Long-term treatment with the streptococcal exotoxin streptolysin O inhibits vascular smooth muscle contraction by inducing iNOS expression in endothelial cells.

Streptolysin O (SLO), a bacterial toxin produced by common hemolytic streptococci, including and resident microbiota, may be associated with inflammation in the cardiovascular system. We previously reported that short-term treatment with SLO at relatively high concentrations (10-1000 ng/mL) diminished acetylcholine-induced, endothelial-dependent relaxation in a concentration-dependent manner. However, the vascular function effects of long-term exposure to SLO at lower concentrations are poorly understood.