Bicarbonate dialysis, unlike acetate-free biofiltration, triggers mediators of inflammation and apoptosis in endothelial and smooth muscle cells.

BACKGROUND: We previously demonstrated that bicarbonate dialysis solutions incubated with endothelial cells (EC) enhance nitric oxide synthase (NOS). We then investigated whether blood circulated in simulated dialysis circuits triggers inflammatory and apoptotic mediators in vessel wall cells, aiming to compare the effects of bicarbonate hemodialysis (BHD) and acetate-free biofiltration (AFB). METHODS: Blood units from 22 healthy donors were dialyzed on AN69 with BHD in 11 sessions and AFB in another 11 sessions. Each dialysate remained endotoxin-free during the 60 min of dialysis. Blood samples having been re-circulated for 15 and 60 min were incubated with EC and smooth muscle cells (SMC), which were then investigated for NOS activity (3H citrulline production from 3H arginine), mRNAs transcription of the inducible isoforms of NOS (iNOS) and cyclooxygenase (COX-2) and the pro-apoptotic p53 protein. To investigate cell-cell interactions, in an-other series of 16 simulated dialyses, lympho-monocytes from blood circulated in either BHD or AFB were incubated with EC co-cultured in transwell devices with SMC. NOS activity was measured in EC and SMC. RESULTS: In comparison to AFB, blood circulated in BHD induced a significantly greater enhancement of NOS activity in EC, SMC and mRNAs transcription of pro-inflammatory iNOS, COX-2 and pro-apoptotic p53 (for each BHD data series p < 0.01 to p < 0.0001 vs. AFB). Lympho-monocytes from blood circulated in BHD but not in AFB, triggered the final SMC activation. CONCLUSIONS: Ex vivo AFB is less effective than BHD in activating vessel wall cells to synthesis/release of pro-inflammatory and pro-apoptotic mediators.

Procalcitonin as a marker of micro-inflammation in hemodialysis.

In searching for a rapid and sensitive test to detect micro-inflammation in patients on hemodialysis (HD), we measured serum procalcitonin (PCT) levels and made a comparison with other traditional markers such as C-reactive protein (CRP), serum amyloid (SAA) and homocysteine, considered related to vascular damage. We investigated 51 HD patients, without signs of infection, in basal conditions (during standard bicarbonate dialysis and unselected filters: X) and after 4 months of possibly more biocompatible treatments (on-line hemofiltration (HF) or HD with ultra-pure dialysate and biocompatible membranes: Y). Serum PCT (measured by immunoluminometric assay), CRP and SAA (nephelometric assay) and plasma homocysteine (measured by high performance liquid chromatography) concentrations were assessed at the beginning of dialysis (T0) and after 4 hr (T4). Patients on unselected dialysis displayed mean PCT values significantly increased after 4 hr of dialysis in comparison to those at the start of the sessions (XT4 1.56 +/- 3.93 vs. XT0 0.4 +/- 0.34 ng/mL; p < 0.05). The PCT levels detected after 4 hr of biocompatible treatments were significantly lower than those detected after 4 hr of unselected treatments (YT4 0.78 +/- 0.34 ng/mL; p < 0.05), even though the percentage of patients with positive PCT values (> 0.5 ng/mL) remained almost unchanged. No significant modification in mean levels or in the frequency of positive values was observed for CRP, SAA and homocysteine. After 4 months of highly biocompatible treatments, a reduction in intradialytic enhancements of all inflammation markers was detected. Our data support the conclusion that PCT is a more precise marker than other traditional tests to evaluate micro-inflammation and biocompatibility in HD.

In human IgA nephropathy uteroglobin does not play the role inferred from transgenic mice.

BACKGROUND: Uteroglobin (UG)-knockout and UG-antisense transgenic mice develop clinical and pathological features of immunoglobulin A (IgA) nephropathy with heavy proteinuria. These models suggested that UG, an anti-inflammatory protein with high affinity for fibronectin (Fn), prevents the formation of IgA-Fn complexes and mesangial deposits in mice. We aim to elucidate whether similar mechanisms underlie the development and severity of human IgA nephropathy. METHODS: Specific enzyme-linked immunosorbent assays were devised to detect serum levels of UG binding to Fn or incorporated into IgA-Fn complexes and IgA binding to Fn or collagen IV. Sera from 75 patients with IgA nephropathy with normal renal function and various degrees of proteinuria (0.2 to 5 g/d of protein) stable over the previous 3 months without therapy were investigated and compared with healthy controls. RESULTS: Levels of UG binding to Fn were similar in patients with IgA nephropathy and healthy controls. UG incorporated into circulating IgA-Fn complexes, as well as levels of IgA-Fn complexes and IgA binding Fn and collagen IV, were significantly greater in patients than healthy controls. Greater amounts of UG incorporated into IgA-Fn complexes reduced the risk for proteinuria with protein greater than 1 g/d (odds ratio = 0.67; P < 0.001). Logistic regression analysis assigned a predictive value for proteinuria persistently greater than 1 g/d of protein to lower amounts of UG incorporated into IgA-Fn complexes (R = -0.267; P = 0.008) and increased binding of IgA to collagen IV (R = 0.214; P = 0.0003). CONCLUSION: This first report of human IgA nephropathy after the publication of the mouse model shows that UG is not reduced in circulation and is even increased in IgA-Fn complexes. Because aberrant IgA1 glycosylation is the event initiating IgA nephropathy in humans, we speculate that the enhanced incorporation of UG into IgA-Fn complexes might represent feedback to reduce the formation of macromolecular aggregates.

Serological and genetic factors in early recurrence of IgA nephropathy after renal transplantation.

BACKGROUND: The relative role of IgA anomalies and genetic factors in IgA nephropathy (IgAN) recurrence after transplantation has never been investigated in a single cohort. METHODS: Sixty-one transplanted patients who had IgAN as an original disease (30 with biopsy-proved early recurrence, median 2.9 yr post-transplant), and 120 controls, were investigated for aberrantly glycosylated IgA1, IgA binding to mesangial matrix, macromolecular IgA (IgA/fibronectin and uteroglobulin/IgA/fibronectin complexes), and polymorphisms of cytokines [tumor necrosis factor alpha (TNFalpha), interleukin 10 (IL-10), IL-6, interferon gamma and transforming growth factor beta 1] and renin-angiotensin system (angiotensinogen converting enzyme, angiotensin II receptor 1, and angiotensinogen) genes. RESULTS: At multivariate logistic regression analysis, recurrence showed a border-line association with aberrantly glycosylated IgA1 [odds ratio (OR) 8.172, p = 0.077], and was significantly less frequent in carriers of -308 AG/AA TNF-alpha"high producer" genotype (OR 0.125, p = 0.036) and -1082, -819, -592 ACC/ATA IL-10 "low producer" (OR 0.038, p = 0.009) genotypes. CONCLUSION: High levels of aberrantly glycosylated IgA1 do not appear to play a strong crucial role in recurrence of IgAN. Polymorphisms of TNFalpha and IL-10 known to condition Th1 prevalence were associated with protection from early recurrence of IgAN.