Role of HIV-1 Nef in reduced migration of Macrophages in the Lung of HIV-Tg Mice

Abstract

Background: Past studies have shown that antiretroviral therapy significantly improved the longevity of HIV-infected patients. However, chronic long-term HIV-1 infection is complicated by the increased rates of age-associated chronic diseases, particularly non-infectious respiratory disorders. The mechanism of increased lung non-infectious lung diseases in people living with HIV is poorly understood. An HIV-transgenic mouse model was used to study LPS-induced lung injury. Reduced lung macrophage infiltration and increased lung neutrophil infiltrations with increased lung injury after LPS injection was demonstrated in HIV-transgenic (HIV-Tg) compared to wild-type mice (WT). Activated macrophages accumulated in the capillaries of HIV-Tg mice after LPS injection. The results further showed that Inhibition of HIV-1 transcription significantly increased macrophages' lung infiltration and reduced lung injury in HIV-Tg mice. Hypothesis: We, therefore, hypothesize that reduced LPS-induced lung macrophage migration in HIV-Tg mice is associated with the activation of Src kinase by HIV-1 Nef. We further hypothesize that inhibition of Src activation by PPi inhibitor will restore regular lung macrophage migration and reduces lung injury. Methods: HIV Tg mice and wild-type littermates (WT) were injected with LPS, and blood and lungs were collected 24h after injection. RT-PCR was used to detect the expression of proinflammatory cytokines (IL-1β and IL-18) and Nef in the lung. ELISAs were used to detect the plasma levels of pro-inflammatory cytokines (IL-6 and TNF-α). Levels of Src kinase and phosphorylated Src were determined by Western Blot and flow cytometry. Hematoxylin and eosin staining was used to evaluate lung injury—immunohistochemistry and immunofluorescence staining were used to assess lung macrophage infiltration. Results: Our results demonstrate higher levels of LPS-induced inflammation in HIV-Tg mice. Nef was not expressed in the lung of HIV-Tg mice but was detected in the infiltrated immune cells after LPS injection. Src was expressed and was highly phosphorylated in the lungs of both HIVTg and WT mice. LPS injection significantly reduced lung Src phosphorylation, but Src was highly phosphorylated in the capillary macrophages of HIV-Tg mice. PPI inhibitor of Src significantly reduces lung injury and increases macrophage migration in the lung of HIV Tg mice. Conclusion: Inhibition of Src with PPi improves migration of macrophages and reduces lung injury of HIV-Tg mice.