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C Inhibition (c + inhibition)
Kinds of C Inhibition Selected AbstractsInhibition of Lamin A/C Attenuates Osteoblast Differentiation and Enhances RANKL-Dependent Osteoclastogenesis,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 1 2009Martina Rauner Abstract Age-related osteoporosis is characterized by low bone mass, poor bone quality, and impaired osteoblastogenesis. Recently, the Hutchinson-Gilford progeria syndrome (HGPS), a disease of accelerated aging and premature osteoporosis, has been linked to mutations in the gene encoding for the nuclear lamina protein lamin A/C. Here, we tested the hypothesis that inhibition of lamin A/C in osteoblastic lineage cells impairs osteoblastogenesis and accelerates osteoclastogenesis. Lamin A/C was knocked-down with small interfering (si)RNA molecules in human bone marrow stromal cells (BMSCs) differentiating toward osteoblasts. Lamin A/C knockdown led to an inhibition of osteoblast proliferation by 26% and impaired osteoblast differentiation by 48% based on the formation of mineralized matrix. In mature osteoblasts, expression levels of runx2 and osteocalcin mRNA were decreased by lamin A/C knockdown by 44% and 78%, respectively. Furthermore, protein analysis showed that osteoblasts with diminished levels of lamin A/C also secreted less osteocalcin and expressed a lower alkaline phosphatase activity (,50%). Lamin A/C inhibition increased RANKL mRNA and protein levels, whereas osteoprotegerin (OPG) expression was decreased, resulting in an increased RANKL/OPG ratio and an enhanced ability to support osteoclastogenesis, as reflected by a 34% increase of TRACP+ multinucleated cells. Our data indicate that lamin A/C is essential for proper osteoblastogenesis. Moreover, lack of lamin A/C favors an osteoclastogenic milieu and contributes to enhanced osteoclastogenesis. [source] Characterization of p21Ras -mediated apoptosis induced by protein kinase C inhibition and application to human tumor cell linesJOURNAL OF CELLULAR PHYSIOLOGY, Issue 2 2004James S. Liou Suppression of PKC activity can selectively induce apoptosis in cells expressing a constitutively activated p21Ras protein. We demonstrate that continued expression of p21Ras activity is required in PKC-mediated apoptosis because farnesyltransferase inhibitors abrogated the loss of viability in p21Ras -transformed cells occurring following PKC inhibition. Studies utilizing gene transfer or viral vectors demonstrate that transient expression of oncogenic p21Ras activity is sufficient for induction of apoptosis by PKC inhibition, whereas physiologic activation of p21Ras by growth factor is not sufficient to induce apoptosis. Mechanistically, the p21Ras -mediated apoptosis induced by PKC inhibition is dependent upon mitochondrial dysregulation, with a concurrent loss of mitochondrial membrane potential (,m). Cyclosporine A, which prevented the loss of ,m, also inhibited HMG-induced DNA fragmentation in cells expressing an activated p21Ras. Induction of apoptosis by PKC inhibition in human tumors with oncogenic p21Ras mutations was demonstrated. Inhibition of PKC caused increased apoptosis in MIA-PaCa-2, a human pancreatic tumor line containing a mutated Ki,ras allele, when compared to HS766T, a human pancreatic tumor line with normal Ki,ras alleles. Furthermore, PKC inhibition induced apoptosis in HCT116, a human colorectal tumor line containing an oncogenic Ki,ras allele but not in a subline (Hke3) in which the mutated Ki,ras allele had been disrupted. The PKC inhibitor 1- O -hexadecyl-2- O -methyl-rac-glycerol (HMG), significantly reduced p21Ras -mediated tumor growth in vivo in a nude mouse MIA-PaCa-2 xenograft model. Collectively these studies suggest the therapeutic feasibility of targeting PKC activity in tumors expressing an activated p21Ras oncoprotein. J. Cell. Physiol. 198: 277,294, 2004. © 2003 Wiley-Liss, Inc. [source] Prostanoids induce egr1 gene expression in cementoblastic OCCM cellsJOURNAL OF PERIODONTAL RESEARCH, Issue 5 2007L. Pham Background and Objective:, Prostanoids that activate protein kinase C signaling are potent anabolic stimulators of cementoblastic OCCM cells. Using cDNA subtractive hybridization, we identified early growth response gene-1 (egr1) as a prostanoid-induced gene. Egr1, a zinc-finger transcription factor expressed during tooth development, regulates cell growth and differentiation. We hypothesize that Egr1 may mediate part of the prostanoid-induced anabolic effect in cementoblasts. Our objective was to characterize prostanoid-induced egr1 gene expression in OCCM cells. Material and Methods:, Total RNA and proteins were assayed by northern blot and western immunoblot assays. Results:, Prostaglandin E2 -, prostaglandin F2, - and fluprostenol-induced egr1 mRNA levels peaked at 0.5 h and returned to baseline by 4 h. Prostaglandin F2, and fluprostenol more potently induced egr1 compared with prostaglandin E2. The phorbol ester, phorbol 12-myristate 13-acetate, which activates protein kinase C signaling, induced egr1 mRNA levels 66-fold over the control, whereas forskolin (a cAMP-protein kinase A activator) and ionomycin (a calcium activator) had no effect. Protein kinase C inhibition significantly inhibited prostaglandin E2 -, prostaglandin F2, - and fluprostenol-induced egr1 mRNA levels. Finally, prostanoids maximally induced Egr1 protein at 1 h. Conclusion:,egr1 is a primary response gene induced by prostaglandin E2, prostaglandin F2, and fluprostenol in OCCM cells through protein kinase C signaling, suggesting that Egr1 may be a key mediator of anabolic responses in cementoblasts. Cementum is vital for periodontal organ maintenance and regeneration. Periodontal ligament fibers (Sharpey's fibers) insert into bone and cementum, thereby supporting the tooth in the alveolus (1). If the periodontal organ is lost, its regeneration requires cementoblast differentiation in order to form new cementum for periodontal ligament fiber insertion. Early attempts to regenerate cementum have proven difficult and rarely generate sufficient tissue (2). A better understanding of the molecular and cellular regulators that promote cementoblast differentiation is critical for developing targeted periodontal regeneration. [source] Protein kinase C inhibition in diabetic retinopathy and microvascular diseasePRACTICAL DIABETES INTERNATIONAL (INCORPORATING CARDIABETES), Issue 5 2007Dr C Walton FRCP Abstract Protein kinase C (PKC) activation by hyperglycaemia may play an important role in the evolution of diabetic retinopathy and other microvascular complications. The PKC-, inhibitor ruboxistaurin belongs to a new class of drugs and has been studied in several clinical trials in microvascular disease, the outcomes of which are described in this review. Ruboxistaurin exhibits promise as the first oral treatment shown to reduce visual loss and the need for laser treatment for macular oedema in patients with moderate to severe non-proliferative diabetic retinopathy. Copyright © 2007 John Wiley & Sons. [source] Efficacy of a protein kinase C inhibitor (tamoxifen) in the treatment of acute mania: a pilot studyBIPOLAR DISORDERS, Issue 6 2007Carlos A Zarate Jr Objectives:, Considerable preclinical biochemical and behavioral data suggest that protein kinase C inhibition would bring about antimanic effects. Notably, the structurally highly dissimilar antimanic agents lithium and valproate, when administered in therapeutically relevant paradigms, attenuate protein kinase C inhibition function. There is currently only one relatively selective protein kinase C inhibitor that crosses the blood,brain barrier available for human use , tamoxifen. Our group recently conducted a single-blind study with tamoxifen in acute mania and found that it significantly decreased manic symptoms within a short period of time (3,7 days). In this study, we investigated whether antimanic effects can be achieved with a protein kinase C inhibitor in subjects with mania. Methods:, In a double-blind, placebo-controlled study, 16 subjects with bipolar disorder, manic or mixed, with or without psychotic features, were randomly assigned to receive tamoxifen (20,140 mg/day; n = 8) or placebo (n = 8) for three weeks. Primary efficacy was assessed by the Young Mania Rating Scale. Results:, Subjects on tamoxifen showed significant improvement in mania compared to placebo as early as five days, an effect that remained significant throughout the three-week trial. The effect size for the drug difference was very large (d = 1.08, 95% confidence interval 0.45,1.71) after three weeks (p = 0.001). At study endpoint, response rates were 63% for tamoxifen and 13% for placebo (p = 0.12). Conclusions:, Antimanic effects resulted from a protein kinase C inhibitor; onset occurred within five days. Large, controlled studies with selective protein kinase C inhibitors in acute mania are warranted. [source] | ||||||||||