Morphine priming rescues high-dose morphine-induced biological perturbations.

In in vitro studies, macrophage morphine priming (MP; preincubation with low-dose morphine) attenuated the effects of high-dose morphine (HDM) on macrophage capabilities of killing and containment of phagocytosed bacteria. In in vivo studies, mice received either normal saline (control), HDM, or MP twice daily for 10 consecutive days. All HDM-treated mice showed a significant peritoneal bacterial leak; none of the control and only 2 of 12 mice receiving MP showed peritoneal bacterial leak. HDM-treated mice showed decreased macrophage migration into the peritoneal cavity; however, MP inhibited this effect. In in vitro studies, macrophages and bone-marrow cells harvested from HDM-treated mice showed not only enhanced apoptosis but also decreased migration across the filter of a Boyden chamber; nevertheless, MP inhibited these effects of HDM. MP also attenuated the proapoptotic effect of HDM; however, this effect was prevented by treatment with pyrrolidine derivative of dithiocarnamate, an inhibitor of nuclear factor- kappa B. These results suggest that MP provides protection against HDM-induced degradation of the host defense barrier through preservation of macrophage function.

Scatter factor mitigates HIV-1 gp120-induced human mesangial cell injury.

HIV-1 gp120 protein has been shown to promote mesangial cell (MC) injury. Scatter factor (SF) is a growth factor that plays a reparative role in various experimental models of renal lesions. We hypothesize that SF protects MC against HIV-1 gp120-induced MC injury. gp120 at a low dose, stimulated HMC proliferation (p < 0.0001). SF (50 ng/ml) further enhanced low-dose gp120-induced HMC proliferation. However, gp120 at higher doses (10-100 ng/ml) promoted HMC apoptosis. Nevertheless, SF attenuated the high-dose gp120-induced HMC apoptosis. Interestingly, gp120 at a low dose not only induced NF-kappaB activation but also increased p21(cip1/waf1) andp27(kip1) protein levels.

p300 modulates HIV-1 gp120-induced apoptosis in human proximal tubular cells: associated with alteration of TGF-beta and Smad signaling.

p300 is a key protein, which determines acceleration or deceleration of signal transduction. Recently, renal proximal tubular cells have not only been found to be a harboring site for HIV-1 but have also been shown to undergo apoptosis in response to HIV-1 exposure. Both HIV-1 and its envelop glycoprotein, i.e. gp120, triggered tubular cell apoptosis in the same magnitude. In the present study, we evaluated the role of p300 in gp120-induced tubular cell apoptosis and associated downstream signaling. We have demonstrated that by transient transfection assays, p300 significantly increases susceptibility of human proximal renal tubular HK-2 cells to apoptosis triggered by HIV-1 gp120. A mutant p300, missing the E1A/TFIIB binding site, fails to produce such sensitization potential. Smad7 and an anti-TGF-beta antibody rescue the p300 sensitization. Furthermore, p300 and HIV-1 gp120 synergistically increase TGF-beta, ATF-2 and activating protein-1 (AP-1) expression. In addition, HIV-1 gp120 results in phosphorylation of Smad2 and decreases c-Jun. These findings suggest that p300 acts as a potent transcriptional cofactor in HIV-1 gp120-induced apoptosis via TGF-beta and Smad signaling.

Morphine modulates HIV-1 gp160-induced murine macrophage and human monocyte apoptosis by disparate ways.

We studied the effect of HIV-1 gp160 protein and morphine on murine macrophage and human monocyte apoptosis. gp160 not only promoted murine macrophage apoptosis but also enhanced macrophage iNOS expression/NO generation. gp160 also altered macrophage bax and bcl-2 expression. Morphine enhanced (P<0.001) the effect of gp160 on macrophage apoptosis as well as iNOS expression/NO generation. Nevertheless, both morphine- and gp160-induced murine macrophage apoptosis was attenuated by nitric oxide synthase (NOS) inhibitors (L-NAME and L-NMMA). On the other hand, free radical scavengers such as superoxide dismutase (SOD), dimethylthiourea (DMTU) and catalase attenuated morphine and gp160-induced human monocyte apoptosis.

Ethanol promotes T cell apoptosis through the mitochondrial pathway.

Clinical reports suggest that acute ethanol intoxication is often associated with lymphopenia. Previously, ethanol was reported to invoke thymocyte apoptosis. We studied the effect of ethanol on T cell apoptosis. In addition, we evaluated the molecular mechanism of ethanol-induced T cell apoptosis. Human T cells harvested from healthy subjects after an alcohol drinking binge showed enhanced T cell apoptosis (before, 0.4 +/- 0.2% versus after, 19.6 +/- 2.5% apoptotic lymphocytes/field; P < 0.001). In in vitro studies, ethanol in a concentration of 50 mm and higher enhanced the apoptosis of Jurkat cells. DNA isolated from ethanol-treated Jurkat cells displayed integer multiples of 180 base pairs. Ethanol decreased Jurkat cell expression of Bcl-2, whereas ethanol increased Jurkat cell expression of Bax. Jurkat cells treated with ethanol also showed translocation of cytochrome C into cytosol. Moreover, a caspase-9 inhibitor partially inhibited ethanol-induced Jurkat cell apoptosis. In in vivo studies, after binge drinking, T cell expression of Bcl-2 also decreased. In addition, binge drinking induced the cleavage of caspase-3, suggesting activation of caspase-3 in T cells. These results suggest that ethanol promotes T cell apoptosis through the activation of intrinsic or mitochondrial pathway.

Angiotensin II induces apoptosis in rat glomerular epithelial cells.

ANG II has been shown to modulate kidney cell growth and contribute to the pathobiology of glomerulosclerosis. Glomerular visceral epithelial cell (GEC) injury or loss is considered to play a pivotal role in the initiation and progression of glomerulosclerosis. In the present study, we investigated the effect of ANG II on GEC apoptosis. Rat GECs were incubated with increasing doses of ANG II for variable time periods. Apoptosis was evaluated by cell nucleus staining and DNA fragmentation assay. ANG II induced GEC apoptosis in a dose- and time-dependent manner. The proapoptotic effect was attenuated by the ANG II receptor type 1 antagonist losartan or the ANG II receptor type 2 antagonist PD-123319 and was completely blocked by incubation with the combined antagonists. Moreover, ANG II stimulated transforming growth factor (TGF)-beta1 production as measured by ELISA. GECs exposed to TGF-beta1 demonstrated a dose- and time-dependent increase in apoptosis. ANG II-induced apoptosis was significantly inhibited by addition of anti-TGF-beta1 antibody. ANG II also upregulated the expression of Fas, FasL, and Bax and downregulated the expression of Bcl-2 in GECs. These studies suggest that ANG II induces GEC apoptosis by a mechanism involving TGF-beta1 expression that may, importantly, contribute to the pathogenesis of glomerulosclerosis.

Role of p38 mitogen-activated protein kinase phosphorylation and Fas-Fas ligand interaction in morphine-induced macrophage apoptosis.

In this study, we evaluated the molecular mechanisms involved in morphine-induced macrophage apoptosis. Both morphine and TGF-beta promoted P38 mitogen-activated protein kinase (MAPK) phosphorylation, and this phosphorylation was inhibited by SB 202190 as well as by SB 203580. Anti-TGF-beta Ab as well as naltrexone (an opiate receptor antagonist) inhibited morphine-induced macrophage P38 MAPK phosphorylation. Anti-TGF-beta Ab also attenuated morphine-induced p53 as well as inducible NO synthase expression; in contrast, N(G)-nitro-L-arginine methyl ester, an inhibitor of NO synthase, inhibited morphine-induced P38 MAPK phosphorylation and Bax expression. Morphine also enhanced the expression of both Fas and Fas ligand (FasL), whereas anti-FasL Ab prevented morphine-induced macrophage apoptosis. Moreover, naltrexone inhibited morphine-induced FasL expression. In addition, macrophages either deficient in FasL or lacking p53 showed resistance to the effect of morphine. Inhibitors of both caspase-8 and caspase-9 partially prevented the apoptotic effect of morphine on macrophages. In addition, caspase-3 inhibitor prevented morphine-induced macrophage apoptosis. These findings suggest that morphine-induced macrophage apoptosis proceeds through opiate receptors via P38 MAPK phosphorylation. Both TGF-beta and inducible NO synthase play an important role in morphine-induced downstream signaling, which seems to activate proteins involved in both extrinsic (Fas and FasL) and intrinsic (p53 and Bax) cell death pathways.

HIV-1 gp120-induced tubular epithelial cell apoptosis is mediated through p38-MAPK phosphorylation.

BACKGROUND: HIV-associated nephropathy is accompanied by significant tubular alterations in the form of tubular cell proliferation, apoptosis, and microcystic dilatation. In the present study we evaluated the role of CD4 receptors in HIV-1-induced tubular cell injury. METHODS: To confirm the presence of CD4 receptors in tubular cells, immunocytochemical, Western and Northern blot studies were carried out. To determine the downstream effect of CD4 and gp120 interaction, we evaluated the effect of gp120 on tubular cell p38 mitogen-activated protein kinase (MAPK) activity and phosphorylation. To establish causal relationships between gp120, CD4, and p38 MAPK pathways, we studied the effect of anti-CD4 antibody and SB 202190 (an inhibitor of p38 MAPK) on gp120-induced tubular cell apoptosis. RESULTS: Proximal tubular cells in culture as well as in intact tissue showed expression of CD4 (immunocytochemical and Western blot studies). Cultured tubular cells also showed mRNA expression for CD4 (Northern blot studies). Gp120, at concentrations of 10-100 ng/ ml, triggered tubular cell apoptosis; however, this effect of gp120 was inhibited by anti-CD4 antibody. SB 202190 also inhibited gp120-induced tubular cell apoptosis. In addition, gp120 promoted tubular cell p38 MAPK phosphorylation in a time- and dose- dependent manner. CONCLUSION: Gp120 through interaction with CD4 triggers tubular cell apoptosis. This effect of gp120 on tubular cells is mediated through phosphorylation of p38 MAPK.