Hepatitis G virus infection in haemodialysis and in peritoneal dialysis patients.

The aim of this study was to detect hepatitis G virus RNA (HGV RNA) and antibodies against the virus envelope protein E2 (anti-E2) in 107 patients either on maintenance haemodialysis (n = 78) or peritoneal dialysis (n = 29) to evaluate the prevalence of HGV infection and to establish its role in liver disease. The total prevalence of HGV infection was of 15.4% among haemodialysis patients, whereas it was 10.3% among peritoneal dialysis patients. HGV RNA was detected in 2 haemodialysis patients (2.6%) and in 3 peritoneal dialysis patients (10.3%). Anti-E2 was found in 10 haemodialysis patients (7.8%), whilst all peritoneal dialysis patients resulted negative. In only 1 patient the alanine aminotransferase level was elevated. This patient underwent liver biopsy that did not reveal evidence of chronic hepatitis. The lower HGV prevalence in haemodialysis patients, when compared with data reported by other European authors, should be related to the lower rate of polytransfused patients in our series (29.5%). Multiple blood transfusions should be considered as the main factor to explain the different prevalence of HGV infection among various European dialysis centres. Detection of both antibody and viraemia is important to establish the real rate of the infection.

Protein oxidation in hemodialysis and kidney transplantation.

Oxidative damage of plasma proteins determined with the markers carbonyl group (CG) content and thiobarbituric acid-reactive substances (TBARS) was studied in 13 hemodialyzed and eight kidney-transplanted patients. The level of CGs was 38% higher in hemodialysis (HD) patients (1.49 +/- 0.05 nmol/mg protein) than in the healthy subjects (1.08 +/- 0.03 nmol/mg protein); the TBARS level was also higher in HD patients than in the control group (2.64 +/- 0.15 v 1.81 +/- 0.09 nmol/mL, P < .001). These data confirm that in end-stage renal failure, an increased oxidative stress is present and is able to induce protein damage. After transplantation, the CG content in protein was reduced (1.34 +/- 0.08 nmol/mg protein), but it was not significantly different from the level in the HD group. The failure to return to the normal range suggests that an impaired redox status is maintained, resulting in a sustained elevation of CG. Conversely, the level of TBARS in transplanted patients (1.99 +/- 0.22 nmol/mL) was not significantly different from that in the control group (1.81 +/- 0.09), suggesting that lipoperoxidation may be inhibited. These results may be explained by the different turnover rates of the molecules and by the distinct origin of the two markers, resulting from the damage of proteins or lipids. Thus, lipoperoxidation would produce rapidly removable molecules, whereas protein oxidation damage would tend to accumulate. However, the significant correlation found between CGs and TBARS indicates that a common cause (oxidative stress) binds the two markers of damage.

Plasma advanced glycosylation end-products in maintenance haemodialysis patients.

BACKGROUND: Pentosidine is a useful marker of advanced glycation end-products (AGE) which form cross-links between proteins and have been found elevated in plasma and tissues of uraemic and haemodialysed subjects. The origin and fate of these molecules are not clearly understood, but they might play a role in the cardiovascular complications of end stage renal failure. The aim of this study was to evaluate the effect of different types of substitutive therapy on the removal of pentosidine. METHODS: Pentosidine was measured by a two-step HPLC methodology. Its concentration was evaluated in plasma before and after dialysis session, in 24-h urine, and in dialysate of subjects treated with three types of chronic substitutive therapy: bicarbonate haemodialysis, acetate-free biofiltration, and haemofiltration. Pentosidine levels were compared among the three therapy modalities and correlated with clinical and biochemical parameters. RESULTS: Plasma pentosidine level was extremely high (23.7 +/- 2.0 pmol/mg protein) in the patients treated with the different dialysis modalities. The dialysis session had no significant effect on its plasma concentration, but haemofiltration seemed to be the most efficient method (300-2000 nmol of pentosidine removed per session versus 250-700 nmol per session with the two other approaches). An interesting correlation was found between pentosidine and blood urea nitrogen (r = 0.58, P < 0.01) and pentosidine with uric acid (r = 0.48, P < 0.05). CONCLUSIONS: These results suggest that none of the methodology showed a good removal of pentosidine, but among them haemofiltration has the best efficiency. The statistical relationships between pentosidine and urea and uric acid respectively might provide insight into the origin of pentosidine. The accumulation of reactive AGE in uraemic patients may be implicated in the organ and tissue damage observed in uraemia.

Anti-hepatitis C virus antibodies and hepatitis C virus viraemia in haemodialysis patients.

Sera from 82 haemodialysis patients were tested for anti-HCV, HCV-RNA, and HBsAg. Alanine aminotransferase (ALT) activity was monitored weekly for 2 months. Anti-HCV was positive in 31 patients (37.8%), showing different single-peptide patterns. HCV-RNA was detected in 26 anti-HCV-positive patients (84%) and also in two of 21 anti-HCV-negative patients. Twenty-seven (87%) of the 31 anti-HCV-positive patients had persistently normal ALT values; 22 of these patients were HCV-RNA positive. The four patients with elevated ALT values had HCV viraemia. HBsAg was positive in nine anti-HCV-negative patients. The close correlation between HCV viraemia and HCV status, independently of ALT values, requires that anti-HCV dialysis patients must be considered potentially infective and dialysed with reserved machines and/or in separate shifts.

Erythropoietin treatment and amino acid metabolism in hemodialysis patients.

A previous report suggests that treatment with recombinant human erythropoietin (rH-EPO) significantly improves many abnormalities in circulating amino acids (AA) in hemodialysis patients. We evaluated the effects of a 12-month treatment with rH-EPO (150-250 U/kg/week) on blood AA levels in 10 patients with chronic renal failure under regular dialytic treatment. During treatment, hemoglobin levels increased from 7.0 +/- 0.3 to 10.1 +/- 0.3 g/dl at 3 months remaining steady thereafter. Before the treatment, patients showed reduced levels of essential AA (EAA), mainly valine, leucine and threonine (p < 0.05-0.01); among non-EAA (NEAA), aspartate and serine were reduced, whereas glycine, alanine, proline, citrulline and cyst(e)ine were increased (p < 0.05-0.001). Val/Gly, Ser/Gly and Tyr/Phe ratios were low (p < 0.05-0.01). Total EAA and total NEAA (619 +/- 21 and 1,382 +/- 75 mumol/l, respectively, before the study) were unchanged (639 +/- 22 and 1,410 +/- 89 mumol/l, respectively) at 12 months. Abnormalities in AA levels observed before the treatment persisted throughout the study. Only serine increased at the end of the study (p < 0.05). In conclusion, contrary to what has been reported, treatment with rH-EPO is not associated with an amelioration of AA metabolism in hemodialysis patients.

[Recent findings on the pathogenesis and therapy of anemia in chronic kidney failure]. / Recenti acquisizioni sulla patogenesi e terapia dell'anemia dell'insufficienza renale cronica.

Recent studies showed that the blood BFU-E, when subtracted from the uremic milieu, normally responds to the stimulating factor produced by T lymphocytes. The serum of uremic patients inhibits the in vitro growth of normal BFU-E, however, the inhibition is almost completely reversed by hemodialysis. These data allow to understand why the therapy with erythropoietin relieves the anemia of CRF. Uremic T lymphocytes fail to stimulate the BFU-E growth. Normal T lymphocytes are inhibited by uremic serum and the hemodialysis does not correct the defect. Lymphopenia, decreased number of both T4 and T8 lymphocytes and low T4/T8 ratio were found in 50% of patients. Cimetidine was still able to increase the burst-stimulating activity of uremic T lymphocytes through inhibition of the suppressor T subset. In conclusion, one can say that in CRF T8 lymphocytes are normal and that uremic toxins decrease both number and function of T4 lymphocytes. The deficiency of BPA appears to significantly contribute to the pathogenesis of the anemia of CRF. The experience from our and other Institutions shows the effectiveness of the recombinant human erythropoietin in relieving the anemia of CRF, notwithstanding the hematological milieu is highly modified by uremia.

Effect of cimetidine on peripheral blood lymphocytes from chronic uremic patients: improvement of burst-promoting activity.

We have studied the in vitro effect of cimetidine, an inhibitor of suppressor T lymphocytes, on T lymphocytes of 6 uremic subjects and on normal T lymphocytes preincubated with the serum from the same patients. Cimetidine has been shown to increase the burst-promoting activity (BPA) of uremic T lymphocytes and to partially improve the BPA of normal T lymphocytes preincubated with uremic serum. The present study shows that suppressor T lymphocytes are not affected by uremic inhibitors and that chronic uremia, besides inducing a decrease in the number of helper T lymphocytes, impairs their ability to stimulate the BFU-E in vitro growth.

Proliferation in autologous mixed lymphocyte reactions, expression of HLA-class II antigen and serum immunomodulatory activity in patients with renal insufficiency on chronic dialysis.

The proliferative and stimulatory capacities in allogeneic and autologous mixed lymphocyte reactions were evaluated in 5 patients affected by renal insufficiency undergoing maintenance hemodialysis. The expression of HLA class II antigens and Interleukin 2 production by PHA-activated T cells were also investigated. Furthermore the immunomodulatory effects of uremic serum and serum fractions on mixed lymphocyte reactions performed with lymphocytes from normal subjects were analyzed. The results show that both responsive and stimulatory capacities in allogeneic and autologous mixed lymphocyte reactions of non-T/T and T/T type are clearly impaired. The expression of HLA class II antigens by PHA-activated T cells was reduced whereas the production of Interleukin 2 was normal. The autologous and allogeneic mixed lymphocyte reactions of normal lymphocytes were inhibited by unfractionated uremic serum and by a wide range of serum fractions with different molecular weights. All the above mentioned immune defects were not corrected by the dialytic treatment. The present study extends previous reports concerning the defective immunocompetence associated with chronic renal insufficiency showing that: a) the autologous mixed lymphocyte reactions of both non-T/T and T/T type are impaired; b) the uremic serum contains several factors inhibiting the autologous mixed lymphocyte reactions of normal lymphocytes; c) the chronic hemodialytic treatment does not correct these defects.

T lymphocyte subsets in chronic uremic patients treated with maintenance hemodialysis.

Blood T lymphocyte subsets have been studied using monoclonal antibodies in 10 chronic uremic patients treated with maintenance hemodialysis. Both total T lymphocytes identified by the antibody OKT3, and the helper-inducer T lymphocyte subset identified by the antibody OKT4 were found to be significantly lower than normal. The cytotoxic-suppressor T cell subset was only moderately, even if significantly reduced, so that the T4/T8 ratio in uremic patients was significantly lower than normal. These data provide an additional contribution to the interpretation of immunological and hematological deficiencies observed in chronic uremia.

Five years' experience with Hickman catheters as temporary access for haemodialysis.

Two different types of Hickman catheters were used as central venous access for haemodialysis. The device was implanted in 58 patients with chronic renal failure, already undergoing haemodialysis, because of thrombosis or infection of the previous vascular access, in order to permit immediate treatment and in nine patients with acute renal failure, as a 'first choice' method suitable either for dialysis or for parenteral infusions and nutrition. The catheter was inserted, under local anaesthesia, through the external jugular vein up to the right atrium; the haemodialysis treatment was carried out by single-needle technique 3-4 times weekly and all the catheters were filled daily with heparinised saline and Miconazole solution. The mean duration was 76 +/- 93 days with an overall of 2253 treatments. The flow rate ranged between 150 and 290 ml/min, with acceptable recirculation rate and biochemistry similar to that of standard dialysis. The complication rate was 20%, including thromboses and infections; no operative mortality nor major complications were observed. Based on these data, we believe that the Hickman catheter represents the ideal method of temporary access for haemodialysis.

Inhibition of BFU-E in vitro growth and of burst-promoting activity of T lymphocytes by serum of chronic uremic patients receiving hemodialysis.

The effects of uremic serum on the in vitro growth of normal BFU-E and on the burst-promoting activity by normal T-lymphocytes were evaluated separately. The effect of hemodialysis on the removal of possible serum inhibitor(s) was also tested. Sera of 12 uremic patients were shown to provoke a 60% inhibition of the in vitro growth of normal BFU-E and almost complete abolition of burst-promoting activity by T lymphocytes. While hemodialysis significantly removed the inhibition of uremic sera on BFU-E growth, it was rather ineffective in removing the inhibitor(s) of T lymphocytes. The different effects of uremic serum on BFU-E and on T lymphocytes are discussed.

Free and sulfoconjugated catecholamines in normotensive uremic patients: effects of hemodialysis.

In 9 normotensive uremic patients undergoing chronic hemodialysis, the baseline plasma catecholamines varied widely from low-normal to very high; sulfoconjugated plasma catecholamines were constantly high. A dialysis-induced fall of all sulfated catecholamines and epinephrine was observed. Norepinephrine decreased in 5 patients and increased in 4, with a strong inverse correlation between predialysis norepinephrine and delta norepinephrine (p less than 0.0001). No correlation was evident between clinical parameters (mean arterial pressure, heart rate) and catecholamines (both predialysis and postdialysis). Significant (p less than 0.0001 and p less than 0.0002) inverse correlations between epinephrine and norepinephrine and their sulfoconjugation degree were demonstrated only in predialysis. Our data may support the presence of a uremic autonomic neuropathy and adrenoceptor damage.

Inadequate ability of T-lymphocytes from chronic uremic subjects to stimulate the in vitro growth of committed erythroid progenitors (BFU-E).

The growth of normal burst-forming units (BFU-E) is known to depend on a burst-promoting activity (BPA) produced by T-lymphocytes. Few BFU-E colonies have been observed in cultures of blood mononuclear cells (MNC) of uremic patients. The aim of the present study was to examine the concentration of BFU-E in the blood of uremic patients and to evaluate the ability of uremic T-lymphocytes to produce BPA. We have studied 6 chronic uremic patients treated with maintenance hemodialysis. When 5 X 10(5) blood MNC depleted of T-lymphocytes of uremic subjects were stimulated by 1 X 10(6) normal T-lymphocytes in a methylcellulose culture system we observed the growth of a number of BFU-E colonies that did not differ significantly from normal (29 +/- 11.8 colonies). On the contrary, when 5 X 10(5) blood MNC depleted of T-lymphocytes of normal subjects were stimulated by 1 X 10(6) T-lymphocytes of uremic patients, the number of BFU-E colonies obtained was significantly lower than normal (1.9 +/- 3.1 colonies). These data show that the decreased number of BFU-E colonies obtained from blood MNC of uremic patients is due to a defect of uremic T-lymphocytes. The impairment of T-lymphocytes can be due to inhibitors of T-lymphocyte function or to variations in T cell subsets, leading to a decrease in the OKT4/OKT8 cell ratio. In any case it is a significant pathogenetic mechanism contributing to anemia in chronic uremia.

Alterations of erythropoiesis in chronic uremic patients treated with intermittent hemodialysis.

The in vitro growth of the blood burst-forming cells (BFU-E) of 9 chronic uremic patients, treated with intermittent hemodialysis three times a week has been studied at the time of maximum and minimum level of retained nitrogen catabolites. The effect of uremic sera on the vitro growth of normal BFU-E was also studied. The in vitro growth of blood BFU-E was shown to be greatly reduced in all uremic patients and dialysis did not modify their growth. The sera of uremic patients significantly inhibited the in vitro growth of normal blood BFU-E when it was taken at the time of maximum retention of nitrogen catabolites. However, inhibition of normal BFU-E growth was not seen when uremic sera were taken at the time of minimum retention of nitrogen catabolites. These data seem to indicate a long lasting suppression of BFU-E in chronic uremia due to serum inhibitor/s.