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Partial Complement Factor H Deficiency Associates with C3 Glomerulopathy and Thrombotic Microangiopathy.

ABSTRACT: The complement-mediated renal diseases C3 glomerulopathy (C3G) and atypical hemolytic uremic syndrome (aHUS) strongly associate with inherited and acquired abnormalities in the regulation of the complement alternative pathway (AP). The major negative regulator of the AP is the plasma protein complement factor H (FH). Abnormalities in FH result in uncontrolled activation of C3 through the AP and associate with susceptibility to both C3G and aHUS. Although previously developed FH-deficient animal models have provided important insights into the mechanisms underlying susceptibility to these unique phenotypes, these models do not entirely reproduce the clinical observations. FH is predominantly synthesized in the liver. We generated mice with hepatocyte-specific FH deficiency and showed that these animals have reduced plasma FH levels with secondary reduction in plasma C3. Unlike mice with complete FH deficiency, hepatocyte-specific FH-deficient animals developed neither plasma C5 depletion nor accumulation of C3 along the glomerular basement membrane. In contrast, subtotal FH deficiency associated with mesangial C3 accumulation consistent with C3G. Although there was no evidence of spontaneous thrombotic microangiopathy, the hepatocyte-specific FH-deficient animals developed severe C5-dependent thrombotic microangiopathy after induction of complement activation within the kidney by accelerated serum nephrotoxic nephritis. Taken together, our data indicate that subtotal FH deficiency can give rise to either spontaneous C3G or aHUS after a complement-activating trigger within the kidney and that the latter is C5 dependent.

SUBMITTER: Vernon KA

PROVIDER: S-EPMC4849824 | biostudies-other | 2016 May

REPOSITORIES: biostudies-other

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Partial Complement Factor H Deficiency Associates with C3 Glomerulopathy and Thrombotic Microangiopathy.

Vernon Katherine A KA Ruseva Marieta M MM Cook H Terence HT Botto Marina M Malik Talat H TH Pickering Matthew C MC

Journal of the American Society of Nephrology : JASN 20150915 5

The complement-mediated renal diseases C3 glomerulopathy (C3G) and atypical hemolytic uremic syndrome (aHUS) strongly associate with inherited and acquired abnormalities in the regulation of the complement alternative pathway (AP). The major negative regulator of the AP is the plasma protein complement factor H (FH). Abnormalities in FH result in uncontrolled activation of C3 through the AP and associate with susceptibility to both C3G and aHUS. Although previously developed FH-deficient animal ...[more]

PMID: 26374608

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Project description:Background and objectivesC3 glomerulopathy (C3G) applies to a group of renal diseases defined by a specific renal biopsy finding: a dominant pattern of C3 fragment deposition on immunofluorescence. The primary pathogenic mechanism involves abnormal control of the alternative complement pathway, although a full description of the disease spectrum remains to be determined. This study sought to validate and define the association of complement dysregulation with C3G and to determine whether specific complement pathway abnormalities could inform disease definition.Design, setting, participants, & measurementsThis study included 34 patients with C3G (17 with C3 glomerulonephritis [C3GN] and 17 with dense deposit disease [DDD]) diagnosed between 2008 and 2013 selected from the C3G Registry. Control samples (n=100) were recruited from regional blood drives. Nineteen complement biomarkers were assayed on all samples. Results were compared between C3G disease categories and with normal controls.ResultsAssessment of the alternative complement pathway showed that compared with controls, patients with C3G had lower levels of serum C3 (P<0.001 for both DDD and C3GN) and factor B (P<0.001 for both DDD and C3GN) as well as higher levels of complement breakdown products including C3d (P<0.001 for both DDD and C3GN) and Bb (P<0.001 for both DDD and C3GN). A comparison of terminal complement pathway proteins showed that although C5 levels were significantly suppressed (P<0.001 for both DDD and C3GN) its breakdown product C5a was significantly higher only in patients with C3GN (P<0.05). Of the other terminal pathway components (C6-C9), the only significant difference was in C7 levels between patients with C3GN and controls (P<0.01). Soluble C5b-9 was elevated in both diseases but only the difference between patients with C3GN and controls reached statistical significance (P<0.001). Levels of C3 nephritic factor activity were qualitatively higher in patients with DDD compared with patients with C3GN.ConclusionsComplement biomarkers are significantly abnormal in patients with C3G compared with controls. These data substantiate the link between complement dysregulation and C3G and identify C3G interdisease differences.

Project description:BackgroundLipoprotein glomerulopathy (LPG) is a rare inherited renal disease characterized by intraglomerular lipoprotein within the lumina of severely dilated glomerular capillaries. The common clinical presentation of LPG includes proteinuria or nephrotic syndrome. Hypertension and anemia were thought to be mild in LPG. Thrombotic microangiopathy (TMA) in LPG has not been previously reported. In this report, we present a patient with LPG that developed TMA. To the best of our knowledge, this is the first report of TMA in LPG.Case presentationFour years ago (2005), a 19-year-old Chinese woman was diagnosed with nephrotic syndrome and provided prednisone treatment. A combination of prednisone and cyclophosphamide did not have any effect and was discontinued after six months. Although she was steroid-resistant, over the next subsequent three years, she maintained normal renal function without anemia and thrombocytopenia. In February 2009, she had a severe headache and blurry vision and presented at a local hospital with severe hypertension. Blood pressure was 220/160 mmHg. Laboratory data showed hemoglobin 3.8 g/dL; platelet counts 29 × 10(9)/L; urinary protein 7.90 g/d; total bilirubin 29.9 umol/L; indirect bilirubin 28.2 umol/L; LDH 1172 U/L; ALB 2.66 g/dL; urea nitrogen 52 mg/dL; serum creatinine 3.2 mg/dL; triglyceride 25 mg/dL; total cholesterol 273 mg/dL. ANA, ds-DNA, ANCA, anti-GBM antibody and anticardiolipin were all negative. A renal biopsy revealed LPG with TMA. Genetic evaluation showed the patient carried the APOE Kyoto mutation. Adequate control of blood pressure improved microangiopathic anemia and thrombocytopenia, however, renal function did not improve and she eventually developed uremia and became hemodialysis dependent.ConclusionWe report on a rare case of TMA probably due to malignant hypertension in LPG. Early lipid-lowering and antihypertensive treatment may improve outcome. The pathophysiologic relationship between LPG and TMA should be investigated further.

Dataset Information

Partial Complement Factor H Deficiency Associates with C3 Glomerulopathy and Thrombotic Microangiopathy.

Publications

Partial Complement Factor H Deficiency Associates with C3 Glomerulopathy and Thrombotic Microangiopathy.

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