H2O2-induced Kinetic and Chemical Modifications of Smooth Muscle Myosin

Abstract

The effect of H 2 O 2 on smooth muscle heavy meromyosin (HMM) and subfragment 1 (S1) was examined. The number of molecules that retained the ability to bind ATP and the actinactivated rate of P i release were measured by single-turnover kinetics. H 2 O 2 treatment caused a decrease in HMM regulation from 800-to 27-fold. For unphosphorylated and phosphorylated heavy meromyosin and for S1, ϳ50% of the molecules lost the ability to bind to ATP. H 2 O 2 treatment in the presence of EDTA protected against ATPase inactivation and against the loss of total ATP binding. Inactivation of S1 versus time correlated to a loss of reactive thiols. Treatment of H 2 O 2 -inactivated phosphorylated HMM or S1 with dithiothreitol partially reactivated the ATPase but had no effect on total ATP binding. H 2 O 2 -inactivated S1 contained a prominent cross-link between the N-terminal 65-kDa and C-terminal 26-kDa heavy chain regions. Mass spectral studies revealed that at least seven thiols in the heavy chain and the essential light chain were oxidized to cysteic acid. In thiophosphorylated porcine tracheal muscle strips at pCa 9 ؉ 2.1 mM ATP, H 2 O 2 caused a ϳ50% decrease in the amplitude but did not alter the rate of force generation, suggesting that H 2 O 2 directly affects the force generating complex. Dithiothreitol treatment reversed the H 2 O 2 inhibition of the maximal force by ϳ50%. These data, when compared with the in vitro kinetic data, are consistent with a H 2 O 2 -induced loss of functional myosin heads in the muscle.Contraction of smooth muscle is controlled largely by phosphorylation of the 20-kDa myosin regulatory light chain (RLC), 2 resulting in the cyclic attachment and detachment of myosin to actin (cross-bridge cycling) and the hydrolysis of ATP by actin-activated myosin ATPase (1). The level of RLC phosphorylation depends on the balance between the activities of MLCK and SMM phosphatase. MLCK is primarily activated (through Ca 2ϩ -calmodulin) by an increase in [Ca 2ϩ ] i from intracellular stores or influx of extra-cellular Ca 2ϩ , whereas inhibition of myosin phosphatase, which contributes to the amount of force at a given [Ca 2ϩ ] i (Ca 2ϩ sensitivity), occurs through a receptor-G protein-catalyzed signal transduction cascade (2-5).Reactive oxygen species, such as H 2 O 2 , modulate smooth muscle contractility (6) and contribute to the severity of numerous diseases, including acute lung injury, asthma, pulmonary hypertension, ischemia-reperfusion, and arthritis (7). H 2 O 2 reversibly inhibits receptor agonist-induced contraction of both vascular (8 -10) and ASM (11-15).The mechanisms for H 2 O 2 inhibition of smooth muscle contraction are not well understood but have been proposed to involve effects on kinase-mediated signaling cascades, cytoskeletal effects, ionotropic effects, lipid oxidation, direct inhibitory effect on smooth muscle contractile proteins, and potentially confounding effects on epithelial cells (11)(12)(13)(14)(15)(16)(17)(18)(19)(20). In general, healthy smooth muscle is quite resis...

Functional, structural, and chemical changes in myosin associated with hydrogen peroxide treatment of skeletal muscle fibers

“…Oxidation of methionines by peroxide has been previously detected in isolated skeletal muscle actin (49,50), smooth muscle myosin subfragments (59), and calmodulin (26). Oxidation of cysteine residues has been detected in isolated myosin fragments treated in solution with peroxide (49,50,59) or peroxynitrite (86). In contrast, our study clearly showed that H 2 O 2 treatment of myosin in the muscle filament lattice does not affect myosin cysteines, particularly the most reactive, Cys707 (Fig.…”

“…Oxidation of methionines by peroxide has been previously detected in isolated skeletal muscle actin (49,50), smooth muscle myosin subfragments (59), and calmodulin (26). Oxidation of cysteine residues has been detected in isolated myosin fragments treated in solution with peroxide (49,50,59) or peroxynitrite (86).…”

“…H 2 O 2 is naturally produced in many tissues, including skeletal muscle. It is involved in multiple physiological processes necessary for normal functioning of cells (29, 69, 76), but it can also have deleterious effects and has been used to study the mechanism of cardiac and smooth muscle dysfunction (37,57,59,98).Previously reported physiological studies on the effects of H 2 O 2 on skeletal muscle contractility have been performed with a variety of muscles, such as permeabilized extensor digitorum longus (EDL) and soleus muscle from rat, intact fibers from mouse foot, and permeabilized rat diaphragm fibers (2, 14, 38, 61) We have selected as our model muscle permeabilized rabbit psoas muscle fibers because these fibers have been routinely used to determine molecular changes in myosin during muscle contraction (20, 55), and because permeabilization diminishes the number of possible targets of peroxide by removing soluble proteins and the membrane-based excitationcontraction system. The majority of proteins remaining in the permeabilized psoas are actin (22%) and myosin (43%) (99).…”

“…H 2 O 2 is naturally produced in many tissues, including skeletal muscle. It is involved in multiple physiological processes necessary for normal functioning of cells (29, 69, 76), but it can also have deleterious effects and has been used to study the mechanism of cardiac and smooth muscle dysfunction (37,57,59,98).…”

Prolonged NO treatment decreases α-adrenoreceptor agonist responsiveness in porcine pulmonary artery due to persistent soluble guanylyl cyclase activation

“…Possible mechanisms contributing to this include NO-induced reduction in contractile agonist responsiveness, decreased catecholamine bioavailability due to conversion to less active forms by NO (18,25) or superoxide (19), cGMP-independent effects on agonist-receptor coupling (26,27), and oxidative effects converging on contractile proteins (28,29). Endotoxin-mediated shock is associated with low peripheral vascular resistance resistant to agents such as norepinephrine and epinephrine (3,14,38), an effect that is variably reversible with nonspecific NOS inhibitors (10).…”