ATF4 inhibits TRPV4 function and controls itch perception in rodents and nonhuman primates.

ABSTRACT: Acute and chronic itch are prevalent and incapacitating, yet the neural mechanisms underlying both acute and chronic itch are just starting to be unraveled. Activated transcription factor 4 (ATF4) belongs to the ATF/CREB transcription factor family and primarily participates in the regulation of gene transcription. Our previous study has demonstrated that ATF4 is expressed in sensory neurons. Nevertheless, the role of ATF4 in itch sensation remains poorly understood. Here, we demonstrate that ATF4 plays a significant role in regulating itch sensation. The absence of ATF4 in dorsal root ganglion (DRG) neurons enhances the itch sensitivity of mice. Overexpression of ATF4 in sensory neurons significantly alleviates the acute and chronic pruritus in mice. Furthermore, ATF4 interacts with the transient receptor potential cation channel subfamily V member 4 (TRPV4) and inhibits its function without altering the expression or membrane trafficking of TRPV4 in sensory neurons. In addition, interference with ATF4 increases the itch sensitivity in nonhuman primates and enhances TRPV4 currents in nonhuman primates DRG neurons; ATF4 and TRPV4 also co-expresses in human sensory neurons. Our data demonstrate that ATF4 controls pruritus by regulating TRPV4 signaling through a nontranscriptional mechanism and identifies a potential new strategy for the treatment of pathological pruritus.

[Mechanism of thioridazine-induced apoptosis of human colorectal cancer SW480 cells].

OBJECTIVE: To study the effect of thioridazine on the proliferation and apoptosis of human colorectal cancer SW480 cells. METHODS: SW480 cells were treated with different concentrations of thioridazine, and MTT assay was used to evaluate the cell inhibition rate. Hoechst 33342 staining was performed to demonstrate the cell morphology changes. Flow cytometry was used to determine the cell apoptosis and cell cycle changes. RT-qPCR was used to detect PDCD4, c-MYC, BCL2, CCND1, CASPASE3, PARP1, CDK4 and EIF4A mRNA expressions, and Western blotting was employed to assay AKT, p-AKT, and PDCD4 protein expression levels. RESULTS: MTT results showed that thioridazine inhibits the proliferation of SW480 cells. SW480 cells treated with thioridazine presented with such typical features of apoptosis of karyopyknosis, chromatin condensation and nuclear fragmentation. Flow cytometry showed that thioridazine was a cell cycle-specific drug and caused cell cycle arrest at G(1)/G(0) phase and an increased cell apoptosis rate. Thioridazine treatment of the cells resulted in up-regulated PDCD4 mRNA expression and down-regulated mRNA expressions of CCND1, CDK4, c-MYC, BCL2, CASPASE3, PARP1 and EIF4A, increased PDCD4 protein expression and reduced p-AKT protein expression. CONCLUSION: Thioridazine inhibits the proliferation and induces apoptosis of SW480 cells by up-regulating PDCD4 and inhibiting PI3K/Akt pathway.