ABSTRACT
Objective@#To investigate the effects and potential mechanisms of tolvaptan on chronic intermittent hypoxia (CIH)-induced atrial remodeling in rats.@*Methods@#A total of 45 Sprague-Dawley rats were divided into 3 groups by the random number table: control group, CIH group (6 h/d for 30 days), CIH plus tolvaptan group (8 mg·kg-1·d-1 per gavage for 30 days). Echocardiography examination was performed after 30 days. Thereafter, 5 rats were randomly chosen for histology evaluation, 5 for molecular biological examinations and another 5 rats underwent isolated heart electrophysiology study in each group. Protein and mRNA expression levels of miRNA-21, Spry1, PTEN, ERK/p-ERK, MMP-9, PI3K, AKT/p-AKT were detected.@*Results@#Compared to the rats in control group, rats in the CIH group showed higher atrial interstitial collagen deposition (P<0.001), increased atrial fibrillation inducibility (P=0.022). The results of immunohistochemistry staining showed that the mean optical density (MOD) of ERK, p-ERK and MMP-9 were significantly increased (all P<0.05), the MOD of Spry1 and PTEN were significantly decreased (both P<0.05), above changes could be significantly reversed by cotreatment with tolvaptan. No significant differences were detected in PI3K and AKT among the three groups (P>0.05). In addition, compared with rats in control group, mRNA levels of miRNA-21, MMP-9, PI3K, AKT, and protein levels of ERK, p-ERK, MMP-9 were significantly increased in CIH group(all P<0.05), whereas protein levels of Spry1, PI3K, p-AKT were significantly decreased (all P<0.05). Above changes could be significantly attenuated.@*Conclusions@#CIH induces significant atrial remodeling in this rat model, which can be attenuated by tolvaptan possibly through modulating miRNA-21/Spry1/ERK/MMP-9 and miRNA-21/PTEN/PI3K/AKT signaling pathways.
ABSTRACT
Objective To investigate the potential effects and mechanism on peroxisome proliferator-activated receptor γ-toll-like receptor 4-tumor necrosis factor-α (PPARγ-TLR4-TNF-α) targeted pathway on hyperglycemia induced myocardium inflammation and oxidative stress. Methods Thirty-two Japanese healthy adult rabbits were randomly divided into four groups with 8 rabbits in each group: normal control group (NC group), diabetes mellitus group (DM group), diabetes mellitus + pioglitazone 4 mg·kg-1·d-1 and 8 mg·kg-1·d-1 groups (DM+PGZ 4 mg and 8 mg groups). DM model was reproduced by alloxan of 150 mg/kg through auricular vein injection. On the same day of successful DM model reproduction, the diabetic rabbits were fed with corresponding dose of pioglitazone in DM+PGZ 4 mg and 8 mg groups, but the rabbits in NC group were not challenged. After 8 weeks of feeding, venous blood of left jugular vein bifurcation and myocardium tissue were harvested respectively for the determination of inflammation and oxidative stress parameters. TNF-α, interleukin-1 (IL-1), adiponectin (ADP), nitric oxide (NO) and total nitric oxide synthase (NOS) levels were determined by enzyme linked immunosorbent assay (ELISA), myeloperoxidase (MPO) activity was determined by colorimetric method, superoxide dismutase (SOD) activity was determined by hydroxylamine method, malondialdehyde (MDA) was determined by thiobarbituric acid colorimetric method, and catalase (CAT) activity was determined by UV spectrophotometry method. In addition, the mRNA expressions of TNF-α and TLR4 were determined by real-time quantitate reverse transcription-polymerase chain reaction (RT-qPCR). Results ① IL-1 and TNF-α in serum and myocardium of model rabbits were significantly increased, ADP was significantly decreased, and the mRNA expressions of TNF-α and TLR4 in myocardium were significantly increased, indicating a significant inflammatory reaction. The inflammatory reaction in pioglitazone intervention groups was significantly reduced, TNF-αand IL-1 levels in serum and myocardium of DM+PGZ 4 mg and 8 mg groups were significantly decreased as compared with those of DM group [serum: TNF-α(ng/L) was 268.33±46.57, 261.34±33.73 vs. 331.40±69.05, myocardium: TNF-α (ng/L) was 144.72±26.90, 139.59±14.59 vs. 177.48±27.40; serum: IL-1 (ng/L) was 24.40±2.56, 23.35±3.13 vs. 30.08±5.44, myocardium: IL-1 (ng/L) was 21.26±2.85, 20.54±2.75 vs. 24.78±3.60, all P < 0.05], and ADP levels were significantly increased [serum (μg/L): 19.64±8.85, 20.54±7.47 vs. 15.45±3.06, myocardium (μg/L): 10.31±2.22, 11.49±3.42 vs. 7.76±1.77, all P < 0.05], and the mRNA expressions of TNF-α and TLR4 in myocardium were significantly decreased (TNF-αmRNA: 0.15±0.05, 0.14±0.06 vs. 0.25±0.09; TLR4 mRNA: 0.57±0.17, 0.40±0.18 vs. 0.75±0.35, all P < 0.05). ②Oxidative stress in serum and myocardium of model rabbits was significantly increased, SOD, NO, and total NOS levels were significantly decreased while the serum CAT and MDA levels were significantly increased without effect on MPO. Compared with the DM group, SOD and NO levels in serum and myocardium were significantly increased in DM+PGZ 4 mg and 8 mg groups [serum: SOD (U/L) was 571.39±40.85, 609.28±54.47 vs. 535.10±37.08, myocardium:SOD (U/mg) was 55.74±8.12, 53.60±9.87 vs. 42.26±12.34; serum: NO (μmol/L) was 2.95±0.51, 2.99±0.43 vs. 2.03±0.78, myocardium: NO (nmol/mg) was 1.95±0.37, 2.11±0.26 vs. 1.56±0.33, all P < 0.05], the serum MDA levels were significantly decreased (μmol/L: 20.11±2.34, 19.70±2.02 vs. 23.07±3.06, both P < 0.05), while no significant effect on CAT. There was no significant difference in parameter of inflammatory and oxidative stress between the two pioglitazone intervention groups. Conclusion 4 mg·kg-1·d-1 pioglitazone could activate PPARγ-TLR4-TNF-α targeted pathway, thus inhibit inflammatory and oxidative stress factors expression, and down-regulate hyperglycemia induced myocardium inflammatory and oxidative stress level, but the effect did not show a dose dependent manner.