Substance P involvement in the interaction between Streptococcus mutans and human aortic endothelial cells

Streptococcus mutans, a causative organism of dental caries, has also been implicated in the pathogenesis of cardiovascular disease (CVD). Substance P (SP) involvement in physiological and pathological processes within the cardiovascular system is currently the foci of research. The role of SP in modulating the human aortic endothelial cells (HAECs) response to S. mutans within the context of CVD pathogenesis has not been examined. This study aimed to investigate SP expression in S. mutans-stimulated HAECs and to clarify the role of SP in the interaction between S. mutans and HAECs, considering its cooperative action with an innate immune factor DMBT1.

HAECs were stimulated with S. mutans strains. SP expression was analyzed by dot blot assay and RT-PCR. S. mutans binding to SP was determined using ELISA. S. mutans aggregation was evaluated by monitoring decrease in optical density and phase-contrast microscopy. Effects of SP and/or DMBT1 on the interaction between S. mutans and HAECs were examined by invasion assay, cytokine assay, and cytotoxicity assay.

All tested S. mutans strains induced SP production in HAECs. S. mutans bound directly to SP. SP agglutinated S. mutans and pronounced aggregation was induced by SP when used with DMBT1. SP reduced S. mutans invasion of HAECs, suppressed S. mutans-induced cytokine production in HAECs, and decreased S. mutans-mediated cytotoxicity to HAECs. These inhibitory effects of SP were further enhanced by DMBT1.

These findings suggest that SP, acting in concert with DMBT1, exerts a protective role against S. mutans-induced CVD processes in HAECs.