Effect of EGF on H₂O₂‐induced inhibition of α‐MG uptake in renal proximal tubule cells: Involvement of MAPK and AA release

Abstract

Both oxidative stress and epidermal growth factor (EGF) contribute to the initiation and progression of renal proximal tubular dysfunction under pathophysiologic conditions. Thus, this study was performed (1) to examine both the individual, and the combined effects of H2O2 and EGF on alpha-methyl-D-glucopyranoside uptake (alpha-MG uptake) in the primary cultured renal proximal tubule cells (PTCs), and (2) to elucidate the involvement of p44/42 mitogen activated protein kinase (MAPK) and phospholipase A2 in mediating these actions. Both H2O2 and EGF inhibited alpha-MG uptake individually, while the combination of H2O2 and EGF further potentiated the inhibitory effect on alpha-MG uptake, which was elicited by each agent. H2O2 not only caused a rapid increase in the phosphorylation of p44/42 MAPK, but also promoted the translocation of cytosolic phospholipase A2 (cPLA2) from the cytosolic to particulate fraction, and stimulated cellular [3H]-arachidonic acid (AA) release. EGF similarly activates phosphorylation of p44/42 MAPK and stimulates [3H]-AA release. When PTCs were exposed to 100 microM H2O2 and 50 ng/ml EGF simultaneously, a further increase in the phosphorylation of p44/42 MAPK, of [3H]-AA release, and of prostaglandin E2 (PGE2) production was elicited as compared with the effects of each individual agonist alone. Moreover, the additive phosphorylation of p44/42 MAPK, [3H]-AA release, and PGE2 production by H2O2 and EGF was almost completely inhibited by the p44/42 MAPK inhibitor, PD 98059. In conclusion, these results are consistent with the hypothesis that under conditions of oxidative stress, the H2O2-induced inhibition of alpha-MG uptake in the renal proximal tubule is mediated through a modulation of the EGF signaling pathway, promoting further phosphorylation of p44/42 MAPK, activation of PLA2.

Hydrogen peroxide stimulates chloride secretion in primary inner medullary collecting duct cells via mPGES-1-derived PGE2

“…We attempted to determine the intracellular mediators of H 2 O 2 -induced activation of CFTR in cultured IMCD cells with emphasis on prostaglandins. ROS have been reported to stimulate PGE 2 release from both collecting duct and proximal tubule cells (7,35). We found that H 2 O 2 -stimulated I sc was significantly attenuated by the nonselective COX inhibitor indomethacin, indicating a requirement of COX activity for the activation of CFTR.…”

“…Role of PGE 2 in H 2 O 2 -stimulated I sc . H 2 O 2 has been reported to stimulate PGE 2 release from proximal tubule and collecting duct cells (7,35), raising a possibility that PGE 2 may mediate the H 2 O 2 -stimulated Cl Ϫ transport. To test this hypothesis, the monolayers were preincubated with 10 M indomethacin, a nonselective cyclooxygenase (COX) inhibitor, for 30 min and then with 100 M amiloride for 5 min, followed by a final addition of 300 M H 2 O 2 to the basolateral side.…”

Interleukin-6 stimulates α-MG uptake in renal proximal tubule cells: involvement of STAT3, PI3K/Akt, MAPKs, and NF-κB

“…Indeed, low levels of ROS (which is endogenous origin) have been demonstrated to cause an increase in cell cycle progression, while high levels of oxidative stress inhibited cell growth and function (15,35). This study showed that the endogenous ROS production in PTCs exposed to IL-6 was higher than in the control, and an antioxidant blocked the activation of many signal molecules involving the IL-6-induced increase in ␣-MG uptake.…”

“…Differentiated functions including the apical Na ϩ /glucose cotransport system (50), apical ␥-glutamyltranspeptidase (11), basolateral PAH transport system (58), and mitochondrial phosphoenolpyruvate carboxykinase (55), are indicative of the gluconeogenic capacity of cells (28). Moreover, the uptake studies with ␣-methyl-D-[ 14 C]glucopyranoside (␣-MG) indicate that the activity of the transport system is stably maintained in culture (15,34). Therefore, membrane transport studies carried out with such PTCs have a particular advantage in that the results can be compared directly with the original renal tissue.…”

The Prostaglandin E2Type 4 Receptor Participates in the Response to Acute Oxidant Stress in Airway Epithelial Cells

“…In the present study, we were interested in how H 2 O 2 was able to rapidly mediate this anion secretion from Calu-3 cells, because there has been no report to date indicating that CFTR structure can directly be affected by H 2 O 2. Of interest, however, was the observation that H 2 O 2 induces PGE 2 production in the kidney (Han et al, 2005), because PGE 2 is also a potent mediator of anion efflux from Calu-3 cells (Joy and Cowley, 2008). Using iodide efflux as a measure of CFTRmediated anion release, in combination with I sc recordings, we found that the rapid efflux in response to H 2 O 2 is abolished by indomethacin, SC-5690, Cay10589, and Cay10526 (Figs.…”