Serum alkaline phosphatase is a strong predictor of mortality in ESKD patients: analysis of the RISCAVID cohort.

BACKGROUND: Mortality in hemodialysis (HD) patients remains unacceptably high compared with that of the general population and despite the continuous improvement of dialysis techniques. This study aimed to assess the role of alkaline phosphatase serum levels on cardiovascular and overall mortality in the RISCAVID study cohort through a long follow-up period, looking for associations with known risk factors for poor outcome. METHODS: In June 2004, a prospective observational study was started focusing on the cardiovascular risk in hemodialysis patients who lived in the north-west area of Tuscany (RISCAVID, "RISchio CArdiovascolare nei pazienti afferenti all'Area Vasta In Dialisi"). The RISCAVID cohort included 572 prevalent patients on maintenance HD for at least three months. Morbid or fatal events were prospectively recorded at 6-month intervals for a follow up time of 216 months. RESULTS: In univariable Cox regression analysis, dialysis technique, Geriatric Nutritional Risk Index, peripheral vascular disease, and intact parathyroid hormone and total calcium serum levels were significantly associated with baseline alkaline phosphatase serum levels. Cox multivariable analysis showed that elevated serum alkaline phosphatase levels (the highest quartile), advanced age, dialysis vintage, type of vascular access, Geriatric Nutritional Risk Index, C-reactive protein and calcium serum levels, history of cardiovascular disease and peripheral vascular disease were independent predictors of overall mortality in maintenance HD patients. The fourth quartile of alkaline phosphatase was associated with all-cause 10-year mortality (HR: 1.47; 95% CI: 1.177-1.834) with a 47% increase with respect to the 1st, 2nd, and 3rd quartiles. This was also observed for 18-year all-cause mortality. CONCLUSIONS: Adjusted proportional analysis showed the alkaline phosphatase value to be an independent and powerful predictor of overall mortality in the hemodialysis population.

NGAL (Lcn2) monomer is associated with tubulointerstitial damage in chronic kidney disease.

The type and the extent of tissue damage inform the prognosis of chronic kidney disease (CKD), but kidney biopsy is not a routine test. Urinary tests that correlate with specific histological findings might serve as surrogates for the kidney biopsy. We used immunoblots and ARCHITECT-NGAL assays to define the immunoreactivity of urinary neutrophil gelatinase-associated lipocalin (NGAL) in CKD, and we used mass spectroscopy to identify associated proteins. We analyzed kidney biopsies to determine whether specific pathological characteristics associated with the monomeric NGAL species. Advanced CKD urine contained the NGAL monomer as well as novel complexes of NGAL. When these species were separated, we found a significant correlation between the NGAL monomer and glomerular filtration rate (r=-0.53, P<0.001), interstitial fibrosis (mild vs. severe disease; mean 54 vs. 167 µg uNGAL/g Cr, P<0.01), and tubular atrophy (mild vs. severe disease; mean 54 vs. 164 µg uNGAL/g Cr, P<0.01). Monospecific assays of the NGAL monomer demonstrated a correlation with histology that typifies progressive, severe CKD.

[Plasma cell dyscrasias and renal damage]. / Il coinvolgimento del rene nelle discrasie plasmacellulari.

Kidney damage caused by immunoglobulin free light chains in the setting of plasma cell dyscrasias is common and may involve all renal compartments, from the glomerulus to the tubulointerstitium, in a wide variety of histomorphological and clinical patterns. The knowledge of how free light chains can promote kidney injury is growing: they can cause functional changes, be processed and deposited, mediate inflammation, apoptosis and fibrosis, and obstruct nephrons. Each clone of the free light chain is unique and its primary structure and post-translation modification can determine the type of renal disease. Measurement of serum free light chain concentrations and calculation of the serum kappa/lambda ratio, together with renal biopsy, represent essential diagnostic tools. An early and correct diagnosis of renal lesions due to plasma cell dyscrasias will allow early initiation of disease-specific treatment strategies. The treatment of free light chain nephropathies is evolving and knowledge of the pathways that promote renal damage should lead to further therapeutic developments.

Evidence for a Prehypertensive Water Dysregulation Affecting the Development of Hypertension: Results of Very Early Treatment of Vasopressin V1 and V2 Antagonism in Spontaneously Hypertensive Rats.

In addition to long-term regulation of blood pressure (BP), in the kidney resides the initial trigger for hypertension development due to an altered capacity to excrete sodium and water. Betaine is one of the major organic osmolytes, and its betaine/gamma-aminobutyric acid transporter (BGT-1) expression in the renal medulla relates to interstitial tonicity and urinary osmolality and volume. This study investigated altered water and sodium balance as well as changes in antidiuretic hormone (ADH) activity in female spontaneously hypertensive (SHR) and normotensive Wistar Kyoto (WKY) rats from their 3-5 weeks of age (prehypertensive phase) to SHR's 28-30 weeks of age (established hypertension-organ damage). Young prehypertensive SHRs showed a reduced daily urine output, an elevated urine osmolarity, and higher immunostaining of tubule BGT-1, alpha-1-Na-K ATPase in the outer medulla vs. age-matched WKY. ADH circulating levels were not different between young prehypertensive SHR and WKY, but the urine aquaporin2 (AQP2)/creatinine ratio and labeling of AQP2 in the collecting duct were increased. At 28-30 weeks, hypertensive SHR with moderate renal failure did not show any difference in urinary osmolarity, urine AQP2/creatinine ratio, tubule BGT-1, and alpha-1-Na-K ATPase as compared with WKY. These results suggest an increased sensitivity to ADH in prehypertensive female SHR. On this basis, a second series of experiments were set to study the role of ADH V1 and V2 receptors in the development of hypertension, and a group of female prehypertensive SHRs were treated from the 25th to 49th day of age with either V1 (OPC21268) or V2 (OPC 41061) receptor antagonists to evaluate the BP time course. OPC 41061-treated SHRs had a delayed development of hypertension for 5 weeks without effect in OPC 21268-treated SHRs. In prehypertensive female SHR, an increased renal ADH sensitivity is crucial for the development of hypertension by favoring a positive water balance. Early treatment with selective V2 antagonism delays future hypertension development in young SHRs.

Autoimmunity in membranous nephropathy targets aldose reductase and SOD2.

Glomerular targets of autoimmunity in human membranous nephropathy are poorly understood. Here, we used a combined proteomic approach to identify specific antibodies against podocyte proteins in both serum and glomeruli of patients with membranous nephropathy (MN). We detected specific anti-aldose reductase (AR) and anti-manganese superoxide dismutase (SOD2) IgG(4) in sera of patients with MN. We also eluted high titers of anti-AR and anti-SOD2 IgG(4) from microdissected glomeruli of three biopsies of MN kidneys but not from biopsies of other glomerulonephritides characterized by IgG deposition (five lupus nephritis and two membranoproliferative glomerulonephritis). We identified both antigens in MN biopsies but not in other renal pathologies or normal kidney. Confocal and immunoelectron microscopy (IEM) showed co-localization of anti-AR and anti-SOD2 with IgG(4) and C5b-9 in electron-dense podocyte immune deposits. Preliminary in vitro experiments showed an increase of SOD2 expression on podocyte plasma membrane after treatment with hydrogen peroxide. In conclusion, our data support AR and SOD2 as renal antigens of human MN and suggest that oxidative stress may drive glomerular SOD2 expression.

Urinary NGAL marks cystic disease in HIV-associated nephropathy.

Nephrosis and a rapid decline in kidney function characterize HIV-associated nephropathy (HIVAN). Histologically, HIVAN is a collapsing focal segmental glomerulosclerosis with prominent tubular damage. We explored the expression of neutrophil gelatinase-associated lipocalin (NGAL), a marker of tubular injury, to determine whether this protein has the potential to aid in the noninvasive diagnosis of HIVAN. We found that expression of urinary NGAL was much higher in patients with biopsy-proven HIVAN than in HIV-positive and HIV-negative patients with other forms of chronic kidney disease. In the HIV-transgenic mouse model of HIVAN, NGAL mRNA was abundant in dilated, microcystic segments of the nephron. In contrast, urinary NGAL did not correlate with proteinuria in human or in mouse models. These data show that marked upregulation of NGAL accompanies HIVAN and support further study of uNGAL levels in large cohorts to aid in the noninvasive diagnosis of HIVAN and screen for HIVAN-related tubular damage.

Alterations of type IV collagen alpha chains in patients with chronic acquired glomerulopathies: mRNA levels, protein expression and urinary loss.

BACKGROUND: Type IV collagen is a major structural component of the normal kidney glomerulus. However, its role in chronic acquired glomerulopathies has been only partially elucidated. METHODS: Urinary levels of col(IV)alpha1, col(IV)alpha3 and col(IV)alpha5 collagen chains were analyzed in 107 patients with chronic acquired glomerulopathies. In a subgroup of 33 patients, tissue mRNA levels, protein expression and urinary excretion were evaluated for all col(IV)alpha chains, from col(IV)alpha1 to col(IV)alpha5. The renal specimens were examined to get a semiquantitative score of the acute and chronic activity of the histological lesions. Urines obtained from 13 healthy subjects and 10 normal renal tissue samples were used as controls. RESULTS: Urinary levels of col(IV)alpha1, col(IV)alpha3, col(IV)alpha5 chains were significantly higher in patients than in controls [p < 0.01 for all], while only col(IV)alpha1 and col(IV)alpha3 urinary excretion correlated with the degree of chronic histological damage [col(IV)alpha1 R = 0.44, p < 0.001; col(IV)alpha3: R = 0.47, p < 0.001]. Compared with controls, patients showed a renal expression of mRNA for col(IV)alpha5 chain significantly higher [p = 0.001], while having a significantly lower protein expression of col(IV)alpha3, col(IV)alpha4 and col(IV)alpha5 chains [p < 0.01 for all]. CONCLUSION: Patients with chronic acquired glomerulopathies show important alterations in the col(IV)alpha chain network mimicking some molecular features of the X-linked Alport's syndrome. Further studies are needed to show whether urinary levels of the col(IV)alpha chains may be used as markers for monitoring renal injury.

A novel option for reducing free light chains in myeloma kidney: supra-hemodiafiltration with endogenous reinfusion (HFR).

BACKGROUND: In myeloma cast nephropathy, fast reduction of serum free light chain (FLC) levels correlates with renal recovery. Recently, extracorporeal treatments using filters with a high-molecular weight cut-off have been successfully used for FLC removal. However, using these new filters, high cost and elevated albumin leakage are common drawbacks. We studied a new and cheaper therapeutic approach with adsorbent resins to evaluate its efficacy. METHODS: We treated four patients, affected by dialysis-dependent acute kidney injury (AKI) due to biopsy proven de novo FLC myeloma cast nephropathy. Each patient underwent bortezomib chemotherapy and extracorporeal treatment with the supra-hemodiafiltration with endogenous reinfusion (HFR) technique (Supra-HFR, Bellco Mirandola, Modena, Italy). Supra-HFR is a kind of hemodiafiltration that utilizes separated convection, diffusion and adsorption. The sorbent cartridge has a high affinity for FLC (both κ and λ) but is able to re-infuse albumin, avoiding the need for albumin perfusions. Supra HFR treatments (4 h each) were carried out for eight consecutive days and then every other day. RESULTS: All patients showed a significant reduction of serum FLC, whereas serum albumin concentration remained unchanged. Renal function recovered in three out of four patients. CONCLUSIONS: FLC removal with adsorbent resins represents an effective therapeutic strategy that does not require replacement with albumin .