Ligand-stereoselective allosteric activation of cold-sensing TRPM8 channels by an H-bonded homochiral menthol dimer with head-to-head or head-to-tail

T-2 toxin induces dermal inflammation and toxicity in mice: The healing potential of menthol

According to the World Health Organization and the Food and Agricultural Organization of the United Nations, T-2 is one of the most harmful food-toxic chemicals, penetrates intact skin. The current study examined the protective benefits of menthol topical treatment on T-2 toxin-induced cutaneous toxicity in mice. Lesions were observed on the skin of the T-2 toxin-treated groups at 72 and 120 h. The T-2 toxin (2.97 mg/kg/bw)-treated group developed skin lesions, skin inflammation, erythema, and necrosis of skin tissue in contrast to the control group. Our findings reveal that topical application of 0.25% and 0.5% MN treated groups resulted in no erythema or inflammation, and normal skin was observed with growing hairs. The 0.5% MN administered group demonstrated an 80% blister and erythema healing effect in in vitro tests. In addition, MN dose-dependently suppressed ROS and lipid peroxidation mediated by the T-2 toxin up to 120%. Histology discoveries and the immunoblotting investigations with the downregulation of i-NOS gene expression confirmed the validity of menthol activity. Further molecular docking experiments of menthol against the i-NOS protein demonstrated stable binding efficacy with conventional hydrogen bond interactions, indicating compelling evidence of menthol's anti-inflammatory effects on the T-2 toxin-induced skin inflammation.

Lipid-dependent sequential allosteric activation of heat-sensing TRPV1 channels by anchor-stereoselective "hot" vanilloid compounds and analogs

Both a silent resident phosphatidylinositol lipid and a “hot” vanilloid agonist capsaicin or resiniferatoxin have been shown to share the same inter-subunit binding pocket between a voltage sensor like domain and a pore domain in TRPV1. However, how the vanilloid competes off the resident lipid for allosteric TRPV1 activation is unknown. Here, the in silico research suggested that anchor-stereoselective sequential cooperativity between an initial recessive transient silent weak ligand binding site and a subsequent dominant steady-state strong ligand binding site in the vanilloid pocket may facilitate the lipid release for allosteric activation of TRPV1 by vanilloids or analogs upon non-covalent interactions. Thus, the resident lipid may play a critical role in allosteric activation of TRPV1 by vanilloid compounds and analogs.

•

Four active vanilloid binding pockets as revealed by the cryo-EM structure of TRPV1 have no cooperativity between subunits.

•

Allosteric activation of TRPV1 by vanilloid compounds and analogs is lipid-dependent and anchor-stereoselective.

•

The resident and occluded lipid must be competed off for allosteric activation of TRPV1 by vanilloid compounds and analogs.

•

The first ligand binding is needed to release the resident lipid for the second ligand binding in the vanilloid pocket.

•

A lipid-free anchor facilitates the vanilloid ligand binding to remove the resident lipid from the active site in TRPV1.

•

Site accessibility controls sequential cooperative interactions of TRPV1 with vanilloids or analogs to open the channel.

•

The anchor stereoselectivity depends on the formation of a vanilloid bridge between two separated residues at the active site.

•

Different anchor stereoselectivities produce diverse recessive transient reaction intermediates or steps for TRPV1 opening.

•

Membrane hyperpolarization and depolarization may stabilize and loosen the resident lipid for TRPV1 gating, respectively.

•

Phospholipids at N- and C- terminal domains may affect the cooperativity or the potency of the vanilloid ligands.