AMTB, a TRPM8 channel blocker: evidence in rats for activity in overactive bladder and painful bladder syndrome

Abstract

The activation of the TRPM8 channel, a member of the large class of TRP ion channels, has been reported to be involved in overactive bladder and painful bladder syndrome, although an endogenous activator has not been identified. In this study, N-(3-aminopropyl)-2-{[(3-methylphenyl) methyl]oxy}-N-(2-thienylmethyl)benzamide hydrochloride salt (AMTB) was evaluated as a TRPM8 channel blocker and used as a tool to evaluate the effects of this class of ion channel blocker on volume-induced bladder contraction and nociceptive reflex responses to noxious bladder distension in the rat. AMTB inhibits icilin-induced TRPM8 channel activation as measured in a Ca(2+) influx assay, with a pIC(50) of 6.23. In the anesthetized rat, intravenous administration of AMTB (3 mg/kg) decreased the frequency of volume-induced bladder contractions, without reducing the amplitude of contraction. The nociceptive response was measured by analyzing both visceromotor reflex (VMR) and cardiovascular (pressor) responses to urinary bladder distension (UBD) under 1% isoflurane. AMTB (10 mg/kg) significantly attenuated reflex responses to noxious UBD to 5.42 and 56.51% of the maximal VMR response and pressor response, respectively. The ID50 value on VMR response was 2.42 +/- 0.46 mg/kg. These results demonstrate that TRPM8 channel blocker can act on the bladder afferent pathway to attenuate the bladder micturition reflex and nociceptive reflex responses in the rat. Targeting TRPM8 channel may provide a new therapeutic opportunity for overactive bladder and painful bladder syndrome.

Blockade of TRPM8 activity reduces the invasion potential of oral squamous carcinoma cell lines

“…In conclusion, taken as a whole our results, obtained using a selective agonist and selective antagonist, clearly demonstrate that TRPM8 channels are expressed on the plasma membrane and/or in the intracellular region in the oral SCC lines, and that the agonist-induced and constitutive activities of TRPM8 channels are likely to be positively involved in the cell-invasion process via this channel's ability to increase MMP-9 activity. A TRPM8 antagonist has been reported to be effective for the treatment of bladder pain (30), and potent and selective TRPM8 antagonists have been supported as potential candidates for the treatment of neuropathic pain (11,31). The present study is the first to provide evidence for a pathophysiological involvement of TRPM8 channels in the tumor cell invasion process.…”

Tryptamine-Based Derivatives as Transient Receptor Potential Melastatin Type 8 (TRPM8) Channel Modulators

“…The results obtained are normalized to the effects prompted by 100 M of the canonical agonist menthol 29 or by 10 M of the TRPM8 antagonist AMTB + 100 M menthol, 11 whose effects were reported as + 100% (activation) or -100% (inhibition), respectively (Figures 1A and 1B).…”

“…The non-substituted N-1 indole derivatives (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) were quite productive. A direct linkage of the amine moiety with different bulky aromatic groups, such as naphthalene and quinolines, gives compounds 8-11 unable to act as TRPM8 modulators ( Figures 1A and 1B).…”

“…10 Concurrently, TRPM8 blockers have been investigated for the treatment of overactive and painful bladder syndromes. 11 In particular, N-(3-Aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl) benzamide (AMTB), a well-recognized TRPM8 antagonist, can attenuate the bladder micturition reflex and the nociceptive reflex response in the rat, thus decreasing the frequency of volume-induced bladder contraction. 12 Finally, TRPM8 modulators could be of interest in treating dry eye syndrome and excessive lacrimation dysfunction, due to extensive TRPM8 expression in corneal afferent neurons.…”

Ligand-gated Ion Channels

“…Chemical Activators WS-12, (-)-menthol (inhibited by intracellular Ca 2+ ), icilin (requires intracellular Ca 2+ as a co-factor for full agonist activity); agonist activities are temperature dependent and potentiated by cooling Blockers AMTB (Lashinger et al, 2008), 5-benzyloxytrytamine, clotrimazole, BCTC, capsazepine, 2-APB, La 3+ , ACA, anandamide, NADA, linoleic acid, cannabinoids (e.g., cannabidiol, THC); insensitive to ruthenium red Functional characteristics g = 40-83 pS at positive potentials; conducts mono-and di-valent cations non-selectively (PCa/PNa = 1.0-3.3); pronounced outward rectification; demonstrates densensitization to chemical agonists and adaptation to a cold stimulus in the presence of Ca 2+ ; modulated by lysophospholipids and PUFAs…”