Abstract. It has been demonstrated that 2,4,6-trimethyl-N-[3-(trifluoromethyl)phenyl]benzenesulfonamide (m-3M3FBS) activates phospholipase C (PLC) and stimulates apoptosis in smooth muscle cells, which may increase vascular reactivity. The primary aim of the present study was to evaluate the physiological effects of the direct stimulation of PLC by m-3M3FBS on vascular smooth muscle reactivity in arteries pre-treated with lipopolysaccharides (LPS) as a model of septic shock. Experiments were performed on isolated and perfused tail arteries of Wistar rats. The contraction force in the model was measured by assessing increases in perfusion pressure at a constant flow. Parameters describing the concentration-response curves (CRCs) obtained for phenylephrine and arginine-vasopressin in the presence of LPS confirmed a decrease in vessels reactivity. In comparison with the controls, m-3M3FBS treatment caused a significant increase in LPS-untreated as well as pre-treated arteries. Furthermore, in the presence of m-3M3FBS, calcium influx from intra-as well as extracellular calcium stores was significantly higher for LPS-untreated and pre-treated arteries. The results of the present study suggested that m-3M3FBS significantly increased the reactivity of vascular smooth muscle cells pre-treated with LPS by increasing the calcium influx from intra-and extracellular calcium stores. Further studies investigating this mechanism are required to evaluate whether this pathway may be a potential therapeutic strategy to treat sepsis.
IntroductionNitric oxide synthase (NOS) is an enzyme that catalyzes a reaction which generates nitric oxide in two different stages. The first stage is the oxidation of L-arginine to N-omega-hydroxy-L-arginine, which is degraded to L-citrulline in the second stage by NOS and oxygen, and accompanied by the release of nitric oxide from endothelial cells. There are three main types of nitric oxide synthase: NOS-1, -2 and -3. NOS-2 is localized mainly in macrophages, striated heart muscle, liver, vascular smooth muscle or vascular endothelium, and is activated as a response to infection, inflammation or sepsis following the release of pro-inflammatory cytokines, including interleukin (IL)-1, interferon (IFN)-γ or tumor necrosis factor (TNF)-α. The activated enzyme is active for a few h and synthesizes large quantities of nitric oxide (1). Nitric oxide produced by NOS-3 acts predominantly as a regulator of muscle tension in the local regulation of vascular tone. It is also a factor inhibiting the adhesion and aggregation of platelets, as well as angiogenesis. The role of NOS-3 as part of the initiation of NOS-2 activation in the presence of lipopolysaccharides (LPS) has been investigated over the past decade. The first study suggesting that NOS-3 has a role in the generation of NO-associated hyporeactivity during early sepsis was published in 2001 (2,3). A study on isolated animal tissue treated with short acting LPS (~5 h) showed a statistically significant inhibition of NOS-2 expression following blockad...