title: Integrin-regulated secretion of interleukin 4: A novel pathway of mechanotransduction in human articular chondrocytes.
abstract: Chondrocyte function is regulated partly by mechanical stimulation. Optimal mechanical stimulation maintains articular cartilage integrity, whereas abnormal mechanical stimulation results in development and progression of osteoarthritis (OA). The responses of signal transduction pathways in human articular chondrocytes (HAC) to mechanical stimuli remain unclear. Previous work has shown the involvement of integrins and integrin-associated signaling pathways in activation of plasma membrane apamin-sensitive Ca2+-activated K+ channels that results in membrane hyperpolarization of HAC after 0. 33 Hz cyclical mechanical stimulation. To further investigate mechanotransduction pathways in HAC and show that the hyperpolarization response to mechanical stimulation is a result of an integrin-dependent release of a transferable secreted factor, we used this response. Neutralizing antibodies to interleukin 4 (IL-4) and IL-4 receptor alpha inhibit mechanically induced membrane hyperpolarization and anti-IL-4 antibodies neutralize the hyperpolarizing activity of medium from mechanically stimulated cells. Antibodies to interleukin 1beta (IL-1beta) and cytokine receptors, interleukin 1 receptor type I and the common gamma chain/CD132 (gamma) have no effect on me- chanically induced membrane hyperpolarization. Chondrocytes from IL-4 knockout mice fail to show a membrane hyperpolarization response to cyclical mechanical stimulation. Mechanically induced release of the chondroprotective cytokine IL-4 from HAC with subsequent autocrine/paracrine activity is likely to be an important regulatory pathway in the maintenance of articular cartilage structure and function. Finally, dysfunction of this pathway may be implicated in OA.
authors: Department of Pathology, University of Edinburgh Medical School, Edinburgh, United Kingdom EH8 9AG.
authors: S J
authors: SJ
authors: Millward-Sadler
authors: M O
authors: MO
authors: Wright
authors: H
authors: H
authors: Lee
authors: K
authors: K
authors: Nishida
authors: H
authors: H
authors: Caldwell
authors: G
authors: G
authors: Nuki
authors: D M
authors: DM
authors: Salter
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D001030:Apamin / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002358:Cartilage, Articular / Q000166:cytology / Q000502:physiology*; D005260:Female; D005444:Flunarizine / Q000494:pharmacology; D005682:Gadolinium / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D006801:Humans; D019012:Integrin beta1 / Q000502:physiology; D015847:Interleukin-4 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D009355:Neomycin / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D015221:Potassium Channels / Q000187:drug effects; D019948:Receptors, Interleukin-4 / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D013314:Stress, Mechanical; D010738:Type C Phospholipases / Q000502:physiology
chemical_list: D019012:Integrin beta1; D015221:Potassium Channels; D019948:Receptors, Interleukin-4; D015847:Interleukin-4; D001030:Apamin; D005682:Gadolinium; D019833:Genistein; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D009355:Neomycin; D005444:Flunarizine; D002118:Calcium