RN 1734

RN-1734 is selective antagonist of the TRPV4 channel, completely antagonizes 4αPDD-mediated activation of TRPV4 with comparable, low micromolar IC50values for all three species (hTRPV4: IC50 = 2.3 μM, mTRPV4: IC50 = 5.9 μM, rTRPV4: IC50 = 3.2 μM). IC50 value: 2.3 μM (hTRPV4), 5.9 μM (mTRPV4), IC50 = 3.2 μM (rTRPV4) Target: TRPV4 in vitro: RN-1734 completely inhibits both ligand- and hypotonicity-activated TRPV4. In addition, RN-1734 is selective for TRPV4 in a TRP selectivity panel including TRPV1, TRPV3 and TRPM8, and could thus be a valuable pharmacological probe for TRPV4 studies. [1]

References:
[1]. Kato K, et al. Acidosis environment promotes osteoclast formation by acting on the last phase of preosteoclast differentiation: a study to elucidate the action points of acidosis and search for putative target molecules. Eur J Pharmacol. 2011 Aug 1;663(1- [2]. Vincent F, et al. Identification and characterization of novel TRPV4 modulators. Biochem Biophys Res Commun. 2009 Nov 20;389(3):490-4.

Fatty acid amide hydrolase (FAAH) inhibitor PF-3845 reduces viability, migration and invasiveness of human colon adenocarcinoma Colo-205 cell line: an in vitro study.[Pubmed:28850633]

Acta Biochim Pol. 2017;64(3):519-525.

Earlier reports suggest that the endocannabinoids may play a role of endogenous tumor growth modulators. In this study, we investigated whether inhibition of the enzymes involved in the synthesis and degradation of endocannabinoids may reduce colorectal cancer cell invasion and migration. The human colon adenocarcinoma Colo-205 cells were incubated with PF-3845, JZL-184 and RHC-80267 (fatty acid amide hydrolase (FAAH), mono- (MAGL) and diacylglycerol lipase (DAGL) inhibitors, respectively) for 48 h. The MTT colorimetric assay was performed to quantify cell viability. Next, Colo-205 cells were incubated with PF-3845 alone or with PF-3845 together with selected antagonists: AM 251, AM 630, SB 366791, RN 1734 and G-15 (CB1, CB2, TRPV1, TRPV4 and GPR30 antagonists, respectively). Western blot assay was applied to identify the changes in CB1 and CB2 receptor expression. Migration and invasion assays were employed to characterize the effect of PF-3845 on colorectal cancer cell invasion. We found that of all the inhibitors used, the FAAH inhibitor PF-3845 reduced the Colo-205 cell line viability the most effectively (IC50=52.55 muM). We also showed that the effect of decreased cell viability was enhanced when Colo-205 cells were incubated with PF-3845 and RN-1734, a TRPV4 antagonist (IC50=30.54 muM). Western blot assay revealed significantly decreased CB1 receptor expression levels, while CB2 expression was increased in response to PF-3845 when compared to control. Furthermore, PF-3845 inhibited migration and invasion of Colo-205 cell line. These results suggest that pharmacological inhibition of FAAH and consequent enhancement of the endocannabinoid levels may reduce the colorectal cancer growth and progression.

TRPV4 channels contribute to renal myogenic autoregulation in neonatal pigs.[Pubmed:28768667]

Am J Physiol Renal Physiol. 2017 Nov 1;313(5):F1136-F1148.

Myogenic response, a phenomenon in which resistance size arteries and arterioles swiftly constrict or dilate in response to an acute elevation or reduction, respectively, in intravascular pressure is a key component of renal autoregulation mechanisms. Although it is well established that the renal system is functionally immature in neonates, mechanisms that regulate neonatal renal blood flow (RBF) remain poorly understood. In this study, we investigated the hypothesis that members of the transient receptor potential vanilloid (TRPV) channels are molecular components of renal myogenic constriction in newborns. We show that unlike TRPV1-3, TRPV4 channels are predominantly expressed in neonatal pig preglomerular vascular smooth muscle cells (SMCs). Intracellular Ca(2+) concentration ([Ca(2+)]i) elevation induced by osmotic cell swelling was attenuated by TRPV4, L-type Ca(2+), and stretch-activated Ca(2+) channel blockers but not phospholipase A2 inhibitor. Blockade of TRPV4 channels reversed steady-state myogenic tone and inhibited pressure-induced membrane depolarization, [Ca(2+)]i elevation, and constriction in distal interlobular arteries. A step increase in arterial pressure induced efficient autoregulation of renal cortical perfusion and total RBF in anesthetized and mechanically ventilated neonatal pigs. Moreover, intrarenal arterial infusion of the TRPV4 channel blockers HC 067047 and RN 1734 attenuated renal autoregulation in the pigs. These data suggest that renal myogenic autoregulation is functional in neonates. Our findings also indicate that TRPV4 channels are mechanosensors in neonatal pig preglomerular vascular SMCs and contribute to renal myogenic autoregulation.

Detection of TRPV4 channel current-like activity in Fawn Hooded hypertensive (FHH) rat cerebral arterial muscle cells.[Pubmed:28472069]

PLoS One. 2017 May 4;12(5):e0176796.

The transient receptor potential vallinoid type 4 (TRPV4) is a calcium entry channel known to modulate vascular function by mediating endothelium-dependent vasodilation. The present study investigated if isolated cerebral arterial myocytes of the Fawn Hooded hypertensive (FHH) rat, known to display exaggerated KCa channel current activity and impaired myogenic tone, express TRPV4 channels at the transcript and protein level and exhibit TRPV4-like single-channel cationic current activity. Reverse transcription polymerase chain reaction (RT-PCR), Western blot, and immunostaining analysis detected the expression of mRNA transcript and translated protein of TRPV4 channel in FHH rat cerebral arterial myocytes. Patch clamp recording of single-channel current activity identified the presence of a single-channel cationic current with unitary conductance of ~85 pS and ~96 pS at hyperpolarizing and depolarizing potentials, respectively, that was inhibited by the TRPV4 channel antagonist RN 1734 or HC 067074 and activated by the potent TRPV4 channel agonist GSK1016790A. Application of negative pressure via the interior of the patch pipette increased the NPo of the TRPV4-like single-channel cationic current recorded in cell-attached patches at a patch potential of 60 mV that was inhibited by prior application of the TRPV4 channel antagonist RN 1734 or HC 067047. Treatment with the TRPV4 channel agonist GSK1016790A caused concentration-dependent increase in the NPo of KCa single-channel current recorded in cell-attached patches of cerebral arterial myocytes at a patch potential of 40 mV, which was not influenced by pretreatment with the voltage-gated L-type Ca2+ channel blocker nifedipine or the T-type Ca2+ channel blocker Ni2+. These findings demonstrate that FHH rat cerebral arterial myocytes express mRNA transcript and translated protein for TRPV4 channel and display TRPV4-like single-channel cationic current activity that was stretch-sensitive and activation of which increased the open state probability of KCa single-channel current in these arterial myocytes.

Low intravascular pressure activates endothelial cell TRPV4 channels, local Ca2+ events, and IKCa channels, reducing arteriolar tone.[Pubmed:23071308]

Proc Natl Acad Sci U S A. 2012 Oct 30;109(44):18174-9.

Endothelial cell (EC) Ca(2+)-activated K channels (SK(Ca) and IK(Ca) channels) generate hyperpolarization that passes to the adjacent smooth muscle cells causing vasodilation. IK(Ca) channels focused within EC projections toward the smooth muscle cells are activated by spontaneous Ca(2+) events (Ca(2+) puffs/pulsars). We now show that transient receptor potential, vanilloid 4 channels (TRPV4 channels) also cluster within this microdomain and are selectively activated at low intravascular pressure. In arterioles pressurized to 80 mmHg, ECs generated low-frequency (~2 min(-1)) inositol 1,4,5-trisphosphate receptor-based Ca(2+) events. Decreasing intraluminal pressure below 50 mmHg increased the frequency of EC Ca(2+) events twofold to threefold, an effect blocked with the TRPV4 antagonist RN1734. These discrete events represent both TRPV4-sparklet- and nonsparklet-evoked Ca(2+) increases, which on occasion led to intracellular Ca(2+) waves. The concurrent vasodilation associated with increases in Ca(2+) event frequency was inhibited, and basal myogenic tone was increased, by either RN1734 or TRAM-34 (IK(Ca) channel blocker), but not by apamin (SK(Ca) channel blocker). These data show that intraluminal pressure influences an endothelial microdomain inversely to alter Ca(2+) event frequency; at low pressures the consequence is activation of EC IK(Ca) channels and vasodilation, reducing the myogenic tone that underpins tissue blood-flow autoregulation.

Identification and characterization of novel TRPV4 modulators.[Pubmed:19737537]

Biochem Biophys Res Commun. 2009 Nov 20;389(3):490-4.

TRPV4, a close relative of the vanilloid receptor TRPV1, is activated by diverse modalities such as endogenous lipid ligands, hypotonicity, protein kinases and, possibly, mechanical inputs. While its multiple roles in vivo are being explored with KO mice and selective agonists, there is a dearth of selective antagonists available to examine TRPV4 function. Herein we detail the use of a focused library of commercial compounds in order to identify RN-1747 and RN-1734, a pair of structurally related small molecules endowed with TRPV4 agonist and antagonist properties, respectively. Their activities against human, rat and mouse TRPV4 were characterized using electrophysiology and intracellular calcium influx. Significantly, antagonist RN-1734 was observed to completely inhibit both ligand- and hypotonicity-activated TRPV4. In addition, RN-1734 was found to be selective for TRPV4 in a TRP selectivity panel including TRPV1, TRPV3 and TRPM8, and could thus be a valuable pharmacological probe for TRPV4 studies.

RN-1734 is selective antagonist of the TRPV4 channel, completely antagonizes 4αPDD-mediated activation of TRPV4 with comparable, low micromolar IC50s for all three species (hTRPV4: 2.3 μM, mTRPV4: 5.9 μM, rTRPV4: 3.2 μM). RN-1734 clearly decreases the production of tumor necrosis factor α (TNF-α) and interleukin 1β (IL-1β) without altering the number of olig2-positive cells.

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