This subproject is one of many research subprojects utilizing theresources provided by a Center grant funded by NIH/NCRR. The subproject andinvestigator (PI) may have received primary funding from another NIH source,and thus could be represented in other CRISP entries. The institution listed isfor the Center, which is not necessarily the institution for the investigator.The gastrointestinal (GI) tract is a major target for HIV/SIV infection due to the presence of a large population of CD4+ CCR5+ T lymphocytes of the memory phenotype. Intestinal disease and inflammation are common sequelae to HIV/SIV infection. Nevertheless, the molecular mechanisms that lead to GI dysfunction following CD4+ T cell depletion remain unclear. We investigated changes in proinflammatory cytokine mediated signal transduction pathways associated with intestinal inflammation in SIV-infected rhesus macaques. We examined jejunum and colon collected at necropsy from 12 SIV-infected macaques with diarrhea (group 1), 10 non-SIV infected macaques with diarrhea (group 2) and 7 control uninfected macaques (group 3). All group 1 and group 2 macaques had chronic diarrhea, wasting and colitis but only group 1 animals also had significant enteritis. Gene expression analysis for interleukin-6 (IL-6), and suppressor of cytokine signaling-3 (SOCS-3) was performed using quantitative real-time SYBR Green one-step RT-PCR. The activation state and DNA binding capability of STAT3 was assessed using immunoprecipitation/western blotting and biotin streptavidin pull down assay, respectively. A significant increase in IL-6 and SOCS-3 gene expression along with constitutive activation of STAT3 was observed in the colon of all group 1 and group 2 macaques compared to controls. However, in the jejunum, together with constitutive activation of STAT3 statistically significant increases in IL-6 and SOCS-3 gene expression was observed only in group 1 macaques. Further, in the colon, histopathology severity scores correlated significantly with gene expression for IL-6 (groups 1 & 2) and SOCS-3 (group 2). In the jejunum, a significant correlation was observed for IL-6 and SOCS-3 only in group 1 animals. Similarly phosphorylated STAT3 (p-STAT3) was immunohistochemically localized to the lymphocyte (CD3+) and macrophage (CD68+) population in the intestinal lamina propria. In contrast, fewer CD3+ lymphocytes expressing p-STAT3 were detected in the SIV-infected macaque compared to the non-SIV infected animal. Despite high SOCS-3 expression, STAT3 remained constitutively active and provides a likely mechanism by which high IL-6 concentrations in the inflamed GI tract could induce and maintain intestinal inflammation and favor viral replication and disease progression.
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