Showing papers by "Alok C. Bharti published in 2004"

Curcumin (Diferuloylmethane) Inhibits Receptor Activator of NF-κB Ligand-Induced NF-κB Activation in Osteoclast Precursors and Suppresses Osteoclastogenesis

Abstract: Numerous studies have indicated that inflammatory cytokines play a major role in osteoclastogenesis, leading to the bone resorption that is frequently associated with cancers and other diseases. Gene deletion studies have shown that receptor activator of NF-kappaB ligand (RANKL) is one of the critical mediators of osteoclastogenesis. How RANKL mediates osteoclastogenesis is not fully understood, but an agent that suppresses RANKL signaling has potential to inhibit osteoclastogenesis. In this report, we examine the ability of curcumin (diferuloylmethane), a pigment derived from turmeric, to suppress RANKL signaling and osteoclastogenesis in RAW 264.7 cells, a murine monocytic cell line. Treatment of these cells with RANKL activated NF-kappaB, and preexposure of the cells to curcumin completely suppressed RANKL-induced NF-kappaB activation. Curcumin inhibited the pathway leading from activation of IkappaBalpha kinase and IkappaBalpha phosphorylation to IkappaBalpha degradation. RANKL induced osteoclastogenesis in these monocytic cells, and curcumin inhibited both RANKL- and TNF-induced osteoclastogenesis and pit formation. Curcumin suppressed osteoclastogenesis maximally when added together with RANKL and minimally when it was added 2 days after RANKL. Whether curcumin inhibits RANKL-induced osteoclastogenesis through suppression of NF-kappaB was also confirmed independently, as RANKL failed to activate NF-kappaB in cells stably transfected with a dominant-negative form of IkappaBalpha and concurrently failed to induce osteoclastogenesis. Thus overall these results indicate that RANKL induces osteoclastogenesis through the activation of NF-kappaB, and treatment with curcumin inhibits both the NF-kappaB activation and osteoclastogenesis induced by RANKL.

Induction of cell cycle arrest and apoptosis by the proteasome inhibitor PS-341 in Hodgkin disease cell lines is independent of inhibitor of nuclear factor-κB mutations or activation of the CD30, CD40, and RANK receptors

Abstract: Purpose: The malignant Hodgkin and Reed-Sternberg cells of Hodgkin disease (HD) are known to constitutively express high levels of activated nuclear factor κB (NF-κB), which plays an important role in their survival. The proteasome inhibitor PS-341 has been recently shown to modulate tumor cell proliferation and survival by inhibiting NF-κB and modulating critical cellular regulatory proteins, but its activity in cells carrying IκBα gene mutations has not been reported previously. Experimental Design: The activity of PS-341 in four well-characterized, HD-derived cell lines. Cell proliferation and apoptosis were determined by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfonyl)-2 H -tetrazolium (MTS) and Annexin-V binding methods, respectively. Cell cycle analysis was determined by flow cytometry. Intracellular protein levels were determined by Western blot. Results: PS-341 demonstrated a strong antiproliferative activity, which was irrespective of the status of mutations in IκBα and even the presence of CD30, CD40, or RANK receptor activation. This effect was attributable to the induction of apoptosis and cell cycle arrest at the G 2 -M phase. PS-341 not only inhibited nuclear localization of NF-κB but also activated the caspase cascade, increased p21 and Bax levels, and decreased Bcl-2 levels. Furthermore, PS-341 enhanced the effect of gemcitabine chemotherapy and potentiated the effect of tumor necrosis factor-related apoptosis-inducing ligand/APO2L and two agonistic antibodies to tumor necrosis factor-related apoptosis-inducing ligand death receptors R1 and R2. Conclusions: The in vitro activity of PS-341 against HD-derived cell lines suggests that PS-341 may have a therapeutic value for the treatment of HD.

Ranking the role of RANK ligand in apoptosis

Abstract: Many members of tumor necrosis factor (TNF) superfamily are characterized by their ability to induce apoptosis once they bind in a homotrimeric manner to their cognate receptors. The receptor activator of nuclear factor-κB ligand (RANKL), a member of the TNF superfamily identified seven years ago, was originally described as a factor that induced osteoclastogenesis and dendritic cell survival. Recent observations indicate that a growth inhibitory and apoptosis-inducing activity is associated with RANKL, as is the case for other members of TNF superfamily. This review describes the possible mechanisms of induction of RANKL-induced growth inhibition/apoptosis and discusses the role of various components in RANKL-signaling in this phenomenon, including TNF receptor-associated factor (TRAF)-6, nuclear factor-κB (NF-κB), c-jun N-terminal kinase JNK), phosphatidylinositol-3 kinase (PI3K).