Study of the possible protective role of estrogen in experimentally-induced liver cirrhosis in rats

Chronic liver diseases, such as fibrosis or cirrhosis, are more common in men than in women. This gender difference may be related to the effects of sex hormones on the liver. The aim of the present work was to investigate the effects of estrogen on CCL 4 induced fibrosis of the liver rats. Liver fibrosis was induced in male and female rats by CCL 4 administration in a dose of 2mg/kg/SC/twice weekly. Along with CCL 4 treatment a subgroup of the male rats received estradiol [1mg/kg] twice weekly, while tamoxifen [6mg/kg/day/orally] was given to a female subgroup. At the end of 8 weeks, all the rats were sacrified to study the serum indicators and the livers. The fibrotic response of the female liver to CCL 4 treatment was significantly weaker than that of male liver. In addition, estradiol treatment reduced aspartate aminotransferase [AST] and alanine aminotransferase [ALT] in sera, suppressed hepatic collagen content and malondialdehyde [MDA], decreased the areas of hepatic cirrhosis significantly in male fibrotic rats induced by CCL 4 administration. Whereas, tamoxifen had the opposite effect in female fibrotic rats. We concluded that estradiol reduces CCL 4 induced hepatic fibrosis in rats. The antifibrogenic role of estrogen in the liver may be one reason for the sex associated differences in the progression from hepatic fibrosis to cirrhosis

Vascular endothelial growth factor modulates systemic blood pressure changes in chronic intermittent hypoxia

Systemic arterial hypertension is a common association to chronic intermittent hypoxia. However, little is known about the molecular mechanisms that might mediate long term adaptive responses. Hypoxia inducible factor-la [HIF-1alpha] is upregulated in hypoxia and is linked to activation of several downstream proteins concerned with protective mechanisms. Most importantly, HIF-1-alpha is strongly linked to VEGF. However, whether the expression of both cytokines in chronic intermittent hypoxia could be specifically increased in renal and aortic tissue is unclear. VEGF is a potent vasodilator both in vitro and in vivo and systemic administration causes hypotensive effects in various animal models. Therefore, we sought to explore the gene expression pattern of HIF-1alpha and VEGF in rat kidney and aorta in response to chronic intermittent hypoxia, to investigate a possible role for VEGF in reducing blood pressure elevation in such cases. Adult male Wistar rats were randomly assigned intro CIH group: exposed to one hr intermittent hypoxia [fractional inspiredFIO2: 10%] for 5 day/week for 5 weeks. CIH-SU group [received SU54l6, a potent selective blocker for KDR-flk VEGF receptor, were subjected to the same hypoxia protocol as CIH group] and normoxic Nx control rats. Mean and systolic blood pressure were recorded at day 1,7,15,21,28 and 35 of hypoxic exposure and at the same time points in normoxic rats. At the end of the hypoxia protocol, the thoracic aortas from all groups were excised for studying the functional reactivity of vessels to phenylephrinePE induced contraction and Acetyl choline induced relaxation. Parts of excised aorta and rat renal tissue were also collected for RT PCR analysis of HIF-1alpha and VEGF mRNA. Chronic intermittent hypoxia caused a significant elevation in SBP and MAP in CIH and CIH-SU compared to normoxic controls. However a significant elevation in SBP and MAP was observed upon blocking VEGF receptors [CIH-SU] versus CIH group. A significant increase in aortic contractile responses together with reduced dilator responses was observed in chronically hypoxic rats compared to controls and a significant increase in aortic reactivity was observed in CIH-SU versus CIH. Detection of mRNA encoding for both HIF- 1alpha and VEGF by RT-PCR showed increased expression pattern for both cytokines which was evident in both renal and aortic tissues. Chronic intermittent hypoxia upregulates mRNA for both HIF-1alpha and VEGF in rat renal and aortic tissues. Blocking VEGF receptor action resulted in a significant elevation in arterial blood pressure. These data point to an important role for VEGF in preventing marked elevation in arterial pressure in chronic intermittent hypoxia

Induction of vascular endothelial growth facor and erythrpoeitin by rat cardiomyocytes exposed to acute intermittent systemic hypoxia: possible role in hypoxic preconditioning

Exposure to systemic hypoxia induces cardiac adaptive responses similar to ischemic preconditioning. However, the subcellular mechanisms involved in hypoxic preconditioning are still unclear. We therefore, tested the role of hypoxia sensitive agents such as VEGF and erythropoietin in mediating hypoxic preconditioning in response to acute intermittent hypoxia. 48 male Wistar rats were randomly assigned into normoxic nx group [n=12], kept in normoxic conditions, Acute intermittent hypoxia AIH group [n=12] subjected to brief cycles [5 min] hypoxia/reoxygenation for one hour hearts from both groups were isolated 24 hours later perfused in a retrograde manner in Langendorff apparatus and subjected to in vitro global ischemia for 30 mins followed by reperfusion. The following parameters were measured at baseline, during and at the end of 120 min reperfusion: Left ventricular developed pressure [LVDP]; left ventricular end diastolic pressure [LVEDP]; rate pressure product [RPP]; peak left ventricular pressure rise [AP/At max] and heart rate [HR] At the end of reperfusion hearts were collected for subsequent reverse transcriptase polymerase chain reaction [RT PCR] and immu-histochemical analysis for VEGF and Erythropoietin. AIH 3 [n=12], AIH8 [n=12] groups, were subjected to one hour brief cycles [5 min] hypoxia reoxygenation as described above, were then sacrificed after 3, 8 hours [respectively], Hearts were collected for studying the time course for the expression pattern of VEGF and erythropoietin: Hearts of AIH displayed a significant improvement in postischemic hemodynamic measures compared to controls, indicated by higher LVDP [76% recovery versus 39% in nx], RPP [76% recovery versus 38%] and AP/At [66% recovery versus 43%]. AIH caused a significant increased expression of VEGF and Epo by cradiomyocytes. This increased expression was detected at 3 and 8hrs [AIH3, AIH8] denoting early induction of VEGF and Epo genes by acute intermittent hypoxia. Increased expression of VEGF and Epo genes was also detected 24 hours [AIH] following hypoxic exposure. Exposure of rat hearts to acute intermittent systemic hypoxia confers cardioprotective effects. This was evident by improved cardiac performance following ischemia reperfusion. The improved postischmeic cardiac function was associated with rapid induction of VEGF and erythropoietin by cardiac cells that lasted for 24 hours later, therefore theses cytokines appear to play a role in mediating early and delayed cardiac adaptive responses to acute intermittent hypoxia. Hypoxic training could thus provide a new approach to enhance endogenous cardioprotective mechanisms