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Sustained Isoprostane E2 Elevation, Inflammation and Fibrosis after Acute Ischaemia-Reperfusion Injury Are Reduced by Pregnane X Receptor Activation.

Amer AO, Probert PM, Dunn M, Knight M, Vallance AE, Flecknell PA, Oakley F, Cameron I, White SA, Blain PG, Wright MC - PLoS ONE (2015)

Bottom Line: The anti-inflammatory effects of the activated pregnane X receptor have previously been shown to be beneficial in a number of inflammatory liver conditions.Administration of pregnenolone-16α-carbonitrile--a rodent-specific pregnane X receptor activator--resulted in significant reductions in cholestasis, hepatic injury, ischaemic lobe isoprostane E2 levels, peri-portal inflammation and fibrosis.Drug-mediated activation of the pregnane X receptor reduced these adverse changes in rats, suggesting that the pregnane X receptor is a viable drug target to reduce ischaemic-type biliary lesions in recipients of liver transplants donated after cardiac death.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle, United Kingdom.

ABSTRACT
Liver grafts donated after cardiac death are increasingly used to expand the donor pool but are prone to ischaemic-type biliary lesions. The anti-inflammatory effects of the activated pregnane X receptor have previously been shown to be beneficial in a number of inflammatory liver conditions. However, its role in reducing peri-portal inflammation and fibrosis following ischaemia-reperfusion injury has not been investigated. Hepatic injury and its response to pregnane X receptor activation was examined after partial hepatic ischaemia-reperfusion injury induced by surgically clamping the left and middle lobar blood vessels in rats. Molecular and pathological changes in the liver were examined over the following 28 days. Ischaemia-reperfusion injury resulted in transient cholestasis associated with microvillar changes in biliary epithelial cell membranes and hepatocellular injury which resolved within days after reperfusion. However, in contrast to chemically-induced acute liver injuries, this was followed by sustained elevation in isoprostane E2, peri-portal inflammation and fibrosis that remained unresolved in the ischaemic reperfused lobe for at least 28 days after clamping. Administration of pregnenolone-16α-carbonitrile--a rodent-specific pregnane X receptor activator--resulted in significant reductions in cholestasis, hepatic injury, ischaemic lobe isoprostane E2 levels, peri-portal inflammation and fibrosis. Hepatic ischaemia-reperfusion injury therefore results in inflammatory and fibrotic changes that persist well beyond the initial ischaemic insult. Drug-mediated activation of the pregnane X receptor reduced these adverse changes in rats, suggesting that the pregnane X receptor is a viable drug target to reduce ischaemic-type biliary lesions in recipients of liver transplants donated after cardiac death.

No MeSH data available.


Related in: MedlinePlus

PXR activation reduces hepatocellular injury and peri-portal inflammation associated with IRI, and stimulates liver growth.(A) H&E staining of liver sections–typical views from the indicated treatment group post and time point. Scale bar represents 100μm. (B) Comparison of liver damage severity scores between IRI + PCN and IRI+vehicle groups assessed [9] on H&E slides (scale of 0–5: normal–extensive damage). (C) Serum ALT pre and post-reperfusion. (D) Comparison of the isoprostane F2 IV and E2 levels in the ischaemic and non ishaemic lobes from rats subjected to IRI with PCN treatment (+) or DMSO vehicle only treatment (-). (E-F) Comparison of inflammatory cell counts in peri-portal and centrilobular areas between the IRI+PCN and IRI-vehicle groups. (G-I) Gross changes in size and features of rat liver 10 days following IRI in animals treated with PCN versus vehicle control, non-ischaemic lobes are shown for comparison. Data are the mean and standard deviation from 5 separate animals at each time point and treatment, *Significantly different compared to sham IRI group, p<0.05.
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pone.0136173.g007: PXR activation reduces hepatocellular injury and peri-portal inflammation associated with IRI, and stimulates liver growth.(A) H&E staining of liver sections–typical views from the indicated treatment group post and time point. Scale bar represents 100μm. (B) Comparison of liver damage severity scores between IRI + PCN and IRI+vehicle groups assessed [9] on H&E slides (scale of 0–5: normal–extensive damage). (C) Serum ALT pre and post-reperfusion. (D) Comparison of the isoprostane F2 IV and E2 levels in the ischaemic and non ishaemic lobes from rats subjected to IRI with PCN treatment (+) or DMSO vehicle only treatment (-). (E-F) Comparison of inflammatory cell counts in peri-portal and centrilobular areas between the IRI+PCN and IRI-vehicle groups. (G-I) Gross changes in size and features of rat liver 10 days following IRI in animals treated with PCN versus vehicle control, non-ischaemic lobes are shown for comparison. Data are the mean and standard deviation from 5 separate animals at each time point and treatment, *Significantly different compared to sham IRI group, p<0.05.

Mentions: To determine whether these observed PXR-dependent effects on cholestasis and oxidative stress are sufficient to impact on liver injury, the severity of liver damage in both groups was examined. Fig 7A and 7B show that PCN treatment resulted in a significant reduction in liver damage severity scores on day 1 post-reperfusion. Evidence for ongoing necrosis was minimal in both groups by day 10 after IRI in accordance with the findings in study 1. These observations are supported by serum liver enzyme levels which show that ALT levels were significantly lower in the IRI-PCN group on day 1 compared to vehicle control, indicating a significant reduction in hepatocellular injury (Fig 7C). In contrast, serum ALP levels were unaffected by PCN treatment at any time (see S4 Fig). An examination of isoprostane levels in both ischaemic and non-ischaemic lobes demonstrated that the elevated level of isoprostane E2 found in the ischaemic lobe were significantly reduced at both day 1 and day 10 in rats treated with PCN compared to the vehicle control, with no effects seen with isoprostane F2 IV (Fig 7D) or F2 II and VI (data not included). Fig 7E and 7F demonstrate that PCN treatment significantly reduced the number of peri-portal and centrilobular inflammatory cells on day 1 compared to the IRI-vehicle group. The inflammatory cell count in the peri-portal areas remained significantly higher in the vehicle control group on day 10 (Fig 7E). Fig 7G and 7H indicate that PCN treatment also resulted in an increase in the relative wet weight of lobes subjected to IRI at 10 days after clamp release. Recent work has shown that PXR activation alone (by PCN) mediates hepatic hypertrophy but not hyperplasia [21,22]. However, PXR activation by PCN potentiates the hepatic hyperplastic effects of activators of other nuclear receptors (CAR or PPARα) [21,22]. Although it is not possible to determine whether the effect of PCN on the IRI lobe is hypertrophic or hyperplastic, it is most likely that PCN via PXR potentiated a response to the injury in the IRI lobe, since there was no increase in relative wet weight of lobes that were not subjected to IRI.


Sustained Isoprostane E2 Elevation, Inflammation and Fibrosis after Acute Ischaemia-Reperfusion Injury Are Reduced by Pregnane X Receptor Activation.

Amer AO, Probert PM, Dunn M, Knight M, Vallance AE, Flecknell PA, Oakley F, Cameron I, White SA, Blain PG, Wright MC - PLoS ONE (2015)

PXR activation reduces hepatocellular injury and peri-portal inflammation associated with IRI, and stimulates liver growth.(A) H&E staining of liver sections–typical views from the indicated treatment group post and time point. Scale bar represents 100μm. (B) Comparison of liver damage severity scores between IRI + PCN and IRI+vehicle groups assessed [9] on H&E slides (scale of 0–5: normal–extensive damage). (C) Serum ALT pre and post-reperfusion. (D) Comparison of the isoprostane F2 IV and E2 levels in the ischaemic and non ishaemic lobes from rats subjected to IRI with PCN treatment (+) or DMSO vehicle only treatment (-). (E-F) Comparison of inflammatory cell counts in peri-portal and centrilobular areas between the IRI+PCN and IRI-vehicle groups. (G-I) Gross changes in size and features of rat liver 10 days following IRI in animals treated with PCN versus vehicle control, non-ischaemic lobes are shown for comparison. Data are the mean and standard deviation from 5 separate animals at each time point and treatment, *Significantly different compared to sham IRI group, p<0.05.
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Related In: Results  -  Collection

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pone.0136173.g007: PXR activation reduces hepatocellular injury and peri-portal inflammation associated with IRI, and stimulates liver growth.(A) H&E staining of liver sections–typical views from the indicated treatment group post and time point. Scale bar represents 100μm. (B) Comparison of liver damage severity scores between IRI + PCN and IRI+vehicle groups assessed [9] on H&E slides (scale of 0–5: normal–extensive damage). (C) Serum ALT pre and post-reperfusion. (D) Comparison of the isoprostane F2 IV and E2 levels in the ischaemic and non ishaemic lobes from rats subjected to IRI with PCN treatment (+) or DMSO vehicle only treatment (-). (E-F) Comparison of inflammatory cell counts in peri-portal and centrilobular areas between the IRI+PCN and IRI-vehicle groups. (G-I) Gross changes in size and features of rat liver 10 days following IRI in animals treated with PCN versus vehicle control, non-ischaemic lobes are shown for comparison. Data are the mean and standard deviation from 5 separate animals at each time point and treatment, *Significantly different compared to sham IRI group, p<0.05.
Mentions: To determine whether these observed PXR-dependent effects on cholestasis and oxidative stress are sufficient to impact on liver injury, the severity of liver damage in both groups was examined. Fig 7A and 7B show that PCN treatment resulted in a significant reduction in liver damage severity scores on day 1 post-reperfusion. Evidence for ongoing necrosis was minimal in both groups by day 10 after IRI in accordance with the findings in study 1. These observations are supported by serum liver enzyme levels which show that ALT levels were significantly lower in the IRI-PCN group on day 1 compared to vehicle control, indicating a significant reduction in hepatocellular injury (Fig 7C). In contrast, serum ALP levels were unaffected by PCN treatment at any time (see S4 Fig). An examination of isoprostane levels in both ischaemic and non-ischaemic lobes demonstrated that the elevated level of isoprostane E2 found in the ischaemic lobe were significantly reduced at both day 1 and day 10 in rats treated with PCN compared to the vehicle control, with no effects seen with isoprostane F2 IV (Fig 7D) or F2 II and VI (data not included). Fig 7E and 7F demonstrate that PCN treatment significantly reduced the number of peri-portal and centrilobular inflammatory cells on day 1 compared to the IRI-vehicle group. The inflammatory cell count in the peri-portal areas remained significantly higher in the vehicle control group on day 10 (Fig 7E). Fig 7G and 7H indicate that PCN treatment also resulted in an increase in the relative wet weight of lobes subjected to IRI at 10 days after clamp release. Recent work has shown that PXR activation alone (by PCN) mediates hepatic hypertrophy but not hyperplasia [21,22]. However, PXR activation by PCN potentiates the hepatic hyperplastic effects of activators of other nuclear receptors (CAR or PPARα) [21,22]. Although it is not possible to determine whether the effect of PCN on the IRI lobe is hypertrophic or hyperplastic, it is most likely that PCN via PXR potentiated a response to the injury in the IRI lobe, since there was no increase in relative wet weight of lobes that were not subjected to IRI.

Bottom Line: The anti-inflammatory effects of the activated pregnane X receptor have previously been shown to be beneficial in a number of inflammatory liver conditions.Administration of pregnenolone-16α-carbonitrile--a rodent-specific pregnane X receptor activator--resulted in significant reductions in cholestasis, hepatic injury, ischaemic lobe isoprostane E2 levels, peri-portal inflammation and fibrosis.Drug-mediated activation of the pregnane X receptor reduced these adverse changes in rats, suggesting that the pregnane X receptor is a viable drug target to reduce ischaemic-type biliary lesions in recipients of liver transplants donated after cardiac death.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle, United Kingdom.

ABSTRACT
Liver grafts donated after cardiac death are increasingly used to expand the donor pool but are prone to ischaemic-type biliary lesions. The anti-inflammatory effects of the activated pregnane X receptor have previously been shown to be beneficial in a number of inflammatory liver conditions. However, its role in reducing peri-portal inflammation and fibrosis following ischaemia-reperfusion injury has not been investigated. Hepatic injury and its response to pregnane X receptor activation was examined after partial hepatic ischaemia-reperfusion injury induced by surgically clamping the left and middle lobar blood vessels in rats. Molecular and pathological changes in the liver were examined over the following 28 days. Ischaemia-reperfusion injury resulted in transient cholestasis associated with microvillar changes in biliary epithelial cell membranes and hepatocellular injury which resolved within days after reperfusion. However, in contrast to chemically-induced acute liver injuries, this was followed by sustained elevation in isoprostane E2, peri-portal inflammation and fibrosis that remained unresolved in the ischaemic reperfused lobe for at least 28 days after clamping. Administration of pregnenolone-16α-carbonitrile--a rodent-specific pregnane X receptor activator--resulted in significant reductions in cholestasis, hepatic injury, ischaemic lobe isoprostane E2 levels, peri-portal inflammation and fibrosis. Hepatic ischaemia-reperfusion injury therefore results in inflammatory and fibrotic changes that persist well beyond the initial ischaemic insult. Drug-mediated activation of the pregnane X receptor reduced these adverse changes in rats, suggesting that the pregnane X receptor is a viable drug target to reduce ischaemic-type biliary lesions in recipients of liver transplants donated after cardiac death.

No MeSH data available.


Related in: MedlinePlus