Downregulated expression in high IgA (HIGA) mice and the renal protective role of meprinbeta

Antiinflammatory constituents of Atractylodes chinensis rhizome improve glomerular lesions in immunoglobulin A nephropathy model mice

The crude drug Sojutsu, as defined by the Japanese Pharmacopoeia, is the rhizome of Atractylodes lancea De Candolle, Atractylodes chinensis Koidzumi, or their interspecific hybrids (Asteraceae). Sojutsu is one of the traditional Kampo formulas, which are administered to patients suffering from stomach disorders, edema, and nephrotic syndrome. Although antiinflammatory effects of Sojutsu have been reported, its effects on the liver and kidney have not been extensively investigated. Here, we used a Sojutsu sample identified as A. chinensis rhizome and isolated several constituents from its ethyl acetate (EtOAc)-soluble fraction that decreased production of the proinflammatory mediator nitric oxide (NO) in interleukin 1β-treated rat hepatocytes. Among the constituents in this fraction, atractylodin showed the highest activity to suppress NO production, whereas hinesol, β-eudesmol, and α-bisabolol showed low activity. Atractylodin decreased the levels of inducible nitric oxide synthase, tumor necrosis factor α, and lipocalin 2 messenger RNAs (mRNAs). The EtOAc-soluble fraction of the A. chinensis rhizome extract was administered daily for 20 weeks to high immunoglobulin A (HIGA) mice, whose pathological findings resemble human immunoglobulin A nephropathy. This fraction decreased the weight of white adipose tissue and decreased mesangial proliferation and immunoglobulin A deposition in glomeruli. These results indicate that the EtOAc-soluble fraction, which included antiinflammatory constituents, may be responsible for improvement of the mesangial lesions in HIGA mice.

Pathogenic Role of a Proliferation-Inducing Ligand (APRIL) in Murine IgA Nephropathy

A proliferation-inducing ligand (APRIL) is a member of the tumor necrosis factor (TNF) superfamily. Despite advances in clinical and genetic studies, the details of the pathological roles of APRIL in IgA nephropathy (IgAN) remain to be fully defined. The present study aimed to further assess the pathological role of APRIL using a mouse model of IgAN. Mice with IgAN designated “grouped ddY” (gddY) were intraperitoneally administered an anti-APRIL monoclonal antibody (anti-APRIL Ab) or control IgG (Control Ab) twice each week for 2 weeks starting during the early stage of IgAN (6–7 weeks of age). Urinary albumin, serum IgA, and glomerular IgA deposition were evaluated. We further assessed the inflammatory responses during treatment by measuring the levels of the chemokine fractalkine (FKN) and its receptor CX3CR1 as well as the level of peripheral blood monocytosis. Anti-APRIL Ab treatment significantly decreased albuminuria and tissue damage combined with decreases in serum IgA levels and deposition of glomerular IgA. In contrast, the abundance of IgA⁺/B220⁺ or CD138⁺/B220⁺ B cells in the spleen and bone marrow, respectively, was unchanged. Treating gddY mice with anti-April Ab reduced the overexpression of FKN/CX3CR1 in the kidney and the increase in the population of circulating Gr1⁻/CD115⁺ monocytes. The size of the population of Gr1⁻/CD115⁺ monocytes correlated with renal FKN and urinary albumin levels. Moreover, mice treated with anti-APRIL Ab exhibited reduced progression of IgAN, serum IgA levels, and glomerular IgA deposition as well as an attenuated inflammatory process mediated by FKN-associated activation of monocytes. To the best of our knowledge, this is the first study to implicate the APRIL signal transduction pathway in the pathogenesis of nephrogenic IgA production. Moreover, our findings identify APRIL as a potential target of therapy.

Development of a model of early-onset IgA nephropathy

ddY mice spontaneously develop IgA nephropathy (IgAN) with a variable age of disease onset. Establishing a model with early-onset IgAN could aid the investigation of mechanisms that underlie the pathogenesis of this disease. On the basis of histologic grading in serial biopsies, we previously classified ddY mice into early-onset, late-onset, and quiescent groups. Here, we selectively mated mice with the early-onset phenotype for >20 generations and established "grouped ddY" mice that develop IgAN within 8 weeks of age. Similar to human IgAN, the prognosis was worse for male mice than females. These mice homogeneously retained genotypes of four marker loci previously associated with the early-onset phenotype, confirming a close association of these loci with early-onset IgAN in ddY mice. Grouped ddY mice comprised two sublines, however, which had distinct genotypes at a susceptibility locus for high serum IgA levels, which maps within the Ig heavy-chain gene complex. The subline bearing the Igh-2(a) IgA allotype had a more rapid course of fatal disease and lower oligosaccharide content, suggesting that aberrant IgA glycosylation may promote the progression of murine IgAN. Taken together, these data indicate that grouped ddY mice may be a useful model for the identification of susceptibility genes and the underlying molecular mechanisms involved in the pathogenesis of human IgAN.