V SHEN1, G ZHANG1, M HU2, J ZHOU1, S ROBINSON1, H MCCARTHY1, Y WANG2, Q CAO2, G ZHENG2, N ROGERS2, T BARBOUR3, I ALEXANDER4, D HARRIS2, S ALEXANDER1, Y WANG1
1Centre for Kidney Research, The Children’s Hospital at Westmead, Sydney, Australia, 2Centre for Transplant and Renal Research, University of Sydney at Westmead Hospital, Sydney, Australia, 3Department of Nephrology, Royal Melbourne Hospital, Melbourne, Australia, 4Gene Therapy Research Unit, The Children’s Hospital at Westmead, Sydney, Australia
Aim: To evaluate whether TLR4 and TLR7 agonists induce acute kidney injury in CFH mutant mice.
Background: Atypical haemolytic uremic syndrome (aHUS) is associated with mutations in the complement alternative pathway, most commonly complement factor H (CFH), a negative regulator of C3 activation. Mice carrying CFH mutations associated with functionally impaired CFH protein in human aHUS have been generated by ENU mutagenesis. The role of infection in triggering disease in these mice was tested by treatment with lipopolysaccharide (LPS, TLR4 agonist) and Imiquimod (IMQ, TLR7 agonist).
Methods: For LPS, a single low dose (4mg/kg) was administrated intraperitoneally to homozygous, heterozygous and wild type (WT) mice. For IMQ, 25μg was administered on alternate days for 3 weeks in the corresponding groups. After treatment, kidney function, histology and C3 immunofluorescence were assessed. Serum and liver CFH levels were measured using western blot.
Results: Homozygous mice showed spontaneous deposition of glomerular C3 and had minimal serum concentrations of CFH compared to WT and heterozygous mice. Following LPS treatment, homozygous mice showed significantly higher levels of proteinuria (3.1±0.2mg/16h) and serum creatinine (28.3±3umol/L) compared to heterozygous (1.3±0.4mg/16h, 20.3±2umol/L, p<0.01 and p<0.05 respectively) and WT mice (1.2±0.2mg/16h, 17.6±1.6umol/L, p<0.01 and p<0.05 respectively). IMQ treatment also had a worse effect on renal function in homozygous mice. LPS or IMQ treated homozygous mice exhibited significantly more glomerulosclerosis, tubular damage and interstitial inflammation than heterozygous and WT mice (p<0.01).
Conclusions: Mice homozygous for the aHUS-associated CFH mutation develop glomerular C3 deposition and are sensitive to LPS or IMQ, developing acute kidney injury and renal histological damage. This suggests a significant role for infection in triggering aHUS in susceptible individuals.
Victor completed his Bachelor of Medical Science studies at the University of Sydney, majoring in immunobiology and physiology. He is currently studying his Honours year at the Centre for Kidney Research, The Children’s Hospital at Westmead under the supervision of Prof Stephen Alexander and Dr Yuan Min Wang. His area of interest involves hematology and role of complement regulators in glomerular injuries.