OBJECTIVETo explore the mechanism of Astragalus polysaccharides (APS) for improving the cardiac function of Sjogren's syndrome (SS) model rats based on Keapl-Nrf2/ARE signaling pathway.

METHODSTotally 48 male Wistar rats were randomly divided into four groups by random digit table, i.e., the blank control group,the model control group,the APS group, and the hydroxychloroquine group, 12 in each group. Except those in the blank control group, 0. 1 mL mixed antigen protein of sufficiently emulsified Freund's complete adjuvant and submandibular gland protein was injected from two feet plantar to induce SS model. The intervention was started from 19th day after inflammation induction. Equal volume of normal saline was given to rats in the blank control group (1 mL/100 g), APS was administered to those in the APS group (1 mg/100 g), and hydroxychloroquine (0.03 125 g/kg) was administered to those in the hydroxychloroquine group. All rats were intervened once per day for 30 consecutive days. Changes of rats' body mass and drinking water quantity, submandibular gland index, spleen index, histological changes of glands were observed. Changes of the heart function were monitored using invasive hemodynamics. Serum reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), total antioxidant capacity (TAC), tumor necrosis factor alpha (TNF-alpha), and interleukin-35 (IL-35)were detected using ELISA method. The pathological changes were observed using HE staining. The protein expression of ROS, reactive nitrogen species (RNS), glutathione (GSH), and thioredoxin (TRX) were observed by immunohistochemical staining. The mRNA expression of Keap1, Nrf2, and ARE was detected using real time fluorescent quantitative PCR. The protein expression levels of gamma-glutamic acid and a half long glycine synthetase (gamma-GCS) and heme oxygenase 1 (HO-1) in the myocardial tissue were determined by Western blot method. Results Compared with the blank control group, the quantity of drinking water, submandibular gland index, spleen index, heart rate (HR), cardiac index (HI), left ventricular systolic pressure (LVSP), left ventricular diastolic pressure (LVEDP), MDA, ROS, TNF-alpha, ROS protein expression, RNS protein expression, Keap 1 mRNA expression, Maf mRNA expression, Nfr2 mRNA expression, and HO-1 protein expression, and gamma-GCS protein expression significantly increased (P <0.01); body mass, +/-dp/dtmax, SOD, TAC, IL-35, GSH, and TRX significantly decreased (P <0.01) in the model group. Compared with the model group, the quantity of drinking water, submandibular gland index, spleen index, LVEDP, MDA, ROS, TNF-alpha, ROS protein expression, RNS protein expression, Keap1 mRNA expression, Maf mRNA expression, Nfr2 mRNA expression, and HO-1 protein expression, and gamma-GCS protein expression significantly decreased (P<0.05); body mass, +/-dp/dtmax, SOD, TAC, IL-35, GSH protein expression, and TRX protein expression significantly increased (P < 0.05, P <0.01) in the AR group and the hydroxychloroquine group. In the hydroxychloroquine group HR increased (P <0.05). In the AR group HR and LVSP decreased (P <0. 05, P <0. 01). Compared with the hydroxychloroquine group, HR, LVEDP, - dp/dtmax, y-GCS protein expression significantly decreased (P <0. 05, P <0. 01); SOD, TAC, GSH, TRX, HO-1 protein expression increased (P <0.01 )in the AR group. HI was positively correlated with ROS (P <0. 05). LVSP and LVEDP were positively correlated with Keap1 -Nrf2/ARE signaling pathways (P <0. 01) , and negatively correlated with TAC (P <0. 05, P <0. 01 ). +/-dp/dtmax was negatively correlated with Keap1-Nrf2/ARE signaling pathways(P <0.05), and positively correlated with TNF alpha (P <0. 05).

CONCLUSIONSDeclined heart function exists in SS rats. The mechamechanism of APS for improving the heart function might be closely correlated with activating Keap1-Nrf2/ARE signaling pathway.