Selective Activation of Nociceptor TRPV1 Channel and Reversal of Inflammatory Pain in Mice by a Novel Coumarin Derivative Muralatin L from Murraya alata

Abstract

Coumarin and its derivatives are fragrant natural compounds isolated from the genus Murraya that are flowering plants widely distributed in East Asia, Australia, and the Pacific Islands. Murraya plants have been widely used as medicinal herbs for relief of pain, such as headache, rheumatic pain, toothache, and snake bites. However, little is known about their analgesic components and the molecular mechanism underlying pain relief. Here, we report the bioassay-guided fractionation and identification of a novel coumarin derivative, named muralatin L, that can specifically activate the nociceptor transient receptor potential vanilloid 1 (TRPV1) channel and reverse the inflammatory pain in mice through channel desensitization. Muralatin L was identified from the active extract of Murraya alata against TRPV1 transiently expressed in HEK-293T cells in fluorescent calcium FlexStation assay. Activation of TRPV1 current by muralatin L and its selectivity were further confirmed by whole-cell patch clamp recordings of TRPV1-expressing HEK-293T cells and dorsal root ganglion neurons isolated from mice. Furthermore, muralatin L could reverse inflammatory pain induced by formalin and acetic acid in mice but not in TRPV1 knock-out mice. Taken together, our findings show that muralatin L specifically activates TRPV1 and reverses inflammatory pain, thus highlighting the potential of coumarin derivatives from Murraya plants for pharmaceutical and medicinal applications such as pain therapy.Murraya is a popular genus of flowering plants in the Rutaceae family known for their specific fragrance. Most plants from this genus have been used as traditional Chinese medicines for treating psychogenic pain or somatoform pain disorders, including toothache, gastralgia, lumbago, rheumatic pain, etc. (1). Previous phytochemical and pharmacological investigations have shown that coumarins isolated from Murraya plants are the main bioactive agents responsible for analgesic properties of these medicinal herbs (2). However, the bioactive ingredients have always been a riddle, and their mechanisms of action remain largely unknown.The transient receptor potential vanilloid member 1 (TRPV1) channel, also known as capsaicin receptor, is a nonselective cation and heat-activated channel with a temperature threshold above 43°C (3). In addition to chili pepper and temperature, TRPV1 is also activated by acidic pH, and a plethora of other chemicals from plants and toxins (3-7). TRPV1 belongs to the TRPV 4 subfamily that is composed of six members divided into two groups as follows: TRPV1-4 channels that are modestly permeable to Ca 2ϩ , and TRPV5-6 channels that are only highly Ca 2ϩ -selective, based on their homology and biophysical properties (8, 9). The expression of TRPV1 has been primarily demonstrated in pain pathways, including small diameter primary sensory neurons (10) and keratinocytes in the skin where it plays a key role in nociception induced by capsaicin or noxious thermal stimuli (11,12). Mice lacking Trpv1 show dramatic reduction of pain...

A Precise Microfluidic Assay in Single‐Cell Profile for Screening of Transient Receptor Potential Channel Modulators

“…Murraya plants have been widely used as medical herbs for relief of psychogenic and somatoform pain. [ 43 ] Our findings not only demonstrate the mechanism of action for the novel compounds, but also point to the possibility of identifying structurally diversified natural products targeting TRP channels. One of the positive hits, B‐304, inhibits TRPA1 channel and attenuates the formalin‐ and AITC‐evoked pain sensitization behavior in vivo.…”

Osthole alleviates neuropathic pain in mice by inhibiting the P2Y1-receptor-dependent JNK signaling pathway

“…Glutamate in presynaptic element liberation increased, causing glutamic acid receptor in postsynaptic element activated, such as AMPA and NMDA. Excitatory receptors in neurons leads to increased calcium influx [28], initiating a series of downstream signal pathways, including p-ERK, p-CREB and c-Fos, which are closely related with pain sensitivity [3]. Postsynaptic receptor was also detected to further prove the influence of osthole on neuronal excitability.…”

DIC/Oxyma‐based accelerated synthesis and oxidative folding studies of centipede toxin RhTx

“…The TRPV1 ion channel, an important nociceptor that responds to heat with exquisite sensitivity, is a potential drug target for the treatment of inflammation and hematological malignancies 30–32 . The novel centipede toxin RhTx that is recently isolated from the venom of the Chinese red‐headed centipede contains 27 amino acid residues and two pairs of disulfide bonds (Figure 1).…”

“…The TRPV1 ion channel, an important nociceptor that responds to heat with exquisite sensitivity, is a potential drug target for the treatment of inflammation and hematological malignancies. [30][31][32] The novel centipede toxin RhTx that is recently isolated from the venom of the Chinese red-headed centipede contains 27 amino acid residues and two pairs of disulfide bonds (Figure 1). [33][34][35] RhTx could rapidly target and activate the extracellular domain of TRPV1 with high specificity and affinity, inducing conformational rearrangement and causing severe pain.…”