The GFP viral constructs indicate that these cells support viral gene expression, which was blocked by AZT. Despite the low level expression of CD4 on buy AZD2281 HSCs, and the previously reported expression of the HIV coreceptors, CXCR4 and CCR5, our results suggest that HIV entry occurs by way of mechanisms independent of receptor engagement. Two interesting findings from our study may enhance our understanding of the role of HIV in chronic liver disease:
(1) HSCs are able to retain viral particles that can subsequently be transferred to and infect susceptible cells; and (2) exposure to HIV results in increased collagen I expression as well as secretion of the potent proinflammatory chemokine MCP-1, thereby providing a direct link between HIV and fibrosis through effects on HSCs. These findings add a new perspective to our growing understanding of the mechanisms by which HIV promotes inflammation and accelerates fibrosis and must be placed in the context of other important observations. In vivo studies in seropositive patients support the presence of HIV proviral DNA by polymerase chain reaction in whole liver tissue, as well as HIV RNA in liver cells (particularly Kupffer cells, but also isolated hepatocytes) by way of in situ hybridization.
In addition, HIV proteins have been detected in parenchymal and nonparenchymal liver cells by immunohistochemistry.23-25 The specific cell type expressing HIV proteins, however, remains unclear given the lack of co-immunostaining. In vitro, several liver cell types are infectable by HIV, including hepatoma cell lines, Kupffer cells, and sinuosoidal endothelial cells (reviewed in Blackard and Selleck U0126 Sherman26). Previously proposed mechanisms by which HIV may promote inflammation and fibrosis include: (1) hepatocyte apoptosis in response to HCV and HIV envelope proteins27, 28; (2) induction of hepatocyte-derived transforming growth factor-β1 by HIV and 上海皓元医药股份有限公司 gp12029; and (3) reduced interleukin-10 secretion by intrahepatic CD4+ cells derived from HIV/HCV patients in response to HCV proteins.30 Since interleukin-10 may be both anti-inflammatory and antifibrotic by directly inhibiting
HSC apoptosis, reduced interleukin-10 secretion may contribute to accelerated fibrosis in coinfected patients.29 Increased transforming growth factor-β1 may promote fibrosis by way of (1) direct profibrogenic effects on HSCs and; (2) reduction in the IFN-γ response of CD8+ cells to viral infection which could promote HCV persistence.31 Our group as well as others have reported profibrogenic effects of HIV-1 gp120 on HSCs.10, 11 Therefore, it is likely that HIV and its proteins promote liver injury, inflammation, and fibrosis by effects on both parenchymal and nonparenchymal cells of the liver. Upon activation, HSCs exhibit features of professional antigen-presenting cells where they acquire the ability to endocytose external particles and to stimulate T lymphocyte proliferation.