Background A growing body of evidence has demonstrated the vital roles of circular RNAs (circRNAs) in cancer progression and drug resistance. We intended to explore the roles and mechanisms of circ_ZFR in the paclitaxel (PTX) resistance and progression of non-small cell lung cancer (NSCLC). Methods Two NSCLC cell lines A549 and H460 were used in this study. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was conducted to measure the levels of circ_ZFR, ZFR, miR-195-5p and karyopherin subunit alpha 4 (KPNA4) mRNA. RNase R assay was used to analyze the characteristic of circ_ZFR. MTT assay was carried out to assess PTX resistance and cell proliferation. Flow cytometry analysis was utilized to analyze cell cycle and apoptosis. Transwell assay was used to examine cell migration and invasion. Western blot assay was conducted to measure the protein levels of Ki67, Twist1, E-cadherin and KPNA4. Dual-luciferase reporter assay was adopted to verify the combination between miR-195-5p and circ_ZFR or KPNA4. Murine xenograft model assay was used to investigate the effect of circ_ZFR on PTX resistance of NSCLC in vivo. Results Circ_ZFR level was enhanced in PTX-resistant NSCLC tissues and cells. Knockdown of circ_ZFR suppressed PTX resistance, cell cycle process, proliferation, migration and invasion and induced apoptosis in PTX-resistant NSCLC cells. For mechanism analysis, circ_ZFR knockdown markedly downregulated the expression of KPNA4 by sponging miR-195-5p, thereby promoting PTX sensitivity and suppressing cell progression in PTX-resistant NSCLC cells. In addition, circ_ZFR silencing enhanced PTX sensitivity of NSCLC in vivo. Conclusion Circ_ZFR knockdown played a positive role in overcoming PTX resistance of NSCLC via regulating miR-195-5p/KPNA4 axis, which might provide a possible circRNA-targeted therapy for NSCLC.

Chronic morphine intake for treating various pain is frequently concomitant with morphine-induced hyperalgesia and tolerance. The mechanisms can be explained by the activation of p38-MAPK proteins in microglia in the spinal cord horn. Exercise has been shown to prevent the development of microglia overactivation. Thus, we designed to test whether exercise prevents the morphine-induced hyperalgesia and tolerance as well as suppression of p38 phosphorylation. A p38 inhibitor SB203580, exercise, and exercise preconditioning were used for treating morphine-induced hyperalgesia and tolerance development in the present study. The behavior tests for hyperalgesia and tolerance were performed in male Wistar rats before and after morphine administration. Western blotting and immunostaining for examining phosphorylated-p38 expression were performed after the behavior tests. Our results showed that SB203580 and exercise, but not exercise preconditioning, prevented the occurrence of morphine-induced hyperalgesia and tolerance. Meanwhile, exercise decreased morphine-induced phosphorylated-p38 overexpression. In summary, exercise prevented the development of morphine-induced hyperalgesia and tolerance. The mechanism may be related to inhibition of p38 phosphorylation.