Estrogen receptor-alpha, sexual dimorphism and reduced-size liver ischemia and reperfusion injury in mice

Influence of Sex in the Development of Liver Diseases

The liver is a sexually dimorphic organ. Sex differences in prevalence, progression, prognosis, and treatment prevail in most liver diseases, and the mechanism of how liver diseases act differently among male versus female patients has not been fully elucidated. Biological sex differences in normal physiology and disease arise principally from sex hormones and/or sex chromosomes. Sex hormones contribute to the development and progression of most liver diseases, with estrogen- and androgen-mediated signaling pathways mechanistically involved. In addition, genetic factors in sex chromosomes have recently been found to contribute to the sex disparity of many liver diseases, which might explain, to some extent, the difference in gene expression pattern, immune response, and xenobiotic metabolism between men and women. Although increasing evidence suggests that sex is one of the most important modulators of disease prevalence and outcomes, at present, basic and clinical studies have long been sex unbalanced, with female subjects underestimated. As such, this review focuses on sex disparities of liver diseases and summarizes the current understanding of sex-specific mechanisms, including sex hormones, sex chromosomes, etc. We anticipate that understanding sex-specific pathogenesis will aid in promoting personalized therapies for liver disease among male versus female patients.

The impact of recipient and donor gender-match and mismatch on the post-liver transplant outcomes of patients with primary biliary cholangitis

BACKGROUND & AIMS

In this study, we evaluate the effects of donor gender on post-liver transplant (LT) prognosis. We specifically consider patients with primary biliary cholangitis (PBC).

METHODS

The 2005 to 2019 UNOS transplant registry was used to select patients with PBC. The study cohort was stratified by donor gender. All-cause mortality and graft failure hazards were compared using iterative Cox regression analysis. Subanalyses were performed to evaluate gender mismatch on post-LT prognosis.

RESULTS

There were 1885 patients with PBC. Of these cases, 965 entries had male donors and 920 had female donors. Median follow-up was 4.82 (25-75% IQR 1.83-8.93) years. Having a male donor was associated with higher all-cause mortality (aHR 1.28 95%CI 1.03-1.58) and graft failure (aHR 1.70 95%CI 1.02-2.82). Corresponding incidence rates were also relatively increased. In the sub-analysis of female recipients (n = 1581), those with gender-mismatch (male donors, n = 769) were associated with higher all-cause mortality (aHR 1.41 95%CI 1.11-1.78) but not graft failure. In the male recipient subanalysis (n = 304), no associations were found between gender-mismatch (female donors, n = 108) and all-cause mortality or graft failure.

CONCLUSION

This study shows that recipients who have male donors experienced higher rates of all-cause mortality following LT. This finding was consistent in the female recipient-male donor mismatch cohort.

Impact of donor sex on hepatocellular carcinoma recurrence in liver transplantation after brain death

BACKGROUND

Hepatocellular carcinoma (HCC) is predominantly seen in males but has a better prognosis in females. No prior studies have investigated HCC recurrence based on sex combination following liver transplant donated after brain death (DBDLT). This study sought to elucidate the effects of donor and recipient sex on HCC recurrence rates.

METHODS

9232 adult recipients from the United Network for Organ Sharing (UNOS) database who underwent DBDLT for HCC from 2012 to 2018 were included. Donor-recipient pairs were divided into (1) female donor/female recipient (F-F) (n = 1089); (2) male donor/female recipient (M-F) (n = 975); (3) female donor/male recipient (F-M) (n = 2691); (4) male donor/male recipient (M-M) (n = 4477). The primary prognostic outcome was HCC recurrence. A multivariable competing risk regression analysis was used to assess prognostic influences.

RESULTS

The median recipient age and model for end-stage liver disease (MELD) scores were similar among the four groups. Livers of male recipients demonstrated greater in size and number of HCC (both p-values were <.0001). There was also a higher rate of vascular invasion in male recipients compared to female (p < .0001). Competing risk analyses showed that the cumulative HCC recurrence rate was significantly lower in the M-F group (p = .013). After adjusting for tumor characteristics, liver grafts from male donors were associated with a lower HCC recurrence rate in female recipients (HR: .62 95%CI: .42-.93) (p = .021).

CONCLUSION

In DBDLT, male donor to female recipient pairing exhibited lower HCC recurrence rates.

SUMMARY

Lowest rates of HCC recurrence were confirmed among the female recipients of male donor grafts group in the deceased donor LT cohort. A competing risk multivariable regression analysis demonstrated that male donor sex was significantly associated with low HCC recurrence in female but not male recipients.

Estrogen receptor agonists protect against acetaminophen-induced hepatorenal toxicity in rats

AIMS

Acetaminophen-induced hepatorenal toxicity varies among sexes with controversial results among species. The aim was to compare the impact of sex and ovarian hormones on hepatorenal toxicity and to elucidate protective effects of estrogen and estrogen receptor (ER) agonists.

MAIN METHODS

Under anesthesia, female rats underwent ovariectomy (OVX) or sham-OVX. Starting at postsurgical 40th day, OVX-rats received subcutaneously (each, 1 mg/kg/day) 17β-estradiol (E₂), ERβ-agonist (DPN) or ERα-agonist (PPT) for 10 days, while male and sham-OVX rats received vehicle for 10 days. Then, rats received either acetaminophen (3 g/kg) or saline by orogastric gavage and were decapitated at 24th h. Blood samples were obtained to measure serum ALT, AST, BUN, creatinine levels. Liver and kidney samples were obtained for histopathologic examination and for analyzing levels of luminol- and lucigenin-chemiluminescence, glutathione and myeloperoxidase activity.

KEY FINDINGS

Compared to their control groups, levels of AST, ALT, BUN, creatinine, hepatic and renal myeloperoxidase activity and chemiluminescence levels were increased, and hepatic glutathione level was decreased in acetaminophen-administered male groups, while ALT and hepatic chemiluminescence levels were not elevated in sham-OVX-rats. Both ER-agonists and E₂ reduced BUN, creatinine and reversed all oxidative parameters in renal tissues of OVX-rats. Additionally, ERα-agonist reversed all hepatic injury parameters, while ERβ-agonist elevated hepatic glutathione level.

SIGNIFICANCE

Acetaminophen toxicity in female rats presented with a more preserved hepatic function, while renal toxicity was not influenced by sex or by the lack of ovarian hormones. Pretreatment with estrogen or ER agonists, via their antioxidant actions, provided protective effects on acetaminophen-induced hepatorenal toxicity.

Estrogen Accelerates Cell Proliferation through Estrogen Receptor α during Rat Liver Regeneration after Partial Hepatectomy

Although estrogen is implicated in the regulation of cell growth and differentiation in many organs, the exact mechanism for liver regeneration is not completely understood. We investigated the effect of estrogen on liver regeneration in male and female Wistar rats after 70% partial hepatectomy (PHx) and performed immunohistochemistry, western blotting and Southwestern histochemistry. 17β-estradiol (E₂) and ICI 182,780 were injected into male rats on the day before PHx. The proliferating cell nuclear antigen (PCNA) labeling index reached a maximum at 48 hr after PHx in males, and at 36 hr in females and E₂-treated male rats. Estrogen receptor α (ERα) was expressed in zones 1 and 2 in male rats, but was found in all zones in female rats. Interestingly, ERα was not detected at 6-12 hr after PHx but was found at 24-168 hr in male rats. However, ERα expression was found at all sampling time-points in female and E₂-treated male rats. The activity of estrogen responsive element binding proteins was detected from 12 hr after PHx in male rats but was found from 6 hr in female and E₂-treated male rats. ERα was co-expressed with PCNA during liver regeneration. These results indicate that estrogen may play an important role in liver regeneration through ERα.

Amelioration of lipopolysaccharide-induced liver injury by aqueous rooibos (Aspalathus linearis) extract via inhibition of pro-inflammatory cytokines and oxidative stress

BACKGROUND

Acute liver injury occur after intraperitoneal administration of lipopolysaccharide (LPS). Oxidative stress and release of pro-inflammatory cytokines are both implicated in the pathogenesis of LPS-induced acute liver injury. This study investigated the ameliorative effect of fermented rooibos (Aspalathus linearis) extract on LPS-induced acute liver injury.

METHOD

Major phenolic compounds in the fermented rooibos extract by HPLC-DAD, as well as the in vitro antioxidant capacity were quantified before the start of the experiment. Male Wistar rats were randomized into 4 groups (n = 10 per group) and given either water or fermented rooibos extract for 4 weeks before LPS injection. Hepatic function markers, including aminotransferases and lactate dehydrogenase, lipid peroxidation markers, antioxidant enzymes, glutathione redox status, as well as cytokine levels were monitored in the rats.

RESULTS

Injection of LPS significantly increased serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH). Oxidative stress, evidenced by increased thiobarbituric acid reactive substances (TBARS) measured as malondialdehyde (MDA) in plasma and liver, and decreased glutathione redox status (GSH: GSSG ratio) in whole blood and liver was induced in LPS-challenged rats. Furthermore, hepatic levels of pro-inflammatory response markers TNF-α, IL-1β and IL-6 were increased significantly. Pre-feeding the fermented rooibos extract for 4 weeks decreased LPS-induced elevated levels of serum AST and LDH (significantly, p < 0.05) as well as ALT marginally. Consuming rooibos caused an attenuation of the observed increase in plasma and hepatic MDA, decrease in whole blood and liver GSH:GSSG ratio, as well as the changes noted in various antioxidant enzymes. The elevation in TNF-α and IL-6 was significantly suppressed, indicating an inhibition of the induced inflammatory response by rooibos.

CONCLUSION

Overall, our data showed that aqueous rooibos extract attenuated LPS-induced liver injury possibly by modulating oxidative stress and suppressing pro-inflammatory cytokines formation.

Sex differences of oxidative stress to cholestatic liver and kidney injury in young rats

BACKGROUND

Sexual dimorphism plays a role in the liver and in renal injuries. However, whether sex is a risk factor in bile duct ligation (BDL) in young rats has never been examined.

METHODS

Six male and six female rats treated with BDL were sacrificed 2 weeks after surgery and were designated as BDL-M and BDL-F groups. The other six male and six female rats that received sham ligation were designated as sham-M and sham-F groups. Plasma biochemistry and liver and kidney asymmetric dimethylarginine (ADMA)-related molecules were examined.

RESULTS

Both BDL-M and BDL-F groups had elevated plasma aspartate transaminase (AST), alanine transaminase (ALT), bilirubin, and transforming growth factor-β1 levels. The BDL-F group had lower plasma AST and ALT levels than the BDL-M group. The BDL-M and BDL-F groups had elevated plasma ADMA levels. The cationic amino acid transporter 1 (CAT1) level was increased in the BDL-F group as compared to the sham-F group, whereas the CAT2 level was reduced in the both BDL-M and BDL-F groups.

CONCLUSION

We found that young male rats were prone to higher degrees of biochemical liver and kidney injury to cholestasis. Sex differences in modulation of oxidative stress markers, such as ADMA, may play a role. Our results support careful monitoring and optimal treatment of cholestatic disease, especially in young male patients.

Hepatoprotective effect of tamoxifen on steatosis and non-alcoholic steatohepatitis in mouse models

Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic lipid accumulation that starts with steatosis and progresses to non-alcoholic steatohepatitis (NASH). Recently, the number of patients with such liver diseases has increased, but the understanding of the fundamental mechanisms and appropriate therapies are lacking. Tamoxifen (TAM) is a selective estrogen receptor modulator. We previously reported that TAM plays a protective role against drug-induced and chemical-induced acute liver injuries. However, the effects of TAM on chronic liver injury, including steatosis and NASH, remain to be addressed. We first found that the administration of TAM to mouse models of steatosis and NASH significantly decreased the plasma ALT and AST levels. The administration of TAM decreased the accumulated fat and inflammation in the livers in both mouse models. In addition, we observed decreased hepatic mRNA levels of triglyceride synthesis, acyl-CoA: diacylglycerol acyltransferase 2 (DGAT2), proinflammatory cytokines, tumor necrosis factor (TNF) α, and chemokines, monocyte chemoattractant protein (MCP) -1. TAM increased the extracellular signal-regulated kinase (ERK) phosphorylation, which is related to the proliferation and regeneration of liver and to decreased DGAT2 gene expression. Furthermore, a decrease in eukaryotic translational initiation factor (eIF2α), which is involved in apoptosis, was observed in both models. These findings suggest that TAM treatment exerts a hepatoprotective effect against steatosis and NASH, presumably via up-regulation of the ERK pathways and attenuation of eIF2α activation. These pathways represent a potential therapeutic target for steatosis and NASH in drug development.

Mechanisms of the hepatoprotective effects of tamoxifen against drug-induced and chemical-induced acute liver injuries

Although estrogen receptor (ER)α agonists, such as estradiol and ethinylestradiol (EE2), cause cholestasis in mice, they also reduce the degree of liver injury caused by hepatotoxicants as well as ischemia-reperfusion. The functional mechanisms of ERα have yet to be elucidated in drug-induced or chemical-induced liver injury. The present study investigated the effects of an ERα agonist, selective ER modulators (SERMs) and an ER antagonist on drug-induced and chemical-induced liver injuries caused by acetaminophen, bromobenzene, diclofenac, and thioacetamide (TA). We observed hepatoprotective effects of EE2, tamoxifen (TAM) and raloxifene pretreatment in female mice that were exposed to a variety of hepatotoxic compounds. In contrast, the ER antagonist did not show any hepatoprotective effects. DNA microarray analyses suggested that monocyte to macrophage differentiation-associated 2 (Mmd2) protein, which has an unknown function, is commonly increased by TAM and RAL pretreatment, but not by pretreatment with the ER antagonist. In ERα-knockout mice, the hepatoprotective effects of TAM and the increased expression of Mmd2 mRNA were not observed in TA-induced liver injury. To investigate the function of Mmd2, the expression level of Mmd2 mRNA was significantly knocked down to approximately 30% in mice by injection of siRNA for Mmd2 (siMmd2). Mmd2 knockdown resulted in a reduction of the protective effects of TAM on TA-induced liver injury in mice. This is the first report of the involvement of ERα in drug-induced or chemical-induced liver injury. Upregulation of Mmd2 protein in the liver was suggested as the mechanism of the hepatoprotective effects of EE2 and SERMs.

17β-Estradiol protects the liver against cold ischemia/reperfusion injury through the Akt kinase pathway

BACKGROUND

Hepatic ischemia-reperfusion (IR) injury occurs during liver resection and transplantation. Recent studies have shown that 17β-estradiol (E2) can protect the heart and liver against warm IR. The present study focused on the cytoprotective effects of E2 on cold IR injury to the liver.

MATERIALS AND METHODS

Sprague-Dawley male rats were randomly divided into three groups: sham, IR, and IR plus E2. The model of rat orthotopic liver transplantation was used. The rats in the IR plus E2 group were intraperitoneally injected with E2 (100 μg/kg/d) for 7 d before surgery. The sham and IR group received the same quantity of saline. The donor livers were then orthotopically transplanted into rats after cold ischemia preservation for 4 h at 4°C lactated Ringer's solution. After 6 h reperfusion, liver function, bile flow volume, hepatocyte apoptosis, and activation of Akt, glycogen synthase kinase-3β, and Bcl-2-associated death promoter were assessed. The survival rate of the rats was also investigated.

RESULTS

The administration of E2 significantly prolonged the survival of liver grafts by improving liver function and decreasing hepatocyte apoptosis. Rats undergoing E2 demonstrated a greater level activation of Akt in the liver compared with the IR group. In addition, E2 also inhibited the activities of glycogen synthase kinase-3β, Bcl-2-associated death promoter, and caspase-3-induced by IR injury.

CONCLUSIONS

E2 pretreatment attenuated the hepatocellular damage caused by hepatic cold IR injury through the Akt pathway. Estrogen therapy might be important in clinical settings associated with cold IR injury during liver transplantation.

Sex differences in nuclear receptor-regulated liver metabolic pathways

Liver metabolism is markedly sex-dimorphic; accordingly, the prevalence of liver diseases is different between sexes. The superfamily of nuclear receptors (NRs) governs the proper expression of key liver metabolism genes by sensing lipid-soluble hormones and dietary lipids. When the expression of those genes is deregulated, disease development is favored. However, we lack a comprehensive picture of the differences between NR actions in males and females. Here, we reviewed explorative studies that assessed NR functions in both sexes, and we propose a first map of sex-dimorphic NR expression in the liver. Our analysis suggested that NRs in the female liver exhibited cross-talk with more liver-protective potential than NRs in male liver. This study provides empirical support to the hypothesis that women are more resilient to some liver diseases than men, based on a more compensative NR network. This article is part of a Special Issue entitled: Translating nuclear receptors from health to disease.

Revealing genes associated with vitellogenesis in the liver of the zebrafish (Danio rerio) by transcriptome profiling

Background

In oviparous vertebrates, including fish, vitellogenesis consists of highly regulated pathways involving 17β-estradiol (E2). Previous studies focused on a relatively small number of hepatic expressed genes during vitellogenesis. This study aims to identify hepatic genes involved in vitellogenesis and regulated by E2, by using zebrafish microarray gene expression profiling, and to provide information on functional distinctive genes expressed in the liver of a vitellogenic female, using zebrafish as a model fish.

Results

Genes associated with vitellogenesis were revealed by the following paired t-tests (SAM) comparisons: a) two-month old vitellogenic (Vit2) females were compared with non-vitellogenic (NV) females, showing 825 differentially expressed transcripts during early stages of vitellogenesis, b) four-month old vitellogenic (Vit4) females were compared with NV females, showing 1,046 differentially expressed transcripts during vitellogenesis and c) E2-treated males were compared with control males, showing 1,828 differentially expressed transcripts regulated by E2. A Venn diagram revealed 822 common transcripts in the three groups, indicating that these transcripts were involved in vitellogenesis and putatively regulated by E2. In addition, 431 transcripts were differentially expressed in Vit2 and Vit4 females but not in E2-treated males, indicating that they were putatively not up-regulated by E2. Correspondence analysis showed high similarity in expression profiles of Vit2 with Vit4 and of NV females with control males. The E2-treated males differed from the other groups. The repertoire of genes putatively regulated by E2 in vitellogenic females included genes associated with protein synthesis and reproduction. Genes associated with the immune system processes and biological adhesion, were among the genes that were putatively not regulated by E2. E2-treated males expressed a large array of transcripts that were not associated with vitellogenesis.

The study revealed several genes that were not reported before as being regulated by E2. Also, the hepatic expression of several genes was reported here for the first time.

Conclusion

Gene expression profiling of liver samples revealed 1,046 differentially expressed transcripts during vitellogenesis of which at least ~64% were regulated by E2. The results raise the question on the regulation pattern and temporal pleiotropic expression of hepatic genes in vitellogenic females.

Effect of temperature control upon a mouse model of partial hepatic ischaemia/reperfusion injury

In vivo models of hepatic ischaemia/reperfusion injury (IRI) are widely used to study both the mechanisms of hepatic ischaemic injury and to seek means of hepatic protection. Achieving high-quality reproducible data are essential if the results of multiple studies are to be compared and reconciled. This paper presents our findings concerning the effect of intraoperative thermoregulation upon signal to noise ratios of hepatic IRI experiments in mice. Four experiments were conducted, using three different strategies for core temperature maintenance. Animals underwent hepatic IRI and euthanized 24 h postoperatively for measurement of plasma alanine aminotransferase (ALT). Duration of ischaemia was used to adjust the severity of injury. Experiment 1 utilized a constant output heating system and resulted in rising postoperative ALTs following increasing durations of hepatic ischaemia. Experiment 2, using the same constant output heating system confirmed a difference between ischaemic and sham-operated animals. Experiment 3 used a thermostatically controlled heating system and resulted in highly variable results with a small, but statistically significant correlation between ALT levels and rectal temperature readings. Experiment 4 used a homeothermic warming system and demonstrated highly reproducible data from increasing durations of ischaemia. High-quality data from hepatic ischaemia/reperfusion models are dependent upon careful control of intraoperative temperature. The use of homeothermic warming systems is recommended and conversely, the use of thermostatically controlled warming mats is to be avoided in these models.

The effect of estrogen on hepatic microcirculation after ischemia/reperfusion

BACKGROUND AND AIMS

Gender dimorphism in clinical manifestation of sepsis, hemorrhage, and trauma is still under investigation. Several experimental studies have indicated a protective effect of estrogen. Nonetheless, the effect of gender on hepatic ischemia/reperfusion remains controversially discussed, and the influence of estrogen is still unclear. In the present study, we investigated whether hepatic ischemia/reperfusion (I/R) injury is gender-dependent and if hepatic microvascular reperfusion injury can be prevented by estrogen.

MATERIALS AND METHODS

Eight female and eight male Sprague-Dawley rats were subjected to 90 min left lobar ischemia followed by 60 min reperfusion. Additional six males were pretreated with 17beta-estradiol 24 h before I/R. Six female and six male rats served as nonischemic sham animals. By means of intravital microscopy, sinusoidal perfusion, leukocyte-endothelial cell interaction, and Kupffer cell activity were analyzed. Finally, arterial blood and liver tissue samples were taken for histomorphological analysis and liver enzyme determination.

RESULTS

After hepatic ischemia/reperfusion, animals revealed a significant gender-specific impairment of hepatic microcirculation, whereas Kupffer cell depression, sinusoidal perfusion failure, leukocyte-endothelial cell interaction within post sinusoidal venules, and parenchymal liver cell damage were more pronounced in male animals. Pretreatment with estrogen caused a normalization of Kupffer cell dysfunction and an amelioration of sinusoidal perfusion failure and venular leukocyte-endothelial cell interaction. However, estrogen did not protect from manifestation of post ischemic parenchymal cell damage.

CONCLUSION

Hepatic ischemia and reperfusion generate a gender-specific occurrence of microvascular injury, which seems to be partially mediated by estrogen. However, additional factors may contribute to the initial post ischemic parenchymal cell damage.

Which Gender is Better Positioned in the Process of Liver Surgery? Male or Female?

Liver surgery is a process which induces various types of stress on the liver including the total occlusion of the blood inflow, hemorrhage, massive volume reduction, and postoperative infection. Animal studies have shown a gender dimorphic response of the liver for various stresses such as ischemia/reperfusion, hemorrhage/resuscitation, hepatectomy, portal branch ligation, and endotoxemia. Most of these studies demonstrated the female liver to be more tolerant under stressful conditions than the male liver. Estrogen, which is a representative female sex hormone, may be one of the responsible factors for this gender dimorphism. The mechanism of estrogen's salutary effect includes circulatory improvement, a reduced inflammatory response, a reduced oxygen radical production, and an improved hepatic regeneration. However, the clinical evidence that supports the results of these experimental studies is still insufficient. A well-controlled prospective clinical study is necessary to clarify the role of gender or sex hormone in the process of liver surgery. This may not only lead to a deeper understanding of the liver pathophysiology, but also to the possibility of hepatoprotective therapy using sex hormone modulators. This review summarizes the current understanding of gender dimorphism in the tolerance of the liver to various hepatic stresses, which occur during the process of major liver surgery.

The role of estrogen receptor subtypes in ameliorating hepatic injury following trauma-hemorrhage

BACKGROUND/AIMS

The aim of this study was to determine which of the estrogen receptor (ER) subtypes plays a predominant role in ameliorating hepatic damage following trauma-hemorrhage.

METHODS

Adult male rats were subjected to hemorrhagic shock (40 mmHg for 90 min) and resuscitation. ER-alpha agonist (PPT) or ER-beta agonist (DPN) was administered during resuscitation; rats were sacrificed 24h thereafter.

RESULTS

PPT or DPN decreased elevated plasma alpha-glutathione S-transferase levels; however, PPT was more effective. PPT or DPN increased hepatic heat shock protein 32 (Hsp32) mRNA/protein expressions above levels observed after trauma-hemorrhage. PPT reduced hepatic NF-kappaB and AP-1 activity and iNOS expression. Although DPN reduced hepatic NF-kappaB activity, AP-1 activity remained higher than in shams; hepatic iNOS induction remained elevated. PPT/DPN reduced nitrate/nitrite production and iNOS mRNA in Kupffer cells following trauma-hemorrhage; however, these levels in DPN-treated animals remained higher than sham.

CONCLUSIONS

Although both PPT and DPN decreased hepatic injury following trauma-hemorrhage, ER-alpha agonist PPT appears to be more effective in downregulating NF-kappaB and AP-1 activity, and iNOS induction. Thus, ER-alpha appears to play a predominant role in mediating the salutary effects of E2 in ameliorating hepatic damage following trauma-hemorrhage.

Mitochondria play an important role in 17beta-estradiol attenuation of H(2)O(2)-induced rat endothelial cell apoptosis

Studies have shown salutary effects of 17beta-estradiol following trauma-hemorrhage on different cell types. 17beta-Estradiol also induces improved circulation via relaxation of the aorta and has an anti-apoptotic effect on endothelial cells. Because mitochondria play a pivotal role in apoptosis, we hypothesized that 17beta-estradiol will maintain mitochondrial function and will have protective effects against H(2)O(2)-induced apoptosis in endothelial cells. Endothelial cells were isolated from rats' aorta and cultured in the presence or absence of H(2)O(2), a potent inducer of apoptosis. In additional studies, endothelial cells were pretreated with 17beta-estradiol. Flow cytometry analysis revealed H(2)O(2)-induced apoptosis in 80.9% of endothelial cells; however, prior treatment of endothelial cells with 17beta-estradiol resulted in an approximately 40% reduction in apoptosis. This protective effect of 17beta-estradiol was abrogated when endothelial cells were cultured in the presence ICI-182780, indicating the involvement of estrogen receptor (ER). Fluorescence microscopy revealed a 17beta-estradiol-mediated attenuation of H(2)O(2)-induced mitochondrial condensation. Western blot analysis demonstrated that H(2)O(2)-induced cytochrome c release from mitochondrion to cytosol and the activation of caspase-9 and -3 were decreased by 17beta-estradiol. These findings suggest that 17beta-estradiol attenuated H(2)O(2)-induced apoptosis via ER-dependent activation of caspase-9 and -3 in rat endothelial cells through mitochondria.

Effects of 17beta-estradiol and flutamide on splenic macrophages and splenocytes after trauma-hemorrhage

Since splenic immune functions are depressed in metestrus females following trauma-hemorrhage, we hypothesized that administration of the androgen receptor antagonist flutamide at the onset of resuscitation will maintain the immune function of the spleen following trauma-hemorrhage. Female C57BL6/J mice (metestrus state, 8-12 weeks old), underwent laparotomy and hemorrhagic shock (35.0+/-5.0 mm Hg for 90 min) and received 17beta-estradiol (50 microg/25 g), flutamide (625 microg/25 g) or 17beta-estradiol+flutamide. Four hours after resuscitation, the in vitro productive capacity of different cytokines (TNF-alpha, IL-6, IL-10, and IFN-gamma) by splenic MPhi and splenocytes were determined by flow cytometry. A significantly decreased cytokine production by both splenocytes and splenic MPhi was observed following trauma-hemorrhage compared to shams. Administration of 17beta-estradiol, flutamide and 17beta-estradiol+flutamide following trauma-hemorrhage resulted in a significant increase in the in vitro IL-6 release by splenic MPhi. The TNF-alpha productive capacity, however, was only restored by 17beta-estradiol and 17beta-estradiol+flutamide administration following trauma-hemorrhage. No significant effect of either treatment was observed with regard to the suppressed splenic MPhi IL-10 release. Anti-CD3 stimulation, administration of 17beta-estradiol and 17beta-estradiol+flutamide, but not the administration of flutamide alone resulted in a significant increased release of TNF-alpha, IL-6 and IFN-gamma compared to vehicle-treated animals. No significant effect of either treatment was found on IL-10 productive capacity. These results collectively suggest that flutamide administration following trauma-hemorrhage in females has beneficial effects on splenic immune function. However, flutamide administration in combination with estrogen does not provide any significant, additional effects over 17beta-estradiol administration alone.

Sex differences in inflammatory cytokine production in hepatic ischemia-reperfusion

BACKGROUND

The inflammatory response to hepatic ischemia-reperfusion (I/R) is associated with an increase in cytokine production. Studies have documented that sex hormones modulate both the innate and adaptive immune responses, and that females are more robust than males. The aim of this study was to determine whether a sex difference in cytokine response to hepatic I/R exists under normal pathophysiologic condition without hormone intervention.

METHODS

Adult C57BL/6 mice underwent 90 min of hepatic ischemia followed by various reperfusion periods (0, 1.5, 3, 6 hr). Plasma cytokine TNF-alpha, IL-6, MIP-2, and KC were measured. Liver injury was assessed by plasma alanine transaminase (ALT) levels and liver histopathology.

RESULTS

A reperfusion time-dependent increase in hepatocellular injury was observed in both males and females, as indicated by increasing levels of plasma ALT and liver histopathology. The plasma cytokines were significantly increased in both female and male I/R groups compared to their respective sham counterparts. However, there was a significant difference in cytokine kinetics between the female and male I/R groups. Female mice initially had a higher level of IL-6, KC, and MIP-2 in response to I/R, which began to decline after 3 hr of reperfusion and were significantly lower than the male I/R counterparts by 6 hr of reperfusion. In contrast, the hepatocellular injury and TNF production were only moderately lower in female IR than male IR.

CONCLUSION

The study underscores role of the gender in differential inflammatory cytokine expression in response to hepatic I/R, which may reflect the host response outcome.

Kupffer cells and their mediators: the culprits in producing distant organ damage after trauma-hemorrhage

Posttraumatic activation of macrophages enhances development of systemic inflammation/immunosuppression and organ dysfunction. We hypothesized that Kupffer cells are the main source of monocyte chemoattractant protein-1 (MCP-1) production after trauma-hemorrhage, that administration of 17beta-estradiol (E2) after trauma-hemorrhage modulates MCP-1 release and reduces remote organ damage, and that salutary effects of E2 are mediated via estrogen receptor (ER)-alpha. To test these hypotheses, female B57BL/J6 mice received E2 (50 microg/25 g) or vehicle after trauma-hemorrhage and female 129 Sve ER-beta-/- transgenic mice and ovariectomized wild-type mice received E2 or ER-alpha agonist propyl pyrazole triol (50 microg/25 g) after trauma-hemorrhage. Systemic MCP-1 and interleukin-6 and their release by liver, spleen, and lung macrophages were determined by flow cytometry 4 hours after trauma-hemorrhage. Prior Kupffer cell depletion with gadolinium chloride significantly decreased systemic MCP-1 and interleukin-6 after trauma-hemorrhage and was associated with decreased edema/neutrophil infiltration in lung and liver. Kupffer cells were the only macrophages showing significant MCP-1 release, which was markedly reduced by E2 or propyl pyrazole triol in wild-type and in ER-beta-/- mice. Pretreatment of mice with anti-MCP-1 antiserum prevented an increase in myeloperoxidase and edema in lung and liver. These findings suggest that Kupffer cell-derived MCP-1 plays a major role in remote organ dysfunction after trauma-hemorrhage.

Effects of 17beta-estradiol and flutamide on inflammatory response and distant organ damage following trauma-hemorrhage in metestrus females

We hypothesized that administration of androgen receptors antagonist flutamide following trauma-hemorrhage (T-H) in metestrus females will maintain immune function and reduce remote organ damage under those conditions. Female B57BL/J6 mice (metestrus state, 8-12 weeks old) underwent laparotomy and hemorrhagic shock (35.0+/-5.0 mmHg for 90 min) and then received 17beta-estradiol (E2; 50 microg/25 g), flutamide (625 microg/25 g), or E2 + flutamide. Four hours after resuscitation, plasma cytokine and chemokine (TNF-alpha, IL-6, IL-10, IFN-gamma, and MCP-1) concentrations and their release in vitro by hepatic and pulmonary tissue macrophages (M Phi) were determined by flow cytometry. Organ damage was assessed by edema formation (wet-to-dry weight ratio) and neutrophil infiltration [myeloperoxidase (MPO) activity]. Administration of E2, flutamide, or E2 + flutamide following T-H resulted in a significant decrease in systemic TNF-alpha, IL-6, and MCP-1 concentrations under those conditions. This was accompanied by significantly decreased in vitro TNF-alpha release by Kupffer cells after administration of E2, flutamide, or E2 + flutamide. The in vitro release of proinflammatory cytokines by alveolar M Phi, however, was reduced significantly only by the addition of E2 or E2 + flutamide but not by the addition of flutamide. A significant decrease in pulmonary and hepatic edema formation as well as neutrophil infiltration in the lung was observed after E2, flutamide and E2 + flutamide administration. In contrast, hepatic neutrophil infiltration was only significantly reduced following E2 and E2 + flutamide administration. Thus, although flutamide does not produce synergistic, salutary effects with E2, its administration in females following T-H also produces salutary effects on the immune and organ function, similar to E2 administration under those conditions.

Current Understanding of Gender Dimorphism in Hepatic Pathophysiology1

Studies have shown gender dimorphic response of the liver for various hepatic stresses including ischemia/reperfusion, hemorrhagic shock-resuscitation, hepatectomy, liver cirrhosis, endotoxemia, and chronic alcoholic consumption. The mechanisms responsible for the gender dimorphic response include differences in pro-inflammatory cytokine release, production of reactive oxygen species, and alteration in hepatic vasoregulatory action. These effects were shown to be modulated by circulating sex steroid levels. In this regard, modulation of sex steroid levels by agents/drugs has been proposed as a therapeutic option for preventing hepatic damage in various hepatic stress models. Further elucidation of precise mechanisms responsible for the gender-related differences in the hepatic pathophysiology is essential for the potential clinical application of sex hormone modulation therapy. In this article, current progress in our understanding the gender difference in the hepatic pathophysiology under the condition of hepatic stress is reviewed and discussed.

Estrogen can act via estrogen receptor alpha and beta to protect hippocampal neurons against global ischemia-induced cell death

Estradiol at physiological concentrations intervenes in apoptotic death cascades and ameliorates neuronal death in experimental models of focal and global ischemia. The cellular targets that mediate estradiol protection of hippocampal neurons in global ischemia are, however, unclear. The present study examined the hypothesis that estradiol protects hippocampal neurons in ovariectomized rats via estrogen receptor (ER)alpha and/or beta. Estradiol (14 d pretreatment) afforded robust protection of CA1 neurons against global ischemia-induced death. The broad-spectrum ER antagonist ICI 182,780 (intracerebroventricularly, 0 and 12 h after ischemia) abolished estrogen protection, consistent with a role for ERs. To evaluate the potential roles of ERalpha vs. ERbeta in estrogen protection, we administered subtype-selective agonists for 14 d before and 7 d after ischemia. The ERalpha-selective agonist propyl pyrazole triol (PPT, 10 mg/kg) and ERbeta-selective agonist WAY 200070-3 (1 mg/kg) produced nearly complete protection of CA1 neurons in approximately 50% of the animals. PPT, but not WAY 200070-3, at doses used for protection, elicited lordosis, induced negative feedback inhibition of LH release, and reduced weight gain. These findings establish the efficacy of the PPT dose in neuroendocrine assays and specificity of WAY 200070-3 for ERbeta. We also examined the ability of estradiol and neuronal injury to regulate ERalpha and ERbeta expression. Both estradiol and global ischemia markedly increased ERalpha, but not ERbeta, protein in CA1. These data indicate that estradiol can act via ERalpha and ERbeta to protect CA1 neurons from global ischemia-induced death and that both estradiol and global ischemia modulate ERalpha expression in hippocampal CA1.

Mechanism of salutary effects of androstenediol on hepatic function after trauma-hemorrhage: role of endothelial and inducible nitric oxide synthase

Recent studies have shown that administration of dehydroepiandrosterone (DHEA) after trauma-hemorrhage (T-H) improves cardiovascular and hepatic function in male animals. Although androstenediol, one of the DHEA metabolites, has been recently reported to produce salutary effects on cardiac function and splanchnic perfusion after T-H, it remains unknown whether androstenediol per se has any salutary effects on hepatic function under those conditions. To study this, male Sprague-Dawley rats underwent laparotomy and approximately 90 min of hemorrhagic shock (35-40 mmHg), followed by resuscitation with four times the shed blood volume in the form of Ringer lactate. Androstenediol (1 mg/kg body wt iv) was administered at the end of resuscitation, and the animals were killed 24 h later. T-H significantly reduced portal blood flow, bile production, and serum albumin levels. Portal pressure, serum alanine aminotransferase, hepatic nitrate/nitrite, inducible nitric oxide synthase (iNOS), and endothelin-1 markedly increased after T-H. The alterations in these parameters induced by T-H were significantly attenuated in rats treated with androstenediol. Endothelial NOS (eNOS) expression, which was not different between T-H and sham, was found to be significantly elevated in T-H androstenediol-treated rats. These data suggest that improvement in hepatic perfusion by androstenediol after T-H is likely due to a decrease in endothelin-1 and induction of eNOS. Moreover, the decrease in hepatic damage after androstenediol administration is likely related to liver iNOS downregulation. Thus androstenediol appears to be a novel and useful adjunct for restoring hepatic function in male animals after adverse circulatory conditions.