CP-25

Methotrexate (MTX) is frequently administered with the proton pump inhibitor omeprazole (OPZ) to relieve gastrointestinal adverse reactions of MTX, but the coadministration increases the risk of kidney injury. In this study, we investigated the mechanisms of combined OPZ and MTX-induced acute kidney injury (OPZ + MTX-AKI), which was induced in rats or mice by administration of OPZ plus MTX for 14 days. Analysis of the FAERS database revealed that AKI was the principal form of kidney injury when OPZ was administered with MTX. We showed that coadministration of OPZ and MTX to rats resulted in the development of AKI. We found that OPZ and MTX, by inhibiting the expression and activity of SERCA2 and IP3R, respectively, jointly disrupted Ca²⁺ homeostasis, thereby causing cell damage. Transcriptomic analysis of clinical samples revealed that G protein-coupled receptor kinase 2 (GRK2) served as a key protein in OPZ + MTX-AKI. In Grk2^+/- mice and in mice with renal tubular epithelial cell (RTEC)-specific Grk2 knockdown, the manifestations of kidney injury, along with the levels of oxidative stress and apoptosis in the context of OPZ + MTX-AKI, were notably ameliorated. Conversely, in mice with RTEC-specific Grk2 overexpression, the kidney injury was markedly aggravated. Administration of GRK2 inhibitor CP-25 (17.5, 35, 70 mg/kg/d, i.g.) for 14 days dose-dependently alleviated OPZ + MTX-AKI in mice with RTEC-specific Grk2 overexpression. This study elucidates a novel mechanism of AKI induced by the combination of OPZ and MTX and identifies potential therapeutic targets. We provide an essential theoretical foundation for the rational clinical application of OPZ and MTX, as well as for prevention and treatment of the related kidney injury.

Primary Sjögren's syndrome (pSS) is an autoimmune disease with incompletely elucidated pathological mechanisms and a current lack of effective therapeutic agents. CP-25, a structurally modified derivative of paeoniflorin, demonstrates significant therapeutic effects in experimental Sjögren's syndrome (ESS) mouse models; however, its underlying mechanism remains elusive. In this study, we constructed an ESS mouse model induced by autoantigen immunization to explore the biological effects of CP-25 on pSS and its potential mechanisms. The study first revealed the overactivation of endoplasmic reticulum stress (ERS) and the impaired function of M₃R-IP₃R-Ca²⁺-AQP5 signaling pathway in human labial gland tissue. Critically, inhibiting ERS (using 4-PBA) was found to directly ameliorate the impaired M₃R-IP₃R-Ca²⁺-AQP5 signaling pathway function, as evidenced by normalized M₃R expression, restored IP₃R and AQP5 levels, and enhanced intracellular Ca²⁺ intensity in IFNα-stimulated HSGECs, resulting in significantly increased salivary flow rate and reduced salivary gland inflammation in vivo. Furthermore, CP-25 exerted its therapeutic effect by upregulating the M₃R-IP₃R-Ca²⁺-AQP5 signaling pathway function, regulating M₃R membrane expression, and critically inhibiting ERS. Crucially, the beneficial effects of CP-25 on both ERS suppression and pathway restoration were demonstrated to be mechanistically dependent on disrupting the pathological interaction between the key ERS chaperone GRP78 and the IP₃R calcium channel. In summary, impaired M₃R-IP₃R-Ca²⁺-AQP5 signaling contributes to pSS pathogenesis. CP-25 treats pSS by restoring this pathway through regulating M₃R membrane expression, inhibiting ERS, reducing apoptosis, and decreasing GRP78-IP₃R co-expression in HSGECs. This study provides experimental support for CP-25's mechanism and potential clinical application in pSS.