Quantitative analysis of interleukin 6 (IL-6) in patients with IgA nephropathy after tonsillectomy

Assay for galactose-deficient IgA1 enables mechanistic studies with primary cells from IgA nephropathy patients

AIMS

IgA nephropathy, the most common primary glomerulonephritis worldwide, is characterized by glomerular deposition of galactose-deficient IgA1 and elevated serum levels of this IgA1 glycoform. Current ELISA methods lack sensitivity to assess galactose deficiency using small amounts of IgA1, which limits studies in primary cells due to modest IgA1 production in isolated peripheral-blood lymphocytes.

METHODS

Lectin from Helix pomatia was conjugated to biotin or acridinium ester and used in ELISA to detect galactose deficiency of IgA1 using small amounts of IgA1.

RESULTS

Lectin conjugated to acridinium had an approximately a log-fold increased sensitivity compared with biotin-labeled lectin.

CONCLUSIONS

The new method of using lectin from Helix pomatia conjugated to acridinium increased assay sensitivity, allowing future mechanistic studies with cultured primary cells.

n-3 polyunsaturated fatty acids and autoimmune-mediated glomerulonephritis

Consumption of n-3 polyunsaturated fatty acids (PUFAs) found in fish oil suppresses inflammatory processes making these fatty acids attractive candidates for both the prevention and amelioration of several organ-specific and systemic autoimmune diseases. Both pre-clinical and clinical studies have been conducted to determine whether fish oils containing the n-3 PUFAs docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) can be used in the prevention and treatment of immunoglobulin A nephropathy (IgAN) and lupus nephritis. In a toxin-induced mouse model that mimics the early stages of IgAN, n-3 PUFA consumption suppresses aberrant interleukin (IL)-6-driven IgA production and mesangial IgA immune complex deposition by impairing phosphorylation of upstream kinases and activation of transcription factors essential for IL-6 gene transcription. n-3 PUFAs can also suppress production of anti-double-stranded DNA IgG antibodies and the resultant development of lupus nephritis in the NZBW F1 mouse and related models. These effects have been linked in part to impaired expression of proinflammatory cytokines and adhesion molecules as well as increases in antioxidant enzymes in kidney and immune organs. Several recent clinical trials have provided compelling evidence that n-3 PUFA supplementation could be useful in treatment of human IgAN and lupus nephritis, although some other studies suggest such supplementation might be without benefit. Future investigations employing genomics/proteomics and novel genetically altered mice should provide further insight into how n-3 PUFAs modulate these diseases as well help to identify clinically relevant biomarkers. The latter could be employed in future well-designed, long-term clinical studies that will resolve current controversies on n-3 PUFA efficacy in autoimmune-mediated glomerulonephritis.

Dietary fish oil suppresses experimental immunoglobulin a nephropathy in mice

Dietary fish oil (FO) supplementation reportedly retards the progression of renal disease in patients with immunoglobulin (Ig)A nephropathy (IgAN), the most common glomerulonephritis worldwide. Using an experimental mouse model in which early immunopathological hallmarks of IgAN are induced by the mycotoxin vomitoxin (VT), the ameliorative effects of FO ingestion on this disease were evaluated in two studies. In Study 1, the capacity of VT to induce IgAN was evaluated in mice fed for 12 wk AIN-76A diets containing 50 g/kg corn oil (CO), 50 g/kg CO plus 9 mg/kg tert butylhydroquinone (TBHQ), or 5 g/kg CO plus 45 g/kg menhaden FO that contained 200 mg/kg TBHQ. Serum IgA, serum IgA immune complexes and kidney mesangial IgA deposition were greater in mice fed VT + CO compared with the CO control group, whereas all three variables were significantly attenuated in mice fed VT + FO. Although TBHQ also had attenuating effects, these were significantly less than those for the VT + FO group. In Study 2, the effects of feeding modified AIN 93G diets containing either 70 g/kg CO or 10 g/kg CO plus 60 g/kg FO for 20 wk on VT-induced IgAN were compared. Again, consumption of FO attenuated all three immunopathological variables. In addition, spleen cell cultures from the VT + FO group produced markedly less IgA than those cultures from mice fed VT + CO. Taken together, the results suggested that diets containing FO may impair early immunopathogenesis in VT-induced IgAN and that this was not totally dependent on the presence of the antioxidant TBHQ.

Interleukin-6-deficient mice refractory to IgA dysregulation but not anorexia induction by vomitoxin (deoxynivalenol) ingestion

Dietary exposure to the trichothecene vomitoxin (VT) causes feed refusal and elevates IgA production in the mouse. Based on the observations that IL-6 can cause anorexia and promote IgA production and that gene expression of this cytokine is increased in vivo and ex vivo on VT exposure, we hypothesized that IL-6 is an essential cytokine in VT-induced feed refusal and IgA dysregulation. To test this hypothesis, the effects of dietary VT on feed intake, weight gain, serum IgA levels and kidney mesangial IgA deposition in an IL-6-"knockout" mouse (B6129-IL6(tmi Kopf)) were compared to those in both a corresponding "wildtype" (B6129F2) and a previously characterized "sentinel" strain (B6C3F1) that possess the intact gene for this cytokine. IL-6 deficiency did not alter the capacity of VT to cause feed refusal or impair weight gain. VT-fed B6129F2 and B6C3F1 mice had significantly higher serum IgA concentrations than did their corresponding controls fed clean diet, whereas significant differences were not observed between IL-6 KO mice fed VT or control diets. Kidneys taken from VT-fed wild-type and sentinel mice had significantly increased mesangial IgA deposition as compared to controls. While slight increases in mesangial IgA were observed in VT-fed IL-6 KO mice, mean fluorescence intensities were significantly less than that found in the corresponding wild-type and sentinel strains. IL-6 KO mice appeared to be less prone to the development of microscopic haematuria following VT exposure than were the corresponding wild-type and sentinel strains. In total, the results suggested that IL-6-deficient mice were refractory to VT-induced dysregulation of IgA production and development of IgA nephropathy, whereas chronic VT-mediated nutritional effects related to feed intake and weight gain were unaffected.