Cyclosporine A induced histological changes of Cathepsin L and CD2AP expression in renal glomeruli and tubules.

BACKGROUND: Cyclosporine A (CsA) is used globally as an immunosuppressant for the treatment of immune-mediated nephrotic syndrome (NS). However, its long-term use causes nephrotoxicity characterized by tubulointerstitial injury and glomerulosclerosis. The present study aimed to investigate the associations between histomorphological findings and immunohistological expression of Cathepsin L (CatL) and CD2-associated protein (CD2AP) in patients with NS mediated with CsA. METHODS: A total of 18 patients with child-onset NS were divided into two groups after treatment with CsA for 2 years (group A; n = 10) and more than 4 years (group B; n = 8), respectively. Analyses of relationships between tubulointerstitial disorders and expression of CatL and CD2AP proteins were performed using immunohistochemistry of paired renal specimens. RESULTS: Glomeruli with arteriole hyalinization were significantly increased in both groups depending on dosage periods, although degrees of tubule and interstitial injury did not differ between groups. CD2AP expression was significantly greater in podocytes (P = 0.046) and was significantly less in proximal tubule cells (P = 0.014) in patients of group B compared with those of group A. Moreover, CD2AP expression was significantly increased in lateral tubule cells in both groups (group A, P = 0.02; group B, P = 0.001), and CatL expression in glomeruli and tubule cells did not change with the duration of CsA treatment in either patient group. CONCLUSIONS: CD2AP expression in renal tubules may histologically associate with tissue hypoxia and reflected recovery from CsA-mediated renal injury in patients, even with mild histological features of tubulointerstitial disorder.

C3 glomerulonephritis associated with a missense mutation in the factor H gene.

The complement system, the major component of the innate immune functions resisting microbial infection, includes the classical complement pathway, the alternate pathway, and the mannose-binding lectin pathway. All of these merge at the level of complement component (C) 3. Complement factor H (CFH), a soluble complement mediator in blood, regulates alternate pathway activation; a conformational change of C3 molecules by C3 convertases leads to an enzyme complex formation resulting in opsonization and cell lysis. Clinical manifestations arising from CFH gene (CFH) abnormalities include hemolytic uremic syndrome and membranoproliferative glomerulonephritis. We encountered a 24-year-old woman initially diagnosed with C3 glomerulonephritis associated with persistently low circulating C3. Definitive diagnosis of C3 glomerulonephritis was made from immunohistologic demonstration of isolated mesangial C3 deposits. The biopsy specimen showed moderately increased mesangial proliferation, without thickening of the glomerular capillary walls. Genetic analysis disclosed a homozygous CFH missense mutation, a G-to-T transversion at nucleotide 3,048 in exon 18, resulting in substitution of Asp for Glu at position 936. A low serum CFH concentration (110 µg/mL) might reflect the consequences of this CFH mutation. C3 glomerulonephritis is associated with a CFH mutation, the mutation of which results in the unexpected activation of alternate pathway complement with clinical laboratory fluctuations, such as varying reduction of serum CFH and C3. The finding of a patient with a CFH mutation associated with C3 glomerulonephritis represents an opportunity to expand the phenotypic spectrum of the CFH mutations.