We exploited leukocyte-endothelial cell adhesion chemistry to generate biodegradable particles that exhibit highly selective accumulation on inflamed endothelium in vitro and in vivo. Leukocyte-endothelial cell adhesive particles exhibit up to 15-fold higher adhesion to inflamed endothelium, relative to noninflamed endothelium, under in vitro flow conditions similar to that present in blood vessels, a 6-fold higher adhesion to cytokine inflamed endothelium relative to non-cytokine-treated endothelium in vivo, and a 10-fold enhancement in adhesion to trauma-induced inflamed endothelium in vivo due to the addition of a targeting ligand. The leukocyte-inspired particles have adhesion efficiencies similar to that of leukocytes and were shown to target each of the major inducible endothelial cell adhesion molecules (E-selectin, P-selectin, vascular cell adhesion molecule 1, and intercellular adhesion molecule 1) that are up-regulated at sites of pathological inflammation. The potential for targeted drug delivery to inflamed endothelium has significant implications for the improved treatment of an array of pathologies, including cardiovascular disease, arthritis, inflammatory bowel disease, and cancer.

Rationale T-type (CaV3.1/CaV3.2) Ca2+ channels are expressed in rat cerebral arterial smooth muscle. Although present, their functional significance remains uncertain with findings pointing to a variety of roles. Objective This study tested whether CaV3.2 channels mediate a negative feedback response by triggering Ca2+ sparks, discrete events that initiate arterial hyperpolarization by activating large-conductance Ca2+-activated K+ channels. Methods and Results Micromolar Ni2+, an agent that selectively blocks CaV3.2 but not CaV1.2/CaV3.1, was first shown to depolarize/constrict pressurized rat cerebral arteries; no effect was observed in CaV3.2−/− arteries. Structural analysis using 3-dimensional tomography, immunolabeling, and a proximity ligation assay next revealed the existence of microdomains in cerebral arterial smooth muscle which comprised sarcoplasmic reticulum and caveolae. Within these discrete structures, CaV3.2 and ryanodine receptor resided in close apposition to one another. Computational modeling revealed that Ca2+ influx through CaV3.2 could repetitively activate ryanodine receptor, inducing discrete Ca2+-induced Ca2+ release events in a voltage-dependent manner. In keeping with theoretical observations, rapid Ca2+ imaging and perforated patch clamp electrophysiology demonstrated that Ni2+ suppressed Ca2+ sparks and consequently spontaneous transient outward K+ currents, large-conductance Ca2+-activated K+ channel mediated events. Additional functional work on pressurized arteries noted that paxilline, a large-conductance Ca2+-activated K+ channel inhibitor, elicited arterial constriction equivalent, and not additive, to Ni2+. Key experiments on human cerebral arteries indicate that CaV3.2 is present and drives a comparable response to moderate constriction. Conclusions These findings indicate for the first time that CaV3.2 channels localize to discrete microdomains and drive ryanodine receptor–mediated Ca2+ sparks, enabling large-conductance Ca2+-activated K+ channel activation, hyperpolarization, and attenuation of cerebral arterial constriction.