Activation and cellular localization of the p38 and JNK MAPK pathways in rat crescentic glomerulonephritis.
BACKGROUND
The p38 and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAPK) are intracellular signal transduction pathways involved in the production of inflammatory mediators. Little, however, is known about the contribution of these pathways to renal inflammation, nor the cell types in which these pathways are activated within normal and inflamed kidneys. The aim of this study was therefore to delineate the pattern and cellular localization of p38 and JNK activation in normal rat kidney and rat acute and chronic inflammatory renal disease.


METHODS
Normal male Sprague-Dawley rats and groups of rats given accelerated anti-glomerular basement membrane (GBM) disease were killed at 3 hours, day 1, day 7, or day 28 and examined for p38 and JNK pathway activation by Western blotting and immunolocalization of the phosphorylated p38 (p-p38) and JNK (p-JNK) kinases.


RESULTS
In terms of glomerular MAPK activation, Western blotting identified the presence of both p-p38 and p-JNK in normal glomeruli, localized by immunohistochemistry to podocytes and epithelial cells of Bowman's capsule. In anti-GBM disease, Western blotting showed that p38 activation peaked at 3 hours and remained elevated above normal throughout the disease time course. JNK activation (via the 54 kD isoform) likewise increased at 3 hours of anti-GBM disease and remained elevated throughout disease. At 3 hours, p-p38, but not p-JNK, was localized to neutrophils and glomerular endothelial cells. p-JNK was localized to glomerular endothelial cells at day 7. Macrophages, lymphocytes, activated podocytes, and myofibroblasts were positive for both p-p38 and p-JNK. In terms of tubular MAPK activation, Western blotting identified p38 and JNK activation in tubules of normal kidney. Immunostaining showed that most cortical tubules contained some p-p38 and p-JNK stained cells. There was a significant increase in tubular p38 activation at 3 hours of anti-GBM disease, followed by increased JNK activation of the 54 kD isoform from day 7 onward, and the 46 kD isoform at day 28. Immunostaining of diseased tissue localized p-p38 and p-JNK to virtually all cortical tubular cells.


CONCLUSIONS
The p38 and JNK MAPK pathways are activated in glomeruli and tubules of normal kidney. In acute anti-GBM disease, there was an increase in p38 activation within glomerular endothelial cells and within infiltrating neutrophils, suggesting an important role for p38 MAPK in acute inflammation. In progressive anti-GBM disease, p38 and JNK activation in podocytes, glomerular endothelial cells, infiltrating macrophages, T cells, and myofibroblasts suggests that both the p38 and JNK MAPK pathways are important in chronic inflammation and fibrosis. Blockade of these pathways may therefore be potentially therapeutic in the treatment of acute and chronic renal inflammation.
Stambe
Cosimo
C
Department of Nephrology and Monash University Department of Medicine, Monash Medical Centre, Clayton, Melbourne, Australia. cosimo.stambe@med.monash.edu.au
Atkins
Robert C
RC
Hill
Prudence A
PA
Nikolic-Paterson
David J
DJ
D000818:Animals; D019867:Anti-Glomerular Basement Membrane Disease / Q000201:enzymology* / Q000473:pathology; D000918:Antibody Specificity; D015153:Blotting, Western; D004789:Enzyme Activation; D005347:Fibroblasts / Q000201:enzymology; D007150:Immunohistochemistry / Q000379:methods; D048031:JNK Mitogen-Activated Protein Kinases; D007668:Kidney / Q000201:enzymology* / Q000473:pathology; D007678:Kidney Glomerulus / Q000201:enzymology / Q000473:pathology; D007684:Kidney Tubules / Q000201:enzymology; D008297:Male; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D032389:Myocytes, Smooth Muscle / Q000201:enzymology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013194:Staining and Labeling; D014018:Tissue Distribution; D048051:p38 Mitogen-Activated Protein Kinases
D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases