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Fluid shear stress inhibits TNF-alpha-induced apoptosis in osteoblasts: a role for fluid shear stress-induced activation of PI3-kinase and inhibition of caspase-3
External Online Source: doi:10.1002/jcp.10221
Author and Affiliation:
Pavalko, Fredrick M.(Indiana University School of Medicine, Department of Cellular and Integrative Physiology, Indianapolis, Indiana 46202, United States)
Gerard, Rita L.
Ponik, Suzanne M.
Gallagher, Patricia J.
Jin, Yijun
Norvell, Suzanne M.
Abstract: In bone, a large proportion of osteoblasts, the cells responsible for deposition of new bone, normally undergo programmed cell death (apoptosis). Because mechanical loading of bone increases the rate of new bone formation, we hypothesized that mechanical stimulation of osteoblasts might increase their survival. To test this hypothesis, we investigated the effects of fluid shear stress (FSS) on osteoblast apoptosis using three osteoblast cell types: primary rat calvarial osteoblasts (RCOB), MC3T3-E1 osteoblastic cells, and UMR106 osteosarcoma cells. Cells were treated with TNF-alpha in the presence of cyclohexamide (CHX) to rapidly induce apoptosis. Osteoblasts showed significant signs of apoptosis within 4-6 h of exposure to TNF-alpha and CHX, and application of FSS (12 dyne/cm(2)) significantly attenuated this TNF-alpha-induced apoptosis. FSS activated PI3-kinase signaling, induced phosphorylation of Akt, and inhibited TNF-alpha-induced activation of caspase-3. Inhibition of PI3-kinase, using LY294002, blocked the ability of FSS to rescue osteoblasts from TNF-alpha-induced apoptosis and blocked FSS-induced inhibition of caspase-3 activation in osteoblasts treated with TNF-alpha. LY294002 did not, however, prevent FSS-induced phosphorylation of Akt suggesting that activation of Akt alone is not sufficient to rescue cells from apoptosis. This result also suggests that FSS can activate Akt via a PI3-kinase-independent pathway. These studies demonstrate for the first time that application of FSS to osteoblasts in vitro results in inhibition of TNF-alpha-induced apoptosis through a mechanism involving activation of PI3-kinase signaling and inhibition of caspases. FSS-induced activation of PI3-kinase may promote cell survival through a mechanism that is distinct from the Akt-mediated survival pathway. Copyright 2002 Wiley-Liss, Inc.
Publication Date: Feb 01, 2003
Document ID:
20040087926
(Acquired Sep 07, 2004)
Subject Category: LIFE SCIENCES (GENERAL)
Document Type: Journal Article
Publication Information: Journal of cellular physiology; p. 194-205; (ISSN 0021-9541); Volume 194; 2
Publisher Information: United States
Contract/Grant/Task Num: AR45218; AR45831
Description: In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: APOPTOSIS; ENZYME ACTIVITY; ENZYMES; NECROSIS; OSTEOBLASTS; SHEAR STRESS; TUMORS; CELLS (BIOLOGY); CULTURED CELLS; ONCOGENES; PROTEINS; RATS; STRESSES; SURVIVAL
Other Descriptors: 1-PHOSPHATIDYLINOSITOL 3-KINASE/METABOLISM; APOPTOSIS/PHYSIOLOGY; CASPASES/ANTAGONISTS & INHIBITORS; OSTEOBLASTS/DRUG EFFECTS/PHYSIOLOGY; TUMOR NECROSIS FACTOR/PHARMACOLOGY; ANIMALS; CELL SURVIVAL/PHYSIOLOGY; CELLS, CULTURED; ENZYME ACTIVATION/PHYSIOLOGY; PROTO-ONCOGENE PROTEINS/PHYSIOLOGY; RATS; STRESS, MECHANICAL; SUPPORT, NON-U.S. GOV'T; SUPPORT, U.S. GOV'T, NON-P.H.S; SUPPORT, U.S. GOV'T, P.H.S; NASA DISCIPLINE CELL BIOLOGY; NON-NASA CENTER
Availability Source: Other Sources
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