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Leptospira outer membrane protein activates NF-kappaB and downstream genes expressed in medullary thick ascending
Chih-Wei Yang1, Mai-Szu Wu1, Ming-Jeng Pan2
1Division of Nephrology, Chang Gung Memorial Hospital, Taipei, Taiwan, Republic of China.
Abstract:
Tubulointerstitial nephritis is the main manifestation of acute renal damage caused by leptospirosis, but the mechanism remains unexplored. Patients infected with LEPTOSPIRA: shermani in Taiwan disclosed tubular dysfunction particularly in the medullary thick ascending limb of loop of Henle (mTAL), and the related renal damage seems to be underestimated. To elucidate the mechanism of tubular damage, outer membrane protein extract from LEPTOSPIRA: was administered to a model of cultured mTAL cells derived from normal mice. The addition of outer membrane protein extract from L. shermani to cultured mTAL cells induced a significant nuclear DNA binding of the NF-kappa B transcription factor by electrophoresis mobility shift assay. Forty-eight h after adding the outer membrane protein extract (0.2 microg/ml) to the cultured cells, the expression of inducible nitric oxide mRNA increased by 4.2-fold, monocyte chemoattractant protein-1 by 3-fold, and tumor necrosis factor-alpha by 2.4-fold when compared with untreated cells examined by reverse transcription competitive-PCR. Supernatant nitrite, monocyte chemoattractant protein-1, and tumor necrosis factor-alpha protein levels also increased by 1.8-, 7.1-, and 5-fold, respectively. An antiserum raised against L. shermani largely prevented these effects. Outer membrane protein extract from L. bratislava induced fewer effects than L. shermani, and the avirulent nonpathogenic L. biflexa serovar patoc did not induce significant effects in the mTAL cells. In conclusion, L. shermani infection may cause mTAL cell damage and inflammation through the NF-kappa B-associated pathway. Findings of this study may be important in understanding the pathogenesis of tubulointerstitial nephritis caused by these organisms.
Insights
Leptospira shermani outer membrane proteins trigger inflammation in kidney tubule cells via the NF-kappa B pathway, contributing to tubulointerstitial nephritis. This research clarifies a key mechanism of leptospirosis-induced kidney damage.
Area of Science:
- Nephrology
- Microbiology
- Immunology
Background:
- Tubulointerstitial nephritis is a primary renal manifestation of leptospirosis.
- The precise mechanisms underlying leptospirosis-induced renal damage, particularly tubular dysfunction, are not fully understood.
- Leptospira shermani infection is associated with tubular dysfunction in the medullary thick ascending limb of Henle (mTAL).
Purpose of the Study:
- To investigate the molecular mechanisms by which Leptospira shermani causes damage to mTAL cells.
- To elucidate the role of the NF-kappa B pathway in mediating inflammation in response to L. shermani outer membrane proteins.
Main Methods:
- Cultured mouse mTAL cells were exposed to outer membrane protein extract from L. shermani.
- Electrophoresis mobility shift assay (EMSA) was used to assess NF-kappa B DNA binding.
- Reverse transcription competitive-PCR (RT-cPCR) quantified mRNA expression of inflammatory mediators.
- Nitrite, monocyte chemoattractant protein-1 (MCP-1), and tumor necrosis factor-alpha (TNF-α) levels in cell supernatant were measured.
- The effect of anti-L. shermani antiserum was evaluated.
Main Results:
- L. shermani outer membrane proteins significantly induced NF-kappa B nuclear DNA binding in mTAL cells.
- Expression of inducible nitric oxide synthase (iNOS), MCP-1, and TNF-α mRNA increased substantially post-exposure.
- Supernatant levels of nitrite, MCP-1, and TNF-α proteins were significantly elevated.
- An antiserum against L. shermani largely abrogated these effects.
- Outer membrane proteins from L. bratislava showed milder effects, while L. biflexa serovar patoc had no significant impact.
Conclusions:
- Leptospira shermani infection can induce mTAL cell damage and inflammation through activation of the NF-kappa B pathway.
- These findings provide insights into the pathogenesis of tubulointerstitial nephritis caused by Leptospira species.
- The study highlights the specific role of L. shermani outer membrane proteins in initiating renal inflammatory responses.