dizocilpine-maleate and Kidney-Diseases

This study investigated the role of NMDA receptor in hyperhomocyteinemia (hHcys)-induced NADPH oxidase (Nox) activation and glomerulosclerosis. Sprague-Dawley rats were fed a folate-free (FF) diet to produce hHcys, and a NMDA receptor antagonist, MK-801, was administrated. Rats fed the FF diet exhibited significantly increased plasma homocysteine levels, upregulated NMDA receptor expression, enhanced Nox activity and Nox-dependent O(2)(.-) production in the glomeruli, which were accompanied by remarkable glomerulosclerosis. MK-801 treatment significantly inhibited Nox-dependent O(2)(.-) production induced by hHcys and reduced glomerular damage index as compared with vehicle-treated hHcys rats. Correspondingly, glomerular deposition of extracellular matrix components in hHcys rats was ameliorated by the administration of MK-801. Additionally, hHcys induced an increase in tissue inhibitor of metalloproteinase-1 (TIMP-1) expression and a decrease in matrix metalloproteinase (MMP)-1 and MMP-9 activities, all of which were abolished by MK-801 treatment. In vitro studies showed that homocysteine increased Nox-dependent O(2)(.-) generation in rat mesangial cells, which was blocked by MK-801. Pretreatment with MK-801 also reversed homocysteine-induced decrease in MMP-1 activity and increase in TIMP-1 expression. These results support the view that the NMDA receptor may mediate Nox activation in the kidney during hHcys and thereby play a critical role in the development of hHcys-induced glomerulosclerosis.

Topics: Animals; Cell Line; Dizocilpine Maleate; Extracellular Matrix; Folic Acid; Gene Expression; Hyperhomocysteinemia; Kidney; Kidney Diseases; Kidney Glomerulus; Matrix Metalloproteinase 1; Matrix Metalloproteinase 9; N-Methylaspartate; NADPH Oxidases; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Tissue Inhibitor of Metalloproteinase-1

Podocytes possess the complete machinery for glutamatergic signaling, raising the possibility that neuron-like signaling contributes to glomerular function. To test this, we studied mice and cells lacking Rab3A, a small GTPase that regulates glutamate exocytosis. In addition, we blocked the glutamate ionotropic N-methyl-d-aspartate receptor (NMDAR) with specific antagonists. In mice, the absence of Rab3A and blockade of NMDAR both associated with an increased urinary albumin/creatinine ratio. In humans, NMDAR blockade, obtained by addition of ketamine to general anesthesia, also had an albuminuric effect. In vitro, Rab3A-null podocytes displayed a dysregulated release of glutamate with higher rates of spontaneous exocytosis, explained by a reduction in Rab3A effectors resulting in freedom of vesicles from the actin cytoskeleton. In addition, NMDAR antagonism led to profound cytoskeletal remodeling and redistribution of nephrin in cultured podocytes; the addition of the agonist NMDA reversed these changes. In summary, these results suggest that glutamatergic signaling driven by podocytes contributes to the integrity of the glomerular filtration barrier and that derangements in this signaling may lead to proteinuric renal diseases.

Topics: Animals; Cells, Cultured; Cytoskeleton; Dizocilpine Maleate; Excitatory Amino Acid Antagonists; Exocytosis; Female; Glomerular Filtration Rate; Glutamic Acid; Ketamine; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Mice, Knockout; Podocytes; rab3A GTP-Binding Protein; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Signal Transduction

The N-methyl-d-aspartate (NMDA) receptor is expressed in the kidney. The receptor plays a major role in gentamicin ototoxicity. We assessed the role of the renal NMDA receptor subunits NR1 and NR2C in a model of gentamicin nephrotoxicity.. Rats were exposed to either saline (control), high-dose, short-term gentamicin, or short-term gentamicin plus the NMDA antagonist MK-801 (short-term gentamicin + MK-801) for 3 days.. Real-time reverse transcription-polymerase chain reaction (RT-PCR) revealed that NR1 mRNA expression was significantly higher (P= 0.03) in the renal cortex of short-term gentamicin rats. NR2C subunit mRNA expression was unaltered in short-term gentamicin rats. Western blot analysis revealed that NR1 (P= 0.009) and NR2C (P= 0.003) protein abundance was significantly higher in the renal cortex short-term gentamicin rats. We assessed two potential intracellular pathways that may mediate short-term gentamicin/NMDA. Calpain I and II expression was similar in short-term gentamicin and control rats. Endothelin type B receptor (ETBR) expression was significantly increased in the renal cortex of short-term gentamicin rats (P= 0.0003), and urinary nitrite concentration (reflecting nitric oxide) was significantly increased in short-term gentamicin rats (P= 0.03). Serum creatinine was significantly elevated in short-term gentamicin animals (P= 0.03), and this increase was attenuated in short-term gentamicin + MK-801 rats. Blood pressure was higher in short-term gentamicin rats; this was attenuated in short-term gentamicin + MK-801 rats. Urine pH was significantly lower in short-term gentamicin (P < 0.0001) rats; this was reversed in short-term gentamicin + MK-801 (P= 0.005) rats. Urinary nitrite was significantly higher in short-term gentamicin rats; this was normalized in short-term gentamicin + MK-801 rats. MK-801 alone had no effect on clinical parameters.. NMDA receptor subunit expression is increased in short-term gentamicin animals, and the receptor likely mediates cell damage via the endothelin-ETBR-nitric oxide pathway. NMDA antagonism ameliorated renal damage after exposure to short-term gentamicin.

Topics: Animals; Anti-Bacterial Agents; Dizocilpine Maleate; Excitatory Amino Acid Agonists; Excitatory Amino Acid Antagonists; Gentamicins; Intracellular Membranes; Kidney; Kidney Diseases; Male; N-Methylaspartate; Nitrites; Protein Isoforms; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; RNA, Messenger