NO inhibits stretch-induced MAPK activity by cytoskeletal disruption

Mesangial cells (MC) grown on extracellular matrix protein-coated plates an d exposed to cyclic strain/relaxation proliferate and produce extracellular matrix protein, providing an in vitro model of signaling in stretched MC, Intracellular transduction of mechanical strain involves mitogen-activated protein kinases, and we have shown that p42/44 mitogen-activated protein ki nase (extracellular signal-regulated kinase (ERK)) is activated by cyclic s train in MC,ln vivo studies show that increased production of nitric oxide (NO) in the remnant kidney limits glomerular injury without reducing glomer ular capillary pressure, and we have observed that NO attenuates stretch-in duced ERK activity in MC via generation of cyclic guanosine monophosphate ( cGMP), Accordingly, we sought to determine whether NO affects strain-induce d ERK activity after strain and how this is mediated. Strain-induced ERK ac tivity was dependent on time and magnitude of stretch and was maximal after 10 min at -27 kilopascals, Actin cytoskeleton disruption with cytochalasin D abrogated this. The non-metabolizable cGMP analogue 8-bromo cyclic GMP ( 8-Br-cGMP) dose-dependently attenuated strain-induced ERK activity. Cytoske letal stabilization with jas-plakinolide prevented this inhibitory effect o f 8-Br-cGMP, Cyclic strain increased nuclear translocation of phospho-ERK b y immunofluorescent microscopy, again attenuated by 8-Br-cGMP. Jasplakinoli de prevented the inhibitory effect of 8-Br-cGMP on activated ERK nuclear tr anslocation after strain. Strain increased ERK-dependent AP-1 nuclear prote in binding, which was attenuated by cytochalasin D and 8-Br-cGMP, These dat a indicate that cGMP can inhibit cyclic strain-induced ERK activity, nuclea r translocation, and AP-1 nuclear protein binding. Cytoskeletal disruption leads to the same effect, whereas cytoskeleton stabilization reverses the e ffect of 8-Br-cGMP, Thus, NO inhibits strain-induced ERK activity by cytosk eletal destabilization.