Plasma factors influencing PGI2-like activity in patients with IgA nephropathy and Henoch-Schönlein purpura

Predictive biomarkers of IgA vasculitis with nephritis by metabolomic analysis

BACKGROUND

IgA vasculitis (IgAV) is the most common vasculitis of childhood. Renal involvement defines late morbidity of the disease. A better understanding of the pathophysiology of the progression to kidney disease and predictive biomarkers are required for better management of IgAV and its nephritis (IgAVN).

OBJECTIVES

An untargeted metabolomics approach was performed to reveal the underlying molecular mechanism of disease pathogenesis and to define potential biomarkers from plasma samples from IgAV and IgAVN patients.

METHODS

Forty-five active IgAV patients (H) and six healthy controls (C) were enrolled in the study. Plasma samples were collected on the same day of diagnosis and before any immunosuppressive treatment was initiated. At the time of diagnosis and sample collection, none of the patients had renal involvement. We used Quadrupole Time of Flight Mass Spectrometry (Q-TOF LC/MS) to investigate the alterations in plasma metabolomic profiles. Three separate pools were created: healthy controls (group C), active IgAV patients who did not develop renal involvement (group H), and patients who developed IgAVN at follow up (group N). Peak picking, grouping, and comparison parts were performed via XCMS (https://xcmsonline.scripps.edu/) software.

RESULTS

At follow-up, IgAVN developed in 6 out of 45 IgAV patients. The median time of renal involvement development is 23 days (range 5-45 days). Of these, 3 had nephritic proteinuria, one had nephrotic proteinuria, and 2 had microscopic hematuria. There were no significant differences in gender, age, clinical manifestations, and laboratory findings between the six patients who developed renal involvement and those who did not. In multivariate analysis, there was no significant association between any of the defined demographic and clinical characteristics (male sex, gastrointestinal system involvement, joint involvement, CRP, WBC, PLT) and the occurrence of renal involvement. Totally 2618 peaks were detected for group H, N, and C. Among them, 355 peaks were found to be statistically significant and reliable (p<0.05), and 155 of these peaks were found to be changed (fold change >1.5) between the groups C and H, and 66 peaks were found to be changed (fold change >1.5) between the groups H and N. The number of the peaks on the intersection of the peaks found to be different between the groups (C and H) and (H and N) was 39. Based on putative identification results, 15 putatively identified metabolites matched with 11 peaks were presented as biomarker candidates after careful evaluation with a clinical perspective.

CONCLUSION

We suggest that DHAP (18:0), prostaglandin D2/I2, porphobilinogen, 5-methyltetrahydrofolic acid, and N-Acetyl-4-O-acetylneuraminic acid/N-Acetyl-7-O-acetylneuraminic acid may serve as biomarkers for predicting kidney disease. Future studies with larger groups of IgAV patients are needed to validate the identified metabolic profile.

What is the difference between IgA nephropathy and Henoch-Schönlein purpura nephritis?

Henoch-Schönlein purpura nephritis (HSPN) and IgA nephropathy (IgAN) are considered to be related diseases since both can be encountered consecutively in the same patient, they have been described in twins, and bear identical pathological and biological abnormalities. Apart from the presence of extrarenal clinical signs found only in HSPN, other differences are noticed between the two diseases. The peak age ranges between 15 and 30 years for a diagnosis of IgAN, whereas HSPN is mainly seen in childhood. Nephritic and/or nephrotic syndromes are more often seen at presentation in HSPN. In contrast to IgAN, HSPN has been described in association with hypersensitivity. Endocapillary and extracapillary inflammations as well as fibrin deposits in the glomerulus are more frequent in HSPN. No major biological differences have been found between the two illnesses, except for a larger size of circulating IgA-containing complexes (IgA-CC) and a greater incidence of increased plasma IgE levels in HSPN. As tissue infiltration by leukocytes is a major feature of HSPN vasculitis, a possible role of a more potent activation of the latter cells by IgA-CC and/or circulating chemokines in HSPN should be considered. Further studies are required to elucidate this possible mechanism as well as the role of hypersensitivity in HSPN.

Impaired activation of the fibrinolytic system in children with Henoch-Schönlein purpura: beneficial effect of hydrocortisone plus Sigma-aminocaproic acid therapy on disappearance rate of cutaneous vasculitis and fibrinolysis

Systemic vasculitis is a predominant clinical symptom in Henoch-Schönlein purpura (HSP), and some studies suggested that decreased blood fibrinolytic activity, as well as blood platelets, is of importance in the development of cutaneous vasculitis. Although patients with HSP have normal blood coagulation, little is known about the fibrinolytic system. On the other hand, it is known that the focus of Sigma-aminocaproic acid (EACA) activity in vivo is probably the blood platelet-vessel wall interaction or a vascular component alone. The aim of this study was, therefore, to investigate blood coagulation and fibrinolytic system as well as the effect of hydrocortisone (H) plus EACA therapy (Group I) on plasma antithrombin-III (AT-III), alpha1-proteinase inhibitor (alpha1-PI), alpha2-antiplasmin (alpha2-A), alpha2-macroglobulin (alpha2-M) activity, fibrinogen and plasminogen concentrations in plasma, euglobulin clot lysis time (ELT), and disappearance rate of cutaneous vasculitis in 14 children with HSP aged 7.6 +/- 3.1 (SD) years. Ten patients (8.6 +/- 2.5 years old) were treated with H alone (Group II), and 8 healthy, age-matched children served as controls. Plasma proteinase inhibitor activity was estimated with the kinetic method using Boehringer chromozyme tests before administration of H (9.2 +/- 3.3 mg/kg/d, i.v.) plus EACA (140 +/- 52 mg/kg/d, p.o.) for 5.93 +/- 2.05 days, and 24 hours after the last dose of EACA, as well as before and after treatment with H alone (8.25 +/- 1.74 mg/kg/24 h, i.v.) for 7.1 +/- 1.2 days. It was found that patients with HSP had the initial fibrinogen and plasminogen plasma concentrations significantly increased compared with the controls (Group I: 3.93 +/- 1.3 g/L and 124 +/- 38%; Group II: 4.24 +/- 0.89 g/L and 134 +/- 42% vs. 2.96 +/- 0.34 g/L, and 90 +/- 14%, respectively). Also, there was a marked decrease of the initial plasma alpha2-A activity in Group II compared with the controls (0.69 +/- 0.29 vs. 0.94 +/- 0.11 IU/mL, respectively, t = 2.33, P <.045). Both treatment regimens significantly improved fibrinolysis, which manifested as a shortening of ELT, but the mean values of this parameter remained within normal range. After treatment with H plus EACA, the skin lesions started to disappear significantly faster compared with the H alone regimen (2.28 +/- 0.45 days vs. 4.12 +/- 1.05, t = 4.41, P <.0023). In four of six patients receiving H plus EACA therapy, an approximately 20% decrease of systolic and diastolic arterial blood pressure lasting for 5 to 7 hours after administration of EACA was observed. These results may suggest that children with HSP have impaired plasma fibrinolytic activity and that an increased release of plasminogen activator inhibitor-1 (PAI-1) might be, at least in part, responsible for this phenomenon. Concomitant use of H (approximately 10 mg/kg/d) plus EACA (approximately 100 mg/kg/d) for a few days opens new therapeutic possibilities in some children with HSP.

Oedema in childhood

Oedema is a common childhood problem with important public health implications. It is an abnormal accumulation of fluid in the interstitial space which might result from a decrease in intravascular oncotic pressure, an increase in intravascular hydrostatic pressure, an increase in capillary permeability or impaired lymphatic drainage. Renal sodium retention is an important factor in generalised oedema. This article reviews the pathophysiology and aetiology of oedema in children and suggests an approach to evaluation, diagnosis and management of the problem.

Reflux nephropathy: the glomerular lesion and progression of renal failure

Reflux nephropathy is the cause of 5%-10% of dialysed end-stage renal failure. Once scarring has occurred, the prognosis depends on the severity of initial damage and the presence of proteinuria, which reflects the development of glomerulosclerosis. It is independent of ongoing reflux or infection. Histological appearances highly suggestive of reflux nephropathy can occur in radiologically normal kidneys. Duplex Doppler scans of ureteric orifices suggest these patients may have lateral insertion, suggesting past reflux. Glomerular hypertrophy correlates well with reduced renal function and severe renal scarring, but poorly with focal and segmental glomerulosclerosis, which correlates with proteinuria. Increasing attention is being paid to the tubulo-interstitium and the relationships between the cellular infiltrates (mainly T4 cells) and glomerular, tubular and vascular damage. Control of hypertension, hyperphosphataemia and a low-protein diet are the only currently widely accepted treatments for slowing progression.

Evidence that the interaction between circulating IgA and fibronectin is a normal process enhanced in primary IgA nephropathy

A solid-phase ELISA was set up to measure the direct binding capacity (BC) of different, commercially available, purified human IgA preparations to plates coated with human fibronectin (FN). It was found that secretory, polymeric, and, to a much lesser extent, monomeric IgA exhibited elevated FN-BC as compared to their BC to plates coated with bovine serum albumin. This binding was specific since not observed with human IgG or IgM antibodies. In addition, we noted that this interaction was dose dependent, Ca2+ dependent, saturable, and not covalent, was inhibited by soluble FN, but not by a prior incubation of FN-coated plates with anti-human fibronectin antibodies, and appeared to involve on the dimeric FN other structures than its heparin-binding, collagen-binding, or C1q-binding domains. Similar experiments conducted with normal plasma indicated that plasma IgA, but not plasma IgG or IgM, was also capable of significant binding to FN-coated plates. In contrast, serum IgA did not significantly bind to those plates under otherwise identical experimental conditions. Thus, the coagulation process induces a strong decrease in the FN-BC of circulating IgA, which implies the necessity of using plasma rather than serum to study such interactions. The apparent molecular weight of plasma IgA interacting with FN-coated plates ranged between 450 and 900 kd, and its major binding characteristics were quite similar to those observed with purified polymeric IgA. The FN-BC of plasma IgA was then measured by the same ELISA in 30 patients with primary IgA nephropathy (IgAN) and in 23 healthy controls. The mean FN-BC of plasma IgA was significantly higher in patients than in normal controls. This enhancement was due mainly to the augmentation in the concentration of circulating "macromolecular" IgA and was significantly correlated with the plasma levels of IgA-FN complexes. However, the pathogenetic role of these findings was probably not determinant since similar observations were made in alcoholic liver cirrhosis without urinary abnormalities and since the FN-BC of plasma IgA or the plasma levels of IgA-FN complexes were not correlated with the various biological parameters of evolutivity of primary IgAN. In conclusion, these studies suggest that the ability of polymeric IgA to directly bind to FN is involved in the formation of circulating IgA-FN complexes and that this normal binding process, although enhanced in IgAN, is probably not responsible for kidney injury, at least in the patients studied.