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The burden of antibiotic resistance necessitates a continued search for new antimicrobials. We evaluated the antimicrobial activities of novel benzothiazoles synthesized by our group. Antibacterial activity was evaluated in vitro in Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, while the antifungal activity was tested in Candida albicans and Aspergillus niger, and expressed as the minimum inhibitory concentration (MIC; µg/mL). MIC values of benzothiazole compounds ranged from 25 to 200 µg/mL. Compounds 3 and 4 gave high antibacterial and moderate antifungal activities, while 10 and 12 showed moderate activity against all tested organisms. In addition, some benzothiazole compounds significantly suppressed the activity of Escherichia coli dihydroorotase and inhibited the dimorphic transition of Candida albicans. Moreover, the active benzothiazole compounds induced DNA and protein leakage in Aspergillus niger spores. Molecular interactions of benzothiazole derivatives with dihydroorotase revealed the formation of hydrogen bonds with the active site residues LEU222 or ASN44. Strong hydrophobic interactions of the bulky thiazole and naphthalene rings at the entrance to the active site might interfere with the access of substrates to their binding sites, which results in dihydroorotase inhibition. Thus, inhibition of dihydroorotase might contribute to the observed antimicrobial actions of these compounds.

BACKGROUND AND PURPOSETransient receptor potential vanilloid-4 (TRPV4) is a calcium-permeant ion channel that is known to affect vascular function. The ability of TRPV4 to cause a vasoconstriction in blood vessels has not yet been mechanistically examined. Further in neuronal cells, TRPV4 signalling can be potentiated by GPCR activation. Thus, we studied the mechanisms underlying the vascular contractile action of TRPV4 and the GPCR-mediated potentiation of such vasoconstriction, both of which are as yet unappreciated aspects of TRPV4 function. EXPERIMENTAL APPROACHThe mechanisms of TRPV4-dependent regulation of vascular tone in isolated mouse aortae were studied using wire myography. TRPV4-dependent calcium signalling and prostanoid production was studied in cultured human umbilical vein endothelial cells (HUVECs). KEY RESULTSIn addition to the well-documented vasorelaxation response triggered by TRPV4 activation, we report here a TRPV4-triggered vasoconstriction in the mouse aorta that involves a COX-generated Tx receptor (TP) agonist that acts in a MAPK and Src kinase signalling dependent manner. This constriction is potentiated by activation of the GPCRs for angiotensin (AT1 receptors) or proteinases (PAR1 and PAR2) via transactivation of the EGF receptor and a process involving PKC. TRPV4-dependent vascular contraction can be blocked by COX inhibitors or with TP antagonists. Further, TRPV4 activation in HUVECs stimulated Tx release as detected by an ELISA. CONCLUSION AND IMPLICATIONSWe conclude that the GPCR potentiation of TRPV4 action and TRPV4-dependent Tx receptor activation are important regulators of vascular function and could be therapeutically targeted in vascular diseases. IntroductionThe transient receptor potential (TRP) superfamily comprises six families of polymodally activated non-selective cation channels (Clapham, 2003). The vanilloid family member TRPV4 was identified originally as a channel activated by hypotonic cell swelling (Liedtke et al., 2000;Peng and Hediger, 2002). Further studies in knockout mice have established the TRPV4 channel as an osmotic sensor in the CNS (Liedtke and Friedman, 2003). However, subsequent studies have also identified remarkable gating promiscuity with other TRPV4 channel activators including vascular shear stress (Gao et al., 2003;Wu et al., 2007), the phorbol-ester, 4-phorbol 12,13-didecanoate (4α-PDD; Watanabe et al., 2002a), temperature (Guler et al., 2002;Watanabe et al., 2002b), pressure (Suzuki et al., 2003) and low pH (Suzuki et al., 2003). TRPV4 channels are also triggered by anandamide and arachidonic acid subsequent to their P450-epoxygenase-dependent metabolism to the agonist, 5′,6′-epoxyeicosatrienoic acid (Watanabe et al., 2003), which can have antihypertensive activity. Pharmacologically, TRPV4 channels can be activated selectively with the synthetic agonist GSK1016790A (GSK101; Thorneloe et al., 2008;Willette et al., 2008). TRPV4 knockout mice have no overt malformations but have impaired hearing (Tabuchi et al., 2005) and osmoregulation (Li...