Parathyroid hormone and T-cellular immunity in uremic patients in replacement dialytic therapy

Beyond Bone: Infectious Diseases and Immunity in Parathyroid Disorders

Parathyroid disorders are characterized by alterations in calcium and phosphate homeostasis due to inappropriately high or low levels of parathyroid hormone (PTH). Despite PTH receptor type 1 has been described in almost all immune lineages and calcium signalling has been confirmed as a crucial mediator for immune response, in vitro studies on the physiological interactions between PTH and immunity are conflicting and not representative of the clinical scenarios seen in patients with parathyroid disorders. Infectious diseases are among the main causes of increased morbidity and mortality in patients with secondary hyperparathyroidism and chronic kidney disease. More, immune alterations have been described in primary hyperparathyroidism. Recent studies have unveiled an increased risk of infections also in hypoparathyroidism, suggesting that not only calcium, but also physiological levels of PTH may be necessary for a proper immune response. Finally, calcium/phosphate imbalance could affect negatively the prognosis of infectious diseases. Our review aimed to collect available data on infectious disease prevalence in patients with parathyroid disorders and new evidence on the role of PTH and calcium in determining the increased risk of infections observed in these patients.

The Effect of Dialysis Modality and Membrane Performance on Native Immunity in Dialysis Patients

Chronic Kidney Disease (CKD) is characterized by immune activation with development of chronic inflammation. However, immune deficiency also exists in CKD patients. The number and the activity of Natural Killer cells (NK-cells) are influenced by the biocompatibility of various dialysis membranes. In this study we investigated the effect of dialysis modality and membrane type on NK-cell number and on phagocytic activity of neutrophils in patients on different dialysis methods. Sixty patients were included in the study and divided in three groups of 20 patients each. Patients on conventional hemodialysis using Low Flux membrane (cHD-LF) were included in Group I, patients on conventional dialysis using High Flux membrane (cHD-HF) were included in Group II and patients treated by on-line hemodiafiltration with High Flux polysulphone membrane (on-line HDF) were included in Group III. Native immunity was investigated using the number of NK-cells and the phagocytic activity of neutrophils. NK-cells count was significantly lower (p<0.001) in the three groups of dialyzed patients in comparison to healthy subjects. However, no significant difference was observed in the NK-cells count among patients treated by conventional dialysis using Low or High Flux membrane and patients treated by on-line hemodiafiltration. Similarly, although the phagocytic activity of neutrophils was significantly decreased in all patients on dialysis (p<0.001), no difference related to the dialysis modality or membrane performance was observed. A strong positive correlation was recognized between parathormone blood levels and number of NK-cells (r=0.305, p<0.01). In conclusion, an impairment of the native immunity represented by NK cell number and phagocytic activity of neutrophils is observed in patients on dialysis. Dialysis modality and membrane performance do not influence the native immunity of dialyzed patients. However, parathormone blood levels are possibly involved in the development of immune system disturbances in such patients.

Effects of Zinc Supplementation on the Immune System and on Antibody Response to Multivalent Influenza Vaccine in Hemodialysis Patients

The depression of the immune system in chronic uremia is a well-known phenomenon but the role of serum zinc (Zn) levels on both cell-mediated and humoral immunity is still controversial. The aim of this study was to investigate the effect of Zn supplementation on the immune system and on antibody response to multivalent influenza vaccine (MIV) in hemodialysis patients (HP).

Twenty-six HP and 11 healthy subjects (HS) were vaccinated with MIV. Hemodialysis patients were randomly divided into two groups. Group 1 (13 HP) was supplemented with 120 mg ZnS04 after each dialysis session. Group II (13 HP) and Grouip III (11 HS) were given placebo. In all cases, the serum Zn levels, CD3, CD4, CD8, CD19, HLA-DR+ cell percentages, CD4/CD8 ratio and CD3+HLA-DR+ cell percentages were determined before and 30 days after vaccination. Antibody levels to subgroups of MIV were also measured.

All the baseline parameters studied were not statistically different between Group I and II. However, there was a significant difference between the basal parameters of Group III and the other two groups, except for CD3 and CD4 cell percentages.

Serum Zn, CD19 cell percentage and antibody levels to MIV subgroups were significantly increased in Group I at the end of the first month of the study (p<0.01, p<0.05, p<0.001, p<0.001, and p<0.01, respectively), but the other parameters showed no significant changes. The only significant change observed in Groups II and III was an increase in antibody levels to MIV subgroups one month after vaccination. Antibody levels to MIV subgroups, were not statistically different between Groups I and II, but in Group III they were strikingly higher than those of HP (p<0.001).

These results led us to conclude that Zn supplementation could not restore the immune parameters and enhance antibody response to MIV in HP.

The effect of cholecalciferol and calcitriol on biochemical bone markers in HIV type 1-infected males: results of a clinical trial

HIV-1-infected patients have an increased risk of osteoporosis and fractures. The main objective of this study was to evaluate the bone metabolism in HIV-1-infected patients exposed to calcitriol and cholecalciferol. We also investigated the relationship between T cells and bone markers. We conducted a placebo-controlled randomized study running for 16 weeks including 61 HIV-1-infected males, of whom 51 completed the protocol. Nineteen participants were randomized to daily treatment with (A) 0.5-1.0 μg calcitriol and 1,200 IU (30 μg) cholecalciferol, 17 participants to (B) 1,200 IU cholecalciferol, and 15 participants to (C) placebo. At baseline and after 16 weeks, we determined collagen type 1 trimeric cross-linked peptide (CTx), procollagen type 1 N-terminal peptide (P1NP), parathyroid hormone (PTH), ionized calcium, 25-hydroxyvitamin D (25OHD), and 1,25-dihydroxyvitamin D [1,25(OH)2D]. We determined naive CD4(+) and CD8(+), activated CD4(+) and CD8(+), and regulatory CD4(+)CD25(+)CD127(low) T lymphocytes. Baseline levels of P1NP and CTx correlated (coefficient 0.5, p<0.001) with each other but not with PTH, 25OHD, or 1,25(OH)2D. In patients receiving calcitriol and cholecalciferol, the mean levels of P1NP (p<0.001) and CTx (p= 0.002) declined significantly compared to our placebo group. Based on changes in P1NP and CTx, we estimated that net bone formation occurred more frequently in group A compared to groups B and C. PTH correlated inversely with naive CD4(+) and CD8(+) cells. Otherwise, no relationships between bone markers and T lymphocytes were demonstrated. Supplementation with calcitriol and cholecalciferol induced biochemical indications of bone formation in HIV-1 patients.

Predictors of Failure of Catheter Salvage in Incident Hemodialysis Patients

Purpose

Catheter-related bloodstream infection is a frequent complication for patients who use catheter as dialysis access. This study was performed to identify the risk factors for failed catheter salvage.

Methods

We enrolled patients who received non-tunneled catheters as initial vascular access during a two-year period. Catheter salvage was attempted in all symptomatically mild patients. Patients were prospectively followed for 8 weeks starting from the day of infection. Risk factors for salvage failure were explored.

Results

A total of 77 bacteremia episodes occurred in 69 patient, with an infection rate of 1.61 per 1,000 catheter days. Salvage was successful in 73.4% of all episodes. We found that higher ferritin levels (greater vs. lower than 500 mg/l, (odds ratio (OR) 6.388, 95% confidence interval (CI) 2.073, 19.686), higher phosphate levels (greater vs. lower than 5.5 mg/dl, OR 4.084, 95% CI 1.391, 11.978) and shorter time intervals between catheterization and infection (within vs. beyond 3 weeks, OR 4.190, 95% CI 1.279, 13.725) predicted salvage failure.

Conclusions

Catheter salvage can be a reasonable initial strategy for symptomatically mild patients. We propose salvaging aggressively and waiting watchfully; however, clinical judgment is prior to any specific management protocol.

The affecting factors and comparison of tuberculin skin test in peritoneal dialysis and hemodialysis patients

Compared with the general population, patients with chronic renal failure have increased tuberculosis (TB) prevalence and mortality rates. In this study, we aimed to investigate tuberculin skin test (TST) positivity rates in hemodialysis (HD) and peritoneal dialysis (PD) patients and the factors influencing TST positivity. Ninety-two HD patients and 44 PD patients who had been on HD and PD treatment for at least 3 months were recruited into the study. TST was administered in all patients. Positivity was defined as an induration diameter >10 mm. At least 5 mm of induration following skin testing together with a chest radiography indicating previous infection was defined as latent TB infection. TST positivity rates, diameter of TST indurations, and serum albumin levels in HD patients were higher than the PD patients. TST induration size was not correlated with any other parameters in both HD and PD groups. TST-positive patients had higher albumin levels and lower leukocyte count than the TST-negative patients. In TST-positive patients, albumin level was correlated with the duration of dialysis but TST induration size was not correlated with the lymphocyte count and albumin level. In our study, TST positivity of patients was found in 30.4% of HD patients, 9% of PD patients, and 23.5% of total patients. It is still recommended to use TST for the screening test of TB. We found a significant relationship between TST and albumin level. It should be remembered that TST response may be lower in PD patients, especially in cases in which TB is suspected.

Effects of parathyroid hormone on immune function

Parathyroid hormone (PTH) function as immunologic mediator has become interesting with the recent usage of PTH analogue (teriparatide) in the management of osteoporosis. Since the early 1980s, PTH receptors were found on most immunologic cells (neutrophils, B and T cells). The in vitro evaluations for a possible role of PTH as immunomodulator have shown inconsistent results mainly due to methodological heterogeneity of these studies: it used different PTH formulations (rat, bovine, and human), at different dosages and different incubating periods. In some of these studies, the lymphocytes were collected from uremic patients or animals, which renders the interpretation of the results problematic due to the effect of uremic toxins. Parathyroidectomy has been found to reverse the immunologic defect in patients with high PTH levels. Nonetheless, the clinical significance of these findings is unclear. Further studies are needed to define if PTH does have immunomodulatory effects.

Uraemic hyperparathyroidism causes a reversible inflammatory process of aortic valve calcification in rats

AIMS

Renal failure is associated with aortic valve calcification (AVC). Our aim was to develop an animal model for exploring the pathophysiology and reversibility of AVC, utilizing rats with diet-induced kidney disease.

METHODS AND RESULTS

Sprague-Dawley rats (n = 23) were fed a phosphate-enriched, uraemia-inducing diet for 7 weeks followed by a normal diet for 2 weeks ('diet group'). These rats were compared with normal controls (n = 10) and with uraemic controls fed with phosphate-depleted diet ('low-phosphate group', n = 10). Clinical investigations included serum creatinine, phosphate and parathyroid hormone (PTH) levels, echocardiography, and multislice computed tomography. Pathological examinations of the valves included histological characterization, Von Kossa staining, and antigen and gene expression analyses. Eight diet group rats were further assessed for reversibility of valve calcification following normalization of their kidney function. At 4 weeks, all diet group rats developed renal failure and hyperparathyroidism. At week 9, renal failure resolved with improvement in the hyperparathyroid state. Echocardiography demonstrated valve calcifications only in diet group rats. Tomographic calcium scores were significantly higher in the diet group compared with controls. Von Kossa stain in diet group valves revealed calcium deposits, positive staining for osteopontin, and CD68. Gene expression analyses revealed overexpression of osteoblast genes and nuclear factor kappaB activation. Valve calcification resolved after diet cessation in parallel with normalization of PTH levels. Resolution was associated with down-regulation of inflammation and osteoblastic features. Low-phosphate group rats developed kidney dysfunction similar to that of the diet group but with normal levels of PTH. Calcium scores and histology showed only minimal valve calcification.

CONCLUSION

We developed an animal model for AVC. The process is related to disturbed mineral metabolism. It is associated with inflammation and osteoblastic features. Furthermore, the process is reversible upon normalization of the mineral homeostasis. Thus, our model constitutes a convenient platform for studying AVC and potential remedies.

Effects of parathyroid hormone and serum calcium on the phenotype and function of mononuclear cells in patients with primary hyperparathyroidism

BACKGROUND

Several studies have demonstrated specific influence of parathyroid hormone (PTH) on immune parameters, especially on T- and B-cell function, migration of polymorphonuclear leucocytes (PMNLs) and antibody synthesis, in patients with secondary hyperparathyroidism and chronic renal failure and recently also in patients with primary hyperparathyroidism (pHPT).

METHODS

We therefore examined 12 patients with pHPT before and 6 months after parathyroidectomy (PTX) and nine sex- and age-matched control subjects to determine the impact of PTH and serum calcium concentrations on several immune parameters, including (a) serum concentrations of immunoglobulins, (b) immunophenotype of peripheral blood lymphocytes, (c) phytohaemagglutinin (PHA)-induced lymphocyte proliferation and (d) monocytic surface marker expression.

RESULTS

Serum concentrations of immunoglobulins (IgG, IgA, IgM) were unaffected by elevated serum PTH and calcium levels. T lymphocytes (CD3), B lymphocytes (CD19), NK cells (CD16/56) and monocytes (CD16) revealed a normal distribution and were not different before and after PTX in patients with pHPT when compared with the control group. CD4+ T-helper lymphocytes were significantly elevated pre- and post-operatively in patients with pHPT. The lymphocyte proliferation response to PHA in the highest concentration (12.5 micrograms L-1) tested was significantly suppressed in patients with pHPT preoperatively when compared with the patients post-operatively and the control group. In addition, both CD4+ and CD8+ lymphocytes showed a lower expression of activation markers, interleukin 2 (IL-2) receptor (CD25) and transferrin receptor (CD71), which could be partially restored 6 months after PTX, but did not reach normal values.

CONCLUSION

In summary, in contrast to the findings in patients with secondary HPT, pHPT appears to be associated with less alterations of immune functions. Chronically elevated serum PTH and calcium concentrations in patients with pHPT induce a higher percentage of CD4+ helper T lymphocytes and a suppressed lymphocyte response to PHA as well as a reduced expression of activation markers on peripheral blood lymphocytes.