Hydrogen sulphide-mediated vasodilatation involves the release of neurotransmitters from sensory nerves in pressurized mesenteric small arteries isolated from rats.

BACKGROUND AND PURPOSE: Hydrogen sulphide (H(2)S) is a gas that has recently been shown to have biological activity. In the majority of blood vessels studied so far, H(2)S has been shown to cause vasorelaxation, although contractile responses have been reported. In the present study, we have made a pharmacological assessment of the effects of H(2)S in mesenteric small arteries isolated from rats. EXPERIMENTAL APPROACH: Rat mesenteric small arteries were studied using pressure myography. In pressurised arteries, responses were obtained to the H(2)S donor, sodium hydrogen sulphide (NaHS), in the absence and presence of the NOS inhibitor L-NAME, raised extracellular potassium, the K(ATP) channel inhibitor glibenclamide, the Cl- channel blockers DIDS, NPPB and A9C, the TRPV1 receptor desensitizing agent, capsaicin, the CGRP antagonist, olcegepant, the TRPV1 channel blocker capsazepine and the TRPA1 channel blocker HC-030031. KEY RESULTS: NaHS produced a vasodilator response in rat mesenteric small arteries held at 90 mmHg. Responses to NaHS were not reproducible. Neither, glibenclamide nor, L-NAME inhibited responses to NaHS. DIDS abolished vasodilator responses to NaHS, but these were unaffected by the chloride channel blockers, NPPB and A9C. Responses to NaHS were attenuated after capsaicin pre-treatment, by a CGRP receptor antagonist and an inhibitor of TRPA1 channels. CONCLUSIONS AND IMPLICATIONS: In small arteries isolated from the rat mesentery, NaHS caused a vasodilatation. This response was not reproducible in vitro, since it was mediated by the release of sensory neurotransmitters in a capsaicin-like action. This release was mediated by a H(2)S-induced activation of TRPA1 channels.

Protection from cerebral ischemia by inhibition of TGFß-activated kinase.

OBJECTIVE: Transforming growth factor-ß-activated kinase (TAK1) is a member of the mitogen-activated protein kinase family that plays important roles in apoptosis and inflammatory signaling, both of which are critical components of stroke pathology. TAK1 has recently been identified as a major upstream kinase that phosphorylates and activates adenosine monophosphate-activated protein kinase (AMPK), a major mediator of neuronal injury after experimental cerebral ischemia. We studied the functional role of TAK1 and its mechanistic link with AMPK after stroke. METHODS: Male mice were subjected to transient middle cerebral artery occlusion (MCAO). The TAK1 inhibitor 5Z-7-oxozeaenol was injected either intracerebroventricularly or intraperitoneally at various doses and infarct size and functional outcome after long term survival was assessed. Mice with deletion of the AMPK α2 isoform were utilized to assess the contribution of downstream AMPK signaling to stroke outcomes. Levels of pTAK1, pAMPK, and other TAK1 targets including the pro-apoptotic molecule c-Jun-N-terminal kinase (JNK)/c-Jun and the pro-inflammatory protein cyclooxygenase-2 were also examined. RESULTS: TAK1 is critical in stroke pathology. Delayed treatment with a TAK1 inhibitor reduced infarct size and improved behavioral outcome even when given several hours after stroke onset. This protective effect may be independent of AMPK activation but was associated with a reduction in JNK and c-Jun signaling. CONCLUSIONS: Enhanced TAK1 signaling, via activation of JNK, contributes to cell death in ischemic stroke. TAK1 inhibition is a novel therapeutic approach for stroke as it is neuroprotective with systemic administration, has a delayed therapeutic window, and demonstrates sustained neuroprotective effects.

Propargyl 4-[F]fluorobenzoate: A Putatively More Stable Prosthetic group for the Fluorine-18 Labeling of Biomolecules via Click Chemistry.

Faster and more efficient approaches for radiolabeling biomolecules with short-lived (18)F are in dire need. Herein we report a new (18)F-labeled prosthetic group containing an acetylene function that permits the labeling of biomolecules via click chemistry. This template, propargyl 4-[(18)F]fluorobenzoate ([(18)F]PFB) was synthesized from a quaternary salt precursor in decay-corrected radiochemical yields of 58 +/- 31%. Several model compounds containing an azide moiety-benzyl azide, two lysine derivatives and a transglutaminase-reactive peptide-were labeled using [(18)F]PFB via a click reaction in decay-corrected radiochemical yields of 88 +/- 4%, 79 +/- 33%, 75 +/- 5%, and 37 +/- 31%, respectively. Our results suggest that the novel agent [(18)F]PFB is a potentially useful template for the (18)F-labeling of biomolecules via click chemistry.