Objective To explore the protective effect of neuregulin-1 (NRG-1) on heart function and myocardium in rats with sepsis and its mechanism . Methods Healthy male Sprague-Dawly (SD) rats were divided into three groups according to random number table method, with 6 rats in each group. Sepsis model was established by cecal ligation and puncture (CLP group); rats in sham operation group (sham group) underwent the same procedure except ligation. Rats in NRG-1 pre-treatment group (NRG group) were intravenously injected with recombinant human NGR-1 (rhNRG-1) at the dose of 10 μg/kg through tail vein; rats in CLP group and sham group were treated with the same amount of saline. At 24 hours after CLP, hemodynamic method was used to evaluate the cardiac function, and myocardial morphology was observed with hematoxylin and eosin (HE) staining, enzyme linked immunosorbent assay (ELISA) was used to detect the levels of cardiac troponin T (cTnT), tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) in serum and macrophage migration inhibitor factor (MIF) in myocardial tissue. Results ① heart function: compared with the sham group, the mean arterial pressure (MAP), left ventricular systolic pressure (LVSP) and left ventricular pressure maximal rate of rise and fall (±dp/dt max) were significantly decreased in CLP group and NRG group, while the MAP, LVSP and ±dp/dt max in NRG group were significantly higher than those in CLP group [MAP (mmHg, 1 mmHg = 0.133 kPa): 125.78±8.15 vs. 113.05±5.85, LVSP (mmHg): 151.27±6.79 vs. 139.39±8.05, +dp/dt max (kPa/s): 4 389.59±332.38 vs. 3 706.85±451.31, -dp/dt max (kPa/s): 4 291.42±323.72 vs. 3 691.17±515.44, all 1 <0.05]. ②Myocardial injury: compared with the sham group, the levels of serum cTnT in CLP group and NRG group were significantly increased, while the levels of serum cTnT in NRG group were significantly lower than those in CLP group (ng/L: 206.37±67.28 vs. 344.13±80.95, 1 < 0.05), and the HE staining showed that myocardial pathological changes in NRG group were improved compared with the CLP group. ③Inflammatory mediators level: compared with the sham group, the levels of serum TNF-α, IL-1β and myocardial MIF were significantly increased in CLP group and NRG group, while the indicators in NRG group were lower than those in CLP group [TNF-α(ng/L): 52.77±3.43 vs. 97.19±13.98, IL-1β (ng/L): 40.25±5.48 vs. 56.05±6.88, MIF (μg/L): 1.92±0.16 vs. 2.87±0.10, all 1 <0.05]. Conclusion NRG-1 can reduce circulating levels of inflammatory factors in rats with sepsis, adjust myocardial MIF level, and alleviate myocardial cell injury, thereby improving cardiac function, and play a role in myocardial protection.

Calcium-binding protein is an indispensable protein which performs extensive and important functions in the growth of Schistosoma japonicum. Based on our primary study on tegument surface proteins of S. japonicun, a cDNA encoding a 66 kDa calcium-binding protein of S. japonicum (Chinese strain) was cloned, sequence analysis revealed that it was identical with that of SjIrV1 of Philippines strains S. japonicum. The expression of SjIrV1 were detected by Real-time PCR, using cDNA templates isolated from 7, 14, 21, 28, 35 and 42 days worms and the results revealed that the gene was expressed in all investigated stages, and the mRNA level of SjIrV1 is much higher in 42 d female worms than that in 42 d male worms. The cDNA containing the open reading frame of IrV1 was subcloned into a pET28a (+) vector and transformed into competent Escherichia coli BL21 for expression. The recombinant protein was purified using a Ni-NTA purification system, and confirmed by high performance liquid chromatography (RP-HPLC) and tandem mass spectrometry (MS/MS). Western blotting analysis showed that recombinant SjIrV1 (rSjIrV1) could be recognized by the S. japonicum infected mouse serum and the mouse serum specific to rSjIrV1, respectively. Immunofluorescence observation exhibited that SjIrV1 was mainly distributed on the tegument of the 35-day adult worms. ELISA test revealed that IgG, IgG1 and IgG2a antibodies are significantly increased in the serum of rSjIrV1 vaccinated mice. The study suggested that rSjIrV1 might play an important role in the development of S. japonicum.
Animals ; Antibodies, Helminth ; blood ; Calcium-Binding Proteins ; genetics ; metabolism ; Cloning, Molecular ; Escherichia coli ; metabolism ; Female ; Genetic Vectors ; Helminth Proteins ; genetics ; metabolism ; Male ; Mice ; Recombinant Proteins ; genetics ; metabolism ; Schistosoma japonicum ; genetics ; metabolism