Investigation of the Potential Therapeutic Effects of Osthole in a Rat Model of Ventilator-Induced Lung Injury (VILI) and Its Possible Relationship with the TRPV4 Channel
Project no. 32108 · Status: Kapanmış (Yayın bekleniyor) · 2023
Summary
<p>Mechanical ventilation is a supportive and life-saving intervention for patients with inadequate spontaneous respiration; however, it may cause structural lung injury and trigger systemic inflammatory responses, leading to a condition known as VILI. This pathological condition can develop not only in previously injured lungs but also in healthy lungs. Although lung protective ventilation protocols are applied to patients, complete prevention of VILI is still not possible. TRPV4 channel is a mechanosensitive calcium (Ca²⁺)-permeable ion channel activated in response to mechanical stretch. Its activation increases intracellular Ca²⁺ concentrations, initiating and maintaining inflammatory signaling, disrupting endothelial barrier integrity, and causing alveolar fluid accumulation, which are key mechanisms in the pathogenesis of VILI. Ca²⁺ influx through TRPV4 can activate KCa3.1 channel, thereby amplifying inflammatory signaling cascades. Although a limited number of studies have suggested potential regulatory roles of TRPV4 and KCa3.1 in VILI, their direct mechanistic contributions have not yet been fully elucidated. Current therapeutic strategies mainly aim to alleviate inflammation and tissue injury, but no effective and safe pharmacological agent has yet been identified. Osthole, a natural coumarin derivative, has been reported to exhibit antiinflammatory, antioxidant, and endothelial-protective effects in various experimental models. Some of these effects involve mechanisms overlapping with TRPV4 inhibition, suggesting that osthole may exert beneficial effects against VILI-related injury. However, its potential role in VILI has not yet been investigated. In this study, the therapeutic potential of osthole (40 mg/kg, intraperitoneal (i.p.)) was evaluated in a rat model of VILI. Two experimental protocols were designed to assess its protective (2-hour (h) VILI) and therapeutic (5-h VILI) effects. Arterial blood gas analysis, lung wet/dry weight ratio, biochemical enzyme assays, western blotting, and histological evaluations were performed. In addition, organ bath experiments using isolated pulmonary artery and tracheal rings from healthy rats were conducted to investigate TRPV4-mediated functional responses and the regulatory role of osthole. While 2- and 5-h VILI caused significant deterioration in blood gas parameters, these parameters were maintained during 2-h VILI and were improved during 5-h VILI in the osthole-treated groups. The increased lung wet/dry weight ratio observed after 5-h VILI was significantly reduced by osthole. Enzymatic activities of hyaluronidase, myeloperoxidase, and chitotriosidase were markedly elevated in VILI but decreased after osthole treatment. The protein expression levels of TRPV4, KCa3.1, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were increased in VILI, and this increase was inhibited in the osthole-treated groups. Histological analyses demonstrated interstitial edema, inflammation, and hemorrhage in 2-h VILI and these parameters progressed to extensive lung injury by the 5th hour; these pathological findings were significantly improved with osthole. Osthole treatment reduced TRPV4, KCa3.1, TNF-α, and IL-6 immunoreactivities in VILI, as shown by immunohistochemistry. Moreover, osthole inhibited TRPV4 mediated contraction responses induced by GSK1016790A (GSK), similar to the selective TRPV4 antagonist HC-067047 (HC). This study provides the first experimental evidence that osthole exerts both protective and therapeutic effects against VILI by inhibiting the TRPV4/KCa3.1-mediated signaling pathway. These findings suggest that osthole may represent a promising pharmacological candidate not only for the treatment of VILI but also for other conditions such as vascular pathologies, asthma, and ischemic stroke in which TRPV4 and KCa3.1 jointly contribute to disease mechanisms.</p><p><strong>Keywords</strong>; VILI; TRPV4; KCa3.1; osthole</p>