Involvement of Calmodulin Kinase II in the Action of Sulphur Mustard on the Contraction of Vascular Smooth Muscle

Abstract

Sulphur mustard (SM) is an alkylating agent whose mechanism is not fully understood. To investigate the early action of SM, we examined the effect of SM on contraction of vascular smooth muscles. Phenylephrine (PE)-induced contraction was reduced by SM, but only marginally by 70 mM KCl -. Additional reduction was induced by nifedipine in SM-treated arteries. In the absence of extracellular Ca 2+ , contraction of arteries by PE was reduced, which was fully recovered by addition of 2 mM Ca 2+ . However, recovery was attenuated by pre-treatment with SM. The effect of SM on contraction by PE was not influenced by pre-and post-treatment with Phorbol 12, 13-dibutyrate. Calmodulin kinase II (CaMKII) was implicated as being responsible for the action of SM, because the contractile mechanisms of vascular smooth muscle via both Ca 2+ -calmodulin-myosin light chain kinase axis and protein kinase C-proline-rich tyrosine kinase axis were not related to the action of SM. Elevation of phosphorylated CaMKII level by Ionomycin or PE was attenuated by treatment of SM on western blot. CaMKII may be a candidate target molecule of SM in early stage contraction of vascular smooth muscle.Sulphur mustard (SM) is a vesicant with cytotoxic and carcinogenic effects. First synthesized over a century ago, SM has been used as a weapon in many conflicts, notably the Iran-Iraq War of the 1980s, in which tens of thousands of people were affected [1]. The main target organs of SM are the skin, eyes and the respiratory system. At a low dose, its effects are restricted mainly to the skin in the form of erythema, itching and an aversion to touch. At higher levels of SM, skin damage is severe and includes blistering, necrosis and inflammation, which can increase the risk of infection [1,2]. Exposure to very high concentrations of SM can cause irreparable skin damage and lethal respiratory failure. Treatments are only supportive.SM is a strong alkylating agent that causes DNA doublestrand breakage and carcinogenesis by mechanisms that are as yet not fully resolved. To repair SM-induced DNA damage, poly (ADP-ribose) polymerase (PARP) is activated, which leads to NAD+ depletion. Replenishment of NAD+ requires the consumption of ATP; exhaustion of whole ATP is lethal for cells [2,3]. Furthermore, proteolytic enzymes such as matrix metalloproteinase (MMP) are increased. MMP-2 and -9 are thought to be important in the blistering of skin because of their collagenase activity and because they both produce dermal-epidermal separation [4]. Increasing mitogen-activated protein kinase (MAPK) also has been reported; in particular, p38 is increased after SM exposure [3,5]. SM induces apoptosis through increased FasL expression and Ca 2+ level [3,6]. SM adducts various molecules such as DNA, RNA and protein, and stimulates production of reactive oxygen species and nitrogen oxygen species [3]. Accordingly, some antioxidants are candidates of treatment designed to relieve SM toxicity. SM-induced toxicity also involves inflammation, perhaps via the stimulat...

Involvement of inducible nitric oxide synthase in radiation-induced vascular endothelial damage

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