Histopathological, biochemical and molecular studies on a model of systemic autoimmune disease induced by sodium silicate in non-genetically prone rats.

Sodium silicate (Na2SiO3) is an inorganic silica salt used in many products. Few studies reported autoimmune diseases (AIDs) due to Na2SiO3 exposure. This study investigates the role of Na2SiO3 exposure by different routes and doses in AID development in rats. We assigned 40 female rats to four groups: G1 control group, G2 rats were subcutaneously injected with 5 mg Na2SiO3 suspension, and G3 and G4 rats were orally administered 5 mg and 7 mg Na2SiO3 suspension, respectively. Na2SiO3 was administered weekly for 20 weeks. Serum anti-nuclear antibodies (ANA) detection, histopathology of kidney, brain, lung, liver, and heart, oxidative stress biomarkers (MDA and GSH) in tissues, Matrix metalloproteinase activity in serum, TNF-α, and Bcl-2 expression in tissues were performed. ANA was significantly increased in silicate groups, especially G2. Creatinine was significantly increased in silicate groups. Histopathology revealed vasculitis and fibrinoid degeneration of blood vessels, a picture of immune-mediated glomerulonephritis in the kidneys, and chronic interstitial pneumonia with medial hypertrophy of pulmonary blood vessels. The activity of gelatinases (MMP-2 and MMP-9) and collagenase (MMP-13), which play role in inflammation, remodeling, and immune complex degradation, were significantly increased in the silicate-exposed groups. Bcl-2 was significantly decreased, indicating apoptosis. Therefore, oral administration and subcutaneous injection of Na2SiO3 induced immune-mediated glomerulonephritis with elevated ANA levels and overexpression of TNF-α in rats.

The anti-inflammatory effect of myrrh ethanolic extract in comparison with prednisolone on an autoimmune disease rat model induced by silicate.

Autoimmune disease is a complex chronic disease that triggers immune activation against autoantigens resulting in tissue damage. Epidemiological data showed that autoimmune diseases are increasing worldwide over the last decades owing to increased environmental pollution. This study investigates the therapeutic effect of myrrh as a natural medicine compared to prednisolone in the treatment of immune-mediated glomerulonephritis induced by silicate. The autoimmune disease model in rats was induced by injecting 5 mg crystalline sodium silicate suspension subcutaneously once weekly for 20 weeks, and then the rats were treated either with myrrh extract or prednisolone or with both for 6 weeks. Liver and kidney function tests, histopathology, and immunohistochemistry of TNF-α expression in kidney tissue were performed. The creatinine significantly elevated in silica-treated group and decreased in other treated groups. Histopathology of the kidney revealed improvement of glomerular and tubular basement thickness in all treated groups, but the inflammatory cell count slightly decreased in the group treated with myrrh than the other treated groups which showed a marked decrease. TNF-α expression was significantly decreased in all treated groups. Interestingly, the myrrh did not produce hepatic lesions and improve the side effect of prednisolone in the liver when taken in combination. Therefore, myrrh extract possessed anti-inflammatory properties and counteracted the side effect of prednisolone on the liver. Myrrh extract can serve as a conjunctive therapy with prednisolone to treat autoimmune diseases.