BET bromodomain inhibitors show anti-papillomavirus activity in vitro and block CRPV wart growth in vivo.

The DNA papillomaviruses infect squamous epithelium and can cause persistent, benign and sometimes malignant hyperproliferative lesions. Effective antiviral drugs to treat human papillomavirus (HPV) infection are lacking and here we investigate the anti-papillomavirus activity of novel epigenetic targeting drugs, BET bromodomain inhibitors. Bromodomain and Extra-Terminal domain (BET) proteins are host proteins which regulate gene transcription, they bind acetylated lysine residues in histones and non-histone proteins via bromodomains, functioning as scaffold proteins in the formation of transcriptional complexes at gene regulatory regions. The BET protein BRD4 has been shown to be involved in the papillomavirus life cycle, as a co-factor for viral E2 and also mediating viral partitioning in some virus types. We set out to study the activity of small molecule BET bromodomain inhibitors in models of papillomavirus infection. Several BET inhibitors reduced HPV11 E1ˆE4 mRNA expression in vitro and topical therapeutic administration of an exemplar compound I-BET762, abrogated CRPV cutaneous wart growth in rabbits, demonstrating translation of anti-viral effects to efficacy in vivo. Additionally I-BET762 markedly reduced viability of HPV16 infected W12 cells compared to non-infected C33A cells. The molecular mechanism for the cytotoxicity to W12 cells is unknown but may be through blocking viral-dependent cell-survival factors. We conclude that these effects, across multiple papillomavirus types and in vivo, highlight the potential to target BET bromodomains to treat HPV infection.

Spatial separation of endothelial small- and intermediate-conductance calcium-activated potassium channels (K(Ca)) and connexins: possible relationship to vasodilator function?

Activation of endothelial cell small- (S) and intermediate- (I) conductance calcium-activated potassium channels (K(Ca)) and current or molecular transfer via myoendothelial gap junctions underlies endothelium-derived hyperpolarization leading to vasodilation. The mechanism underlying the K(Ca) component of vasodilator activity and the characteristics of gap junctions are targets for the selective control of vascular function. In the rat mesenteric artery, where myoendothelial gap junctions and connexin (Cx) 40 are critical for the transmission of the endothelial cell hyperpolarization to the smooth muscle, SK(Ca) and IK(Ca) provide different facets of the endothelium-derived hyperpolarization response, being critical for the hyperpolarization and repolarization phases, respectively. The present study addressed the question of whether this functional separation of responses may be related to the spatial localization of the associated channels? The distribution of endothelial SK(Ca) and IK(Ca) and Cx subtype(s) were examined in the rat mesenteric artery using conventional confocal and high-resolution ultrastructural immunohistochemistry. At the internal elastic lamina-smooth muscle cell interface at internal elastic lamina holes (as potential myoendothelial gap junction sites), strong punctate IK(Ca), Cx37 and Cx40 expression was present. SK(Ca), Cx37, Cx40 and Cx43 were localized to adjacent endothelial cell gap junctions. High-resolution immunohistochemistry demonstrated IK(Ca) and Cx37-conjugated gold to myoendothelial gap junction-associated endothelial cell projections. Clear co-localization of K(Ca) and Cxs suggests a causal relationship between their activity and the previously described differential functional activation of SK(Ca) and IK(Ca). Such precise localizations may represent a selective target for control of vasodilator function and vascular tone.