Browsing by Author "Zunariah Buyong, Ph.D"

Chronic exposure to inorganic arsenic has been linked with multiple medical conditions, which shifted the use of inorganic to the organic-based herbicide, monosodium methyl arsenate (MSMA). However, with increasing numbers of chronic kidney disease of unknown causes (CKDu), chronic exposure to herbicide is believed to be one of the potential explanation. To date, studies on the effects of organic arsenic exposure on the kidney are limited. Therefore, this study aimed to investigate the effect of chronic oral organic arsenic exposure on the rat’s kidney. Thirty-six Sprague Dawley rats (N=36) were randomly divided into MSMA exposed, and its corresponding control groups for 2-,4- and 6-month, each with six animals per group. The exposed groups were given oral MSMA at 63.20 mg/kg body weight, while control groups received distilled water. At the end of each duration, the serum was collected for the creatinine level. The kidney tissues were harvested for arsenic level measurement, histopathological, immunohistochemistry, real-time PCR analysis and ultrastructural analysis. Genes expressions were done for kidney injury marker gene (KIM-1), oxidative stress genes (Catalase, GSR, NOS1), apoptosis genes (Tp53, Caspase-3 and Caspase-9) and inflammatory genes (Interleukin-6 and Interleukin-8). Serum creatinine was not significantly different between exposed and control groups. Tissue arsenic level was significantly higher in exposed groups as compared to that of the control group. All gene expression markers were downregulated at 2-month and upregulated at 4-month except for Catalase which remained downregulated. At 6-month, only KIM-1, GSR and Caspase-3 remained upregulated. Histological, immunohistochemistry and ultrastructural findings showed chronological changes in the glomeruli and proximal tubules with increased expressions of malondialdehyde (MDA) staining, Caspase-3 and TUNEL staining with the duration of exposure. Therefore, chronic oral exposure to low dose organic arsenic has demonstrated evidence of kidney injury in rats possibly due to oxidative stress.

Monosodium methylarsonate (MSMA) is a potent organoarsenical herbicide that is still being used in most Asian countries, despite its restriction in some other countries. Organic arsenic has been given less attention as it thought to be less toxic than inorganic counterpart. In most studies, the reported adverse effects were mainly on gastrointestinal system with little information on its severity to the liver. The objective of this study was to investigate the effect of organic arsenic (MSMA) exposure on the liver. Sixty rats were divided into three groups with different duration of exposure. The rats were given MSMA at 63.20 mg/kg daily for 2, 4 and 6 months through oral gavage. Serum samples were analysed for AST, ALT and ALP. Arsenic accumulation measurement, histomorphometric evaluation (H&E, PAS, reticulin and TUNEL staining) and ultrastructural study (scanning and transmission electron microscopy) were done on liver tissue. LSEC were isolated for gene expression study. Accumulation of arsenic were significantly higher in the MSMA-exposed rats compared to their control with the highest in the 6-month group [2-month (3.97± 2.28, p=0.009), 4-month (4.57±0.47), p<0.001 and 6-month (21.33±9.83, p=0.004) μg/g]. Both ALT [Control: 85.3± 13.0, Exposed: 52.0±5.2, p=0.005] and ALP [Control: 237.6±52.8, Exposed: 162.9± 28.9, p=0.007] were significantly lower in 4-month MSMA-exposed group than their control.The difference in AST level in all groups were not significant. Histopathological and ultra-structurally, focal necrotic, apoptotic and fibrotic changes in the liver with the reduction of organelles in hepatocytes were observed in 4- and 6-month exposed rats. In 4-month exposed group, the liver displayed increased in ballooning degeneration of the hepatocytes at zone 2, focal necrosis with minimal inflammatory infiltrates with fibrosis (mixture of stage 1 and 2). Disrupted hepatic cords with hepatocytes blebs were seen. In 6-month exposed rats, more extensive changes were noted. Cell cycle, apoptotic and DNA repair gene were affected in this exposure. At 2-month, cell cycle (Tp53), apoptotic (Tnfrsf1a) and DNA repair (Xrcc1) genes showed downward trend. However, at 4-month, both apoptotic-gene (Bax, Tnfsrf1a and Caspase 2) and the DNA repair gene (Xrcc1) expression showed upward trend. At chronic (6-month) exposure, only DNA repair gene (Mpg) showed upward trend. In conclusion, chronic MSMA exposure could be associated with potential liver injury. Thus, long term exposure to MSMA-contaminated water source should be taken seriously.