Proximal Tubular Toxicity of Ochratoxin A Is Amplified by Simultaneous Inhibition of the Extracellular Signal-Regulated Kinases 1/2

Abstract

Ochratoxin A (OTA) is a mycotoxin involved in the development of chronic nephropathies and a known carcinogen. As we have shown previously, OTA activates mitogen-activated protein kinases [extracellular signal-regulated kinase 1 and 2 (ERK1/2), c-jun amino-terminal kinase (JNK), and extracellular-regulated protein kinase 38 (p38)] in proximal tubular cells (opossum kidney and normal rat kidney epithelial). ERK1/2, JNK, or p38 are thought to mediate opposite action on apoptosis, fibrosis, and inflammation. As we have already shown, OTA activates the latter processes. Here, we investigated the effect of OTA in the absence or presence of the ERK1/2 inhibitor U0126 [1,4-diamino-2,3-dicyano-1,4bis(2-aminophenylthio)-butadiene] to test whether OTA then will exert increased toxicity. In the presence of ERK1/2 inhibition, OTA decreased cell number and protein to a significantly larger extent compared with OTA alone. The same was true for epithelial tightness, apoptosis (caspase-3 activity), and necrosis (lactate dehydrogenase release). Furthermore, simultaneous inhibition of ERK1/2 amplified the effect of OTA on markers of inflammation (nuclear factor of the -enhancer in B cells activity), fibrosis (collagen secretion), and epithelial mesenchymal transition (␣ smooth muscle actin). OTA induces phenomena typical for chronic interstitial nephropathy and activates ERK1/2, JNK, and p38 in proximal tubular cells. Inhibition of ERK1/2 aggravates the effects of OTA or even induces toxicity at normally nontoxic concentrations. This is highly likely due to activation of JNK and p38. Our data indicate a new mechanistic explanation for the toxic actions induced by OTA, and they are notable with respect to a possible coexposition of the kidney to OTA and naturally occurring ERK1/2 inhibitors. Finally, our data give rise to an attractive hypothesis on the coincidence of increased OTA exposition and urinary tract tumors in humans.

Ochratoxin A mediates MAPK activation, modulates <i>IL-2</i> and <i>TNF-α</i> mRNA expression and induces apoptosis by mitochondria-dependent and mitochondria-independent pathways in human H9 T cells

“…7). The MAPK phosphorylation level remained constant over the next 3 hr; these results are in concordance with those of previous studies and confirm the time-dependent OTA activation of these three MAPKs (Sauvant et al, 2005).…”

Differential Cell Sensitivity between OTA and LPS upon Releasing TNF-α

“…, extracellular signal-regulated kinase 1 and 2 (ERK1/2)), c-jun amino-terminal kinase (JNK), and extracellular-regulated protein kinase 38 (p38) in proximal tubular cells [41,42]. In our paper, we have examined the role of pRaf/MEK1/2 and p38 in OTA-mediated TNF-α release in comparison with LPS.…”

Renal cell apoptosis induced by nephrotoxic drugs: cellular and molecular mechanisms and potential approaches to modulation

“…Cidofovir Human tubules/HK-2 [144] Cisplatin Mouse PTC [71,171,180] Mouse CDC [181] Cyclosporine A MDCK [182] Rat: subcortical and juxtamedullary kidney sections [179] Tubular and interstitial cells [ Endotoxins Human tubular epithelial cells [185,186] Mice (Fas-/-, TNFR1-/-TNFR2-/-) [187] C3H/HeJ Mice [188] Fluoroquinolones Human: distal tubular cells [189] Mercuric chloride Cultured rat proximal tubular cells (WKPT) [178] LLC-PK1 [190] Microcystin Rat: kidney cortex and medulla [191] Ochratoxin A PRK [192] OK [193] NRK-52E [193] Oxalate MDCK [194] Radio-contrast agents MDCK [195][196][197] LLC-PK1 [197,198] …”