The Food and Drug Administration as Gatekeeper and the Menthol Exemption

TRPM8 inhibits substance P release from primary sensory neurons via PKA/GSK-3beta to protect colonic epithelium in colitis

Transient receptor potential melastatin 8 (TRPM8) is a cold sensory receptor in primary sensory neurons that regulates various neuronal functions. Substance P (SP) is a pro-inflammatory neuropeptide secreted by the neurons, and it aggravates colitis. However, the regulatory role of TRPM8 in SP release is still unclear. Our study aimed to investigate TRPM8's role in SP release from primary sensory neurons during colitis and clarify the effect of SP on colonic epithelium. We analyzed inflammatory bowel disease patients' data from the Gene Expression Omnibus dataset. Dextran sulfate sodium (DSS, 2.5%)-induced colitis in mice, mouse dorsal root ganglion (DRG) neurons, ND7/23 cell line, and mouse or human colonic organoids were used for this experiment. Our study found that TRPM8, TAC1 and WNT3A expression were significantly correlated with the severity of ulcerative colitis in patients and DSS-induced colitis in mice. The TRPM8 agonist (menthol) and the SP receptor antagonist (Aprepitant) can attenuate colitis in mice, but the effects were not additive. Menthol promoted calcium ion influx in mouse DRG neurons and inhibited the combination and phosphorylation of PKAca from the cAMP signaling pathway and GSK-3β from the Wnt/β-catenin signaling pathway, thereby inhibiting the effect of Wnt3a-driven β-catenin on promoting SP release in ND7/23 cells. Long-term stimulation with SP inhibited proliferation and enhanced apoptosis in both mouse and human colonic organoids. Conclusively, TRPM8 inhibits SP release from primary sensory neurons by inhibiting the interaction between PKAca and GSK-3β, thereby inhibiting the role of SP in promoting colonic epithelial apoptosis and relieving colitis.

E-cigarette devices, brands, and flavors attract youth: Informing FDA's policies and priorities to close critical gaps

PURPOSE

Identify e-cigarette devices, brands, and flavor types used by adolescents and young adults soon after the enactment of flavor restrictions, youth access laws, FDA's enforcement prioritization against some flavored pod/cartridge-based e-cigarettes, and during COVID-19 pandemic-related school closures.

METHODS

National cross-sectional online survey (N = 4,351) in May 2020 assessed popularity, ever- and past-30-day use of e-cigarette device types (pod/cartridge-based, disposables, others), brands, flavor types and flavor-enhancers, by age group (under age 21 and 21 and over).

RESULTS

While pod/cartridge-based e-cigarettes had the highest ever-use (82.7% <21; 69.8% ≥21) and were most often-used (41.9% <21; 41.4% ≥21), most past 30-day-users (50.8% <21; 61.9% ≥21) and 7-day-users (36.0% <21; 56.7% ≥21) used disposables. Mint/menthol was the most-used flavor type (pod/cartridge-based: 48.2% <21, 48.1% ≥21; disposables: 51.6% <21, 56.4% ≥21), followed by fruit (pod/cartridge-based: 37.4% <21, 35.5%≥ 21; disposables: 51.6% >21, 46.2% ≥ 21), and sweet/dessert/candy flavor types (pod/cartridge-based: 24.4% <21, 24.7% ≥21; disposables: 29.7% <21, 33.8% ≥21). Participants reported using add-on e-cigarette flavor-enhancers (pod/cartridge-based: 24.6%; disposables: 31.3%).

CONCLUSION

Soon after FDA's January 2020 announcement of prioritized enforcement against flavored pod/cartridge-based e-cigarettes and during the pandemic lockdown, adolescents' and young adults' past 30-day use included mostly flavored disposables rather than pod/cartridge-based e-cigarettes, mint/menthol flavors, and some used add-on flavor enhancers. To reduce youth use, comprehensive regulation of e-cigarette devices and flavors should be enacted and enforced at federal, state, and local levels.