HIV-1 gp120 Envelope Protein and Morphine-Tubular Cell Interaction Products Modulate Kidney Fibroblast Proliferation

Abstract

Background

Renal interstitial scarring is an important feature of HIV-associated nephropathy. Intravenous drug abuse has been demonstrated to be a risk factor for the development of HIV-associated nephropathy in patients with HIV infection. We studied the effect of tubular cell-morphine and/or HIV-1 gp120 envelope protein interaction products on kidney fibroblast (KF) proliferation and apoptosis.

Methods

Tubular cell-morphine and/or gp120 interaction products were prepared by incubating confluent human proximal tubular cells with buffer (TCP), morphine (10⁻⁸ mol/L) (TCM-IP), gp120 (0.01 µg/mL)(TC-120IP), or morphine (10⁻⁸ mol/L) + gp120 (0.01 µg/mL) (TCM-120IP). To evaluate the effect of tubular cell interaction products (TCIP) on KF proliferation, growth arrested kidney fibroblasts were treated with variable concentrations (5%, 10%, 20%, 30%, and 50%) of TCP, TCM-IP, TC-120IP, or TCM-120IP for 48 hours. To evaluate the role of cytokines in TCIP-induced KF proliferation, cells were incubated with TCIP with or without cytokine neutralizing antibodies to TGF-β, TNF-a, FGF, or IL-6 for 48 hours. Subsequently, cells were counted in a hemocytometer (n = 3). To evaluate the effect of TCIP on KF apoptosis, cells were treated with 50% TCP, 50% TCM-IP, 50% TC-120IP, or 50% TCM-120IP for 24 hours and stained with H-33342 and propidium iodide. In parallel experiments KFs were harvested under identical conditions, DNA was isolated and run on gel electrophoresis. To evaluate the role of early growth genes in TCM-120-induced KF proliferation, TCM-120IP-treated cells were probed with cDNA for c-fos and c-jun.

Results

TC-120IP at a lower concentration (20%) enhanced (P < 0.001) proliferation of KF when compared with TCP. TCM-IP did not stimulate KF proliferation. On the contrary, TCM-120IP at a lower concentration (20%) promoted (P < 0.001) KF proliferation when compared with TCP, TCM-IP and TC-120IP. TCM-120IP at a lower concentration (20%) also enhanced KF mRNA expression of c-fos and c-jun. TCM-120IP enhanced KF proliferation in a dose-dependent manner. All tubular cell interaction products at a higher concentration (50%) promoted apoptosis of KF.

Conclusions

Tubular cell-gp120 interaction products stimulated KF proliferation. Morphine amplified the effect of tubular cell-gp120 interaction on the proliferation of KF. TCM-120IP-induced KF proliferation may be mediated through the expression of early growth genes; whereas TCM-120IP-induced KF growth suppression may be mediated through the induction of apoptosis.