of cellular growth both 'in vitro' and 'in vivo' models of cancer.Furthermore, GRK2 levels are increased in a very significant proportion of infiltrating ductal carcinoma samples from patients, strongly suggesting that GRK2 is a relevant modulator of tumor survival and progression 331

Hepatic ischemia/reperfusion (I/R) leads to liver injury and dysfunction through the initiation of a biphasic inflammatory response that is regulated by the transcription factor nuclear factor kappaB (NF-kappaB). We have previously shown that there is an age-dependent difference in the injury response to hepatic I/R in mice that correlates with divergent activation of NF-kappaB such that young mice have greater NF-kappaB activation, but less injury than old mice. In this study, we investigated the mechanism by which age alters the activation of NF-kappaB in the liver during I/R. Young (4-5 weeks) and old (12-14 months) mice underwent partial hepatic I/R. Livers were obtained for RNA microarray analysis and protein expression assays. Using microarray analysis, we identified age-dependent differences in the expression of genes related to protein ubiquitinylation and the proteasome. In old mice, genes that are involved in the ubiquitin-proteasome pathway were significantly down-regulated during I/R. Consistent with these findings, expression of a critical proteasome subunit, non-adenosine triphosphatase 4 (PSMD4), was reduced in old mice. Expression of the NF-kappaB inhibitory protein, IkappaB alpha, was increased in old mice and was greatly phosphorylated and ubiquitinylated. The data provide strong evidence that the age-related defect in hepatic NF-kappaB signaling during I/R is a result of decreased expression of PSMD4, a proteasome subunit responsible for recognition and recruitment of ubiquitinylated substrates to the proteasome. It appears that decreased PSMD4 expression prevents recruitment of phosphorylated and ubiquitinylated IkappaB alpha to the proteasome, resulting in a defect in NF-kappaB activation.

Cancer of the prostate is the second most diagnosed cancer in men. The pathogenesis of this disease is complex, but is known to involve multiple factors that affect tumor growth, invasion, and metastasis. One group of such factors are CXC chemokines, which are a subset of chemotactic cytokines which, through their receptors, have angiogenic or angiostatic properties. This review will discuss our current understanding of the various functional roles that CXC chemokines and their receptors play in the development and progression of prostate cancer.

The function of peroxisome proliferator-activated receptor-γ (PPARγ) in hepatic inflammation and injury is unclear. In this study, we sought to determine the role of PPARγ in hepatic ischemia/reperfusion injury in mice. Male mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 8 hours of reperfusion. PPARγ was found to be constitutively activated in hepatocytes but not in nonparenchymal cells. Upon induction of ischemia, hepatic PPARγ activation rapidly decreased and remained suppressed throughout the 8-hour reperfusion period. This reduced activation was not a result of decreased protein availability as hepatic nuclear PPARγ, retinoid X receptor-α (RXRα), and PPARγ/RXRα heterodimer expression was maintained. Accompanying the decrease in PPARγ activation was a decrease in the expression of the natural ligand 15-deoxy-Delta12,14-prostaglandin J2. This was associated with reduced interaction of PPARγ and the coactivator, p300. To determine whether PPARγ activation is hepatoprotective during hepatic ischemia/reperfusion injury, mice were treated with the PPARγ agonists, rosiglitazone and connecting peptide. These treatments increased PPARγ activation and reduced liver injury compared to untreated mice. Furthermore, PPARγ-deficient mice had more liver injury after ischemia/reperfusion than their wild-type counterparts. Conclusion: These data suggest that PPARγ is an important endogenous regulator of, and potential therapeutic target for, ischemic liver injury. (HEPATOLOGY 2007.)

CXC chemokines and their receptor, CXC chemokine receptor-2 (CXCR2), are important components of the hepatic inflammatory response to ischemia/reperfusion (I/R). However, direct effects of CXC chemokines on hepatocytes during this response have not been studied. Wild-type and CXCR2(-/-) mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 96 hours of reperfusion. CXCR2(-/-) mice had significantly less liver injury at all reperfusion times compared with wild-type mice. Early neutrophil recruitment (12 hours) was diminished in CXCR2(-/-) mice, but within 24 hours it was the same as that of wild-type mice. Hepatocyte proliferation and regeneration was accelerated in CXCR2(-/-) mice compared with wild-type mice. These effects were associated with increased activation of nuclear factor kappa B and signal transducers and activators of transcription-3, despite there being no difference in the expression of proliferative factors such as tumor necrosis factor alpha, interleukin-6, and hepatocyte growth factor. To establish whether the accelerated proliferation and regeneration observed in CXCR2(-/-) mice was due to effects on hepatocytes rather than just a generalized decrease in acute inflammatory injury, mice were treated with the CXCR2 antagonist, SB225002, after neutrophil recruitment and injury were maximal (24 hours after reperfusion). SB225002 treatment increased hepatocyte proliferation and regeneration in a manner identical to that observed in CXCR2(-/-) mice. Treatment of primary wild-type hepatocytes with macrophage inflammatory protein-2 revealed that low concentrations protected against cell death, whereas high concentrations induced cell death. These effects were absent in hcpatocytes from CXCR2(-/-) mice. Conclusion: Our data suggest that hepatocyte CXCR2 regulates proliferation and regeneration after I/R injury and reveal important differences in the role of this receptor in liver regeneration and repair induced under different conditions that may be related to ligand concentration.

Hepatic ischemia-reperfusion (I/R) injury is an important complication of liver surgery and transplantation. Mitochondrial function is central to this injury. To examine alterations in mitochondrial function during I/R, we assessed the mitochondrial proteome in C57Bl/6 mice. Proteomic analysis of liver mitochondria revealed 234 proteins with significantly altered expression after I/R. From these, 13 proteins with the greatest expression differences were identified. One of these proteins, peroxiredoxin-6 (Prdx6), has never before been described in mitochondria. In hepatocytes from sham-operated mice, Prdx6 expression was found exclusively in the cytoplasm. After ischemia or I/R, Prdx6 expression disappeared from the cytoplasm and appeared in the mitochondria, suggesting mitochondrial trafficking. To explore the functional role of Prdx6 in hepatic I/R injury, wild-type and Prdx6-knockout mice were subjected to I/R injury. Prdx6-knockout mice had significantly more hepatocellular injury compared with wild-type mice. Interestingly, the increased injury in Prdx6-knockout mice occurred despite reduced inflammation and was associated with increased mitochondrial generation of H2O2 and dysfunction. The mitochondrial dysfunction appeared to be related to complex I of the electron transport chain. These data suggest that hepatocyte Prdx6 traffics to the mitochondria during I/R to limit mitochondrial dysfunction as a protective mechanism against hepatocellular injury.

Ligands of the CXC chemokine receptor, CXCR2, are critical for neutrophil recruitment during hepatic ischemia/reperfusion (I/R) injury. Hepatocytes also express CXCR2, however, direct effects of CXC chemokines on hepatocyte function or recovery during I/R injury is unknown. We sought to determine the role of CXCR2 signaling in injury and recovery from hepatic I/R in mice. Male wild‐type or CXCR2−/− mice were subjected to 90 minutes of partial hepatic ischemia followed by up to 96 hours of reperfusion. Some wild‐type mice were treated with a CXCR2 antagonist after 24 hours of reperfusion. CXCR2−/− mice had less liver injury and accelerated recovery after I/R compared to wild‐type mice. There were no differences noted between groups in the expression of TNFα or IL‐6. Acute neutrophil recruitment was blocked in CXCR2−/− mice, but after 24 or 48 hours of reperfusion, neutrophil accumulation between the groups was similar. Hepatocyte proliferation, measured by PCNA staining, was increased in CXCR2−/− mice and was associated with increased activation of NF‐κB and STAT3. Treatment of wild‐type mice with CXCR2 antagonist after initial neutrophil recruitment had similar effects on injury, proliferation, and activation of NF‐κB and STAT3. The data suggest that signaling via CXCR2 in hepatocytes after I/R prevents proliferation and delays recovery.

Heat shock protein (HSP) 72 is released by cells during stress and injury. HSP-72 also stimulates the release of cytokines in macrophages by binding to Toll-like receptors (TLR) 2 and 4. Circulating levels of HSP-72 increase during hepatic ischemia-reperfusion injury. The role of extracellular HSP-72 (eHSP-72) in the injury response to ischemia-reperfusion is unknown. Therefore, the objective of the present study was to determine whether eHSP-72 has any direct effects on hepatocytes. Primary mouse hepatocytes were treated with purified human recombinant HSP-72. Conditioned media were evaluated by ELISA for the cytokines, TNF-alpha, IL-6, and macrophage inflammatory protein 2 (MIP-2). Stimulation of hepatocytes with eHSP-72 did not induce production of TNFalpha or IL-6 but resulted in dose-dependent increases in MIP-2 production. To evaluate the pathway responsible for this response, expression of TLR2 and TLR4 was confirmed on hepatocytes by immunohistochemistry. Hepatocyte production of MIP-2 was significantly decreased in hepatocytes obtained from TLR2 or TLR4 knockout mice. MIP-2 production was found to be partially dependent on NF-kappaB because inhibition of NF-kappaB with Bay 11-7085 significantly decreased eHSP-72-induced MIP-2 production. Inhibitors of p38 mitogen-activated protein kinase or c-Jun NH(2)-terminal kinase had no effect on production of MIP-2 induced by eHSP-72. The data suggest that eHSP-72 binds to TLR2 and TLR4 on hepatocytes and signals through NF-kappaB to increase MIP-2 production. The fact that eHSP-72 did not increase TNF-alpha or IL-6 production may be indicative of a highly regulated signaling pathway downstream from TLR.

Hepatic ischemia/reperfusion injury is a complication of liver surgery, transplantation, and shock and is known to be age-dependent. Our laboratory has recently shown that peroxisome proliferator-activated receptor-gamma (PPARgamma) is down-regulated during hepatic ischemia and that this exacerbates injury. Here we examined whether activation of PPARgamma during ischemia was age-dependent. Male mice of different ages (young: 4-5 weeks; adult: 10-12 weeks; old: 10-12 months) were subjected to up to 90 min of hepatic ischemia. PPARgamma activation occurred throughout ischemia in young mice, whereas activation in adult and old mice was lost after 30 min. No significant differences were noted in PPARgamma ligand expression among the age groups. However, in young mice we observed a predominance of PPARgamma1 in the nucleus, whereas in old mice this isoform remained largely in the cytoplasm. Finally, the degree of PPARgamma activation was associated with autophagy in the liver, a mechanism of self-preservation. PPARgamma activation is prolonged in young mice as compared to older mice. This appears to be mediated by a selective retention of PPARgamma1 in the nucleus and is associated with increased autophagy. The data suggest that PPARgamma activation is an important component of the age-dependent response to hepatic ischemia/reperfusion injury.

Hepatic ischemia/reperfusion (I/R) injury is an important complication of liver surgery and transplantation. To examine if ischemia itself alters gene expression in the liver we assessed gene expression after different periods of ischemia. Total liver RNA of C57Bl/6 mice (n=3/group) undergoing sham surgery or partial hepatic ischemia for 30, 60, or 90 min were isolated, purified and analyzed by Affymetrix microarray. Genes with 1.5-fold increased or decreased expression (ANOVA, P<0.05) were examined. Using Venn diagram analysis, we found 18 genes that were upregulated within 30 min of ischemia, 14 other genes were upregulated after 60 min of ischemia and 109 other genes were upregulated after 90 min of ischemia. Some of these included genes related to cell cycle control and cell death pathways. Using similar methodology, 38 genes were downregulated after 30 min of ischemia, 18 other genes were downregulated after 60 min, and 29 other genes were downregulated after 90 min of ischemia. Some of these included genes related to energy metabolism and inflammation. Our data demonstrate significant and widespread changes in gene expression in the liver during the period of ischemia. These changes may be important to the responses observed after reperfusion.

Ischemia/reperfusion (I/R) injury of the liver is an important complication of liver surgery and transplantation. Mitochondrial function is central to this injury. In order to examine mitochondrial function, we assessed the hepatic mitochondrial proteome during I/R. C57Bl/6 mice were subjected to sham surgery or 90 min of partial hepatic ischemia and 1 hr of reperfusion. Liver mitochondria were isolated and separated by 2-D PAGE with a pH range of 4–7. Image analysis was performed to assess protein expression between sham and I/R groups. 234 protein spots were increased or decreased in expression more than 2-fold compared to mitochondria from sham mice. From these, 29 proteins were selected for identification. Protein spots were digested with trypsin analyzed by mass spectroscopy and identified using the Mascot database. Increased mitochondrial expression of hydroxyacyl-coenzyme A dehydrogenase, methionine adenosyltransferase Iα, two heat shock protein 70-related proteins, Es31 protein, transmembrane protein 4, glutamate dehydrogenase 1, sorbitol dehydrogenase precursor, fumarylacetoacetase, and peroxiredoxin-6 was found. One protein had decreased expression; ATP5b protein. Our data demonstrate changes in mitochondrial proteins after I/R and are the first to identify mitochondrial expression of peroxiredoxin-6.