Trp-His, a vasorelaxant di-peptide, can inhibit extracellular Ca2+ entry to rat vascular smooth muscle cells through blockade of dihydropyridine-like L-type Ca2+ channels

Our previous findings regarding the biological activities of small peptides revealed that a di-peptide Trp-His (WH) could play a role in the prevention of vascular lesions including cell proliferation and atherosclerosis Its vasoprotective effects could be associated with suppression of the vasocontraction signaling cascade but the underlying mechanism(s) remains obscure In this study we attempted to elucidate the vasoprotective mechanism of WH in opposing the proliferation of rat vascular smooth muscle cells (VSMCs) In VSMCs from 8 week-old male Wistar rat thoracic aortae WH evoked a significant dose-dependent anti-proliferation effect without cytotoxicity In mitogen-stimulated cell experiments 300 mu M WH inhibited cytosolic Ca2+ elevation in VSMCs induced by 10 mu M angiotensin II (Ang II) Furthermore WH suppressed extracellular Ca2+ entry Into CaCl2-stimulated VSMCs The biological capacity of WH as an intracellular Ca2+ ([Ca2+](1)) suppressor was also proven when 50 mu M Bay K8644 was used to enhance Ca2+ entry via a voltage-dependent L-type Ca2+ channel (VDCC) and 300 mu M WH elicited a 23% reduction in [Ca2+](1) The absence of a reduction of the [Ca2+](1) by the mixture of tryptophan and histidine revealed the importance of the peptide backbone in the [Ca2+](1) reduction effect Furthermore the WH-induced [Ca2+](1) reduction was abolished by verapamil but not by nifedipine indicating that WH likely binds to an extracellular site of the VDCC at a site similar to that of the dihydropyridine type-Ca2+ channel blockers (C) 2010 Elsevier Inc All rights reserved