TRPM8, non-selective cation channel of the transient receptor potential (TRP) superfamily, required for the transduction of moderate cold temperatures, regulates proliferation of epidermal cells in cyclin-dependent kinase inhibitor p21/Cip1-dependent manner. Given that downregulation of TRPM8 decreases p21/Cip1 level, increasing risk for carcinogenesis, and other TRP family is regulated by nuclear receptor peroxisome proliferator-activated receptor (PPAR) gamma, we examined whether TRPM8 expression was regulated by PPAR gamma. Knockdown assay and inhibition of PPAR gamma revealed that PPAR gamma negatively regulates the expression of TRPM8 in normal epidermal cells but positively regulates that in squamous carcinoma cells. Later restoration of decreased TRPM8 level in PPAR gamma antagonist-treated squamous carcinoma cells was attributed to feed-back loop regulation between TRPM8 and PPAR gamma using TRPM8 knockdown assay. Consisting with this finding, p21/Cip1 decrease by TRPM8 blocker, N-(4-Tertiarybutylphenyl)-4-(3-chloropyridin- 2-yl) tetrahydropyrazine-1 (2H)-carbox-amide (BCTC), was restored by additional BCTC treatment in squamous carcinoma cells.
Methylphenidate (MPH) is used as a first-line treatment for attention-deficit/hyperactivity disorder (ADHD). Because the onset of ADHD appears in early childhood and the incidence number is increasing, more patients could become adults with long-term use of MPH. In addition, few men would discontinue the medication during a fertile period. Recently, environmental factors such as diet and drug abuse have been reported to produce changes in the sperm epigenome and affect the health of the next generation. However, the effects of long-term administration of a psychostimulant such as MPH on the next generation is unknown. In this study, we examined the effects of paternal administration of MPH on the growth, behavior, and gene expression in offspring using a mouse model. Sires were subcutaneously administered MPH for 21 days and mated with naive dams. Upon reaching 6–7 weeks of age, offspring were subjected to spontaneous locomotor, elevated plus-maze, and passive avoidance tests. Additionally, RNA-seq and RT-qPCR were performed on the striatum. Paternal MPH exposure induced increased atomoxetine-sensitive impulsivity and decreased long-term memory function in the offspring. Enrichment analysis following RNA-seq revealed significant enrichment of terms involved in the nervous system. Gene expression levels of Snap25, Syt1, Drd2, Maoa, and Comt, which are associated with ADHD pathology, are altered in the striatum. These results suggest that continuous administration of MPH to male mice induces ADHD-like behavior and changes in the expression of genes involved in the nervous system in the brain of the next generation.