Non-neurotoxic activity of Malayan krait (Bungarus candidus) venom from Thailand

Background: Envenoming by kraits (genus Bungarus) is a medically significant issue in South Asia and Southeast Asia. Malayan krait (Bungarus candidus) venom is known to contain highly potent neurotoxins. In recent years, there have been reports on the non-neurotoxic activities of krait venom that include myotoxicity and nephrotoxicity. However, research on such non-neurotoxicity activities of Malayan krait venom is extremely limited. Thus, the aim of the present study was to determine the myotoxic, cytotoxic and nephrotoxic activities of B. candidus venoms from northeastern (BC-NE) and southern (BC-S) Thailand in experimentally envenomed rats. Methods: Rats were administered Malayan krait (BC-NE or BC-S) venom (50 g/kg, i.m.) or 0.9% NaCl solution (50 L, i.m.) into the right hind limb. The animals were sacrificed 3, 6 and 24 h after venom administration. The right gastrocnemius muscle and both kidneys were collected for histopathological analysis. Blood samples were also taken for determination of creatine kinase (CK) and lactate dehydrogenase (LDH) levels. The human embryonic kidney cell line (HEK-293) was used in a cell proliferation assay to determine cytotoxic activity. Results: Administration of BC-NE or BC-S venom (50 g/kg, i.m.) caused time-dependent myotoxicity, characterized by an elevation of CK and LDH levels. Histopathological examination of skeletal muscle displayed marked muscle necrosis and myofiber disintegration 24 h following venom administration. Both Malayan krait venoms also induced extensive renal tubular injury with glomerular and interstitial congestion in rats. BC-NE and BC-S venoms (1000.2 g/ mL) caused concentration-dependent cytotoxicity on the HEK-293 cell line. However, BC-NE venom (IC50 =8 ± 1 g/mL; at 24 h incubation; n = 4) was found to be significantly more cytotoxic than BC-S venom (IC50 =15 ± 2 g/mL; at 24 h incubation; n = 4). In addition, the PLA2 activity of BC-NE venom was significantly higher than that of BC-S venom...

Non-neurotoxic activity of Malayan krait (Bungarus candidus) venom from Thailand

Envenoming by kraits (genus Bungarus) is a medically significant issue in South Asia and Southeast Asia. Malayan krait (Bungarus candidus) venom is known to contain highly potent neurotoxins. In recent years, there have been reports on the non-neurotoxic activities of krait venom that include myotoxicity and nephrotoxicity. However, research on such non-neurotoxicity activities of Malayan krait venom is extremely limited. Thus, the aim of the present study was to determine the myotoxic, cytotoxic and nephrotoxic activities of B. candidus venoms from northeastern (BC-NE) and southern (BC-S) Thailand in experimentally envenomed rats. Methods: Rats were administered Malayan krait (BC-NE or BC-S) venom (50 µg/kg, i.m.) or 0.9% NaCl solution (50 µL, i.m.) into the right hind limb. The animals were sacrificed 3, 6 and 24 h after venom administration. The right gastrocnemius muscle and both kidneys were collected for histopathological analysis. Blood samples were also taken for determination of creatine kinase (CK) and lactate dehydrogenase (LDH) levels. The human embryonic kidney cell line (HEK-293) was used in a cell proliferation assay to determine cytotoxic activity. Results: Administration of BC-NE or BC-S venom (50 µg/kg, i.m.) caused time-dependent myotoxicity, characterized by an elevation of CK and LDH levels. Histopathological examination of skeletal muscle displayed marked muscle necrosis and myofiber disintegration 24 h following venom administration. Both Malayan krait venoms also induced extensive renal tubular injury with glomerular and interstitial congestion in rats. BC-NE and BC-S venoms (100­0.2 µg/ mL) caused concentration-dependent cytotoxicity on the HEK-293 cell line. However, BC-NE venom (IC50 =8 ± 1 µg/mL; at 24 h incubation; n = 4) was found to be significantly more cytotoxic than BC-S venom (IC50 =15 ± 2 µg/mL; at 24 h incubation; n = 4). In addition, the PLA2 activity of BC-NE venom was significantly higher than that of BC-S venom. Conclusions: This study found that Malayan krait venoms from both populations possess myotoxic, cytotoxic and nephrotoxic activities. These findings may aid in clinical diagnosis and treatment of envenomed patients in the future.(AU)

Effects of Bungarus candidus (Malayan krait) venom on general circulation and renal hemodynamics in experimental animals.

Background: Many studies have reported the occurrence of lethal acute renal failure after snakebites. Bungarus candidus (Malayan krait) is a medically important venomous snake distributed widely throughout Southeast Asia. The best known features of systemic envenoming by B. candidus are neurotoxic. Objective: Obtain more information on effects of B. candidus venom on changes in systemic and renal hemodynamics in experimental animals. Methods: Twelve adult male New Zealand white rabbits were used to study the effect of B. candidus venom on general circulation and renal hemodynamics. An anesthetized animal was intravenously injected with B. candidus venom at a dosage of 50μg/kg bodyweight. All changes of parameters were observed after initial post venom injection and recorded at 30 min intervals until 150 minutes after envenomation. Results: After envenomation, cardiovascular responses showed a marked decrease in mean arterial pressure within two minutes, afterwards gradually returning closely to baseline values. There were stepwise decreases in heart rate and cardiac output, while total peripheral resistance was slightly increased. The renal hemodynamics significantly decreased by glomerular filtration rate, effective renal plasma flow and effective renal blood flow, while the filtration fraction significantly increased. Envenomed animals showed a reduction in renal fraction, while renal vascular resistance stepwise increased. The plasma potassium level tended to increase. Animals showed stepwise decreases in urinary excretion of Na+, K+ and Cl-. A marked decrease in plasma calcium level was apparent at 120 minutes, while plasma creatine phosphokinase and lactate dehydrogenase levels increased at 30-120 minutes. Conclusion: A significant drop in blood pressure was attributed to a sustained fall in cardiac output, which would be associated with a reduction in heart rate. Sustained hypotension would contribute to reduction of renal blood flow, which results in decreased GFR.

[Bat lyssavirus in Thailand]

A study of bat lyssavirus survey was done in Thailand from 2001 to 2003. A total of 932 bats of 11 species were captured in 8 provinces for blood collection and testing for neutralizing antibodies against rabies virus (RABV), Australian bat lyssavirus (ABLV) and broader panel of other lyssaviruses (Irkut, Aravan and Khujand). All Thai bat samples were negative to RABV Sixteen samples of 394 with sufficient volume of serum had detectable neutralizing antibodies against Irkut, Aravan, Khujand and ABL viruses. Another 13 samples were also found to have antibody to ABLV. However, due to insufficient volume, further analysis to other lyssaviruses could not be performed. Nevertheless, this showed that the prevalence of lyssavirus infection in Thai bats could be as high as 7.3% (29/396). The present study showed that natural occurrence of lyssavirus antibodies found in Thai bats were related to newer putative lyssavirus genotype(s) other than those previously described. These data also suggest that several lyssaviruses are in circulation throughout Thailand as well as other Asian countries, such as in the Philippines, Central Asia, and in certain parts of Russia. The present study and preparation of this article was supported by grants from the Thailand Research Fund and the National Center for Genetic Engineering and Biotechnology, National Science and Technology Development Agency, Thailand.