Yunchao Shi,Ying Fang,Peng Shen,He Liu,Longsheng Xu,Liyan Wang,Maoxian Yang
Purpose Cognitive impairment is a critical complication of acute respiratory distress syndrome (ARDS). However, effective interventions are lacking. Growing evidence demonstrates that c-Jun N-terminal kinase (JNK)-mediated neuroinflammation is involved in the development of ARDS. Therefore, we hypothesized that the JNK pathway is involved in ARDS-induced cognitive impairment. Methods An in vivo rat model of ARDS was established by treating it with lipopolysaccharide. The cognitive function was assessed by behavioral tests. The levels of pro-inflammatory cytokines, JNK and NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) were analyzed by enzyme-linked immunosorbent assay, western blot, or immunohistochemical analysis. Results We found that JNK inhibitor 8 (JNK-IN-8) alleviated cognitive impairment, neuroinflammation, and NLRP3 inflammasome activation in the ARDS rat model. Additionally, an in vivo study showed that the protective effect of JNK-IN-8 on cognitive impairment was blocked by nigericin, an NLRP3 activator. Conclusions Our data suggest that JNK-IN-8 treatment improves ARDS-induced cognitive impairment by inhibiting the JNK/nuclear factor-κB-mediated NLRP3 inflammasome.
Disrupted clearance of all-trans-retinal (atRAL), a component of the visual (retinoid) cycle in the retina, may cause photoreceptor atrophy in autosomal recessive Stargardt disease (STGD1) and dry age-related macular degeneration (AMD). However, the mechanisms underlying atRAL-induced photoreceptor loss remain elusive. Here, we report that atRAL activates c-Jun N-terminal kinase (JNK) signaling at least partially through reactive oxygen species production, which promoted mitochondria-mediated caspase- and DNA damage-dependent apoptosis in photoreceptor cells. Damage to mitochondria in atRAL-exposed photoreceptor cells resulted from JNK activation, leading to decreased expression of Bcl2 apoptosis regulator (Bcl2), increased Bcl2 antagonist/killer (Bak) levels, and cytochrome c (Cyt c) release into the cytosol. Cytosolic Cyt c specifically provoked caspase-9 and caspase-3 activation and thereby initiated apoptosis. Phosphorylation of JNK in atRAL-loaded photoreceptor cells induced the appearance of γH2AX, a sensitive marker for DNA damage, and was also associated with apoptosis onset. Suppression of JNK signaling protected photoreceptor cells against atRAL-induced apoptosis. Moreover, photoreceptor cells lacking Jnk1 and Jnk2 genes were more resistant to atRAL-associated cytotoxicity. The Abca4−/− Rdh8−/− mouse model displays defects in atRAL clearance that are characteristic of STGD1 and dry AMD. We found that JNK signaling was activated in the neural retina of light-exposed Abca4−/−Rdh8−/− mice. Of note, intraperitoneal administration of JNK–IN-8, which inhibits JNK signaling, effectively ameliorated photoreceptor degeneration and apoptosis in light-exposed Abca4−/−Rdh8−/− mice. We propose that pharmacological inhibition of JNK signaling may represent a therapeutic strategy for preventing photoreceptor loss in retinopathies arising from atRAL overload.
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