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.

LC endocytosis leads to production of inflammatory cytokines through activation of NF-kappaB. This may be an important mechanism of chronic tubulointerstitial inflammation process commonly seen in multiple myeloma. These findings also point out a potential role by filterable low-molecular-weight proteins, like LCs, in PTC injury during all proteinuric diseases.

In this study, we evaluated the molecular mechanisms involved in morphine-induced macrophage apoptosis. Both morphine and TGF-β promoted P38 mitogen-activated protein kinase (MAPK) phosphorylation, and this phosphorylation was inhibited by SB 202190 as well as by SB 203580. Anti-TGF-β Ab as well as naltrexone (an opiate receptor antagonist) inhibited morphine-induced macrophage P38 MAPK phosphorylation. Anti-TGF-β Ab also attenuated morphine-induced p53 as well as inducible NO synthase expression; in contrast, NG-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-β 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.

Summary Laboratory and clinical reports indicate that opiate addicts are prone to infections. This effect of opiates is partly attributed to opiate‐induced macrophage (Mφ) apoptosis. In the present study, we evaluated the role of transforming growth factor‐β (TGF‐β) in morphine‐induced apoptosis of murine J774 cells and peritoneal Mφ. Mφ harvested from morphine‐treated mice showed greater (P < 0·0001) apoptosis when compared with control Mφ. Morphine also enhanced apoptosis of J774 cells and peritoneal Mφ. Anti‐TGF‐β antibody inhibited (P < 0·001) the morphine‐induced apoptosis in J774 cells (control 0·7 ± 0·4%; 10−6 m morphine 23·5 ± 0·7%; anti‐TGF‐β antibody (Ab) + 10−6 m morphine 8·1 ± 0·7%; apoptotic cells/field) and peritoneal Mφ (control 1·5 ± 0·9%; 10−6 m morphine 29·1 ± 1·4%; 10−6 m morphine + anti‐TGF‐β Ab 19·1 ± 1·8%; apoptotic cells/field). TGF‐β enhanced (P < 0·001) apoptosis of J774 cells and peritoneal Mφ. TGF‐β also promoted Mφ DNA fragmentation into integer multiples of 180 bp (ladder pattern). Immunocytochemical studies revealed that morphine enhanced the Mφ cytoplasmic content of TGF‐β. In addition, Western blotting showed increased production of TGF‐β by morphine‐treated J774 cells when compared with control cells. Morphine increased J774 cell expression of bax. Interestingly, morphine‐induced bax expression was inhibited by anti‐TGF‐β Ab. As both morphine‐induced J774 cell apoptosis and bax expression were inhibited by anti‐TGF‐β Ab, it appears that morphine‐induced J774 cell apoptosis may be mediated through the generation of TGF‐β.