Faculty Bibliography

Thiopurines play a pivotal role in the management of inflammatory bowel disease. Azathioprine and mercaptopurine have been associated with a number of liver abnormalities, including hepatitis, veno-occlusive disease, nodular regenerative hyperplasia, and peliosis hepatitis. Patients treated with azathioprine and mercaptopurine have their liver chemistry tests routinely checked due to this potential for hepatotoxicity. Hepatoportal sclerosis is a cause of non-cirrhotic portal hypertension that is increasingly being recognized; its etiopathogenesis is not well defined. We present the first case report of mercaptopurine-induced hepatoportal sclerosis leading to non-cirrhotic portal hypertension in a patient with Crohn's disease. He had been treated with mercaptopurine for five years, and his liver chemistry tests were always within normal limits. This case underscores the potential serious liver adverse events that may arise silently and go undetected during treatment with mercaptopurine, and should alert clinicians as to the potential need to discontinue mercaptopurine in this setting.

Niacin therapy, used either alone or in combination with another agent to reduced the risk of coronary heart disease, is effective in raising and lowering, respectively, HDL-c and apoB/VLDL triglyceride (TG) levels in dyslipidemia. To further understand if part of the mechanism is by reducing the secretion of apoB-containing lipoproteins through autophagy, we did a series of niacin studies in isolated primary hepatocytes or in intact mice. Metabolic labeling and pulse-chase results showed niacin increased intracellular apoB degradation by 30%, and decreased apoB/VLDL TG secretions by 40%. These effects were lost in autophagy-deficient cells. Mice fed with diet containing 3% niacin had 40% increases in plasma HDL-c. Feeding high fat diet (HFD) with niacin lowered LDL-c by 50%. Niacin was able to suppress postprandial plasma triglyceride by 30%. Niacin reduced hepatic triglyceride and cholesterol concentrations by 40% and 50%, respectively, in mice fed with HFD. These data suggest niacin decreases hepatic lipid concentrations, apoB/VLDL secretion, and modifies plasma cholesterol levels. Some of the effects required niacin metabolism and autophagy degradation

Both in humans and animal models, an acute increase in plasma insulin levels, typically following meals, leads to transient depression of hepatic secretion of very low density lipoproteins (VLDL). One contributing mechanism for the decrease in VLDL secretion is enhanced degradation of apolipoprotein B100 (apoB100), which is required for VLDL formation. Unlike the degradation of nascent apoB100, which occurs in the endoplasmic reticulum (ER), insulin-stimulated apoB100 degradation occurs post-ER and is inhibited by pan-phosphatidylinositol (PI)3-kinase inhibitors. It is unclear, however, which of the three classes of PI3-kinases is required for insulin-stimulated apoB100 degradation, as well as the proteolytic machinery underlying this response. Class III PI3-kinase is not activated by insulin, but the other two classes are. By using a class I-specific inhibitor and siRNA to the major class II isoform in liver, we now show that it is class II PI3-kinase that is required for insulin-stimulated apoB100 degradation in primary mouse hepatocytes. Because the insulin-stimulated process resembles other examples of apoB100 post-ER proteolysis mediated by autophagy, we hypothesized that the effects of insulin in autophagy-deficient mouse primary hepatocytes would be attenuated. Indeed, apoB100 degradation in response to insulin was significantly impaired in two types of autophagy-deficient hepatocytes. Together, our data demonstrate that insulin-stimulated apoB100 degradation in the liver requires both class II PI3-kinase activity and autophagy.

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease in the Western world. It is closely associated with metabolic syndrome. The alarming epidemics of diabetes and obesity have fueled an increasing prevalence of NAFLD, particularly among these high-risk groups. Histologically, NAFLD encompasses a disease spectrum ranging from simple steatosis to non-alcoholic steatohepatitis (NASH), which is characterized by hepatocyte injury, inflammation, and variable degrees of fibrosis on liver biopsy. Non-alcoholic steatohepatitis can progress to cirrhosis in a fraction of patients. There is currently little understanding of risk factors for disease progression and the disease pathogenesis has not been fully defined. Liver biopsy remains the gold standard for diagnosis. Weight loss, dietary modification, and the treatment of underlying metabolic syndrome remain the mainstays of therapy once the diagnosis is established. There are no well-established pharmacological agents for treatment of NASH, although this is a subject of ongoing research.

Patients coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) develop more rapid fibrosis than those infected with HCV only. In HIV/HCV-coinfected patients, fibrosis progression correlates with HIV RNA levels, suggesting a direct role of HIV in liver fibrogenesis. Chemokine (C-C motif) receptor 5 (CCR5) and cysteine-X-cysteine receptor 4 (CXCR4), the two major coreceptors required for HIV entry into cells, are expressed on activated hepatic stellate cells (HSCs), the principle fibrogenic cell type in the liver. We therefore examined whether HIV can infect HSCs, explored the potential mechanisms of viral entry, and assessed the impact of infection as reflected by the ability of HSCs to transfer virus to T lymphocytes and elicit a proinflammatory and profibrogenic response. We report that the laboratory-adapted viruses HIV-IIIB (CXCR4-tropic or X4) and HIV-BaL (CCR5-tropic or R5) and primary HIV isolates can infect both a human stellate cell line, LX-2, and primary human HSCs. HIV entry and gene expression in HSCs was confirmed using HIV-green fluorescent protein (GFP) expression viral constructs in the presence or absence of the reverse-transcriptase inhibitor azidothymidine. CD4 expression on a subset of primary HSCs was demonstrated using fluorescence-activated cell sorting and immunofluorescence staining. Blocking experiments in the presence of anti-CD4, anti-CXCR4, and anti-CCR5 revealed that HIV entry into HSCs is predominantly CD4/chemokine coreceptor-independent. HIV infection promoted HSC collagen I expression and secretion of the proinflammatory cytokine monocyte chemoattractant protein-1. Furthermore, infected LX-2 cells were capable of transferring GFP-expressing virus to T lymphocytes in a coculture system. Conclusion: Taken together, our results suggest a potential role of HIV in liver fibrosis/inflammation mediated through effects on HSCs. The role of early highly active antiretroviral therapy initiation in patients with HIV/HCV coinfection warrants further investigation

Chemokine interactions with their receptors have been implicated in hepatic stellate cell (HSC) activation. The hepatic expression of CXCR4 messenger RNA is increased in hepatitis C cirrhotic livers and plasma levels of its endogenous ligand, stromal cell-derived factor-1alpha (SDF-1alpha), correlate with increased fibrosis in these patients. The expression of CXCR4 by HSCs has not been reported. We therefore examined whether HSCs express CXCR4 in vivo and in vitro and explored whether SDF-1alpha/CXCR4 receptor engagement promotes HSC activation, fibrogenesis, and proliferation. The hepatic protein expression of both CXCR4 and SDF-1alpha is increased in hepatitis C cirrhotic livers and immunoflourescent and immunohistochemical staining confirms that HSCs express CXCR4 in vivo. Immortalized human stellate cells as well as primary human HSCs express CXCR4, and cell surface receptor expression increases with progressive culture-induced activation. Treatment of stellate cells with recombinant SDF-1alpha increases expression of alpha-smooth muscle actin and collagen I and stimulates a dose-dependent increase in HSC proliferation. Inhibitor studies suggest that SDF-1alpha/CXCR4-dependent extracellular signal-regulated kinase 1/2 and Akt phosphorylation mediate effects on collagen I expression and stellate cell proliferation. CONCLUSION: HSCs express CXCR4 receptor in vivo and in vitro. CXCR4 receptor activation by SDF-1alpha is profibrogenic through its effects on HSC activation, fibrogenesis, and proliferation. Extracellular signal-regulated kinase 1/2 and phosphoinositide 3-kinase pathways mediate SDF-1alpha-induced effects on HSC expression of collagen I and proliferation. The availability of small molecule inhibitors of CXCR4 make this receptor an appealing target for antifibrotic approaches

Recent in vivo studies suggest that hMPV is a poor inducer of inflammatory cytokines and that clinical symptoms may not be related to immune-mediated pathogenesis as it has been proposed for respiratory syncytial virus (RSV) and human parainfluenza 3 (HPF3). Dendritic cells (DCs) are specialized antigen presenting cells, and very effective at inducing specific CTLs after encountering invading viruses. Interactions of hMPV with DCs have not been characterized. We hypothesized that the relatively mild inflammatory responses observed in vivo after hMPV infection might be at least in part due to hMPV's poor ability to stimulate and activate DCs. hMPV actively infected immature monocyte-derived CD11c+/HLA-DR+ DCs. However, in contrast to RSV or HPF3, hMPV caused no gross cytopathic effects such as syncytia, lytic infection, or massive apoptosis. DCs exposed to hMPV show no cytopathic effects under tissue culture conditions permissive for viral replication. The surface maturation markers CD83 and CD86 were not significantly up-regulated in infected DCs as compared to uninfected controls, while expression of CD80 appeared increased. Stimulation of hMPV-infected DCs with LPS resulted in the enhanced expression of all these surface markers indicating that hMPV is not generally suppressing DC maturation. Overall, cytokine expression remained low. These results indicate that hMPV does not induce effective DC maturation in vitro and suggest that the weak stimulation of DCs may account for the overall low immunogenicity of this virus observed in vivo

Viral entry may preferentially occur at the apical or the basolateral surfaces of polarized cells, and differences may impact pathogenesis, preventative strategies, and successful implementation of viral vectors for gene therapy. The objective of these studies was to examine the polarity of herpes simplex virus (HSV) entry using several different human epithelial cell lines. Human uterine (ECC-1), colonic (CaCo-2), and retinal pigment (ARPE-19) epithelial cells were grown on collagen-coated inserts, and the polarity was monitored by measuring the transepithelial cell resistance. Controls were CaSki cells, a human cervical cell line that does not polarize in vitro. The polarized cells, but not CaSki cells, were 16- to 50-fold more susceptible to HSV infection at the apical surface than at the basolateral surface. Disruption of the tight junctions by treatment with EGTA overcame the restriction on basolateral infection but had no impact on apical infection. No differences in binding at the two surfaces were observed. Confocal microscopy demonstrated that nectin-1, the major coreceptor for HSV entry, sorted preferentially to the apical surface, overlapping with adherens and tight junction proteins. Transfection with small interfering RNA specific for nectin-1 resulted in a significant reduction in susceptibility to HSV at the apical surface but had little impact on basolateral infection. Infection from the apical but not the basolateral surface triggered focal adhesion kinase phosphorylation and led to nuclear transport of viral capsids and viral gene expression. These studies indicate that access to nectin-1 contributes to preferential apical infection of these human epithelial cells by HSV

The acidic vaginal milieu is presumed to inactivate pathogens but is neutralized by semen. This notion fostered the development of acid-buffering products, such as ACIDFORM (developed by Program for Topical Prevention of Conception and Disease, Rush University, and licensed by Instead), as microbicides. However, the extent and mechanism of protective activity provided by buffering gels is not known. Exposure of herpes simplex virus (HSV) to pH 4.5 or lower irreversibly inactivated HSV and reduced HSV yields by at least 90%; exposure to pH 5.0 had little or no effect. Pretreatment of HSV-2 with pH 3.5-4.5 triggered proteolysis, disrupting the HSV particle and resulting in a reduction in binding and invasion. ACIDFORM protected 21 (81%) of 26 mice from genital herpes, compared with 3 (12%) of 25 mice who received a placebo gel. ACIDFORM retained significant activity if mice were challenged with HSV delivered in seminal fluid. These findings suggest that ACIDFORM offers considerable protection against HSV and may be an optimal candidate for developing combination microbicides

Prevention of genital herpes and other sexually transmitted infections (STI) is a critical health priority because of the overwhelming impact on women and infants and the epidemiological association with human immunodeficiency virus (HIV)/AIDS. Small animal models are essential for evaluating strategies for prevention or treatment of STI. Neither the murine nor the guinea pig model of genital herpes fully recapitulates human disease. We demonstrate that herpes simplex virus type 2 (HSV-2) readily infects inbred cotton rats (Sigmodon hispidus). Consistent infection does not require pretreatment with medroxyprogesterone, and primary disease resembles that observed in humans. The animals develop genital lesions and fully recover. During primary infection, viral DNA is also detected in liver, lungs, brain, and kidneys. Clinical self-limited recurrences occur spontaneously but may also be induced by dexamethasone. Pretreatment of cotton rats with PRO 2000 gel, a candidate vaginal microbicide being evaluated in clinical trials to prevent HSV and HIV, protects cotton rats from HSV. Together, these studies suggest that the cotton rat may provide an excellent model to study genital herpes and to evaluate preventive strategies