Chemokines play a prominent role in the acute inflammatory response in several models of kidney disease. We reported that monocyte chemotactic peptide-1 (MCP-1) mRNA is increased by ischemia-reperfusion injury. In this report, we examined the effects of ischemia-reperfusion injury on the kinetics and location of MCP-1 protein expression, the excretion of MCP- 1 protein in the urine and on the infiltration of mononuclear cells in the kidney. Pair-fed Sprague-Dawley rats underwent bilateral renal ischemia (50 min) or sham ischemia and placed in metabolic cages for daily urine collections. Kidneys were harvested at d. 1, 3, 7, and 10 after ischemia-reperfusion (I-R) or sham-ischemia (S-I). Kidney MCP-1 mRNA levels were increased on d. I and 3 post-ischemia. Kidney MCP-1 protein levels were increased in the I-R group on d. 1 and 3. MCP-1 expression occurred predominantly in the distal tubule segments by immunohistology. There was an increase in monocytes/macrophages infiltration in the I-R group, compared to the S-I or controls by d. 1. Urinary MCP-1 excretion increased 3-fold in the I-R group, and remained elevated above the S-I group and baseline levels, on d. 3 through d. 8. Kidney MCP-1 mRNA levels, protein levels and urinary MCP-1 excretion rates are increased by ischemia-reperfusion injury. The areas of increase in MCP-1 chemoattractant expression correlates with an increase in monocyte infiltration in the kidney. Although its pathophysiologic role remains to be determined, MCP-1 may participate in, and be a biomarker for, the mononuclear inflammatory processes that occur after ischemia-induced acute renal failure.

P fimbriae are proteinaceous appendages on the surface of Escherichia coli bacteria that mediate adherence to uroepithelial cells. E. coli that express P fimbriae account for the majority of ascending urinary tract infections in women with normal urinary tracts. The hypothesis that P fimbriae on uropathic E. coli attach to renal epithelia and may regulate the immune response to establish infection was investigated. The polymeric Ig receptor (pIgR), produced by renal epithelia, transports IgA into the urinary space. Kidney pIgR and urine IgA levels were analyzed in a mouse model of ascending pyelonephritis, using E. coli with (P؉) and without (P؊) P fimbriae, to determine whether P(؉) E. coli regulate epithelial pIgR expression and IgA transport into the urine. (P؉) E. coli establish infection and persist to a greater amount than P(؊) E. coli. P(؉)-infected mice downregulate pIgR mRNA and protein levels compared with P(؊)-infected or PBS controls at >48 h. The decrease in pIgR was associated with decreased urinary IgA levels in the P(؉)-infected group at 48 h. pIgR mRNA and protein also decline in P(؉) E. coli-infected LPS-hyporesponsive mice. These studies identify a novel virulence mechanism of E. coli that express P fimbriae. It is proposed that P fimbriae decrease pIgR expression in the kidney and consequently decrease IgA transport into the urinary space. This may explain, in part, how E. coli that bear P fimbriae exploit the immune system of human hosts to establish ascending pyelonephritis. Escherichia coli that express P fimbriae are the most common cause for upper urinary tract infections (UTI) or pyelonephritis (1). The P fimbriae mediate adherence to uroepithelial cells by binding to the Gal␣(1 to 4)Gal disaccharide on the apical surface of renal epithelial cells, glomeruli, and endothelia (2). The expression of P fimbriae on E. coli is important in establishing pyelonephritis, as P fimbriae-specific antibodies prevent the adherence of bacteria to uroepithelial cells in vitro (3) and protect animals from ascending E. coli pyelonephritis in vivo (4). Although P fimbriae are not the sole virulence factor on uropathic E. coli, pyelonephritis with P(ϩ) E. coli strains are more often associated with kidney histopathology than P(Ϫ) E. coli (5). In addition to its role as an adhesin, E. coli that express P fimbriae may determine the pattern of the local immune response via interaction with its P-specific glycosphingolipid receptors present on uroepithelial cells (6) and/or by signaling via inflammatory cytokines (7).The secretions that protect the mucosal surface of renal epithelia contain an array of host defense factors, including secretory immunoglobulins, of which IgA is the major class. The polymeric Ig receptor (pIgR) is responsible for transporting these secretory immunoglobulins (S-Ig) in vesicles from the basolateral to the apical surface of epithelial cells (8 -10), including renal tubule cells. The extracellular portion of the pIgR, termed secretory component (SC), is cleaved at the apical surface ...

The polymeric immunoglobulin receptor (pIgR) transports polymeric immunoglobulins (IgA) from the basolateral to the apical surface of epithelial cells. At the apical surface, its amino-terminal domain, termed secretory component (SC), is proteolytically cleaved and released either unbound (free SC) or bound to IgA. We examined the effects of changes in water balance and vasopressin on the production and secretion of the pIgR in the rat kidney in vivo. Water deprivation induced a 2.7-fold increase in the pIgR mRNA and a 2.2-fold increase in intracellular pIgR protein compared with water-loaded animals. Physiological doses of desmopressin reproduced the effects of water deprivation on mRNA and intracellular protein levels, suggesting that pIgR expression may be regulated by a vasopressin-coupled mechanism. Secretion of free SC and secretory IgA in the urine, however, correlated directly with water intake and urine flow. These results suggest that hydration status and vasopressin may affect the mucosal immunity of the kidney by regulating at different steps the epithelial cell production and secretion of the polymeric immunoglobulin transporter/secretory component.

The humoral mucosal immune response of the kidney involves the transport of secretory IgA (S-IgA) through renal epithelial cells by the polymeric immunoglobulin receptor (pIgR). The pIgR is cleaved and released as free secretory component (FSC) or attached to IgA (S-IgA). We examined the effects of an ischemic model of acute renal failure (ARF) on the expression of pIgR and the secretion of FSC and S-IgA in the urine. Kidney pIgR mRNA levels decreased in ischemic animals by 55% at 4 h and by 85% at 72 h compared with controls. pIgR protein expression in the medullary thick ascending limb (TAL) decreased within 24 h and was nearly undetectable by 72 h. Urinary S-IgA and FSC concentrations decreased by 60% between days 3 and 6. pIgR mRNA and pIgR protein in the kidney returned to ∼90% of control levels and urinary FSC and S-IgA concentrations returned to ∼55% of control levels by day 7. We demonstrate that ischemic ARF decreases renal mucosal S-IgA transport in vivo and may contribute to the increased incidence of urinary tract infections.