (nontraumatized) skin from trauma-hemorrhage animals released significantly more IL-6 and TNF-alpha into culture supernatants at 1 and 24 hours and significantly more IL-1beta at 1, 8, and 24 hours than did skin from sham animals. Serum levels of all 3 cytokines were significantly elevated at 1 and 24 hours after trauma-hemorrhage relative to sham animals. Gene expression of all 3 cytokines was detected in skin and liver following trauma-hemorrhage. Furthermore, gene expression of all 3 cytokines was detected in uninjured skin after soft tissue trauma and closed long-bone fracture. CONCLUSIONS: Proinflammatory cytokine gene expression is up-regulated in uninjured skin following trauma, trauma-hemorrhage, and long-bone fracture. This increase in gene expression correlates with increased cytokine production by cultured skin as well as increased circulating cytokine levels. These results suggest that uninjured skin may also contribute to the rise in circulating cytokine levels seen after injury.

Animals↗
PubMed1999

Mechanism of adrenal insufficiency following trauma and severe hemorrhage: role of hepatic 11beta-hydroxysteroid dehydrogenase.

BACKGROUND: Although adrenal insufficiency may not occur with moderate hypotension, it does occur with severe hemorrhage. Since hepatocellular function is depressed following severe hemorrhage, it remains unknown whether the liver plays any role in regulating adrenal function after trauma and hemorrhagic shock. HYPOTHESIS: Hepatic 11beta-hydroxysteroid dehydrogenase (11beta-HSD), a microsomal enzyme responsible for the degradation of bioactive corticosterone, plays a major role in the development of adrenal insufficiency following trauma and severe hemorrhage. DESIGN, INTERVENTIONS, AND MAIN OUTCOME MEASURES: Male rats underwent laparotomy to induce trauma before hemorrhage. They were then bled to and maintained at a blood pressure of 40 mm Hg until 40% of the maximal bleed-out volume was returned in the form of Ringer lactate. The rats were then resuscitated with 4 times the volume of maximal bleed-out with Ringer lactate during a 60-minute period. Plasma levels of corticosterone and corticotropin were measured at various intervals. In additional groups, corticotropin-induced corticosterone release, adrenal contents of corticosterone and cyclic adenosine monophosphate (cAMP), hepatic 11beta-HSD activity, and plasma levels of corticosterone-binding globulin were determined at 1.5 hours after resuscitation. Moreover, a model of moderate hypotension (blood pressure, 80 mm Hg) was used to determine whether adrenal function is depressed under such conditions. RESULTS: At the time of maximal bleed-out, plasma corticosterone and corticotropin levels increased by 245% (P<.001) and 293% (P<.001), respectively. Despite corticotropin levels being similar to those of the animals undergoing sham operation after resuscitation, corticosterone levels in hemorrhaged animals remained elevated up to 4 hours after resuscitation (by 158%-207%; P<.001). In addition, corticotropin-induced corticosterone release decreased by 78% at 1.5 hours after resuscitation (P = .009). In contrast, moderate hypotension did not reduce corticotropin-induced corticosterone release. Adrenal corticosterone content and cAMP levels (i.e., the second messenger of corticotropin action) decreased by 55% (P<.001) and 25% (P = .03), respectively. Hepatic 11beta-HSD activity decreased significantly at 1.5 hours after resuscitation (P<.001). CONCLUSIONS: Sustained increase in plasma corticosterone levels following hemorrhage and resuscitation may be, in part, due to the decreased hepatic 11beta-HSD activity. The high level of corticosterone negatively regulates corticotropin release, further reducing adrenal responsiveness to corticotropin stimulation. Thus, the liver appears to play an important role in regulating adrenal function following trauma and severe hemorrhage.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1999

Dehydroepiandrosterone restores immune function following trauma-haemorrhage by a direct effect on T lymphocytes.

Although a profound depression in immune function occurs following injury, the mechanism responsible for this is not fully understood. Furthermore, steroid hormones are known to be important mediators in the regulation of immune function. Although dehydroepiandrosterone (DHEA), the most plentiful steroid hormone, has been shown to stimulate immune function in normal animals, it is unknown whether DHEA has any salutary or detrimental effects on immune responses after trauma and haemorrhage. To study this, male mice were subjected to trauma, haemorrhage and resuscitation, following which they received either DHEA or vehicle subcutaneously. DHEA administration restored the normally depressed splenocyte proliferation as well as interleukin 2, interleukin 3, and interferon gamma elaboration following trauma and haemorrhage. In an attempt to determine the mechanisms mediating this effect, T cells were stimulated in vitro in the presence of DHEA and a variety of hormone antagonists. The stimulatory effect of DHEA on splenocyte proliferation was unaltered by the testosterone receptor antagonist flutamide, while the oestrogen antagonist tamoxifen completely abrogated its effect. In addition, DHEA administration normalized the elevated serum corticosterone level typically seen following injury. These results indicate, therefore, that DHEA improves splenocyte function after trauma and haemorrhage by directly stimulating T cells and also by preventing a rise in serum corticosterone.

Adjuvants, Immunologic↗
PubMed1999

Reduction in vascular responsiveness to adrenomedullin during sepsis.

BACKGROUND: Although sepsis is characterized by an early, hyperdynamic phase followed by a late, hypodynamic phase, the mechanism responsible for the transition from the hyperdynamic to the hypodynamic state remains unknown. Since recent studies have shown that adrenomedullin (ADM), a novel potent vasodilatory peptide, is upregulated during sepsis, the aim of this study was to determine whether the reduced vascular responsiveness to ADM is associated with the transition from the hyperdynamic phase to the hypodynamic phase of sepsis. MATERIALS AND METHODS: Adult male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 and 10 h (i.e., the hyperdynamic phase of sepsis) or 20 h (the hypodynamic phase) after CLP, the thoracic aorta or small intestine was harvested and preconstricted with norepinephrine. Adrenomedullin (10(-7) M) was applied and the percentage of ADM-induced vascular relaxation in the aortic ring and isolated small intestine was determined. RESULTS: The responsiveness to ADM in the thoracic aorta was not altered at 5-10 h, but decreased significantly at 20 h after CLP. Although ADM-induced relaxation in resistance blood vessels of the small intestine did not change at 5 h, it decreased markedly at 10 and 20 h after the onset of sepsis. CONCLUSIONS: Since the transition from hyperdynamic to hypodynamic sepsis takes place between 10 and 20 h after CLP, it is likely that reduced vascular responsiveness to ADM may be responsible for such an event during the course of polymicrobial sepsis. In view of this, maintenance of vascular ADM responsiveness by pharmacologic agents appears to be a novel approach for preventing or delaying the occurrence of hypodynamic sepsis and septic shock.

Adrenomedullin↗
PubMed1999

Increased inducible apoptosis in CD4+ T lymphocytes during polymicrobial sepsis is mediated by Fas ligand and not endotoxin.

Recent studies suggest that increased lymphocyte apoptosis (Ao) detected in peripheral blood T cells from burn patients appears to contribute to decreased lymphocyte immunoresponsiveness. However, while it is known that sepsis induces a marked depression in the splenocyte immune response (i.e. decreased interleukin-2, interferon-gamma production and proliferation) in response to the T-cell mitogen concanavalin A (Con A), it is unknown whether this depression is associated with an increase in inducible Ao and if so, which mediators control this process. To assess this, splenocytes were harvested from mice at 24 hr (a period associated with decreased Con A response) after the onset of polymicrobial sepsis [caecal ligation and puncture (CLP)] or sham-CLP (Sham) and then stimulated with 2.5 microg Con A/ml (24 hr). Septic mouse splenocytes stimulated with Con A, while not showing a change in their phenotypic make-up, did exhibit a marked increase in the percentage of splenocyte that were Ao+ which was associated with altered cytokine release. This appears to be due to an increase in the percentage of Ao+ cells in the CD4+ CD8- population and was associated with enhanced Fas antigen expression as well as an increase in mRNA for the Fas-FasL gene family. To determine if the changes in Ao are due to either endotoxin (a product of Gram-negative bacteria seen in CLP mice) or the expression of Fas ligand (FasL; a mediator of activation-induced lymphocyte Ao), a second set of studies examining Con A-inducible Ao was performed with splenocytes harvested from septic endotoxin-tolerant C3H/HeJ and the FasL-deficient C3H/HeJ-Fasl gld mice. The results show that increased splenocyte Ao detected following CLP is due to a FasL-mediated process and not to endotoxin. Thus the inadvertent up-regulation of FasL-mediated splenocyte Ao may contribute to the depression of splenocyte immune responses seen during polymicrobial sepsis.

Animals↗
PubMed1999

Hemorrhage decreases macrophage inflammatory protein 2 and interleukin-6 release: a possible mechanism for increased wound infection.

OBJECTIVE: To determine whether alteration in wound exudate cell immune function occurs after trauma-hemorrhage. BACKGROUND: Although clinical and experimental studies indicate that the rate of wound infection is increased after trauma and hemorrhagic shock, the underlying mechanism for this increased susceptibility remains unknown. METHODS: Male C3H/HeN mice were subjected to a midline laparotomy and polyvinyl alcohol sponges were implanted subcutaneously in the abdominal wound before hemorrhage (35+/-5 mm Hg for 90 minutes and resuscitation) or sham operation. The wound exudate cells from the sponges were harvested on the first, third, and fifth postoperative day and cultured for 24 hours in the presence of lipopolysaccharide (10 microg/ml) or heat-killed Staphylococcus aureus. Interleukin (IL)-1beta, IL-6, monocyte chemotactic protein 1, macrophage inflammatory protein 2, and nitrite levels were determined in the supernatants. The distribution of macrophages and polymorphonuclear leukocytes was assessed in the sponge with and without in vivo injection of S. aureus. The phagocytic activity of isolated wound exudate cells was determined using fluorescent S. aureus. RESULTS: The composition of exudate cells was unaltered by hemorrhagic shock; however, in vivo injection of S. aureus significantly decreased the percentage of macrophages under such conditions. Wound exudate cell phagocytic activity and the release of IL-1beta, IL-6, monocyte chemotactic protein 1, and macrophage inflammatory protein 2 was decreased on the first postoperative day. The release of IL-1beta and IL-6 was also decreased on the third postoperative day in hemorrhaged mice. On the fifth postoperative day, wound exudate cell cytokine production was comparable to that in shams. CONCLUSIONS: Because most wound infections occur early after severe trauma, these results suggest that the dysfunction of wound exudate cells after hemorrhage might contribute to the increased incidence of wound infections. Therefore, attempts to enhance or restore wound cell immune function might be helpful for decreasing the incidence of wound infections in trauma victims.

Animals↗
PubMed1999

Salutary effects of ATP-MgCl2 on the depressed endothelium-dependent relaxation during hyperdynamic sepsis.

OBJECTIVES: Studies have shown that endothelium-dependent relaxation (mediated by endothelium-derived nitric oxide) is depressed during the early, hyperdynamic stage of sepsis. Although it is known that ATP-MgCl2 produces beneficial effects following various adverse circulatory conditions, it remains unknown whether this agent attenuates the depressed endothelium-dependent relaxation during early sepsis. The aim of this study, therefore, was to determine whether or not the administration of ATP-MgCl2 early after the onset of sepsis improves or maintains endothelium-dependent relaxation. DESIGN: Prospective, controlled animals study. SETTING: A university research laboratory. SUBJECTS: Adult male Sprague-Dawley rats were subjected to polymicrobial sepsis by cecal ligation and puncture (CLP), followed by administration of 3 mL/100 g body weight normal saline to these and sham-operated rats. INTERVENTIONS: At 1 hr after CLP, ATP-MgCl2 (50 micromol/kg body weight) or an equivalent volume of normal saline was infused intravenously over 90 mins. MEASUREMENTS AND MAIN RESULTS: At 5 hrs or 10 hrs after CLP (i.e., the early, hyperdynamic stage of sepsis), the thoracic aorta was isolated, cut into rings, and placed in organ chambers. Norepinephrine was used to preconstrict vessel rings. Dose responses for an endothelium-dependent vasodilator, acetylcholine (ACh, via endothelium-dependent nitric oxide), and an endothelium-independent vasodilator, nitroglycerin, were determined. These results indicate that endothelium-dependent relaxation induced by ACh was significantly depressed at 5 and 10 hrs after CLP. Administration of ATP-MgCl2 after the onset of sepsis, however, maintained ACh-induced vascular relaxation. In contrast, no significant difference in nitroglycerin-induced vascular relaxation as well as norepinephrine-induced contraction was observed, irrespective of administration of ATP-MgCl2. CONCLUSION: Since administration of ATP-MgCl2 prevents the impaired vascular relaxation to the endothelium-dependent vasodilator ACh, this agent may be a useful adjunct for maintaining endothelial cell function during the hyperdynamic stage of sepsis.

Adenosine Triphosphate↗
PubMed1999

Do different rates of fluid resuscitation adversely or beneficially influence immune responses after trauma-hemorrhage?

BACKGROUND: Although rapid fluid resuscitation continues to be an important component of the initial therapy for trauma patients, it remains unknown whether the rate of fluid administration after trauma-hemorrhage has any deleterious or beneficial effects on immunity. METHODS: Male C3H/HeN mice were subjected to sham operation or soft-tissue trauma (midline laparotomy) and hemorrhagic shock (mean arterial blood pressure of 35+/-5 mm Hg for 90 minutes) followed by resuscitation with four times the volume of shed blood in the form of lactated Ringer's solution over 30 minutes (rapid rate), 60 minutes (moderate rate), or 120 minutes (slow rate). The animals were killed at either 4 hours or 4 days after the end of trauma-hemorrhage. Spleens were harvested and splenocyte interleukin (IL)-3 and interferon-gamma (IFN-gamma) release as well as splenic macrophage IL-1beta and IL-6 release were determined. RESULTS: The results indicate that at 4 hours after trauma-hemorrhage, splenocyte IL-3 and IFN-gamma release were significantly depressed in all animals subjected to trauma-hemorrhage compared with sham-operated animals. At 4 days after trauma-hemorrhage, splenocyte IL-3 and IFN-gamma release were restored in mice resuscitated with the slow rate of resuscitation; however, the release of these cytokines remained significantly depressed in animals resuscitated with the moderate or rapid rates. Splenic macrophage IL-1beta and IL-6 release were significantly depressed at 4 hours after trauma-hemorrhage. At 4 days after trauma-hemorrhage, the release of these proinflammatory cytokines was still depressed in animals resuscitated with the rapid rate. In contrast, splenic macrophage IL-1beta and IL-6 release were restored in mice receiving the slow rate of resuscitation. CONCLUSION: These results suggest that a slower rate of fluid resuscitation after trauma-hemorrhage leads to a faster restoration of the depressed cell-mediated immunity, whereas rapid fluid resuscitation produces a prolonged depression of immune responses. In view of this, we propose that a prospective clinical study of this type must be performed in a select group of trauma patients to determine whether or not a slower rate of fluid resuscitation also improves immune responses in trauma patients.

Animals↗
PubMed1999

L-arginine: a unique amino acid for restoring the depressed macrophage functions after trauma-hemorrhage.

BACKGROUND: Immune responses are markedly depressed very early after the onset of hemorrhage. Furthermore, endothelial cell dysfunction occurs after trauma-hemorrhage and may contribute to alterations in immune function. Recent studies have shown that administration of L-arginine restores the depressed organ blood flow, probably because of the provision of substrate for constitutive nitric oxide synthase. It remains unknown, however, whether administration of L-arginine would have any salutary effect on the depressed macrophage function after trauma-hemorrhage. METHODS: Male rats underwent midline laparotomy (i.e., trauma was induced). After this, the animals were bled to and maintained at a mean blood pressure of 40 mm Hg until 40% of the maximum shed blood volume was returned in the form of lactated Ringer's solution. Sham-operated rats underwent both femoral artery cannulation and ligation, but these animals were neither bled nor resuscitated. Hemorrhaged rats were then resuscitated with lactated Ringer's solution, receiving four times the maximum shed blood volume over 1 hour. During resuscitation, one group received 300 mg/kg L-arginine and the other group received saline (vehicle) intravenously. At 4 hours after resuscitation, splenic and peritoneal macrophage interleukin (IL)-1beta and IL-6 release as well as plasma IL-6 were measured. RESULTS: Splenic and peritoneal macrophage IL-1beta and IL-6 release was significantly decreased in trauma-hemorrhage vehicle-treated rats. Administration of L-arginine after trauma-hemorrhage, however, improved splenic and peritoneal macrophage IL-1beta and IL-6 release. Moreover, the up-regulated plasma levels of IL-6 were attenuated by L-arginine administration. CONCLUSION: L-Arginine administration after trauma-hemorrhage significantly improves the depressed macrophage function, presumably by decreasing the increased plasma IL-6 levels and improving organ blood flow. Early enhancement of the depressed constitutive nitric oxide synthase activity by provision of L-arginine after trauma-hemorrhage, therefore, represents a novel and safe approach for improving the depressed immune function and decreasing plasma IL-6 levels under such conditions.

Animals↗
PubMed1999

Differential alterations in systemic and regional oxygen delivery and consumption during the early and late stages of sepsis.

BACKGROUND: Studies have indicated that regional changes in oxygen utilization during sepsis cannot be predicted from the changes in the whole body oxygen delivery (DO2) and consumption (VO2). The aim of this study, therefore, was to determine whether differential alterations in systemic and regional DO2 and VO2 occur during the early and late stages of sepsis. METHODS: Adult male Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 hours (i.e., the early, hyperdynamic phase of sepsis) or 20 hours (i.e., the late, hypodynamic phase) after CLP, cardiac output, and organ blood flow were measured by radioactive microspheres. Systemic and regional DO2 and VO2 were determined and plasma levels of lactate were measured. RESULTS: Cardiac output and blood flow to the liver, small intestine, and kidneys increased at 5 hours and decreased at 20 hours after CLP. Although both systemic DO2 and VO2 increased at 5 hours after CLP, systemic DO2 but not VO2 decreased at 20 hours. At 5 hours after CLP, intestinal and renal DO2 increased. However, DO2 in all the tested organs decreased at 20 hours after CLP. VO2 increased in the liver, small intestine, and kidneys at 5 hours after CLP but decreased only in the liver and small intestine at 20 hours after the onset of sepsis. Moreover, plasma lactate levels increased at the late stage of sepsis. CONCLUSION: Because hepatic and intestinal VO2 but not systemic and renal VO2 decreased at 20 hours after CLP, the liver and small intestine seem to be more vulnerable to the hypoxic insult during the hypodynamic stage of polymicrobial sepsis.

Animals↗
PubMed1999

Does Fas ligand or endotoxin contribute to thymic apoptosis during polymicrobial sepsis?

Recent studies have shown that with the onset of sepsis there is an increase in apoptosis (Ao) in the thymus, mediated in part by steroids, which may contribute to a loss of T-cell progenitors, thereby, reducing immune functions. However, reports also suggest that these steroid effects could be mediated by Fas ligand (FasL) and/or by endotoxin (ETX). Thus, our study was to determine: 1) if polymicrobial sepsis (cecal ligation and puncture; CLP) alters thymocyte Fas antigen/receptor (Fas+) expression and 2) if the increase in Ao in septic ETX-sensitive C3H/HeN mice is seen in thymocytes from ETX-tolerant, C3H/HeJ, or the FasL-deficient/ETX-tolerant, C3H/HeJ-FasL(gld), male mouse strains subjected to CLP or sham-CLP (Sham) 12 or 24 h before they were killed. The results of flow cytometric analysis indicated that increased %Ao+ seen in thymocytes of CLP C3H/HeN mice was associated with either no change (12 h) or a decrease in %Fas+ expression at 24 h, although the %Bcl-2+ (an antiapoptotic protein) cells was depressed at both times. Additional studies examining C3H/HeJ or C3H/HeJ-FasL(gld) mice subjected to CLP show that as with the ETX-sensitive mouse, thymocyte Fas and Bcl-2 antigen expression as well as Bcl-2/Bcl-X(L/S) mRNA levels decreased although the %Ao+ increased after CLP in both ETX-tolerant and ETX-tolerant/FasL-deficient mice. Furthermore, if ETX-tolerant/FasL-deficient CLP animals were administered the steroid receptor antagonist RU-38486 (s.c., immediately after CLP) the increase in Ao was markedly attenuated, along with restoration of the percentage of cells expressing Bcl-2 and Fas antigen as well as Bcl-2/Bcl-X(L/S) mRNA levels. Thus, we concluded that increased septic thymocyte Ao is not regulated through either Fas mediated pathway or ETX, but is a result of the release of endogenous steroids possibly acting directly or indirectly on Bcl-2 expression.

Animals↗
PubMed1999

Gender dimorphism in trauma-hemorrhage-induced thymocyte apoptosis.

Studies indicate that immune responses after trauma-hemorrhage are significantly depressed in males compared with enhanced immune responses in females under such conditions. Although androgen depletion in male mice by castration before soft tissue trauma and hemorrhagic shock prevents the depression of cell-mediated immunity, the underlying mechanism responsible for this remains unclear. Because the thymus is the primary location of T-cell lymphopoiesis and thymocytes express a large number of androgen receptors, we investigated whether differences in thymic apoptosis might contribute to the divergent immune response in males versus females after trauma-hemorrhage. To study this, male and female C3H/HeN mice were subjected to sham operation or soft tissue trauma (laparotomy) and hemorrhagic shock followed by fluid resuscitation. Animals were killed 72 h thereafter and thymocytes were isolated. Thymocyte interleukin 3 (IL-3) release was significantly suppressed in males, but not females, after trauma-hemorrhage. A parallel increase in thymic apoptosis that was primarily in the CD8+ thymocyte subset was observed in the males. Furthermore, in vitro treatment of thymocytes with 5a-dihydrotestosterone (DHT) increased the rate of apoptosis and decreased IL-3 release in a dose-dependent manner. Thus, the gender-dependent dimorphic immune response after trauma-hemorrhage may be in part due to an androgen-induced increase in thymic apoptosis in males under such conditions.

Animals↗
PubMed1999

L-Arginine restores splenocyte functions after trauma and hemorrhage potentially by improving splenic blood flow.

Several studies indicate that immune responses are markedly depressed early after onset of hemorrhage. Decreased organ blood flow has been implicated in the pathophysiology of altered immune responses after trauma-hemorrhage. In this regard, administration of L-arginine has been shown to restore depressed intestinal and hepatic blood flow after trauma-hemorrhage, probably due to provision of substrate for constitutive nitric oxide synthase (cNOS). It remains unknown, however, whether administration of L-arginine also ameliorates depressed splenic blood flow and whether this agent has any salutary effects on depressed splenocyte functions after trauma-hemorrhage. Male rats underwent sham operation or laparotomy and were bled to and maintained at a mean arterial blood pressure of 40 mmHg until 40% of maximum shed blood volume (MBV) was returned as Ringer lactate (RL). Hemorrhaged rats were then resuscitated with RL (4 times MBV over 1 h). During resuscitation, rats received 300 mg/kg L-arginine or saline (vehicle) intravenously; 4 h later, splenic blood flow, splenocyte proliferation, and splenocyte interleukin (IL)-2 and IL-3 were determined. Administration of L-arginine improved depressed splenic blood flow and restored depressed splenocyte functions after trauma-hemorrhage. Therefore, provision of L-arginine during resuscitation after trauma-hemorrhage should be considered a novel and safe approach for improving splenic organ blood flow and depressed splenocyte functions under such conditions.

Animals↗
PubMed1999

Hypoxemia in the absence of blood loss upregulates iNOS expression and activity in macrophages.

Regional hypoxia, associated with hemorrhage, is thought to induce a variety of alterations in immune cell function, including upregulation of macrophage-inducible nitric oxide synthase (iNOS) expression and activity (NO production). Furthermore, NO may cause immune cell dysfunction similar to that associated with hemorrhagic shock. However, it remains unknown whether hypoxia per se in the absence of any blood loss is a sufficient stimulus to cause iNOS expression and NO production by macrophages. To study this, male Sprague-Dawley rats (275-325 g) were placed in a plastic box flushed with a gas mixture containing 5% O2-95% N2 for 60 min. Peritoneal and splenic macrophages were isolated 0-5.5 h thereafter, and blood samples were obtained. Nitrite and nitrate (stable degradation products of NO) production by splenic and peritoneal macrophages cultured for 48 h was significantly increased 3 and 5.5 h after hypoxemia. The increase in NO production by macrophages was preceded by elevated expression of iNOS mRNA at 1.5 h after hypoxia. Additionally, interferon-gamma (IFN-gamma) levels in plasma from rats subjected to hypoxemia were significantly elevated soon after the insult (0-1.5 h posthypoxemia), suggesting a causal relationship between IFN-gamma production and upregulation of iNOS activity. We propose that a hypoxemia-induced increase in macrophage iNOS activity following hemorrhage may in part be responsible for the observed immune dysfunction. Thus attempts to suppress macrophage iNOS activity after this form of trauma may be helpful in improving immune function under those conditions.

Animals↗
PubMed1999

Sex steroids regulate pro- and anti-inflammatory cytokine release by macrophages after trauma-hemorrhage.

Studies indicate that macrophage immune responses in males are depressed after trauma-hemorrhage, whereas they are enhanced in females under such conditions. Nonetheless, the involvement of male and female sex steroids in this gender-dependent dimorphic immune response after trauma-hemorrhage remains unclear. To study this, male C3H/HeN mice were castrated and treated with pellets containing either vehicle, 5alpha-dihydrotestosterone (DHT), 17beta-estradiol, or a combination of both steroid hormones for 14 days before soft tissue trauma (i.e., laparotomy) and hemorrhagic shock (35 +/- 5 mmHg for 90 min followed by adequate fluid resuscitation) or a sham operation. Twenty-four hours later the animals were killed, plasma was obtained, and Kupffer cell and splenic and peritoneal macrophage cultures were established. For DHT-treated mice, we observed significantly decreased releases of the proinflammatory cytokines interleukin 1beta (IL-1beta) and IL-6 by splenic macrophage (-50 and -57%, respectively) and peritoneal macrophage (-51 and -52%, respectively) cultures after trauma-hemorrhage compared with releases by cultures of cells from mice subjected to a sham operation; in contrast, responses of splenic and peritoneal macrophage cultures from other groups subjected to trauma-hemorrhage did not change significantly. In addition, only DHT-treated animals exhibited increased Kupffer cell IL-6 release (+634%). The release of IL-10 in DHT-treated hemorrhaged animals was increased compared with that in sham-operated animals but was decreased in estrogen-treated mice under such conditions. These results suggest that male and female sex steroids exhibit divergent immunomodulatory properties with respect to cell-mediated immune responses after trauma-hemorrhage.

Animals↗
PubMed1999

Pentoxifylline prevents the transition from the hyperdynamic to hypodynamic response during sepsis.

The cardiovascular response to sepsis includes an early, hyperdynamic phase followed by a late, hypodynamic phase. Although administration of pentoxifylline (PTX) produces beneficial effects in sepsis, it remains unknown whether this agent prevents the transition from the hyperdynamic to the hypodynamic response during the progression of sepsis. To study this, male adult rats were subjected to polymicrobial sepsis by cecal ligation and puncture (CLP). At 1 h after CLP, PTX (50 mg/kg body wt) or vehicle was infused intravenously over 30 min. At 20 h after CLP (i.e., the late stage of sepsis), cardiac output and organ blood flow were measured by radioactive microspheres. Systemic and regional (i.e., hepatic, intestinal, and renal) oxygen delivery (DO2) and oxygen consumption (VO2) were determined. Moreover, plasma levels of lactate and alanine aminotransferase (ALT) were measured, and histological examinations were performed. In additional animals, the necrotic cecum was excised at 20 h after CLP, and mortality was monitored for 10 days thereafter. The results indicate that cardiac output, organ blood flow, and systemic and regional DO2 decreased by 36-65% (P < 0.05) at 20 h after CLP. Administration of PTX early after the onset of sepsis, however, prevented reduction in measured hemodynamic parameters and increased systemic and regional DO2 and VO(2) by 50-264% (P < 0.05). The elevated levels of lactate (by 173%, P < 0.05) and ALT (by 718%, P < 0.05), as well as the morphological alterations in the liver, small intestine, and kidneys during sepsis were attenuated by PTX treatment. In addition, PTX treatment decreased the mortality rate from 50 to 0% (P < 0.05) after CLP and cecal excision. Because PTX prevents the occurrence of hypodynamic sepsis, this agent appears to be a useful adjunct for maintaining hemodynamic stability and preventing lethality from sepsis.

Animals↗