Bradykinin inhibits high glucose- and growth factor-induced collagen synthesis in mesangial cells through the B2-kinin receptor.

Mesangial matrix expansion is an early lesion leading to glomeruloclerosis and chronic renal diseases. A beneficial effect is achieved with angiotensin I-converting enzyme inhibitors (ACEI), which also favor bradykinin (BK) B2 receptor (B2R) activation. To define the underlying mechanism, we hypothesized that B2R activation could be a negative regulator of collagen synthesis in mesangial cells (MC). We investigated the effect of BK on collagen synthesis and signaling in MC. Inflammation was evaluated by intercellular adhesion molecule-1 (ICAM-1) expression. BK inhibited collagen I and IV synthesis stimulated by high glucose, epithelial growth factor (EGF), and transforming growth factor-ß (TGF-ß) but did not alter ICAM-1. Inhibition of collagen synthesis was B2R but not B1R mediated. PKC or phosphatidylinositol 3-kinase (PI3K) inhibitors mimicked the BK effect. B2R activation inhibited TGF-ß- and EGF-induced Erk1/2, Smad2/3, Akt S473, and EGFR phosphorylation. A phosphatase inhibitor prevented BK effects. The in vivo impact of B2R on mesangial matrix expansion was assessed in streptozotocin-diabetic rodents. Deletion of B2R increased mesangial matrix expansion and albuminuria in diabetic mice. In diabetic rats, matrix expansion and albuminuria were prevented by ACEI but not by ACEI and B2R antagonist cotreatment. Consistently, the lowered BK content of diabetic glomeruli was restored by ACEI. In conclusion, deficient B2R activation aggravated mesangial matrix expansion in diabetic rodents whereas B2R activation reduced MC collagen synthesis by a mechanism targeting Erk1/2 and Akt, common pathways activated by EGF and TGF-ß. Taken together, the data support the hypothesis of an antifibrosing effect of B2R activation.

Endothelin-1 expression in scleroderma renal crisis.

The objective of the study was to investigate the role of endothelin-1 in the pathogenesis of scleroderma renal crisis in patients with systemic sclerosis. We used immunohistochemical analysis with anti-endothelin-1 and anti-von Willebrand factor antibodies in comparing kidney biopsies from patients with systemic sclerosis and scleroderma renal crisis (n = 14); from normal kidneys (n = 5); and from patients with typical hemolytic uremic syndrome and thrombotic microangiopathy (n = 5), antiphospholipid syndrome (n = 6), diabetic nephropathy (n = 5), minimal change disease with cyclosporine toxicity (n = 5), or nephroangiosclerosis (n = 5). Kidney biopsies from all systemic sclerosis patients presented specific lesions: glomerular lesions with thickened capillary walls (n = 6, 42.8%), mesangiolysis (n = 3, 21.4%), fibrin thrombi (n = 3, 21.4%), hypertrophy of juxtaglomerular apparatus (n = 5, 35.7%), arteriolar lesions showing mucinous intimal thickening and lumen mucoid occlusions (n = 13, 92.8%), proliferation of intimal cells (ie, "onion-skin" lesions; n = 13, 92.8%), fibrinoid necrosis (n = 3, 21.4%), and fibrin thrombosis (n = 4, 28.6%). Chronic lesions in large arteries showed modifications such as fibrous intimal thickening (n = 13, 92.8%). The pattern of endothelial staining for endothelin-1 in both glomeruli and arteriolar lesions appears to be specific for scleroderma renal crisis. Glomerular endothelin-1 staining without arteriolar staining was seen in hemolytic uremic syndrome; and isolated arteriolar staining (without glomerular staining) was seen in a number of conditions including antiphospholipid nephropathy, cyclosporine toxicity, and diabetic nephropathy. Endothelin-1 is overexpressed in glomeruli and arterioles of patients with scleroderma renal crisis, which suggests that endothelin-1 might be a therapeutic target in this condition.

[Kidney involvement in systemic necrotizing vasculitis]. / Manifestations rénales des vascularites systémiques.

Renal involvement occurs in 75% of the patients with systemic necrotizing small-vessel vasculitis ie microscopic polyangiitis, Wegener's granulomatosis or Churg-Strauss syndrome. Small-vessel vasculitis may also be limited to the kidney. The hallmark of small-vessel pauci-immune vasculitides consists of necrotizing glomerulonephritis and resultant crescent formation, without immune-complex deposits in vessel walls. The resulting renal manifestations consist of haematuria, proteinuria and rapidly progressive renal failure. ANCA testing has a 90% sensitivity for renal-associated pauci-immune small-vessel vasculitis. Kidney biopsy is required for demonstrating necrotizing vasculitis. Early identification and prompt treatment are mandatory to avoid early mortality and end-stage renal failure. Induction therapy combines corticosteroids and IV cyclophosphamide. Plasma exchange in indicated in the patients presenting with active renal lesions and serum creatinine > 500 micromol/L. Maintenance of immunosuppressive therapy is required for 18 months. Twenty to 50% of the patients relapse during follow-up, and close monitoring is warranted for early detection.

Predictive factors for cytomegalovirus reactivation in cytomegalovirus-seropositive kidney-transplant patients.

The aims of the present study were to assess the incidence of cytomegalovirus (CMV) reactivation, and to determine the predictive factors for CMV reactivation in CMV seropositive kidney-transplant patients. One hundred ninety CMV seropositive kidney-transplant patients were included in this study; of these, 39 patients had received CMV prophylaxis. CMV DNAemia was assessed by real-timepolymerase chain reaction assay every 2 weeks until day 120, then every 3-4 weeks until day 180, and then every month until day 365. One hundred seven patients (56.3%) had at least one positive CMV DNAemia within the first year. The time between renal transplantation and the first positive CMV DNAemia was 59 +/- 5 days. The number of positive CMV DNAemia/patient was 3.28 +/- 0.22. CMV viral load at first positive CMV DNAemia was 704 (10-742,000) copies/ml. The donor CMV seropositivity, the absence of CMV prophylaxis, and the occurrence of acute rejection before CMV reactivation were independent factors associated with CMV reactivation within the first year after kidney transplantation. Hence, CMV reactivation is frequent after kidney transplantation. CMV prophylaxis in CMV seropositive kidney-transplant patients should be offered to avoid CMV-related side-effects.

Alpha-interferon therapy for chronic hepatitis C may induce acute allograft rejection in kidney transplant patients with failed allografts.

BACKGROUND: In hepatitis C virus (HCV) positive kidney transplant (KT) patients, the use of alpha-interferon (alphaIFN) is contraindicated due to the risk of acute rejection (AR). Conversely, if these HCV(+) KT patients lose their allograft, re-transplantation might be contemplated provided alphaIFN therapy has been attempted. METHODS: Between 01/01/1989 and 31/12/1994, 261 kidney transplantations were performed; of these 174 were HCV(-) (group I) and 87 were HCV(+) (group II). RESULTS: At last follow-up (2006), in group I, the number of patients with a functioning graft, the number of patients who died with a functioning graft, and the number of patients who lost their graft before or after month (M) 12 were 92 (52.8%), 14 (8%), 20 (11.5%) and 48 (27.7%), respectively. In group II, the corresponding figures were 22 (25.3%; P < 0.0001), 8 (9.1%; ns), 9 (10.3%; ns) and 48 (55.3%; P < 0.0001). In group I, 19 of 48 (39.5%) patients with failed allografts after M12 underwent transplantectomy (TX) compared to 14 of 48 (29%; ns) in group II. In group II, 11 of 48 (23%) patients were offered alphaIFN therapy after their allograft failed: of these, four (36.3%) developed AR during alphaIFN therapy leading to TX. Histology, in addition to chronic allograft lesions, showed acute cellular and vascular lesions. In patients who were not offered alphaIFN therapy, TX was performed less frequently, i.e. in only six cases (16.2%). CONCLUSIONS: We conclude that even alphaIFN-treated KT patients with a failed allograft can experience acute allograft rejection that requires transplantectomy during therapy.

[New perspectives for bradykinin in nephroprotection]. / Bradykinine et néphroprotection: pourquoi? comment? Perspectives.

Various diseases such as arterial hypertension, diabetes and obesity result in renal diseases which are often irreversible and resistant to currently available therapies. Beside the control of glycemia in diabetic patients, only the blockade of the renin-angiotensin system is effective in reducing the occurrence of glomerulosclerosis and its development towards terminal renal failure. Inhibition of this system is based on the use of angiotensin-1 converting enzyme inhibitors (ACEI) and angiotensin AT1 receptor antagonists. For many years, the beneficial effects of these two classes of drugs were attributed mainly to their interference with angiotensin II. However, recent in vitro and in vivo evidences strongly suggest that bradykinin B2 receptor is also involved in the nephroprotective effects of these drugs. A compelling evidence is the finding that the development of glomerulosclerosis is more severe in knock-out B2 receptor mice. The nephroprotective effect of B2 receptor could be the consequence of a reduction of proteinuria, glomerular and interstitial fibrosis, cell proliferation and of the oxidative stress through the contribution of several well identified mechanisms. It is proposed that B2 receptor agonists can offer a novel therapeutic avenue in the treatment of nephropathies associated with diabetes or other vascular diseases.

[Scleroderma renal crisis]. / Crise rénale sclérodermique.

Scleroderma renal crisis (SRC) occurs in patients with systemic sclerosis (SSc) and is defined by otherwise unexplained rapidly progressive renal insufficiency associated with oliguria or rapidly progressive arterial hypertension or both. SRC is a rare and severe complication of SSc, most often encountered during the first 4 years of disease, almost only in patients with diffuse SSc. Factors predicting SRC were identified, including high-dose corticosteroid administration. Use of angiotensin-converting enzyme inhibitors (ACEI) has dramatically impressed the prognosis of SRC, but it mortality rate is still high. Treatment aims at normalizing blood pressure as soon as possible. ACEI should always be used, and additional anti-hypertensive agents, including calcium channel blockers and alpha- and beta-blockers, may be useful. Renal replacement therapy may be needed, but often (for almost half of patients) only temporarily.

Vertigo after renal transplantation: a sign of paucisymptomatic cryptococcal meningitis.

We report what is to our knowledge the first case of severe isolated vertigo that developed after renal transplantation and was a manifestation of cryptococcal meningitis. Treatment with antifungal therapy resulted in the complete resolution of vertiginous symptoms. Immunosuppressed patients with an opportunistic infection of the central nervous system can present with extremely tenuous features of infection and atypical neurologic signs.

Rituximab therapy for de novo mixed cryoglobulinemia in renal transplant patients.

BACKGROUND: Type II or III cryoglobulins are fairly prevalent in renal-transplant (RT) patients, and are often related to chronic hepatitis C virus (HCV) infection. However, they rarely result in graft dysfunction. They are sustained by proliferation of oligoclonal B-cells. Systemic B-cell depletion and clinical remission of the systemic effects of cryoglobulins have been achieved in HCV-positive immunocompetent patients with a human/mouse chimeric monoclonal antibody that specifically reacts with the CD20 antigen (i.e., rituximab). Thus, this provides the rationale to use rituximab for cryoglobulin-related graft dysfunction in RT patients. METHODS: Three RT patients, of whom one was HCV-positive, developed renal-function impairment long after transplantation, as well as de novo nephrotic syndrome (n=2) and severe hypertension (n=2). This latter case was related to type III cryoglobulinemia and was associated with membranoproliferative glomerulonephritis. In addition to their baseline standard immunosuppression, the patients were given weekly rituximab infusions of 375 mg/m (two infusions in patient and four infusions for the other two cases). RESULTS: This treatment resulted in a dramatic improvement in renal parameters, particularly in a sustained remittence of nephrotic syndrome, a sustained clearance of cryoglobulins in two cases, but also in severe infectious complications in two cases. CONCLUSION: We conclude that rituximab therapy is highly effective in cryoglobulin-related renal dysfunction in RT patients; however, due to chronic immunosuppression, this is at the expense of infectious complications.