Nitro-oleic acid targets transient receptor potential (TRP) channels in capsaicin sensitive afferent nerves of rat urinary bladder

Abstract

Nitro-oleic acid (9- and 10-nitro-octadeca-9-enoic acid, OA-NO2) is an electrophilic fatty acid nitroalkene derivative that modulates gene transcription and protein function via post-translational protein modification. Nitro-fatty acids are generated from unsaturated fatty acids by oxidative inflammatory reactions and acidic conditions in the presence of nitric oxide or nitrite. Nitroalkenes react with nucleophiles such as cysteine and histidine in a variety of susceptible proteins including transient receptor potential (TRP) channels in sensory neurons of the dorsal root and nodose ganglia. The present study revealed that OA-NO2 activates TRP channels on afferent nerve terminals in the urinary bladder and thereby increases bladder activity. The TRPV1 agonist capsaicin (CAPS, 1 μM) and the TRPA1 agonist allyl isothiocyanate (AITC, 30 μM), elicited excitatory effects in bladder strips, increasing basal tone and amplitude of phasic bladder contractions (PBC). OA-NO2 mimicked these effects in a concentration-dependent manner (1 μM – 33 μM). The TRPA1 antagonist HC3-030031 (HC3, 30 μM) and the TRPV1 antagonist diaryl piperazine analogue (DPA, 1 μM), reduced the effect of OA-NO2 on phasic contraction amplitude and baseline tone. However, the non-selective TRP channel blocker, ruthenium red (30 μM) was a more effective inhibitor, reducing the effects of OA-NO2 on basal tone by 75% and the effects on phasic amplitude by 85%. In bladder strips from CAPS-treated rats, the effect of OA-NO2 on phasic contraction amplitude was reduced by 65% and the effect on basal tone was reduced by 60%. Pretreatment of bladder strips with a combination of neurokinin receptor antagonists (NK1 selective antagonist, CP 96345; NK2 selective antagonist, MEN 10,376; NK3 selective antagonist, SB 234,375, 1 μM each) reduced the effect of OA-NO2 on basal tone, but not phasic contraction amplitude. These results indicate that nitroalkene fatty acid derivatives can activate TRP channels on CAPS-sensitive afferent nerve terminals, leading to increased bladder contractile activity. Nitrated fatty acids produced endogenously by the combination of fatty acids and oxides of nitrogen released from the urothelium and/or afferent nerves may play a role in modulating bladder activity.

Nitro-fatty acids in cardiovascular regulation and diseases characteristics and molecular mechanisms

“…Herein, we have outlined those relevant to cardiovascular, pulmonary and renal diseases. Further evidences on the anti-inflammatory actions of NO 2 -FAs are included in Table 1 and include inflammatory bowel disease (101), chronic obstructive pulmonary disease (102) or the regulation of transient reaction potential (TRP) A1, C and V1 by NO 2 -FAs in nociceptive neuronal cells, centrally involved in the regulation of symptoms of inflammation and pain control by the central nervous system (103–105). …”

Redox-Dependent Anti-Inflammatory Signaling Actions of Unsaturated Fatty Acids

“…DHA and EPA activate mammalian TRPA1 channels, stimulating the secretion of hormones from enteroendocrine cells and characterizing TRPA1 channels as endogenous PUFA sensors (116). NO 2 -OA also activates sensory neurons (117) and bladder afferent nerve TRP channels (118), which are rich in cysteines and are thus targets for electrophile modulation (119). A biphasic activation of TRP channels is suggested whereby nitroalkene modulation of the nociceptor TRPA1 channel occurs at Cys619, Cys639, Cys663, and Lys708 (120).…”

Nitro-oleic acid desensitizes TRPA1 and TRPV1 agonist responses in adult rat DRG neurons

“…Homologous potentiation with two applications of capsaicin was detected in previous studies of dissociated DRG neurons (Zhang et al, 2011) and was also demonstrated by measuring contractions of bladder strips during repeated applications of low concentrations (5 μM) of OA-NO 2 ; while higher concentrations of OA-NO 2 elicited desensitization (Artim et al, 2011). Repeated applications of mustard oil, which stimulates TRPA1 receptors, can enhance nociceptive behaviors (Schmidt et al, 2009).…”

“…Previous studies on rat DRG neurons (Sculptoreanu et al, 2010) and afferent nerves in the rat urinary bladder (Artim et al, 2011) revealed that OA-NO 2 activates TRPA1, TRPV1 and possibly other ion channels. Also, OA-NO 2 activated TRPA1 but not TRPV1 channels in mouse trigeminal or vagal sensory neurons (Taylor-Clark et al, 2009).…”

“…OA-NO 2 could also activate mast cells indirectly by releasing neurokinins from nociceptive afferent terminals that in turn stimulate NK-1 receptors on mast cells to release mediators (Kulka et al, 2008). OA-NO 2 activation of TRPV1 and TRPA1 channels on bladder afferent nerves also induces the release of neurokinins in bladder strip preparations that in turn elicits delayed contractions of bladder smooth muscle (Artim et al, 2011). Alternatively, the delayed, indirect mechanism might be due in part to the metabolism of OA-NO 2 into other active lipid compounds or release of NO, although a possible contribution of NO to the actions of OA-NO 2 on dissociated neurons in vitro has been eliminated by pharmacological experiments using an NO scavenger (Sculptoreanu et al, 2010).…”