title: Matrix metalloproteinase-2-mediated inhibition of Na+-dependent Ca+ uptake by superoxide radicals (O2*-) in microsomes of pulmonary smooth muscle.
abstract: Treatment of microsomes (preferably enriched with endoplasmic reticulum) isolated from bovine pulmonary artery smooth muscle tissue with the O2*- -generating system (hypoxanthine (HPX) plus xanthine oxidase (XO)), markedly stimulated matrix metalloproteinase-2 (MMP-2) activity and also enhanced Ca2+ ATPase activity and ATP-dependent Ca2+ uptake. Pretreatment with superoxide dismutase (SOD) and tissue inhibitor of metalloproteinase (TIMP-2) (50 microg ml(-1)), preserved the increase in MMP-2 activity, Ca2+ ATPase activity and also ATP-dependent Ca2+ uptake in the microsomes. In contrast, Na+-dependent Ca2+ uptake in the microsomes was found to be inhibited by the O2*- - generating system. Additionally, O2*- -induced inhibition of Na+-dependent Ca2+ uptake was reversed by SOD and TIMP-2 (50 microg ml(-1)). Electron microscopy revealed that treatment with the O2*- -generating system did not cause any noticeable damage to the microsomes. O2*- -induced changes in MMP-2 activity, ATP-dependent Ca2+ uptake and Na+-dependent Ca2+ uptake, were not reversed upon pretreatment of the microsomes with a low dose (5 microg ml(-1)) of TIMP-2 which, on the contrary, reversed MMP-2 (1 microg ml(-1))-mediated alteration on these parameters. The inhibition of Na+-dependent Ca2+ uptake by O2*- and MMP-2, overpowered the stimulation of ATP-dependent Ca2+ uptake in the microsomes. Treatment of TIMP-2 (5 microg ml(-1)) with the O2*- -generating system abolished the inhibitory effect of TIMP-2 (5 microg ml(-1)) on MMP-2 (1 microg ml(-1)) (measured by (14)C-gelatin degradation). Overall, the present study suggests that O2*- inactivated TIMP-2, the ambient inhibitor of MMP-2, leading to activation of the ambient proteinase, MMP-2, which subsequently stimulated Ca2+ ATPase activity and ATP-dependent Ca2+ uptake, but inhibited Na+-dependent Ca2+ uptake, resulting in a marked decrease in Ca2+ uptake in the smooth muscle microsomes.
authors.affiliation: Department of Biochemistry and Biophysics, University of Kalyani, Kalyani 741235, West Bengal, India.
authors.forename: Amritlal
authors.initials: A
authors.lastname: Mandal
authors.forename: Tapati
authors.initials: T
authors.lastname: Chakraborti
authors.forename: Sudip
authors.initials: S
authors.lastname: Das
authors.forename: Biswarup
authors.initials: B
authors.lastname: Ghosh
authors.forename: Amarnath
authors.initials: A
authors.lastname: Ghosh
authors.forename: Sajal
authors.initials: S
authors.lastname: Chakraborti
mesh_terms: D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002417:Cattle; D020778:Matrix Metalloproteinase 2 / Q000502:physiology*; D008861:Microsomes / Q000737:chemistry / Q000201:enzymology; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000201:enzymology*; D011651:Pulmonary Artery / Q000201:enzymology* / Q000378:metabolism; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D013482:Superoxide Dismutase / Q000378:metabolism; D013481:Superoxides / Q000378:metabolism*
chemical_list: D019831:Sodium-Calcium Exchanger; D013481:Superoxides; D013482:Superoxide Dismutase; D020778:Matrix Metalloproteinase 2; D000252:Calcium-Transporting ATPases