The present study was designed to investigate the expression and function of transmembrane protein 16 (TMEM16A), a calcium‑activated chloride channel (CaCC), in the stria vascularis (SV) of the cochlea of guinea pigs at different ages, and to understand the role of CaCCs in the pathogenesis of presbycusis (age‑related hearing loss), the most common type of sensorineural hearing loss that occurs with natural aging. Guinea pigs were divided into the following groups: 2 weeks (young group), 3 months (youth group), 1 year (adult group), D‑galactose intervention (D‑gal group; aging model induced by subcutaneous injection of D‑galactose) and T16Ainh‑A01 (intraperitoneal injection of 50 µg/kg/day TMEM16A inhibitor T16Ainh‑A01 for 2 weeks). Differences in the hearing of guinea pigs between the various age groups were analyzed using auditory brainstem response (ABR), and immunofluorescence staining was performed to detect TMEM16A expression in the SV and determine the distribution. Reverse transcription‑quantitative PCR and western blot analyses were conducted to detect the mRNA and protein levels of TMEM16A in SV in the different age groups. Morris water maze behavior analysis demonstrated that spatial learning ability and memory were damaged in the D‑gal group. Superoxide dismutase activity and malondialdehyde content assays indicated that there was oxidative stress damage in the D‑gal group. The ABR thresholds gradually increased with age, and the increase in the T16Ainh‑A01 group was pronounced. Immunofluorescence analysis in the cochlear SV of guinea pigs in different groups revealed that expression of TMEM16A increased with increasing age (2 weeks to 1 year); fluorescence intensity was reduced in the D‑gal model of aging. As the guinea pigs continued to mature, the protein and mRNA contents of TMEM16A in the cochlea SV increased gradually, but were decreased in the D‑gal group. The findings indicated that CaCCs in the cochlear SV of guinea pigs were associated with the development of hearing in guinea pigs, and that downregulation of TMEM16A may be associated with age‑associated hearing loss.

Gap junctions (GJs) formed by connexins (Cxs) in T lymphocytes have been reported to have important roles in the T lymphocyte‑driven inflammatory response and hypertension‑mediated inflammation. Estrogen has a protective effect on cardiovascular diseases, including hypertension and it attenuates excessive inflammatory responses in certain autoimmune diseases. However, the mechanisms involved in regulating the pro‑inflammatory response are complex and poorly understood. The current study investigated whether β‑estradiol suppresses hypertension and pro‑inflammatory stimuli‑mediated inflammatory responses by regulating Cxs and Cx‑mediated GJs in peripheral blood lymphocytes. Male, 16‑week‑old spontaneously hypertensive rats (SHR) and Wistar‑Kyoto rats (WKY) rats were randomly divided into the following three groups: WKY rats, vehicle (saline)‑treated SHRs, and β‑estradiol (20 µg/kg/day)‑treated SHRs. β‑estradiol was administered subcutaneously for 5 weeks. Hematoxylin and eosin staining was performed to evaluate target organ injury. Flow cytometry and ELISA were used to measure the populations of T lymphocyte subtypes in the peripheral blood, and expression of Cx40/Cx43 in T cell subtypes, and pro‑inflammation cytokines levels, respectively. ELISA, a dye transfer technique, immunofluorescence and immunoblotting were used to analyze the effect of β‑estradiol on pro‑inflammatory cytokine secretion, Cx‑mediated GJs and the expression of Cxs in concanavalin A (Con A)‑stimulated peripheral blood lymphocytes isolated from WKY rat. β‑estradiol significantly decreased blood pressure and inhibited hypertension‑induced target organ injury in SHRs. Additionally, β‑estradiol treatment significantly improved the immune homeostasis of SHRs, as demonstrated by the decreased percentage of cluster of differentiation (CD)4+/CD8+ T‑cell subset ratio, reduced serum levels of pro‑inflammatory cytokines and increased the percentage of CD4+CD25+ T cells. β‑estradiol also markedly reduced the expression of Cx40/Cx43 in T lymphocytes from SHRs. In vitro, β‑estradiol significantly suppressed the production of pro‑inflammatory cytokines, reduced communication via Cx‑mediated gap junctions and decreased the expression of Cx40/Cx43 in Con A‑stimulated lymphocytes. These results indicate that β‑estradiol attenuates inflammation and end organ damage in hypertension, which may be partially mediated via downregulated expression of Cxs and reduced function of Cx‑mediated GJ.

Niflumic acid (NFA) is a novel gap junction (GJ) inhibitor. The aim of the present study was to investigate the effect of NFA on GJ communication and the expression of connexin (Cx) in vascular smooth muscle cells (VSMCs) of mesenteric arterioles of spontaneously hypertensive rats (SHR). Whole‑cell patch clamp recording demonstrated that NFA at 1x10‑4 M significantly inhibited the inward current and its effect was reversible. The time for charging and discharging of cell membrane capacitance (Cinput) reduced from 9.73 to 0.48 ms (P<0.05; n=6). Pressure myograph measurement showed that NFA at 3x10‑4 M fully neutralized the contraction caused by phenylephrine. The relaxation responses of normotensive control Wistar Kyoto (WKY) rats were significantly higher, compared with those of the SHRs (P<0.05; n=6). Western blot and reverse transcription‑quantitative polymerase chain reaction analyses showed that the mRNA and protein expression levels of Cx43 of the third‑level branch of mesenteric arterioles of the SHRs and WKY rats were higher, compared with those of the first‑level branch. The mRNA and protein expression levels of Cx43 of the primary and third‑level branches of the mesenteric arterioles in the SHRs were higher, compared with those in the WKY rats (P<0.05; n=6). The mRNA levels of Cx43 in the mesenteric arterioles were significantly downregulated by NFA in a concentration‑dependent manner (P<0.01; n=6). The protein levels of Cx43 in primary cultured VSMCs isolated from the mesenteric arterioles were also significantly downregulated by NFA in a concentration‑dependent manner (P<0.01; n=6). These results showed that the vasorelaxatory effects of GJ inhibitors were reduced in the SHRs, which was associated with a higher protein expression level of Cx43 in the mesenteric arterioles of the SHRs. NFA also relaxed the mesenteric arterioles by reducing the expression of Cx43, which decreased blood pressure. Therefore, regulation of the expression of GJs may be a therapeutic target for the treatment of hypertension.