Biomedical subjects

E J Kovacs

Publications and source records attributed to E J Kovacs.

At least 19 recordsLinked to original sources

PubMed2001

Wound healing in MIP-1alpha(-/-) and MCP-1(-/-) mice.

A salient feature of normal wound healing is the development and resolution of an acute inflammatory response. Although much is known about the function of inflammatory cells within wounds, little is known about the chemotactic and activation signals that influence this response. As the CC chemokines macrophage inflammatory protein-1alpha (MIP-1alpha) and monocyte chemotactic protein-1 (MCP-1) are abundant in acute wounds, wound repair was examined in MIP-1alpha(-/-) and MCP-1(-/-) mice. Surprisingly, wound re-epithelialization, angiogenesis, and collagen synthesis in MIP-1alpha(-/-) mice was nearly identical to wild-type controls. In contrast, MCP-1(-/-) mice displayed significantly delayed wound re-epithelialization, with the greatest delay at day 3 after injury (28 +/- 5% versus 79 +/- 14% re-epithelialization, P < 0.005). Wound angiogenesis was also delayed in MCP-1(-/-) mice, with a 48% reduction in capillary density at day 5 after injury. Collagen synthesis was impeded as well, with the wounds of MCP-1(-/-) mice containing significantly less hydroxyproline than those of control mice (25 +/- 3 versus 50 +/- 8 microg/wound at day 5, P < 0.0001). No change in the number of wound macrophages was observed in MCP-1(-/-) mice, suggesting that monocyte recruitment into wounds is independent of this chemokine. The data suggest that MCP-1 plays a critical role in healing wounds, most likely by influencing the effector state of macrophages and other cell types.

Animals↗

PubMed2001

Testosterone receptor blockade restores cellular immunity in male mice after burn injury.

Males are known to have increased risk for septic complications after traumatic injury, which appears to be mediated by the inhibitory effects of testosterone on immune function. The role of testosterone in immunity after burn injury, however, remains unclear. Herein, we examined the effects of a testosterone receptor antagonist, flutamide, on delayed type hypersensitivity response (DTH), splenocyte proliferation, interleukin (IL)-2 secretion, and IL-2 receptor (IL-2R) expression in male BALB/c mice subjected to a 15% total body surface area burn or sham injury. Burn- or sham-injured mice were given flutamide s.c. at 30 min and 24 h after injury. At 48 h, burn injury caused a 48% (P<0.001) decrease in DTH response; however, mice that received flutamide treatment did not demonstrate significant suppression of DTH. Likewise, splenocyte proliferation and IL-2 production were depressed in burned animals in comparison with sham-injured controls, and flutamide treatment resulted in a partial restoration of these responses. In vitro studies indicated that splenocytes from sham- and burn-injured mice were equally sensitive to the suppressive effects of 5alpha-dihydrotestosterone in regard to proliferation and IL-2 production. Further evaluation revealed a decrease in IL-2R expression on splenocytes from burned mice and a partial restoration of this expression with flutamide treatment. Thus blocking testosterone receptor activation improves the cellular immunity in thermally injured mice, possibly through restoration of IL-2 production and IL-2R expression. It remains to be determined whether the effects of testosterone in this injury model are direct or indirect.

Animals↗

PubMed2001

Estrogen restores cellular immunity in injured male mice via suppression of interleukin-6 production.

This study examined whether estrogen treatment can improve immunity in male mice after combined ethanol and burn injuries. 17beta-Estradiol [estrogen, given subcutaneously (s.c.)] or oil (control) was administered at 30 min and 24 h postinjury. At 48 h postinjury, ethanol/burn-injured mice demonstrated significant suppression of cellular immunity. Estrogen treatment restored the delayed-type hypersensitivity (P<0.01) and splenocyte-proliferative (P<0.05) responses, reduced macrophage interleukin-6 (IL-6) (P<0.05), and increased survival after bacterial challenge (P<0.01). In vitro neutralization of IL-6, combined with macrophage supernatant experiments, confirmed that the beneficial effects of estrogen treatment were mediated through modulation of macrophage IL-6 production. Moreover, estrogen treatment resulted in a decrease in splenic nuclear factor-kappaB (NF-kappaB) activation in injured mice. There were no changes in cellular NF-kappaB or IkappaBalpha protein expression or IkappaBalpha phosphorylation at serine 32. Taken together, these studies suggest that estrogen treatment of injured male mice improves cellular immunity through direct modulation of NF-kappaB activation.

Alcoholic Intoxication↗

PubMed2000

Differential production of prostaglandin E(2) in male and female mice subjected to thermal injury contributes to the gender difference in immune function: possible role for 15-hydroxyprostaglandin dehydrogenase.

We have previously reported a macrophage-mediated gender difference in postburn immunosuppression, which was dependent upon elevated levels of circulating 17beta-estradiol (E(2)) and, in part, interleukin-6. Herein we examined the role of prostaglandin E(2) (PGE(2)), a potent suppressor of cell-mediated immunity. Circulating levels of PGE(2) were significantly elevated in females but not males at 10 days postburn (P < 0.01), and indomethacin treatment fully restored the delayed-type hypersensitivity and splenocyte proliferative responses of thermally injured females. While there was no difference in cyclooxygenase-2 protein expression in the lungs and liver of thermally injured male and female mice, there was a marked decrease in the protein expression of 15-hydroxyprostaglandin dehydrogenase in females. These data demonstrate that PGE(2) is a critical mediator of immunosuppression in thermally injured female mice and that the increase in circulating PGE(2) is derived, in part, from decreased degradation and clearance of PGE(2).

Animals↗

PubMed2000

The role of interleukin 6 in interferon-gamma production in thermally injured mice.

Following traumatic injury, patients suffer from compromised immunity increasing their susceptibility to infection. Previous studies from this laboratory demonstrated that female BALB/c mice subjected to a 15% total body surface area (TBSA) scald injury exhibit a decrease in cell-mediated immunity 10 days post-burn. Studies described herein revealed that concanavalin A (Con A; 2 microg/ml)-stimulated splenocytes from sham treated animals produced 3557+/-853 pg/ml of IFN-gamma while splenocytes from burn injured animals released two-fold more cytokine (P<0.05). To determine whether leukocyte production of IFN-gamma was under the influence of macrophages, splenic macrophage supernatants generated from burned animals were incubated with splenic lymphocytes from sham and burn animals. The amount of IFN-gamma released by lymphocytes from sham animals increased when cultured with macrophages from burned mice (P<0.05). This suggests that the increase in IFN-gamma production by unfractionated splenocytes in burned mice relative to sham treated animals is macrophage-dependent. Macrophage supernatants from burned mice released twice as much IL-6 as supernatants from sham animals (P<0.05), and when IL-6 was blocked in vivo, the amount of IFN-gamma production in burned mice decreased to sham levels (P<0.05). Thus, IL-6 mediates IFN-gamma production following burn.

Animals↗

PubMed2000

Ethanol exacerbates T cell dysfunction after thermal injury.

To understand the mechanism of suppressed immunity following alcohol consumption and thermal injury, we analyzed T cell functions in a mouse model of acute alcohol exposure and burn injury. Mice with blood alcohol levels at approximately 100 mg/dl were given a 15% scald or sham injury. Mice were sacrificed 48 h after injury. Our data demonstrated a 20-25% decrease in Con A-mediated splenic T cell proliferation (p<0.01) and 45-50% decrease in interleukin-2 (IL-2) production (p<0.01) following burn injury compared to the T cells from sham animals. A further decrease in the proliferation (25-30%) and IL-2 production (40-45%) was detected in T cells derived from burned animals receiving alcohol as compared to burn alone. No significant change in the proliferation and IL-2 production was observed in splenic T cells derived from sham-injured mice regardless of alcohol exposure. Additionally, there was no demonstrable difference in splenocyte apoptosis in any treatment group. These results suggest that alcohol consumption prior to burn injury causes a greater decrease in T cell proliferation and IL-2 production compared to either burn or alcohol injury alone that may further attenuate the cell-mediated immunity and thus enhance susceptibility to infection.

Alcohol Drinking↗

PubMed2000

Cellular immunity after ethanol exposure and burn injury: dose and time dependence.

Acute ethanol exposure prior to burn injury increases the immune dysfunction seen with burn alone, which has been partially attributed to increased circulating and splenic macrophage production of interleukin-6 (IL-6). The current studies examined the effect dose and timing of ethanol exposure prior to burn on cellular immunity. Mice with high (300 mg/dl) circulating levels of ethanol at the time of burn demonstrated further suppression of the delayed type hypersensitivity (DTH) and splenocyte proliferative responses in comparison to mice with moderate (100 mg/dl) ethanol levels. Interestingly, the increase in macrophage IL-6 secretion seen at the moderate dose was not augmented at the high dose; however, the circulating IL-6 levels did reveal a further increase at the high ethanol dose. There were no alterations in splenocyte subset populations and/or apoptosis at the moderate vs. the high ethanol dose. Moderate ethanol exposure 24 h, in comparison to 30 min, before injury resulted in similar decreases in the DTH. These results suggest that the dose-dependent effects of ethanol on immunity following burn injury are not the result of splenic macrophage IL-6 production as shown at the moderate dose and that the immune suppressive effects of ethanol in this model persist after it is cleared from the circulation.

Animals↗

PubMed2000

Estrogen mediates the sex difference in post-burn immunosuppression.

Previous studies in our laboratory have demonstrated that cell-mediated immune function was suppressed in female, but not male, mice at 10 days after burn injury and was mediated, in part, by increased production of interleukin-6 (IL-6). Because 17beta-estradiol (E(2)) influences immune function after trauma and the hormone is known to regulate IL-6 production, the effect of E(2) on immune function after thermal injury was examined. Increased circulating concentrations of E(2) corresponded with suppressed delayed-type hypersensitivity (DTH) and splenocyte-proliferative responses, and increased circulating concentrations of IL-6 in female mice after burn. Ovariectomy restored the suppressed DTH response and decreased IL-6 concentrations, and administration of exogenous E(2) to both ovariectomized females and intact male mice resulted in a suppressed DTH response. In addition, in vitro treatment with E(2) suppressed splenocyte proliferation in a macrophage-dependent manner and enhanced macrophage production of IL-6. These results strongly suggest that the sex difference in cell-mediated immunity 10 days after burn injury is mediated by altered concentrations of E(2), which in turn modulate key macrophage-derived immunoregulatory cytokines.

Animals↗

PubMed2000

Gender difference in cell-mediated immunity after thermal injury is mediated, in part, by elevated levels of interleukin-6.

The gender difference in normal immune function has been well documented, however, there is only limited information regarding whether such a difference occurs after injury. To investigate this, we examined cell-mediated immune responses in male and female mice given a 15% total body surface area dorsal scald or sham injury. Both delayed-type hypersensitivity (DTH) and splenocyte proliferative responses were significantly suppressed in males at 1 day and in females at 7 and 10 days post burn (P < 0.01). The decreased splenocyte proliferation was found to be macrophage-dependent and suppression of both immune parameters corresponded with elevated interleukin-6 (IL-6) levels. Furthermore, post-burn treatment with an anti-IL-6 antibody partially restored the DTH response in males at 1 day and females at 10 days post injury and completely restored splenocyte proliferation. These data demonstrate a possible mechanism for the gender difference in cell-mediated immune responses after thermal injury.

Animals↗

PubMed2000

Anti-interleukin-6 antibody treatment restores cell-mediated immune function in mice with acute ethanol exposure before burn trauma.

BACKGROUND: Previous studies from this laboratory reported that suppression of cell-mediated immune function was coincident with elevated interleukin (IL)-6 production after acute ethanol exposure before burn trauma, compared with either insult alone. The goal of this study was to investigate whether treatment with an anti-IL-6 antibody could restore immunocompetence in mice subjected to burn trauma with previous exposure to alcohol, as assessed by delayed-type hypersensitivity (DTH) and mitogen-induced splenocyte proliferative responses. METHODS: Mice given an ethanol treatment designed to reach a blood alcohol level of 100 mg/dl before a 15% total body surface area burn injury were treated with an anti-IL-6 antibody at 30 min and 24 hr postinjury. RESULTS: Burn/ethanol mice exhibited a 91% suppression of the DTH response ( < 0.01) and a 76% suppression of mitogen-induced splenocyte proliferation (p < 0.01) at 48 hr postinjury, along with increased levels of circulating and splenic macrophage-derived IL-6, compared with all other treatment groups. After anti-IL-6 antibody administration to burn/ethanol mice, there was a 25% (p < 0.05) and 63% (p < 0.01) recovery of the DTH and splenocyte proliferative responses, respectively. Addition of exogenous IL-6 to splenocyte cultures isolated from anti-IL-6 antibody-treated burn/ethanol mice resulted in a 70% inhibition of mitogen-induced proliferative responses (p < 0.03). CONCLUSIONS: These data confirm previous findings that burn in combination with acute ethanol exposure suppresses cell-mediated immune function compared with either insult alone. Furthermore, the ability of the anti-IL-6 antibody treatment to improve cellular immune responses in the burn/ethanol group suggests that blocking this cytokine may be beneficial for the ethanol-exposed, thermally injured individual.

Animals↗

PubMed2000

Dose-dependent effect of ethanol on hepatic oxidative stress and interleukin-6 production after burn injury in the mouse.

BACKGROUND: Burned patients with detectable blood alcohol levels (BAL) show an elevated mortality rate. Interleukin (IL)-6 and reactive oxygen species (ROS) production is stimulated independently by alcohol and burn injury. The aim of the study was to determine whether increasing levels of alcohol differentially enhance the hepatic production of IL-6 and ROS after burn in a murine model of dorsal scald injury. Groups of mice received either saline or alcohol intraperitoneally to reach a BAL of 100 mg/dl or 300 mg/dl at the time of burn (15% total body surface scald) or sham injury. RESULTS: Burn injury alone resulted in a low mortality rate at 24 hr after injury as did the burn group with a BAL of 100 mg/dl (15%), whereas 57% of the mice burned with a BAL of 300 mg/dl did not survive (p = 0.02). Twenty-four hours after burn or sham injury, IL-6 levels were measured by enzyme-linked immunosorbent assay in serum and liver. In the saline-treated group, IL-6 circulating and hepatic levels rose after burn injury (p < 0.03). Circulating IL-6 levels in sham mice increased 1.5-fold in the group with a BAL of 100 mg/dl and 3-fold in those with a BAL of 300 mg/ml (p = 0.005 versus burn-injured, saline-treated). IL-6 hepatic production after burn injury was higher in the mice with a BAL of 300 mg/dl than in those with a BAL of 100 mg/dl and the saline-treated group (p = 0.001). Among the burned mice, alcohol exposure increased hepatic ROS production, measured by lipid peroxidation and protein oxidation, in a dose-dependent manner. CONCLUSIONS: Alcohol enhances in a dose-dependent manner the hepatic production of IL-6 induced by burn injury through the modulation of oxidative stress. The increased mortality rate of mice exposed to alcohol and burn injury may be due to the adverse effect on immune function induced by IL-6 elevation.

Animals↗

PubMed1999

Neutrophil chemokine production in the skin following scald injury.

The present study was conducted to determine whether local production of neutrophil chemoattractant cytokines preceded the influx of neutrophils following dermal scald injury. To accomplish this, dermal tissue was examined for inflammatory infiltrate and the level of KC, a murine homolog of human interleukin-8, at various time points after scald injury. The studies reveal that there was a largely neutrophilic infiltrate at 1 day post-injury which persisted for 4 days. Dermal KC levels increased significantly at 4 h, returned to baseline at 8 h and were elevated again from 1 to 3 days post-burn (P < 0.01). At 3 days post-burn, KC was elevated 15-fold above the level in sham treated mice (P < 0.01). These observations demonstrate that the influx of neutrophils into the skin follows the expression of KC in the skin. This suggests that it should be possible to alter neutrophil accumulation at the wound site by manipulating the local chemokine signal.

Animals↗

PubMed1999

Elevation in pulmonary neutrophils and prolonged production of pulmonary macrophage inflammatory protein-2 after burn injury with prior alcohol exposure.

Various studies have shown that alcohol exposure before thermal injury leads to increased morbidity and mortality. Pulmonary failure is a major complication seen in these patients. This study examines the effects of prior alcohol exposure on lung pathology after burn injury. There is a marked increase in neutrophil recruitment in the lung after thermal injury, and herein we show that this appears to be significantly elevated in animals given alcohol before burn injury. Consequently, we chose to determine whether there is a difference in pulmonary production of macrophage inflammatory protein (MIP)-2, a potent neutrophil chemoattractant, in mice subjected to a 15% total body surface area scald (or sham) injury with or without prior ethanol treatment. Lung tissue was obtained at various time points after injury and homogenates were assayed for MIP-2 by enzyme-linked immunosorbent assay. At 2 h after injury, peak levels of the chemokine were produced in both burn and burn + alcohol-treated mice. This represents a 7-fold increase above baseline. In mice exposed to burn injury alone, the level of MIP-2 returned to baseline within 8 h. In contrast, mice given alcohol before burn injury continued to show elevated levels of the chemokine at 8 h, after which MIP-2 decreased. This study may provide a basis for understanding the mechanism responsible for the increased neutrophil presence in the lung after thermal injury in individuals who have consumed alcohol. Subsequently, this may lead to the enhanced neutrophil-mediated pulmonary damage observed in these patients.

Alcohol Drinking↗

PubMed1999

Fibrin sealant inhibits connective tissue deposition in a murine model of peritoneal adhesion formation.

BACKGROUND: Postoperative peritoneal adhesion formation causes a multitude of disorders, including bowel obstruction and infertility. METHODS: To test whether fibrin sealant inhibits adhesion formation, mice were given an intraperitoneal injection of talc (to induce adhesions) after which sealant was administered. Seven and 14 days later, the thickness of connective tissue between the fragmented mesothelium and the abdominal muscle was measured. RESULTS: At both 7 and 14 days after talc administration, talc-treated mice had a 6-fold increase in connective tissue thickness over vehicle alone (P < .05). Although fibrin sealant alone failed to trigger peritoneal pathologic conditions, administration of sealant to talc-treated mice inhibited connective tissue deposition by 80% at 7 and 14 days (P < .05). Additionally, delaying fibrin sealant administration up to and including 72 hours after talc treatment results in comparable inhibition of connective tissue deposition, as does treatment immediately after talc exposure. CONCLUSIONS: This study demonstrates that fibrin sealant inhibits peritoneal inflammation and peritoneal adhesion formation with use of a quantitative assay of connective tissue deposition. In addition, this is the first report to document the administration of fibrin sealant into the closed abdomen. The success of these studies suggests that fibrin sealant will block peritoneal adhesions when administered laparoscopically. Finally, because fibrin sealant is therapeutic even when administered after the initiation of peritoneal inflammation, it suggests that it may be efficacious in patients who present with adhesions or those undergoing multiple operations.

Animals↗

PubMed1998

Glucocorticoids protect against suppression of T cell responses in a murine model of acute ethanol exposure and thermal injury by regulating IL-6.

Previous reports by this laboratory demonstrated that acute alcohol exposure combined with a 15% body surface area dorsal scald injury results in significant reductions in delayed-type hypersensitivity (DTH) and splenocyte proliferative responses compared to either insult alone. Previous studies by this lab have also shown that these defects are mediated, in part, by increased production of interleukin-6 (IL-6). Because both alcohol exposure and thermal injury are known to modulate glucocorticoid (CORT) levels, and CORT regulates IL-6 gene expression, the relationship between circulating CORT and IL-6 production in burn + ethanol mice was examined. At 24 and 48 h post-burn, a positive correlation existed between circulating CORT levels and measurements of cellular immune function. Administration of exogenous CORT to burn + ethanol-treated mice resulted in significant restoration (to 60% of control) of DTH and splenocyte proliferative responses. This restoration was concomitant with a down-regulation of circulating and macrophage-derived IL-6. The specificity of CORT in modulating these responses was tested by assessing cellular immune function and IL-6 levels after glucocorticoid receptor blockade with RU486. Taken together, these data strongly suggest that under normal circumstances CORT protects burned mice from severe immune dysfunction, a protection that is not afforded to burn + ethanol-treated mice. Furthermore, the immune dysfunction observed in burn + ethanol mice may be due to a lack of glucocorticoid attenuation of IL-6.

Animals↗

PubMed1998

Acute ethanol exposure prior to thermal injury results in decreased T-cell responses mediated in part by increased production of IL-6.

Previous studies by our laboratory have demonstrated that acute ethanol exposure prior to thermal injury results in suppression of cellular immune responses when compared with thermal injury alone. Ethanol exposure and burn injury are independently known to result in elevated IL-6, a cytokine with potent immunosuppressive properties. Therefore, we examined the role of IL-6 in the immune dysfunction in mice following a 15% body surface area scald (or sham) injury combined with acute ethanol (or vehicle) treatment. At 24 h post-injury, we observed slightly suppressed splenocyte proliferative responses and elevated circulating IL-6 (149+/-15 pg/mL) in mice receiving burn alone compared with those receiving sham injury (31+/-7 pg/mL). In contrast, burn + ethanol treated mice showed a profound suppression of splenocyte proliferation (20% of control) and significantly elevated circulating IL-6 levels (738+/-218 pg/mL). The suppressed splenocyte proliferative response was found to be macrophage dependent. Furthermore, IL-6 production was significantly elevated (p < .05) in splenic macrophage cultures from burn + ethanol mice (159+/-6 pg/mL) when compared with burn alone (109+/-10 pg/mL). Treatment of the splenocyte cultures from burn + ethanol mice with an anti-IL6 monoclonal antibody resulted in partial restoration of splenocyte proliferation. Taken together, these data strongly suggest that the immune dysfunction observed in ethanol-exposed, thermally injured mice is mediated in part by elevated levels of IL-6.

Alcohol Drinking↗

PubMed1997

Effects of acute ethanol exposure on cellular immune responses in a murine model of thermal injury.

To test the effects of acute ethanol exposure on immune function after thermal injury, mice with blood alcohol levels of 100 mg/dL were given a 15% total body surface area dorsal scald or sham injury. Bacterial challenge resulted in 100 and 40% mortality in burn + ethanol- and burn + vehicle-treated mice, respectively. Delayed-type hypersensitivity responses were also significantly suppressed in burn + ethanol-treated mice. At 1 and 4 days post-burn, concanavalin A (ConA) -induced total splenocyte proliferation in burn + ethanol-treated groups was significantly decreased (P < 0.01) compared with burn + vehicle- or sham-treated animals. This decrease was not observed in total splenocytes cultured with anti-CD3epsilon or among adherence-depleted splenocytes given ConA or anti-CD3epsilon. FACS analyses revealed no changes in splenocyte sub-type ratios in burn + ethanol mice. The data herein demonstrate that acute ethanol exposure before thermal injury results in enhanced susceptibility to bacterial infection and markedly suppressed cellular immunity, which appears to be macrophage dependent.

Animals↗

PubMed1996

Estrogen suppression of connective tissue deposition in a murine model of peritoneal adhesion formation.

Estrogen's involvement in inflammation and wound healing is poorly understood. To examine the role of estrogen in peritoneal adhesion formation, we gave ovariectomized female C57BL/6 mice time-release pellets containing placebo, 0.05 mg 17 beta-estradiol (low E2), or 5 mg 17 beta-estradiol (high E2) before i.p. injection of talc in saline or saline alone. Analyses of abdominal wall connective tissue thickness and peritoneal cell populations were performed. Talc-treated mice receiving low and high E2 replacement had a decreased amount of abdominal connective tissue deposition (29% and 65% decrease, respectively) as compared with talc-treated mice receiving placebo pellets. At high E2 replacement, the difference in connective tissue deposition was significant statistically (p less than 0.01). Immunohistochemical analysis revealed that the number of macrophages in adhesion tissue was proportionate to the amount of connective tissue present, regardless of the circulating levels of E2. Northern blot analysis of abdominal wall tissue showed that five of six talc-treated animals given placebo expressed mRNA for the murine monocyte chemoattractant protein-1 (MCP-1), JE. Conversely, only one of five talc-treated animals that received E2 replacement expressed JE/MCP-1 mRNA, suggesting that the hormone may inhibit connective tissue deposition by altering the production of chemotactic factors. Furthermore, E2 suppressed talc-induced expression of JE/MCP-1 mRNA in murine macrophages. Since macrophages play a central role in the wound healing process, these studies suggest that E2 inhibition of adhesion formation could be mediated by suppressing macrophage activation and/or recruitment to inflammatory sites.

Abdomen↗