Elevated cytosolic calcium and impaired proliferation of B lymphocytes in type II diabetes mellitus.

Patients with diabetes mellitus have increased susceptibility to infection attributable, at least in part, to defective function of polymorphonuclear leukocytes (PMNLs) and B cells. Certain data suggest that cytosolic calcium ([Ca2+]i) is elevated in various cells in diabetes, and high [Ca2+]i adversely affects cell function. Indeed, the [Ca2+]i of PMNLs of diabetic patients is elevated, and phagocytosis of the PMNLs is impaired. The current study examines whether the [Ca2+]i of B cells is also elevated in diabetes and whether this derangement impairs B cell function. We studied 32 patients with non-insulin-dependent diabetes mellitus (NIDDM) and eight normal subjects. All patients had hyperglycemia (11.6 +/- 0.80 mmol/L) and elevated HbA1c (13.2% +/- 0.99%). The basal levels of [Ca2+]i of the B cells (113 +/- 3.3 nmol/L) were significantly (P < 0.01) higher than the values in normal subjects (85 +/- 1.7 nmol/L). There was a direct and significant correlation (r = 0.88; P < 0.01) between the [Ca2+]i of B cells and the blood levels of glucose. Proliferation of B cells in response to Staphylococcus aureus Cowan I (SAC) was significantly impaired in these patients (7.3 +/- 0.48 x 10(3) cpm v 12.5 +/- 0.61 x 10(3) cpm in normal subjects). Normalization of blood glucose with the hypoglycemic agents, glyburide, was associated with the return of both [Ca2+]i of B cells and their proliferation in response to SAC to normal. The results show that hyperglycemia in type II diabetes mellitus is associated with a significant increase in [Ca2+]i of B cells and with a decrease in their proliferation in response to mitogen. These derangements are reversed after the correction of the hyperglycemia. The data of the current study and those previously reported in PMNLs provide for a new pathogenetic process underlying the dysfunction of these cells in diabetes mellitus.

A longitudinal study on the effect of nifedipine therapy and its discontinuation on [Ca2+]i and proliferation of B lymphocytes of dialysis patients.

The abnormalities in cytosolic calcium ([Ca2+]i) and proliferation of B cells in uremic patients are significantly improved by treatment with nifedipine. The rapidity with which this agent induces its beneficial effect and whether these derangements reemerge after cessation of therapy are not known. We studied six hemodialysis patients before, during, and after treatment with nifedipine. Before treatment, [Ca2+]i of B cells was markedly elevated (125 +/- 4.3 nmol/L) and their proliferation markedly reduced (5.2 +/- 0.36 x 10(3) cpm). After 1 month of therapy, [Ca2+]i fell significantly (P < 0.01) to 95 +/- 1.7 nmol/L and to a normal value of 84 +/- 1.6 after 2 months. The levels of [Ca2+]i rose significantly (P < 0.01) to 95 +/- 2.3 nmol/L after 1 month of cessation of therapy and were 115 +/- 2.8 nmol/L by 2 months. Proliferation of B cells improved significantly (P < 0.01) after 1 month of therapy (9.4 +/- 1.1 x 10(3) cpm) with further improvement during the subsequent month, reaching a normal value (12.2 +/- 1.1 x 10(3) cpm) by the end of the 2 months. Proliferation of B cells decreased after cessation of therapy and was 5.2 +/- 0.17 x 10(3) cpm after 2 months, a value similar to the pretreatment level. The blunted inhibitory effect of PTH-(1-84) on B cell proliferation was reversed by nifedipine treatment and reappeared after discontinuation of therapy. Also, serum globulin levels increased after administration of nifedipine and decreased again after cessation of treatment. The results show that nifedipine rapidly reversed the elevation in [Ca2+]i of B cells, the impairment in their proliferation, and the blunted inhibitory effect of PTH on B cell proliferation, and was associated with increased serum globulin levels. These derangements reemerged after cessation of therapy. These data indicate that nifedipine therapy is effective in the management of the abnormalities in B cell metabolism and function in hemodialysis patients. The treatment with this drug must be maintained to sustain its beneficial effects. Other calcium channel blockers may also be effective, but their effects were not examined in the current study.

Time course of the effect of nifedipine therapy and its discontinuation on [Ca2+]i and phagocytosis of polymorphonuclear leukocytes from hemodialysis patients.

The abnormalities in [Ca2+]i and phagocytosis of polymorphonuclear leukocytes (PMNLs) from hemodialysis (HD) patients are significantly improved by their treatment with nifedipine. However, the rapidity with which this agent induces its beneficial effect and whether these derangements re-emerge after cessation of therapy are not known. We studied 5 HD patients before, during and after treatment with nifedipine. Before treatment with this agent, the basal levels of [Ca2+]i of PMNLs were markedly elevated 73 +/- 3.6 nM (normal: 42 +/- 0.09 nM) and their phagocytic ability markedly reduced (73 +/- 7.4 micrograms oil/10(7) PMNLs/min (normal: 153 +/- 3.8 micrograms oil/10(7) PMNLs/min). After 1 month of therapy, [Ca2+]i fell significantly (p < 0.01) to 53 +/- 1.0 nM with further decrement of a value of 40 +/- 0.9 nM by the end of 3 months of treatment. The levels of [Ca2+]i rose significantly (p < 0.01) to 61 +/- 2.1 nM after 1 month of cessation of therapy and were 69 +/- 2.5 nM by the end of 5 months; these values are not different from those observed before therapy. Phagocytosis improved significantly (p < 0.01) after 1 month of nifedipine therapy (107 +/- 3.9 micrograms oil/10(7) PMNLs/min) with no further improvement during the other 2 months of therapy. Only modest decrement in phagocytosis occurred during the first 3 months after cessation of nifedipine administration; marked and significant impairment (p < 0.01) in phagocytosis (80 +/- 2.6 micrograms oil/10(7) PMNLs/min) became evident at the end of the fifth month. The results show that (1) nifedipine treatment of HD patients rapidly reversed the elevation in [Ca2+]i of their PMNLs but discontinuation of the therapy is followed by rapid re-emergence of the elevation in the [Ca2+]i of the PMNLs; (2) nifedipine therapy causes rapid and significant, but only partial, improvement of phagocytosis, by PMNL of HD patients; almost 5 months is needed before a significant deterioration in phagocytosis becomes evident after stopping nifedipine treatment; (3) the elevation in [Ca2+]i of PMNLs of HD patients plays an important role in the pathogenesis of impaired phagocytosis but is only partially responsible for their derangement, and (4) the beneficial effect of nifedipine therapy on phagocytosis makes this drug a useful therapeutic tool to aid HD patients in their fight against infection.

Nifedipine reverses the abnormalities in [Ca2+]i and proliferation of B cells from dialysis patients.

Both animals and patients with chronic renal failure have impaired B cell function due, in part, to elevated levels of cytosolic calcium ([Ca2+]i). Treatment of HD patients with nifedipine has normalized [Ca2+]i of their polymorphonuclear leukocytes (PMNL) and caused marked improvement in the phagocytic property of the PMNL. This observation may have important clinical implications if this drug exerts a similar effect on other cells such as B cells. We examined [Ca2+]i, proliferation of B cells in response to mitogen, the magnitude of the PTH-induced inhibition of B cell proliferation, and the ATP content of mononuclear cells in 11 hemodialysis patients treated with nifedipine, 12 patients without nifedipine therapy and 11 normal subjects. Serum levels of IgG was also measured in the two groups of patients. There were no significant differences in the age, duration of hemodialysis, blood levels of calcium, phosphorus or PTH (571 +/- 193 vs. 484 +/- 127 pg/ml) among the two groups of patients. The hemodialysis patients without nifedipine therapy compared to those without nifedipine treatment have significantly (P < 0.01) higher levels of [Ca2+]i (120 +/- 1.9 nM vs. 94 +/- 2.2 nM), lower ATP content of mononuclear cells (0.45 +/- 0.06 nmol/10(6) cells vs. 0.68 +/- 0.04 nmoles/10(6) cells), impaired proliferation (5.8 +/- 0.31 x 10(3) cpm vs. 9.8 +/- 0.38 x 10(3) cpm) and smaller inhibition of B cell proliferation by PTH compared to those treated with nifedipine. The values in the patients treated with nifedipine were still modestly but significantly different than in normal subjects. The serum IgG levels of the patients without nifedipine therapy (1210 +/- 71 mg/dl) were significantly lower than those of the patients treated with nifedipine (1594 +/- 81 mg/dl). Thus, the treatment of hemodialysis patients with nifedipine produced marked and significant improvement in the metabolic and functional parameters of B cells despite no changes in blood levels of PTH. These data indicate that the calcium channel blocker, nifedipine, interferes with PTH-induced rise in [Ca2+]i of B cells of hemodialysis patients and consequently improves their metabolism and function. These observations if confirmed in other human cells may provide for a rational therapeutic approach to ameliorate the signs and symptoms of uremia.

Polymorphonuclear leukocytes in non-insulin-dependent diabetes mellitus: abnormalities in metabolism and function.

OBJECTIVE: To determine basal levels of cytosolic calcium ([Ca2+]i) and phagocytic activity in polymorphonuclear leukocytes (PMNLs) from patients with non-insulin-dependent diabetes (NIDDM). DESIGN: Prospective cohort study. SETTING: A university-county hospital. MEASUREMENTS: Cytosolic calcium levels, adenosine triphosphate (ATP) content, and phagocytosis of PMNLs from patients with NIDDM and from controls. INTERVENTION: In patients with NIDDM, we evaluated the effect of treatment with an oral hypoglycemic agent (glyburide) on [Ca2+]i levels, ATP content, and the phagocytosis of PMNLs. PATIENTS: 22 controls and 34 patients with NIDDM were examined. Fifteen patients were studied before and after 3 months of treatment with glyburide. RESULTS: Polymorphonuclear leukocytes from patients with NIDDM showed significantly elevated basal levels of [Ca2+]i (68 +/- 9.6 compared with 43 +/- 4.9 nmol/L; P < 0.01); reduced ATP content (1.30 +/- 0.58 compared with 2.35 +/- 0.45 nmol/10(6) PMNLs; P < 0.01); and impaired phagocytosis (117 +/- 21.0 compared with 145 +/- 17.4 micrograms oil/10(7) PMNLs per minute; P < 0.01) compared with controls. There was a direct and significant correlation (P < 0.01, r = 0.80) between [Ca2+]i levels in PMNLs and serum glucose levels and an inverse correlation between phagocytic ability and [Ca2+]i levels (P < 0.01; r = 0.62) as well as between phagocytic activity and fasting serum glucose levels (P < 0.01, r = 0.54) in patients with NIDDM. Glyburide therapy resulted in significant reduction in fasting serum glucose levels; in PMNLs, this treatment resulted in a significant reduction in [Ca2+]i levels, a significant increase in ATP content, and a significant improvement of phagocytosis. CONCLUSIONS: Patients with NIDDM have elevated [Ca2+]i levels in PMNLs. This abnormality is probably induced by hyperglycemia and is primarily responsible for the imparied phagocytosis seen in these patients.

Effect of treatment of hemodialysis patients with nifedipine on metabolism and function of polymorphonuclear leukocytes.

Both animals and patients with chronic renal failure have impaired phagocytosis, which is most likely due to elevated basal levels of cytosolic calcium ([Ca2+]i) and reduced adenosine triphosphate (ATP) content of their polymorphonuclear leukocytes (PMNLs). In animals with chronic renal failure, these derangements are prevented or reversed by their treatment with a calcium channel blocker. This observation may have important clinical implications if these drugs exert a similar effect in humans with chronic renal failure. We examined the basal levels [Ca2+]i, ATP content, and phagocytosis in PMNLs from 11 normal subjects, 18 hemodialysis patients (seven of whom had diabetes mellitus), and 18 hemodialysis patients treated with nifedipine (eight of whom had diabetes mellitus). The basal levels of the [Ca2+]i content of the PMNLs in hemodialysis patients without nifedipine therapy were significantly (P < 0.01) elevated (nondiabetic patients, 77 +/- 3.2 nmol/L; diabetic patients, 75 +/- 1.9 nmol/L) compared with normal values (42 +/- 0.9 nmol/L). Treatment with nifedipine was associated with the return of [Ca2+]i toward normal values in both the nondiabetic (51 +/- 4.5 nmol/L) and diabetic (54 +/- 2.5 nmol/L) hemodialysis patients. The ATP content of PMNLs from hemodialysis patient was significantly (P < 0.01) reduced compared with normal, and nifedipine therapy restored the ATP content to normal values. Phagocytosis was significantly (P < 0.01) impaired in hemodialysis patients (nondiabetic patients, 78 +/- 4.0 micrograms oil/10(7) PMNLs/min; diabetic patients, 77 +/- 4.8 micrograms oil/10(7) PMNLs/min). Nifedipine therapy returned the impaired phagocytosis toward normal (nondiabetic patients, 133 +/- 2.5 micrograms oil/10(7) PMNLs/min; diabetic patients, 129 +/- 6.4 micrograms oil/10(7) PMNLs/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of dietary sodium intake on intracellular calcium in lymphocytes of salt-sensitive hypertensive patients.

High dietary Na+ raises mean arterial pressure (MAP) by more than 10% in salt-sensitive (SS) patients with essential hypertension. To test whether the rise in MAP in these patients is caused by a Na(+)-linked increase in [Ca2+]i in vascular smooth muscle cells, we measured [Ca2+]i in the lymphocytes of 14 patients with essential hypertension kept on a Na+ intake of 20 mEq/day for 9 days, and 200-mEq/day for 14 days. Nifedipine gastrointestinal transport system (GITS) (30 mg/day) was given during the last 4 days of each diet. We isolated lymphocytes on Ficoll-Hypaque gradient and measured [Ca2+]i levels using Fura-2 fluorescent dye. During low Na+ intake, there was no difference in MAP (102 +/- 3.5 v 93 +/- 3.8 mm Hg) and in lymphocytes [Ca2+]i (80 +/- 3.0 v 87 +/- 5.4 nmol/L) between the seven salt-sensitive and the seven salt-resistant patients. During high Na+ intake, MAP (92 +/- 2.8 mm Hg) and [Ca2+]i (85 +/- 6.8 nmol/L) did not change in salt-resistant patients. On the contrary, MAP (115 +/- 3.4 mm Hg) and [Ca2+]i (130 +/- 11.1 nmol/L) increased significantly (P less than .01) in the salt-sensitive patients. Nifedipine did not significantly alter MAP and [Ca2+]i in both groups of patients during low Na+ and in salt-resistant patients during high Na+ intake. On the contrary, during high Na+ intake, nifedipine decreased significantly (P less than .01) both MAP (104 +/- 2.4 mm Hg) and [Ca2+]i (89 +/- 5.7 nmol/L) in salt-sensitive patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired phagocytosis in chronic renal failure is mediated by secondary hyperparathyroidism.

Patients with chronic renal failure (CRF) display impaired phagocytosis by the polymorphonuclear leucocytes (PMNL), and these cells have elevated basal levels of cytosolic calcium ([Ca2+]i) and reduced ATP content. It has been suggested that these changes in PMNL metabolism and function are mediated by the state of secondary hyperparathyroidism of CRF. To examine the role of excess PTH in these derangements of PMNL, we studied [Ca2+]i, ATP and phagocytic ability of PMNL in five groups of rats including: CRF, CRF normocalcemic parathyroidectomized (CRF-PTX), CRF and normal animals treated with verapamil (CRF-V), and normal-V, respectively. The level of [Ca2+]i in the PMNL of CRF rats (149 +/- 2.7 nM) was significantly (P less than 0.01) higher and the ATP content (4.2 +/- 0.17 nmol/5 x 10(6) PMNL) significantly lower (P less than 0.01) than in normal (108 +/- 2.4 nM; 9.5 +/- 0.15 nmol/5 x 10(6) PMNL), CRF-PTX (103 +/- 2.9 nM; 9.2 +/- 0.19 nmol/5 x 10(6) PMNL), CRF-V (107 +/- 2.2 nM; 9.0 +/- 0.2 nmol/5 x 10(6) PMNL) and normal-V (106 +/- 1.8 nM; 9.2 +/- 0.2 nmol/5 x 10(6) PMNL), despite sustained elevation in blood PTH in the CRF-V group. Phagocytosis was significantly (P less than 0.01) impaired in CRF animals (5.6 +/- 0.25 micrograms oil/10(7) PMNL/min) but was normal in CRF-PTX (9.3 +/- 0.21 micrograms oil/10(7) PMNL/min) and CRF-V (9.5 +/- 0.22 micrograms oil/10(7) PMNL/min) rats. The values of phagocytosis in normal and normal-V rats were 9.6 +/- 44 and 9.6 +/- 0.18 micrograms oil/10(7) PMNL/min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

On the mechanisms of impaired phagocytosis in phosphate depletion.

Phosphate depletion (PD) impairs the phagocytic ability of polymorphonuclear leukocytes (PMNL). This derangement has been attributed to the low ATP content of PMNL in PD. The mechanisms responsible for the low ATP content are not well defined. Phosphorus deficiency, per se, and/or other cellular metabolic consequences of PD such as a rise in cytosolic calcium ([Ca2+]i) could be responsible. Indeed, PD is associated with a rise in [Ca2+]i in other cells, and such an event may inhibit mitochondrial ATP production. It is also not evident whether the impaired phagocytosis in PD is due to low ATP content and/or a rise in the [Ca2+]i of PMNL. The study presented here examined levels of [Ca2+]i, ATP content, and the phagocytic ability of PMNL from PD and pair-weighed (PW) rats and evaluated the potential beneficial effect of treatment with verapamil (V), which may prevent a rise in [Ca2+]i and the consequent effects on ATP content and the phagocytosis of PMNL. The resting levels of [Ca2+]i of PMNL from PD rats (148 +/- 3.9 nM) were significantly (P less than 0.01) higher, and the ATP contents (4.8 +/- 0.2 nmol/5 x 10(6) PMNL) were significantly (P less than 0.01) lower than in PW (111 +/- 2.8 nM and 9.3 +/- 0.3 nmol/5 x 10(6) PMNL), PW-V (114 +/- 2.2 nM and 9.3 +/- 0.28 nmol/5 x 10(6) PMNL), and PD-V (112 +/- 1.8 nM and 6.6 +/- 0.19 nmol/5 x 10(6) PMNL) animals. Despite the normal [Ca2+]i in the PMNL of PD-V rats, their ATP contents were still significantly (P less than 0.01) lower than those of PW or PW-V rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Impaired in vivo antibody production in CRF rats: role of secondary hyperparathyroidism.

Antibody responses to antigens are impaired in humans and animals with chronic renal failure (CRF), and parathyroid hormone (PTH) inhibits Staphylococcus aureus Cowan I (SAC) or pokeweed mitogen (PWM)-induced antibody production by B cells from normal subjects. Since CRF is associated with secondary hyperparathyroidism and elevated blood levels of PTH, it is possible that impaired humoral immunity in CRF is due to chronic excess of PTH. To test this hypothesis we examined in vivo antibody production in response to sheep red blood cells (SRBC), BSA and influenza vaccine in normal rats, CRF rats and parathyroidectomized CRF rats maintained normocalcemic (CRF-PTX). The blood levels of PTH in CRF rats were elevated and significantly (P less than 0.01) higher than those in normal and CRF-PTX rats. The latter groups of animals did not have elevated blood levels of PTH. The antibody response to all three antigens in CRF rats were significantly (P less than 0.01) and markedly lower than in normal or CRF-PTX rats. The antibody response to SRBC, the IgG anti-BSA and the IgG and IgM anti-influenza vaccine in CRF-PTX rats were not different from normal, while the IgM anti-BSA was lower than in normal rats but higher than in CRF rats. The data demonstrate that the state of secondary hyperparathyroidism of CRF plays a paramount role in the genesis of impaired humoral immunity in CRF.

Inhibition of immunoglobulin production by parathyroid hormone. Implications in chronic renal failure.

Available data indicate that B cell proliferation is inhibited in chronic renal failure and this is due to excess blood levels of PTH. This defect may also affect immunoglobulin production. We examined production of IgG, IgM and IgA by B cells stimulated with Staphylococcus aureus Cowan I (SAC) or with pokeweed mitogen (PWM) after eight days of culture and evaluated the effect of PTH on this process in 34 hemodialysis patients and 44 normal subjects. IgG, IgM and IgA production by B cells from patients was lower (P less than 0.01) than by B cells from normal subjects. Both 1-34 and 1-84 PTH inhibited (P less than 0.01) immunoglobulin production by B cells from normal subjects and dialysis patients. However, this inhibitory effect was evident in dialysis patients only with the higher dose of PTH. The inhibition of immunoglobulin production by PTH occurred only when the hormone was added at the initiation of the B cell culture. Inactivation of PTH abolished its inhibitory effect on immunoglobulin production. Agents that stimulate cAMP production (forskolin, cholera toxin) and the cAMP analogue, 8-bromoadenosine 3',5' cyclic monophosphate inhibited immunoglobulin production by B cells from both normal and dialysis patients, and the degree of inhibition was not different between the two groups. The calcium inophore A23187 also inhibited IgG, IgA and IgM production by B cells from normal subjects and dialysis patients; there was no significant difference in the degree of inhibition between the two groups. The resting levels of cytosolic calcium in B cells of dialysis patients was significantly (P less than 0.01) higher than that of B cells from normal subjects. The data show that: (1) immunoglobulin production is impaired in dialysis patients; (2) B cells of dialysis patients have elevated resting levels of cytosolic calcium; (3) PTH inhibits IgG, IgA and IgM production and this effect is at least partly mediated by PTH-induced cAMP production and alterations in cytosolic calcium into B cells; (4) this inhibitory effect is mediated by events that affect initial stages of B cell proliferation and maturation; (5) the requirement for high dose of PTH for its inhibitory effect on B cells from dialysis patients is probably due to desensitization and/or down-regulation of PTH receptors on B cells. The results are consistent with the proposition that impaired immunoglobulin production by B cells from dialysis patients is at least partly due to the state of secondary hyperparathyroidism in these patients.

Impaired phagocytosis in dialysis patients: studies on mechanisms.

Dialysis patients have increased susceptibility to infection and this is, in part, due to impaired phagocytic and bactericidal activities of polymorphonuclear leukocytes (PMNL). The mechanisms responsible for the reduced phagocytosis are not known. Dialysis patients have elevated blood levels of parathyroid hormone (PTH), and available data indicate that PMNL is a target cell for PTH. Chronic exposure to excess PTH may cause accumulation of calcium in PMNL which in turn could adversely affect cellular events leading to their dysfunction. We studied phagocytosis, resting levels of cytosolic calcium [( Ca2+]i), ATP content and the rise in [Ca2+]i in response to ligation of Fc gamma RIII receptors with 3G8 monoclonal antibody in PMNL from 37 dialysis patients and 48 normal subjects. The PMNL from the dialysis patients displayed impaired phagocytosis, elevated resting levels of [Ca2+]i, decreased ATP content and a smaller rise in [Ca2+]i in response to various doses of 3G8 monoclonal antibody as compared to values obtained in PMNL of normal subjects. Our results suggest that derangements in cellular metabolism and possibly an abnormality in Fc gamma RIII interaction with antibody and/or the consequences of such interaction are responsible, at least in part, for the impaired phagocytosis of PMNL of dialysis patients. Our data are consistent with the notion that excess PTH may play an important role in the processes leading to impaired phagocytosis.

Parathyroid hormone inhibits B cell proliferation: implications in chronic renal failure.

B cell proliferation is impaired in patients with chronic renal failure, but the mechanisms underlying this defect are not known. Lymphocytes have receptors for parathyroid hormone, and it is possible that the state of secondary hyperparathyroidism of renal failure is responsible for the B cell defect. Our studies were designed to (a) examine T cell-independent B cell proliferation [3H)thymidine incorporation) induced by Staphylococcus aureus Cowan 1 after 5 days of culture, (b) evaluate the effect of parathyroid hormone on S. aureus Cowan I-induced B cell proliferation, and (c) investigate the mechanisms through which parathyroid hormone may exert its effect on B cell proliferation. Lymphocytes were obtained from 37 normal subjects and 21 dialysis patients. S. aureus Cowan I induced significant stimulation (P less than 0.01) of the proliferation of B cells from both groups, but the effect was smaller on B cells from dialysis patients (10.0 x 10(3) +/- 1.4 x 10(3) cpm) than on those from normal subjects (21.8 x 10(3) +/- 2.0 x 10(3) cpm). Both the intact molecule of parathyroid hormone (1-84 PTH) and its amino-terminal fragment (1-34 PTH) caused significant inhibition of proliferation of B cells from normal subjects in a dose-dependent manner, with the effect being significantly greater (P less than 0.01) with an equimolar concentration of 1-84 PTH than that of 1-34 PTH. Inactivation of 1-84 PTH by oxidation abolished most of its inhibitory effect on B cell proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of parathyroid hormone on human T cell activation.

Lymphocytes have receptors for PTH and patients with chronic renal failure have high blood levels of PTH and impaired lymphocyte function. It is possible, therefore, that PTH affects lymphocyte function. We studied the interaction between PTH and proliferation of human lymphocytes in vitro and examined potential mechanisms for such an interaction. 1-84 PTH stimulated in a dose dependent manner PHA-induced proliferation of T cells but had no effect on PWM-induced proliferation. The hormone did not alter CD4/CD8 ratio. Inactivation of PTH abolished its stimulatory effect. PTH augmented IL-2 production by PHA-activated T cells but did not increase expression of IL-2R. 1-34 PTH also stimulated PHA-induced T cell proliferation. TPA augmented PHA-induced T cell proliferation but the addition of PTH to the culture stimulated by PHA and TPA did not augment further the proliferation of T cells. Staurosporin reversed the stimulation by PTH of the PHA-induced lymphocyte proliferation. Both 1-34 and 1-84 PTH stimulated cyclic AMP production by lymphocytes. Forskolin did not affect PHA-induced T cell proliferation although it stimulated cyclic AMP generation. The results show that: 1) PTH acts on T cells; 2) acute exposure to PTH augments PHA-induced T cell proliferation and IL-2 production; 3) this action of PTH is related to its biological activity and is most likely due to the ability of PTH to enhance entry of calcium into cells and/or stimulation of protein kinase C but is independent of cyclic AMP generation.

Evidence of impaired T cell function in hemodialysis patients: potential role for secondary hyperparathyroidism.

Previous studies in our laboratory showed that the T cell is a target for parathyroid hormone (PTH) action. It is theoretically possible, therefore, that chronic exposure of the T cells to high blood levels of PTH in patients with chronic renal failure may adversely affect T cell function. We examined in both normal subjects and dialysis patients several aspects of T cell function, including (1) T cell proliferation in response to phytohemagglutinin (PHA) mitogen with and without PTH and with and without exogenous interleukin 2 (IL-2); (2) the IL-2 production induced by PHA with and without PTH, and (3) resting levels of cytosolic calcium--[Ca2+]i--and the increment in [Ca2+]i in response to anti-CD3 antibody. Although PHA significantly (p less than 0.01) stimulated proliferation of T cells from both normal subjects and dialysis patients, the magnitude of the stimulation was significantly (p less than 0.01) smaller in the latter group. In both normal subjects and dialysis patients, exogenous IL-2 alone stimulated T cell proliferation, and the magnitude of the stimulation was similar to that produced by PHA. Also, IL-2 augmented PHA-induced proliferation of T cells from normal subjects, but failed to do so in T cells from dialysis patients. PHA did not augment IL-2 production by T cells from dialysis patients, and PTH did not correct this defect. The resting levels of [Ca2+]i in T cells from dialysis patients were significantly (p less than 0.01) higher, and the increments in [Ca2+]i in response to anti-CD3 antibody were significantly (p less than 0.01) lower than in T cells from normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)