Reduction of excessive unfolded protein response by 4-phenylbutyric acid may mitigate procymidone-induced testicular damage in mice by changing the levels of circRNA Scar and circZc3h4

Procymidone (PCM) exposure below the no-observed-effect level triggers changes in circRNA Scar and circZc3h4 and overactivation of the unfolded protein response (UPR) in mice, culminating in testicular injury. The 4-phenyl butyric acid (4-PBA) is known to stabilize proteins and reduce the UPR. This study employed an in vitro system in which mouse testes were cultured with 1 x 10-5 M PCM and varying concentrations (0, 20, 40, and 80 mM) of 4PBA; 4-week-old male mice were subsequently treated with 100 mg/kg/d PCM (suspended in corn oil) and/or 100 mg/kg/d 4-PBA for 21 d, consecutively. The treatments were as follows: the negative control (NC) group was orally administered corn oil; the positive control (PC) group was orally administered PCM; the 4-PBA group was intraperitoneally injected with 4-PBA; the 4-PBA-I group was orally administered PCM and 4-PBA simultaneously; the 4-PBA-II group received daily administration of 4-PBA 24 h prior to PCM; and the 4-PBA-III group was intraperitoneally injected with 4-PBA for 7 d after 21 d of PCM administration. However, the 4-PBA intervention groups showed no considerable changes in the overall or testicular appearance of mice. In vitro, 4-PBA inhibited the PCM-induced testicular injury, with the most significant effect observed at 80 mM. In vivo, the 4-PBA-III group exhibited the best in vivo effects. Our findings indicate that 4-PBA conferred testicular protection by decreasing PCM-induced circRNA Scar, elevating circZc3h4, and suppressing UPR both in vitro and in vivo. It has been hypothesized that 4-PBA mitigates testicular damage by reducing excessive UPR levels.