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Biomedical subjects

R W Watson

Publications and source records attributed to R W Watson.

At least 55 records · Page 3Linked to original sources
PubMed1996

Thiol-mediated redox regulation of neutrophil apoptosis.

BACKGROUND: Intracellular glutathione, an endogenous antioxidant, protects cellular function against oxidative stress. Because oxidative stress has been implicated in neutrophil apoptosis, we hypothesized that reduced thiol levels may induce apoptosis through an alteration in cellular redox state. METHODS: Human polymorphonuclear leukocytes (PMNs), were incubated with medium or with increasing concentrations of the reduced glutathione (GSH)-depleting agents diethylmaleate and diamide and buthionine sulfoximine, an inhibitor of GSH synthesis. Apoptosis was assessed by means of flow cytometry with propidium iodide DNA staining and confirmed morphologically. GSH was measured colorimetrically, and tyrosine phosphorylation was assessed by means of immunoblotting. RESULTS: Diethylmaleate and diamide induced a dose-dependent reduction in GSH and a corresponding increase in PMN apoptosis. This effect could be reversed with N-acetylcysteine, suggesting that diethylmaleate induces apoptosis through the depletion of GSH. The antioxidant pyrolidine dithiocarbamate had no effect. Because oxidants can mediate intracellular signaling via tyrosine phosphorylation, we therefore evaluated the effects of the tyrosine kinase inhibition on diethylmaleate-induced PMN apoptosis. Both genistein and herbimycin A reduced diethylmaleate-induced apoptosis and tyrosine phosphorylation. CONCLUSIONS: Sulfhydryl oxidation by diethylmaleate alone induces apoptosis, providing evidence of a redox-sensitive, thiol-mediated pathway of apoptosis. Furthermore, tyrosine phosphorylation appears to play an important role in this process. Because apoptosis is a critical mechanism regulating PMN survival in vivo, manipulation of PMN intracellular thiols may represents a novel therapeutic target for the regulation of cellular function.

Antioxidants↗
PubMed1996

Diethylmaleate attenuates endotoxin-induced lung injury.

BACKGROUND: Alterations in the cellular redox state play a critical role in cell signaling and cell activation, suggesting that administration of sulfhydryl-reactive agents may have important modulatory effects on the inflammatory response. We postulated that intracellular thiol depletion may attenuate the pulmonary inflammatory response after intratracheal administration of endotoxin (LPS) and that this attenuation would supersede the reduction in antioxidant defenses associated with depletion of the endogenous antioxidant, glutathione. METHODS: Sprague Dawley rats were administered diethylmaleate (6 mmol/kg intraperitoneally), a rapidly acting glutathione-depleting agent, followed by intratracheal administration of LPS. Lung injury was assessed by measuring the transpulmonary flux of 125-I albumin and expressed as a permeability index. RESULTS: Administration of diethylmaleate reduced lung glutathione levels from 1310 +/- 114 to 185 +/- 48 nmol/gm. This was associated with a reduction in the permeability index after LPS treatment (LPS, 0.22 +/- 0.03 versus LPS + diethylmaleate, 0.03 +/- 0.01). Bronchoalveolar lavage fluid polymorphonuclear neutrophil counts were markedly reduced in animals pretreated with diethylmaleate (LPS, 90.5 +/- 24 x 10(6) versus LPS + diethylmaleate, 1.9 +/- 0.4 x 10(6)). Peripheral blood polymorphonuclear neutrophils isolated from animals treated with diethylmaleate had equivalent chemotactic responses to n-formyl-methionyl-leucyl-phenylalanine and normal up-regulation of CD11b as determined by flow cytometry. Levels of bronchoalveolar lavage fluid tumor necrosis factor-alpha were unaffected. CONCLUSIONS: Diethylmaleate attenuates LPS-induced lung injury through a reduction in lung polymorphonuclear neutrophil sequestration. Normal peripheral blood neutrophil chemotactic responses and CD11b expression suggest that thiol depletion might mediate this effect through inhibition of endothelial cell adhesion molecule activity.

Albumins↗
PubMed1996

Bacterial ingestion, tumor necrosis factor-alpha, and heat induce programmed cell death in activated neutrophils.

Resolution of acute inflammation requires the removal of sequestered neutrophils (PMN) from the inflammatory site by apoptosis and ingestion by tissue macrophages; however, sequestered PMN are prevented from undergoing programmed cell death by some of the mediators of the acute inflammatory process, including lipopolysaccharide (LPS), granulocyte-macrophage colony-stimulating factor, and interleukin 2. This delay in apoptosis could lead to necrosis resulting in tissue damage. Tumor necrosis factor-alpha (TNF-alpha), Escherichia coli ingestion resulting in a respiratory burst, and heat have been shown to induce PMN apoptosis. The effects of TNF-alpha, E. coli ingestion, and heat shock on the one hand and LPS on the other, on PMN apoptosis are unknown. The aim of this study was to determine if TNF-alpha, E. coli ingestion, and heat shock, which have been shown to induce PMN apoptosis, could override the delay in apoptosis associated with LPS. PMN (10(6)) isolated from 10 healthy volunteers were cultured in either medium alone or PMN cultured with LPS (10 ng/mL/1 h). PMN activation was assessed subsequently by phagocytosis of E. coli and CD11b expression. PMN were then further studied under four culture conditions: medium alone, TNF-alpha (100 U/mL), E. coli (1:25, PMN:E. coli), and heat shock (42 degrees C for 45 min). Apoptosis was assessed over time by propidium iodide staining of DNA and Fc gamma RIII receptor expression. The results demonstrate, for the first time, that the mechanisms by which LPS delays PMN apoptosis are overridden by the mechanisms by which TNF-alpha, E. coli ingestion, and heat shock induce programmed cell death. Factors regulating PMN apoptosis have an important role to play in the resolution of acute inflammation. Identification of these factors and their interaction have important implications for the development of therapeutic strategies aimed at modulating the acute inflammatory response.

Apoptosis↗
PubMed1996

The beneficial effect of taurine on the prevention of human endothelial cell death.

This study was designed to test the hypothesis that the antioxidant taurine may modulate human endothelial cell (EC) death (apoptosis versus necrosis). Sodium arsenite (80 microM) alone and in combination with tumor necrosis factor-alpha (25 ng/mL) caused EC apoptosis after 24 h of treatment. Taurine (.5 mg/mL) added at 0 and 6 h could significantly attenuate EC apoptosis, and oxidative state in response to lipopolysaccharide and tumor necrosis factor-alpha stimulation. EC necrosis was induced by activated neutrophils (PMNs). Taurine reduced PMN-mediated EC necrosis in a dose-dependent manner. Moreover, treatment of ECs with a calcium ionophore, A23187 (1.0-4.0 microM), resulted in both EC apoptosis and necrosis. Taurine significantly abrogated A23187-mediated intracellular calcium elevation and EC death. These data indicate that taurine, possibly through its antioxidant activity and regulation of intracellular calcium flux, can prevent EC dysfunction and cell death, which may have implications for the application of this amino acid in the amelioration of acute lung injury during systemic inflammatory response syndrome.

Apoptosis↗
PubMed1995

Characterization of the defects in murine peritoneal macrophage function in the early postsplenectomy period.

Postsplenectomy bacterial sepsis may be fatal, due to defects in both cellular and humoral immune responses. The objective of this study was to assess the efficacy of peritoneal macrophage antibacterial function in the early postsplenectomy period. Murine models of splenectomy and sham operation were characterized and peritoneal macrophages were harvested 24 h to 1 wk after surgery. Cells from splenectomized animals demonstrated a nonsignificant delay in phagocytosis of Escherichia coli at 24 h with, however, significantly impaired killing of intracellular organisms at 24 h and 1 wk compared to the sham group. Paradoxically, the production of the macrophage antibacterial product superoxide anion was not impaired at either time point in the splenectomy group compared with sham-operated and control mice. Nitric oxide release was significantly lower in the splenectomized group (p = 0.006), a possible explanation for reduced bacterial killing. Mortality from bacterial peritonitis was significantly higher with concomitant splenectomy than in the sham splenectomy group at 24 h (p < 0.02). The production of TNF from macrophages was up-regulated immediately following splenectomy, a cytokine which may contribute to mortality from bacteremic shock. Local defects in macrophage antimicrobial function may contribute significantly to bacteremia and to subsequent mortality in the early postsplenectomy period.

Animals↗
PubMed1995

Induction of heat shock protein 72 prevents neutrophil-mediated human endothelial cell necrosis.

OBJECTIVE: To examine the hypothesis that induction of heat shock proteins in human endothelial cells (ECs) by either heat shock or sodium arsenite could prevent subsequent EC necrosis induced by activated human polymorphonuclear neutrophil leukocytes (PMNs). DESIGN: Cultures of ECs were exposed to heat shock (42 degrees C, 30 to 60 minutes) or sodium arsenite (40 to 320 mumol/L) for 6 hours to induce the expression of a heat shock protein of 72-kd molecular weight (HSP-72). Activated PMNs were subsequently added to these ECs for 24 hours to evaluate the ability of HSP-72 to prevent activated PMN-mediated EC necrosis. RESULTS: Neither EC necrosis nor apoptosis was induced by heat shock. Sodium arsenite (40 to 80 mumol/L) did not induce EC necrosis, although 320-mumol/L sodium arsenite caused a significant increase in EC necrosis. Sodium arsenite (80 to 320 mumol/L) also induced dose-dependent EC apoptosis. Endothelial cells exposed to heat shock and sodium arsenite (40 and 80 mumol/L) significantly attenuated subsequent EC necrosis induced by activated PMNs. However, sodium arsenite at 320 mumol/L aggravated activated PMN-mediated EC necrosis. Expression of HSP-72 was detected after ECs were treated both with heat shock and sodium arsenite (40 to 320 mumol/L) for 6 hours. CONCLUSION: Induction of HSP-72 in ECs by a thermal or nonthermal mechanism could prevent activated PMN-mediated EC necrosis, which may favor increased vascular permeability during systemic inflammatory response syndrome.

Apoptosis↗
PubMed1995

Failure of macrophage activation in experimental obstructive jaundice: association with bacterial translocation.

Bacterial translocation from the gastrointestinal tract and macrophage activation are central to current theories of sepsis. The relevance of both in obstructive jaundice is unclear. The effect of bile duct ligation for 7 days on bacterial translocation to mesenteric lymph nodes and on macrophage activation in a rat model was examined. Compared with an incidence of zero in sham-ligated controls, bile-duct ligated rats had a 67 per cent incidence of Gram-negative colonization of mesenteric lymph nodes. This was associated with a significant (P < 0.001) decrease in macrophage tumour necrosis factor, superoxide anion and nitric oxide production compared with that in sham controls. Spontaneous bacterial translocation occurs in experimental obstructive jaundice and is associated with marked suppression of macrophage activation. This suggests a mechanism whereby jaundiced patients may be more susceptible to persistent infection but relatively protected against uncontrolled sepsis.

Animals↗
PubMed1995

Exposure of the peritoneal cavity to air regulates early inflammatory responses to surgery in a murine model.

Factors in circulating air may play a role in immune responses after surgery through induction of gut-derived lipopolysaccharide (LPS) translocation across the gut. CD-1 mice were randomized to one of four treatment groups: controls, laparoscopy with carbon dioxide inflation, laparoscopy with air inflation and laparotomy. The peritoneal and systemic immune response was assessed by evaluating peritoneal macrophage, blood monocyte and neutrophil activity. In a second study, the effect of each of the treatments on fluorescein isothiocyanate (FITC)-LPS translocation across the gut was assessed. There were significant (P < 0.05) increases in peritoneal tissue macrophage release of superoxide and tumour necrosis factor after laparoscopy with air and laparotomy compared with control procedures and carbon dioxide laparoscopy. However, peritoneal macrophage FITC-Candida albicans ingestion was significantly decreased after air laparoscopy and laparotomy compared with controls and carbon dioxide laparoscopy (P < 0.05). These findings correlated with a significant (P < 0.05) decrease in CD11b expression. Significant translocation into the peritoneal cavity and systemic circulation occurred after air laparoscopy and laparotomy only. Factors in circulating air can induce LPS translocation and subsequent stimulation of postoperative immune responses. The beneficial effects of laparoscopic surgery may be explained by the minimal air contamination of the peritoneal cavity.

Abdomen↗
PubMed1995

Role of nitric oxide in lung injury associated with experimental acute pancreatitis.

This study evaluated the effect of varying the synthesis of nitric oxide with sodium nitroprusside or N-nitro-L-arginine methyl ester (L-NAME) in a pancreatitis-lung injury model. Rats (n = 45) were randomized to control or caerulein-induced pancreatitis groups, treated with saline, sodium nitroprusside (0.4 micrograms/kg) or L-NAME (10 mg/kg). Myeloperoxidase activity was used as a measure of neutrophil infiltration. Wet to dry (W:D) lung weight and bronchoalveolar lavage (BAL) protein concentrations were used to assess vascular leakage. Pancreatitis was shown to induce pulmonary neutrophil influx: mean(s.e.m.) myeloperoxidase activity 6.79(0.5) units/g in caerulein-treated animals versus 2.08(0.5) units/g in controls (P < 0.001). Animals with pancreatitis showed increased microvascular leakage compared with controls (mean(s.e.m.) W:D lung weight 7.01(0.5) versus 2.85(0.2), P < 0.001; BAL protein concentration 2539(222) versus 347(32) micrograms/ml, P < 0.001). Compared with the saline-treated pancreatitis group, these changes were reduced by sodium nitroprusside (mean(s.e.m.) myeloperoxidase activity to 2.5(0.4) units/g, P < 0.001; W:D lung weight to 3.8(0.37), P < 0.001; BAL protein concentration 1389(182) micrograms/ml, P < 0.05). L-NAME exacerbated the pancreatitis-induced pulmonary oedema (W:D lung weight increased to 11.96(0.6), P < 0.001), protein leakage (BAL protein concentration rose to 3707(309) micrograms/ml, P < 0.05) and neutrophil infiltration (myeloperoxidase activity increased to 9.01(0.3) units/g, P < 0.05). These data suggest that, in vivo, nitric oxide inhibits pancreatitis-induced lung injury, possibly in part by inhibiting pulmonary neutrophil influx.

Acute Disease↗
PubMed1995

Taurolidine, an antilipopolysaccharide agent, has immunoregulatory properties that are mediated by the amino acid taurine.

Taurolidine has bactericidal and antilipopolysaccharide properties. It is broken down into the amino acid taurine, which has been shown to modulate intracellular calcium activity, a critical component in the priming and activation of macrophages and polymorphonuclear leukocytes. We hypothesized that taurolidine may function to enhance immune activity in these cells. The aim of this study was to investigate the immunological effects of taurolidine and correlate findings with survival after a septic challenge in a murine model. Study 1: CD-1 mice underwent cecal ligation and puncture, were randomized to receive taurolidine (200 mg/kg body weight/i.p.) or saline control, and studied for end point survival. Study 2: CD-1 mice were randomized to receive taurolidine (200 mg/kg body weight/i.p.) or saline control. Peritoneal macrophages (PM luminal diameters) were assessed for O2-, NO, tumor necrosis factor-alpha (TNF-alpha), CD11b, phagocytosis, and PMN influx. O2-, TNF-alpha, CD11b expression, and phagocytosis were significantly increased in the taurolidine group. Study 3: PM luminal diameters were cultured in vitro +/- 0.5 mg/ml taurolidine and PM luminal diameter antimicrobial function assessed (O2-, NO, TNF-alpha, and phagocytosis). O2-, TNF-alpha, and phagocytosis were significantly increased, whereas NO was reduced. Study 4: PM luminal diameters were also cultured with taurine (0.5 mg/ml). Similar increase in O2-, TNF-alpha, and phagocytosis were identified. Intracellular PM luminal diameter [Ca2+] was also assessed and increases in free, unbound intracellular [Ca2+] occurred after taurine culture. Thus, in addition to its bactericidal and antilipopolysaccharide activity, taurolidine primes PM luminal diameters for enhanced antimicrobial activity and these effects appear mediated by the amino acid taurine.

Animals↗
PubMed1995

Role of lipopolysaccharide and tumor necrosis factor-alpha in induction of hepatocyte necrosis.

The occurrence of acute hepatic failure during systemic inflammatory response syndrome (SIRS) is related to the extent of hepatocyte (HC) damage and cell death resulting from necrosis or apoptosis. We hypothesized that proinflammatory mediators such as lipopolysaccharide (LPS) and tumor necrosis factor-alpha (TNF-alpha) can, either directly or indirectly through neutrophil (PMN) and Kupffer cell (KC) activation, induce HC damage and cell death, and that the mechanism is cellular necrosis rather than apoptosis. The results in this study demonstrated that LPS and TNF-alpha alone and in combination are directly cytotoxic to cultured rat HC as indicated by the hepatocellular enzyme release and HC necrosis. However, LPS and TNF-alpha, in the presence of sodium arsenite (a heat shock inducer), were unable to induce HC apoptosis. Both KC and PMN activated by either LPS or TNF-alpha induced significant hepatocellular enzyme release and HC necrosis, which was dependent on the ratio of KC and PMN to HC. It is concluded that LPS and TNF-alpha may play a central role in the development of acute hepatic failure after severe trauma and sepsis by directly or indirectly inducing HC necrosis rather than apoptosis.

Animals↗
PubMed1994

Immune function in patients undergoing open vs laparoscopic cholecystectomy.

BACKGROUND: Abnormal release of inflammatory mediators following surgical injury is associated with immunological alteration, which may predispose to sepsis. Laparoscopic surgery is associated with reduced postoperative complications, but mechanisms are unclear. We hypothesized that early recovery following laparoscopic surgery may relate to minimal impairment of immune function. DESIGN: Analysis of the temporal immune responses in two similar groups of patients randomized to open (n = 22) vs laparoscopic (n = 22) cholecystectomy. Patients were matched for age, height, weight, and operation time. Immune parameters, including monocyte superoxide anion (O2-) and tumor necrosis factor release, neutrophil O2- levels and chemotaxis, total white blood cell counts, partial arterial oxygen pressure, and serum cortisol and C-reactive protein levels were assessed preoperatively and on postoperative days 1 and 3. RESULTS: There were significant increases (P < .001) in monocyte release of O2- and tumor necrosis factor, neutrophil release of O2- and chemotaxis, and white blood cell count in the open vs laparoscopic cholecystectomy study groups, with a concommitant decrease in partial arterial oxygen pressure. These findings correlated with significantly higher postoperative septic complications in the open cholecystectomy group (P < .05). There were no significant differences in either plasma cortisol or C-reactive protein levels between groups. All measurements were carried out in a blinded fashion. CONCLUSIONS: This study demonstrates that laparoscopic surgery appears to be associated with similar metabolic responses compared with open surgery, while immune parameters vary greatly between groups. The beneficial effects of laparoscopic surgery may relate, in part, to preservation of immune function in the postoperative period.

Adult↗
PubMed1994

Role of endotoxin in mononuclear phagocyte-mediated inflammatory responses.

Lipopolysaccharide (LPS), which is derived from the cell wall of gram-negative and some gram-positive bacteria, plays a major role is the pathogenesis of septic shock. Initiation of these responses depends on LPS interaction with a number of immune cells, not least the mononuclear phagocyte (MP). Mononuclear phagocytes bind the LPS/lipopolysaccharide-binding protein complex through the CD14 receptor and thus mediate the release of a wide range of inflammatory mediators. Release of these mediators is teleologically beneficial but under certain circumstances may be detrimental, resulting in the systemic inflammatory response syndrome. The development of this syndrome is not clearly understood but appears, in part, to be dependent on the ability of the host to respond to these mediators. This review evaluates the mechanisms of LPS-MP interaction and the therapeutic strategies aimed at inhibiting this interaction.

Animals↗
PubMed1994

Nitric oxide (endothelium-derived relaxing factor) attenuates revascularization-induced lung injury.

Aortic occlusion and revascularization (I-R) may lead to lung injury dependent on activated neutrophil adherence. Nitric oxide (NO) inhibits neutrophil adherence to endothelial cells. We studied the effect of increasing or decreasing NO levels with sodium nitroprusside (SNP) or N-nitro-L-arginine methyl ester (L-NAME) in an I-R lung injury model of 30 min ischemia followed by 120 min reperfusion. Sprague-Dawley rats (10/group) were randomized to controls, I-R, I-R treated with L-NAME (10 mg/ml/hr), and I-R treated with SNP (0.2 mg/ml/hr). Myeloperoxidase activity (MPO) was used as a measure of pulmonary neutrophil influx. Pulmonary endothelial permeability was measured by wet:dry weight ratio and bronchoalveolar lavage protein (BAL prot) and neutrophil counts (BAL PMN). Aortic occlusion and revascularization led to significant increases in pulmonary neutrophil influx (6.1 +/- 0.1 MPO u/g vs 3.05 +/- 0.4 MPO u/g in the control group, P < 0.001) and microvascular leakage; BAL prot (347 +/- 32 mg/ml in controls vs 454 +/- 16 mg/ml in the I-R group, P < 0.05); and BAL PMN (0.7 +/- 0.05 in controls vs 1.8 +/- 0.07 PMN/ml in the I-R group, P < 0.001). These changes were exacerbated further by administration of L-NAME (MPO = 8.9 +/- 0.7; BAL prot = 581 +/- 40 mg/ml; BAL PMN = 2.7 +/- 0.16 PMN/ml). Sodium nitroprusside therapy attenuated the I-R-induced lung injury (3.5 +/- 0.4 MPO u/g, P < 0.05 vs I-R; BAL prot = 330 +/- 61 mg/ml; BAL PMN = 0.9 +/- 0.1 PMN/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

A central executive deficit in patients with Parkinson's disease.

Eight patients with Parkinson's disease and eight matched controls were tested for concurrent task performance to examine whether Parkinson's disease produces deficits in the coordinating and integrating function of the central executive component of Baddeley's working memory model. Consistent with this prediction, the patients showed a significant decline in performance on a random pursuit tracking task while recalling digit span forward sequences, whereas the controls showed no such change. Performance on the component pursuit and digit span tasks, which did not differ between groups, was equated across subjects by varying the size of a target square and by using individual subjects' digit spans. The patient group also produced poorer word fluency scores and reported higher levels of depression, but there was no significant impairment on the Wisconsin card sort test. There was no association between dual task performance and any psychometric measure, target size, or disease related variables. Baddeley's working memory model is advantageous in providing a rich conceptual basis to explore and characterise cognitive abilities in patients with Parkinson's disease.

Aged↗