Effect of TRPV1 channel on the proliferation and apoptosis in asthmatic rat airway smooth muscle cells

ABSTRACT

Background: Hyperplasia of airway smooth muscle cells (ASMC) is a major contributor to airway remodeling in asthma. Transient receptor potential vanilloid 1 (TRPV1) is an important channel to mediate Ca²⁺ influx. This study explores the expression of TRPV1 channel and its effect on the proliferation and apoptosis in rat ASMC, in order to find a new target to treat airway remodeling in asthma. Methods: Rats were sensitized and challenged with ovalbumin to replicate asthmatic models. Proliferating cell nuclear antigen (PCNA) was detected by immunohistochemistry. Reverse transcriptase-polymerase chain reaction, immunocytochemistry, and Western blot were used to detect the mRNA and protein expression of TRPV1 channel. Intracellular calcium ([Ca²⁺]i) was detected using confocal fluorescence Ca²⁺ imaging. [³H] thymidine incorporation and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were used to observe the DNA synthesis and proliferation. TUNEL assay was used to detect the apoptosis of ASMC. Results: (1) The expression of PCNA was significantly increased in intact asthmatic rat ASMC. (2) The expression of TRPV1 channel was significantly increased in asthmatic rat ASMC. (3) [Ca²⁺]i in ASMC of the asthmatic group was significantly increased. After treatment with TRPV1 agonist capsaicin (CAP), [Ca²⁺]i was further increased, whereas [Ca²⁺]i was decreased after administration of TRPV1 antagonist capsazepine (CPZ) in ASMC of the asthmatic group. (4) The DNA synthesis and absorbance of MTT were significantly increased, while apoptosis was significantly decreased in asthmatic ASMC. CAP further enhanced proliferation and decreased apoptosis. CPZ significantly inhibited the effect of CAP in asthmatic ASMC. Conclusion: TRPV1 channel was involved in the regulation of proliferation and apoptosis in asthmatic ASMC.

KEYWORDS :

• airway smooth muscle cells (ASMC)
• apoptosis
• asthma
• proliferation
• transient receptor potential vanilloid 1 (TRPV1)