Ahmed M. Elsharkawy

Nuclear factor‐κB and the hepatic inflammation‐fibrosis‐cancer axis

Nuclear factor‐κB (NF‐κB) is a transcriptional regulator of genes involved in immunity, inflammatory response, cell fate, and function. Recent attention has focused on the pathophysiological role of NF‐κB in the diseased liver. In vivo studies using rodent models of liver disease and cell‐targeted perturbation of NF‐κB activity have revealed complex and multicellular functions in hepatic inflammation, fibrosis, and the development of hepatocellular carcinoma—a process we have termed the “inflammation‐fibrosis‐cancer axis”. This review summarizes the current state of knowledge and provides insight into the vast complexity of the hepatic NF‐κB signaling system, which should provide a rich source of new therapeutic targets. (HEPATOLOGY 2007;46:590–597.)

Multigenerational epigenetic adaptation of the hepatic wound-healing response.

We investigated whether ancestral liver damage leads to heritable reprogramming of hepatic wound healing in male rats. We found that a history of liver damage corresponds with transmission of an epigenetic suppressive adaptation of the fibrogenic component of wound healing to the male F1 and F2 generations. Underlying this adaptation was less generation of liver myofibroblasts, higher hepatic expression of the antifibrogenic factor peroxisome proliferator-activated receptor γ (PPAR-γ) and lower expression of the profibrogenic factor transforming growth factor β1 (TGF-β1) compared to rats without this adaptation. Remodeling of DNA methylation and histone acetylation underpinned these alterations in gene expression. Sperm from rats with liver fibrosis were enriched for the histone variant H2A.Z and trimethylation of histone H3 at Lys27 (H3K27me3) at PPAR-γ chromatin. These modifications to the sperm chromatin were transmittable by adaptive serum transfer from fibrotic rats to naive rats and similar modifications were induced in mesenchymal stem cells exposed to conditioned media from cultured rat or human myofibroblasts. Thus, it is probable that a myofibroblast-secreted soluble factor stimulates heritable epigenetic signatures in sperm so that the resulting offspring better adapt to future fibrogenic hepatic insults. Adding possible relevance to humans, we found that people with mild liver fibrosis have hypomethylation of the PPARG promoter compared to others with severe fibrosis.

The NF-κB p50:p50:HDAC-1 repressor complex orchestrates transcriptional inhibition of multiple pro-inflammatory genes

Background & Aims The pro-inflammatory functions of NF-κB must be tightly regulated to prevent inappropriate tissue damage and remodelling caused by activated inflammatory and wound-healing cells. The p50 subunit of NF-κB is emerging as an important repressor of immune and inflammatory responses, but by mechanisms that are poorly defined. This study aims to delineate p50 target genes in activated hepatic stellate cells and to outline mechanisms utilised in their repression. Methods Hepatic stellate cells were isolated from nfkb1(p50)-deficient or Wt mice and gene expression compared using microarray. Target genes were verified by qRT-PCR and p50-mediated HDAC-1 recruitment to the target genes demonstrated using chromatin immunoprecipitation. Results We identify p50 as transcriptional repressor of multiple pro-inflammatory genes including Ccl2, Cxcl10, Gm-csf, and Mmp-13. These genes are over-expressed in nfkb1(p50)-deficient mice suffering from chronic hepatitis and in fibrogenic/inflammatory hepatic stellate cells isolated from nfkb1−/− liver. We identify Mmp-13 as a bona-fide target gene for p50 and demonstrate that p50 is required for recruitment of the transcriptional repressor histone deacetylase (HDAC)-1 to κB sites in the Mmp-13 promoter. Chromatin immunoprecipitations identified binding of HDAC-1 to specific regulatory regions of the Ccl2, Cxcl10, Gm-csf genes that contain predicted κB binding motifs. Recruitment of HDAC-1 to these genes was not observed in nfkb1−/− cells suggesting a requirement for p50 in a manner similar to that described for Mmp-13. Conclusions Recruitment of HDAC-1 to inflammatory genes provides a widespread mechanism to explain the immunosuppressive properties of p50.

Cognitive impairment in primary biliary cirrhosis: Symptom impact and potential etiology

Qualitative studies suggest that patients with primary biliary cirrhosis (PBC) experience significant problems with memory and concentration. Studies of nonhepatic disease have linked hypotension and cognitive impairment. In this study, we determined the prevalence of cognitive symptoms in PBC, examined the relationship between symptoms and overt cognitive impairment and structural brain lesions, and explored the role of autonomic dysfunction. The prevalence of cognitive symptoms was determined in 198 patients with PBC. Twenty‐eight representative early‐stage female patients with PBC and 11 matched controls underwent formal cognitive testing at baseline and after 2 years of follow‐up. Autonomic nervous system function was assessed according to heart rate variability and baroreflex sensitivity. Eleven subjects with PBC had structural brain lesions quantified via magnetic resonance imaging. Cognitive symptoms were frequent in our PBC population, with 53% of patients experiencing moderate or severe problems with concentration and/or memory, which were unrelated in their severity to biochemical and histological makers of liver disease severity, suggesting that this symptom burden is largely or entirely unrelated to hepatic encephalopathy. Perceived cognitive symptoms correlated with objectively assessed cognitive impairment (r2 = 0.2, P < 0.05). Cognitive deficits were seen in the PBC cohort compared with controls, with significant decline detected over 2 years of follow‐up. Correlations were seen between cognitive performance (full‐scale intelligence quotient) and systolic blood pressure (P = 0.01, r2 = 0.2) with decline in cognitive function associated with autonomic abnormalities. Structural brain lesions were found in PBC, the density of which correlated with degree of cognitive impairment (P = 0.01, r2 = 0.5) and autonomic function (P = 0.03, r2 = 0.2). Conclusion: Cognitive symptoms are prevalent in PBC independent of liver disease severity and are associated with poorer performance on objective cognitive testing. Cognitive impairment is, in turn, associated with structural brain lesions and autonomic dysfunction, which may predict risk of cognitive decline. (HEPATOLOGY 2008.)

Hepatic nuclear factor kappa B regulates neutrophil recruitment to the injured brain.

Acute brain injury is associated with induction of hepatic chemokine expression, which is an essential element in the subsequent recruitment of leukocytes to the damaged brain. To further understand the significance of the hepatic inflammatory response, we focused on nuclear factor (NF)-&kgr;B, a pivotal regulator of inflammation. Nondestructive real-time whole-body imaging was undertaken in the 3XNF-&kgr;B-luciferase mouse to monitor NF-&kgr;B activation. Acute brain injury induced by intracerebral injection of interleukin-1 provoked rapid activation of hepatic and CNS NF-&kgr;B, with only minimal changes in other organs. Elevated NF-&kgr;B in the brain was limited to the site of the lesion, whereas hepatic NF-&kgr;B was widespread. The function of NF-&kgr;B in this model was determined by monitoring leukocyte recruitment to the liver and brain of nf&kgr;b1−/− mice, which lack the anti-inflammatory p50:p50 NF-&kgr;B homodimer. Brain injury in the nf&kgr;b1−/− mice was associated with increased neutrophil recruitment to the liver and brain compared with wild-type mice, thereby confirming a regulatory role for the NF-&kgr;B system. To determine the role of hepatic NF-&kgr;B, it was selectively inhibited by intravenous adenoviral-mediated delivery of an I&kgr;B&agr; super-repressor. This treatment significantly reduced the numbers of neutrophils recruited to the brain. In conclusion, acute brain injury is associated with rapid and robust activation of hepatic NF-&kgr;B, which is required for efficient mobilization of circulating leukocytes to the brain.

The c-rel subunit of nuclear factor-κb regulates murine liver inflammation, wound-healing, and hepatocyte proliferation

In this study, we determined the role of the nuclear factor‐kappaB (NF‐κB) subunit c‐Rel in liver injury and regeneration. In response to toxic injury of the liver, c‐Rel null (c‐rel−/−) mice displayed a defect in the neutrophilic inflammatory response, associated with impaired induction of RANTES (Regulated upon Activation, Normal T‐cell Expressed, and Secreted; also known as CCL5). The subsequent fibrogenic/wound‐healing response to both chronic carbon tetrachloride and bile duct ligation induced injury was also impaired and this was associated with deficiencies in the expression of fibrogenic genes, collagen I and α‐smooth muscle actin, by hepatic stellate cells. We additionally report that c‐Rel is required for the normal proliferative regeneration of hepatocytes in response to toxic injury and partial hepatectomy. Absence of c‐Rel was associated with blunted and delayed induction of forkhead box M1 (FoxM1) and its downstream targets cyclin B1 and Cdc25C. Furthermore, isolated c‐rel−/− hepatocytes expressed reduced levels of FoxM1 and a reduced rate of basal and epidermal growth factor–induced DNA synthesis. Chromatin immunoprecipitation revealed that c‐Rel binding to the FoxM1 promoter is induced in the regenerating liver. Conclusion: c‐Rel has multiple functions in the control of liver homeostasis and regeneration and is a transcriptional regulator of FoxM1 and compensatory hepatocyte proliferation. (HEPATOLOGY 2010.)

p38α inhibits liver fibrogenesis and consequent hepatocarcinogenesis by curtailing accumulation of reactive oxygen species

Most hepatocellular carcinomas (HCC) develop in the context of severe liver fibrosis and cirrhosis caused by chronic liver inflammation, which also results in accumulation of reactive oxygen species (ROS). In this study, we examined whether the stress-activated protein kinase p38α (Mapk14) controls ROS metabolism and development of fibrosis and cancer in mice given thioacetamide to induce chronic liver injury. Liver-specific p38α ablation was found to enhance ROS accumulation, which appears to be exerted through the reduced expression of antioxidant protein HSP25 (Hspb1), a mouse homolog of HSP27. Its reexpression in p38α-deficient liver prevents ROS accumulation and thioacetamide-induced fibrosis. p38α deficiency increased expression of SOX2, a marker for cancer stem cells and the liver oncoproteins c-Jun (Jun) and Gankyrin (Psmd10) and led to enhanced thioacetamide-induced hepatocarcinogenesis. The upregulation of SOX2 and c-Jun was prevented by administration of the antioxidant butylated hydroxyanisole. Intriguingly, the risk of human HCC recurrence is positively correlated with ROS accumulation in liver. Thus, p38α and its target HSP25/HSP27 appear to play a conserved and critical hepatoprotective function by curtailing ROS accumulation in liver parenchymal cells engaged in oxidative metabolism of exogenous chemicals. Augmented oxidative stress of liver parenchymal cells may explain the close relationship between liver fibrosis and hepatocarcinogenesis.

Cholestasis secondary to anabolic steroid use in young men.

Ask about use of anabolic steroids in young men with unexplained cholestasis to prevent progressive liver injury

Wound healing and local neuroendocrine regulation in the injured liver.

The hepatic wound-healing response is a complex process involving many different cell types and factors. It leads to the formation of excessive matrix and a fibrotic scar, which ultimately disrupts proper functioning of the liver and establishes cirrhosis. Activated hepatic myofibroblasts, which are derived from cells such as hepatic stellate cells (HSCs), play a key role in this process. Upon chronic liver injury, there is an upregulation in the local neuroendocrine system and it has recently been demonstrated that activated HSCs express specific receptors and respond to different components of this system. Neuroendocrine factors and their receptors participate in a complex network that modulates liver inflammation and wound healing, and controls the development and progression of liver fibrosis. The first part of this review provides an overview of the molecular mechanisms governing hepatic wound healing. In the second section, we explore important components of the hepatic neuroendocrine system and their recently highlighted roles in HSC biology and hepatic fibrogenesis. We discuss the therapeutic interventions that are being developed for use in antifibrotic therapy.

Fatigue in primary sclerosing cholangitis is associated with sympathetic over‐activity and increased cardiac output

Patients with primary sclerosing cholangitis (PSC) frequently highlight the impact of fatigue on their life quality. The study aims were to evaluate fatigue and its associations in PSC and investigate whether overt autonomic dysfunction contributes to the expression of fatigue.