ABSTRACT
1. The present study was conducted to examine the involvement of oxidative stress in bee venom-induced inhibition of the Na+/glucose cotransporter (alpha-methyl-d-glucopyranoside (alpha-MG) uptake), a typical functional marker of proximal tubules, in primary cultured rabbit renal proximal tubule cells (PTC). 2. Bee venom (> or = 1 microg/mL) increased lipid peroxide (LPO) formation over 30 min. The increase in [(3)H]-arachidonic acid (AA) release and LPO formation and the inhibition of alpha-MG uptake induced by bee venom (1 microg/mL) and melittin (a major component of bee venom; 0.5 microg/mL) were blocked by N-acetyl-l-cysteine, vitamin C and vitamin E, anti-oxidants. 3. Bee venom- and melittin-induced increases in LPO formation and inhibition of alpha-MG uptake were significantly prevented by mepacrine and AACOCF(3), phospholipase A(2) inhibitors. In addition, nordihydroguaiareic acid (a lipoxygenase inhibitor) and econazole (a cytochrome P-450 epoxygenase inhibitor), but not indomethacin (a cyclo-oxygenase inhibitor), prevented bee venom- and melittin-induced increases in LPO formation and inhibition of alpha-MG uptake. 4. Nordihydroguaiareic acid prevented bee venom- and melittin-induced increases in Ca(2+) uptake. Moreover, anti- oxidants significantly prevented bee venom- and melittin-induced increases in Ca(2+) uptake. 5. In conclusion, bee venom inhibits alpha-MG uptake via the phospholipase A(2)-oxidative stress-Ca(2+) signalling cascade in primary cultured rabbit renal proximal tubule cells.
Subject(s)
Bee Venoms/pharmacology , Kidney Tubules, Proximal/metabolism , Lipid Peroxides/metabolism , Monosaccharide Transport Proteins/antagonists & inhibitors , Oxidative Stress/drug effects , Animals , Arachidonic Acid/metabolism , Arachidonic Acids/pharmacology , Biological Transport, Active , Calcium/metabolism , Cells, Cultured , Dose-Response Relationship, Drug , Enzyme Inhibitors/pharmacology , Kidney Tubules, Proximal/cytology , Kidney Tubules, Proximal/drug effects , Male , Phospholipases A/metabolism , Quinacrine/pharmacology , Rabbits , Time FactorsABSTRACT
Human envenomation caused by bee stings has been reported to cause acute renal failure and the pathogenetic mechanisms of these renal functional changes are still unclear. Bee venom is also a complex mixture of enzymes and proteins. Thus, this study was conducted to examine the effects of bee venom (BV, Apis mellifera) fractions on apical transporters' activity and its related signal pathways in primary cultured renal proximal tubule cells. Whole BV was extracted into three fractions according to solubility [a water-soluble fraction (BVA), an ethylacetate-soluble fraction (BVE), and a hexane-soluble fraction (BVH)]. BVA fraction was further separated to three portions according to molecular weights: BF1 (>20 kD), BF2 (10-20 kD), and BF3 (<10 kD). Each fraction was treated to the PTCs to the ratio of BV (1 microg/ml). BVA (930 ng/ml) significantly decreased cell viability, but BVH (27 ng/ml) and BVE (43 ng/ml) did not. BF3 (710 ng/ml) among BVA fractions predominantly decreased cell viability and inhibited alpha-methyl-D-glucopyranoside (alpha-MG), phosphate (Pi), and Na(+) uptake. In addition, BF3 increased [(3)H] arachidonic acid release, lipid peroxide formation, and Ca(2+) uptake. These effects of BF3 were blocked by mepacrine and AACOCF(3) (phospholipase A(2) inhibitors) or N-acetylcysteine, vitamin C, and vitamin E (antioxidants). In conclusion, BF3 (<10 kD) among BV fractions is the most effective portion in BV-induced inhibition of alpha-MG, P(i), and Na(+) uptake and these effects of BF3 are associated with phospholipase A(2)-oxidative stress-Ca(2+) signal cascade in the primary cultured rabbit renal proximal tubule cells.