Calcitriol modulates in vivo and in vitro cytokine production: a role for intracellular calcium

Vitamin D receptor activation and survival in chronic kidney disease

Replacement of activated vitamin D has been the cornerstone of therapy for secondary hyperparathyroidism (SHPT). Recent findings from several large observational studies have suggested that the benefits of vitamin D receptor activators (VDRA) may extend beyond the traditional parathyroid hormone (PTH)-lowering effect, and could result in direct cardiovascular and metabolic benefits. The advent of several new analogs of the activated vitamin D molecule has widened our therapeutic armamentarium, but has also made therapeutic decisions more complicated. Treatment of SHPT has become even more complex with the arrival of the first calcium-sensing receptor (CSR) agonist (cinacalcet hydrochloride) and with the uncovering of novel mechanisms responsible for SHPT. We provide a brief overview of the physiology and pathophysiology of SHPT, with a focus on vitamin D metabolism, and discuss various practical aspects of VDRA therapy and its reported association with survival in recent observational studies. A detailed discussion of the available agents is aimed at providing the practicing physician with a clear understanding of the advantages or disadvantages of the individual medications. A number of open questions are also analyzed, including the present and future roles of CSR agonists and 25(OH) vitamin D replacement.

Rapid effects of 1alpha,25(OH)2D3 in resting human peripheral blood mononuclear cells

The steroid hormone 1alpha,25(OH)2D3 produces biological responses via both genomic and nongenomic mechanisms. Stimulation of rapid, nongenomic responses by 1alpha,25(OH)2D3 has been postulated to result from interaction of the ligand with cell membrane 1alpha,25(OH)2D3 receptors and to involve membrane receptors. We examined the rapid effects of 1alpha,25(OH)2D3 on calcium mobilization and calcium entry into resting human peripheral blood mononuclear cells isolated from healthy volunteers. We also investigated the possible involvement of purinergic receptors in this action. 1alpha,25(OH)2D3 induced a time-dependent increase in intracellular calcium concentration ([Ca2+]i). The initial 1alpha,25(OH)2D3-stimulated calcium increment was sensitive to thapsigargin (Tg), indicating its origins in calcium release from intracellular stores. 2-Aminoethyldiphenyl borate (2APB), an inhibitor of capacitative calcium entry, caused a significant [Ca2+]i decrease in human cells treated with 1alpha,25(OH)2D3. Furthermore, in contrast to observations in osteoblasts and skeletal muscle cells, nifedipine had no effect on 1alpha,25(OH)2D3-induced calcium entry, suggesting that L-type calcium channels were not implicated in this action. Besides, 1alpha,25(OH)(2)D3 prevented the calcium entry induced by 3'-O-(4-benzoyl)benzoyl-adenosine 5'-triphosphate (BzATP), a specific agonist of purinergic P2X7 receptors. This finding was further confirmed by 1alpha,25(OH)2D3-induced reduction of BzATP- and 4-aminopyridine (4AP)-stimulated ethidium bromide fluorescence. The presented results demonstrate, for the first time in healthy, resting human peripheral blood mononuclear cells that 1alpha,25(OH)2D3 is capable of exerting a rapid, nongenomic effect on [Ca2+]i, while inhibiting of the P2X7 channel permeability.

Vitamin K and vitamin D status: associations with inflammatory markers in the Framingham Offspring Study

In vitro data suggest protective roles for vitamins K and D in inflammation. To examine associations between vitamins K and D and inflammation in vivo, the authors used multiple linear regression analyses, adjusted for age, sex, body mass index, triglyceride concentrations, use of aspirin, use of lipid-lowering medication, season, menopausal status, and hormone replacement therapy. Participants were from the Framingham Offspring Study (1997-2001; n = 1,381; mean age = 59 years; 52% women). Vitamin K status, measured by plasma phylloquinone concentration and phylloquinone intake, was inversely associated with circulating inflammatory markers as a group and with several individual inflammatory biomarkers (p < 0.01). Percentage of undercarboxylated osteocalcin, a functional measure of vitamin K status, was not associated with overall inflammation but was associated with C-reactive protein (p < 0.01). Although plasma 25-hydroxyvitamin D was inversely associated with urinary isoprostane concentration, an indicator of oxidative stress (p < 0.01), overall associations between vitamin D status and inflammation were inconsistent. The observation that high vitamin K status was associated with lower concentrations of inflammatory markers suggests that a possible protective role for vitamin K in inflammation merits further investigation.

Animal models--what they can tell us about vascular calcification in CKD

The development of cardiovascular calcifications in chronic kidney disease (CKD) patients involves multiple risk factors with additive effects. However, a number of questions concerning cardiovascular calcifications in CKD patients remain unanswered at present due to lack of clinical data or due to the impossibility of conducting clinical trials to investigate these issues. In this review, we discuss how animal models could help us understand better the pathophysiology and management of calcifying cardiovascular complications associated with CKD.

Simvastatin and fluvastatin reduce interleukin-6 and interleukin-8 lipopolysaccharide (LPS) stimulated production by isolated human monocytes from chronic kidney disease patients

BACKGROUND

Statins reduce lipid levels, inflammation and cardiovascular events in patients with coronary artery disease; CKD patients show increased risk of cardiovascular and increased plasma levels of IL-6 and IL-8.

AIM

To evaluate the in vitro effect of simvastatin (S) or fluvastatin (F) on the lipopolysaccharide (LPS) stimulated secretion of IL-6 and IL-8 from monocytes of chronic kidney disease patients (CKD) in K-DOQI stages 3-5.

METHODS AND SUBJECTS

Monocytes enriched peripheral blood (PBMC) from 28 CKD (15 in K-DOQI stages 3-4, Group I, and 13 in K-DOQI stage 5 on hemodialysis, Group II) and 10 healthy subjects (HS), were isolated by Ficoll-gradient centrifugation. Cells were incubated with LPS 100 ng/ml or with LPS plus increasing doses of statins (from 10(-6) to 10(-8) M ) for 24 h. Surnatant IL-6 and IL-8 concentrations were determined by EIA.

RESULTS

Basally the mean concentration of IL-6 and IL-8 was higher in patients than in HS and in Group II than in Group I (IL6: HS 285 +/- 77 pg/ml, Group I 365 +/- 178 pg/ml, Group II 520 +/- 139 pg/ml- IL8 HS 180 +/- 75 pg/ml, Group I 1722 +/- 582 pg/ml, Group II 4400 +/- 1935 pg/ml). After addition of LPS the mean concentration of IL-6 and IL-8 increased in all groups (IL6: HS 1740 +/- 178 pg/ml, Group I 3754 +/- 672 pg/ml, Group II 4800 +/- 967 pg/ml; IL8: HS 450+/-132 pg/ml, Group I 9700+/-2837 pg/ml, Group II 11608 +/- 2316 pg/ml). After the addition of LPS plus increasing doses of S or F from 10(-10) to 10(-6) M, a significantly lower cytokine concentration compared to the data after LPS alone was observed (IL6: HS 45%, Group I 75%, Group II 50%; IL8: HS 100%, Group I 65%, Group II 35%).

CONCLUSIONS

These data confirm that cytokine release is increased in CKD patients and that is highest in the most severe patients. Furthermore they suggest that fluvastatin or simvastatin can be used in order to reduce the high cardiovascular risk.

Nonclassical Aspects of Differential Vitamin D Receptor Activation

The 'classical' effects of vitamin D receptor activator or agonist (VDRA) therapy for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease primarily involves suppressive effects on the parathyroid gland, and regulation of calcium and phosphorus absorption in the intestine and mobilisation in bone. Observational studies in haemodialysis patients report improved cardiovascular and all-cause survival among those receiving VDRA therapy compared with those not on VDRA therapy. Among VDRAs, the selective VDRA paricalcitol has been associated with greater survival than nonselective VDRAs, such as calcitriol (1,25-dihydroxyvitamin D(3)). The survival benefits of paricalcitol appear to be linked, at least in part, to 'nonclassical' actions of VDRAs, possibly through VDRA-mediated modulation of gene expression. In cardiovascular tissues, VDRAs are reported to have beneficial effects such as anti-inflammatory and antithrombotic effects, inhibition of vascular smooth muscle cell proliferation, inhibition of vascular calcification and stiffening, and regression of left ventricular hypertrophy. VDRAs are also reported to negatively regulate the renin-angiotensin system, which plays a key role in hypertension, myocardial infarction and stroke. The selective VDRAs, paricalcitol and maxacalcitol, are associated with direct protective effects on glomerular architecture and antiproteinuric effects in response to renal damage. Paricalcitol regulates several cardiovascular and renal parameters more favourably than nonselective VDRAs. Complex nonclassical effects, which are not clearly understood, possibly contribute to the improved survival seen with VDRAs, especially paricalcitol.

Mortality risk among hemodialysis patients receiving different vitamin D analogs

Intravenous vitamin D is standard therapy for secondary hyperparathyroidism in hemodialysis (HD) patients. In for-profit dialysis clinics, mortality was higher for patients on calcitriol compared to paricalcitol. Doxercalciferol, a second vitamin D2 analog, is currently available. We assessed mortality associated with each vitamin D analog and with lack of vitamin D therapy in patients who began HD at Dialysis Clinic Inc. (DCI), a not-for-profit dialysis provider. During the 1999-2004 study period we studied 7731 patients (calcitriol: n=3212; paricalcitol: n=2087; doxercalciferol: n=2432). Median follow-up was 37 weeks. Mortality rates (deaths/100 patient-years) were identical in patients on doxercalciferol (15.4, 95% confidence interval (13.6-17.1)) and paricalcitol (15.3 (13.6-16.9)) and higher in patients on calcitriol (19.6 (18.2-21.1)) (P<0.0001). In all models mortality was similar for paricalcitol versus doxercalciferol (hazard ratios=1.0). In unadjusted models, mortality was lower in patients on doxercalciferol (0.80 (0.66, 0.96)) and paricalcitol (0.79 (0.68, 0.92)) versus calcitriol (P<0.05). In adjusted models, this difference was not statistically significant. In all models mortality was higher for patients who did not receive vitamin D versus those who did (1.2 (1.1-1.3)). Mortality in doxercalciferol- and paricalcitol-treated patients was virtually identical. Differences in survival between vitamin D2 and D3 may be smaller than previously reported.

Treatment with 1,25-dihydroxyvitamin D3 preserves glomerular slit diaphragm-associated protein expression in experimental glomerulonephritis

In this study, we investigated the effect of 1,25(OH)2D3 on proteinuria and on the alteration of slit diaphragm-associated proteins induced by anti-Thy 1.1 in Wistar rats. Four groups of animals were studied: group I, anti-Thy 1.1 treated rats; group II, anti-Thy1.1 treated group that at day 2, after the onset of overt proteinuria, started the treatment with 1,25(OH)2D3; group III, normal control rats injected with vehicle alone; group IV, rats that received only 1,25(OH)2D3. At day 2, in group I and II, before the administration of 1,25(OH)2D3, protein excretion was significantly increased when compared to controls. Overt proteinuria was maintained until day 14 in group I whereas in group II protein excretion was significantly reduced from day 3 to day 14. Moreover, treatment with 1,25(OH)2D3 abrogated podocytes injury, detected as desmin expression and loss of nephrin and zonula occludens-1 (ZO-1), two slit diaphragm-associated proteins, and glomerular polyanion staining, that were observed in group I. In conclusion, these results suggest that 1,25(OH)2D3 administrated with a therapeutic regiment may revert proteinuria, counteracting glomerular podocyte injury.

Vitamin D in chronic kidney disease: A systemic role for selective vitamin D receptor activation

Hyperparathyroidism occurs in most patients during the progression of chronic kidney disease (CKD) and one of its initiating events, reduced serum levels of 1,25-dihydroxyvitamin D, results from a decrease in renal 1alpha hydroxylase activity, which converts 25-hydroxyvitamin D to its activated form. The combination of persistently high parathyroid hormone (PTH) and low 1,25-dihydroxyvitamin D is associated with bone loss, cardiovascular disease, immune suppression and increased mortality in patients with end-stage kidney failure. Recent studies in dialysis patients suggest that paricalcitol, a selective activator of the vitamin D receptor (VDR), is associated with a more favorable efficacy to side effect profile than calcitriol, with less morbidity and better survival. One hypothesis derived from such studies suggests that systemic activation of VDRs may have direct effects on the cardiovascular system to decrease mortality in CKD. Although current guidelines for regulating serum calcium, phosphate and PTH recommend specific interventions at the various stages of CKD to prevent or postpone irreversible parathyroid disease and decrease cardiovascular morbidity and mortality, emerging data suggest that vitamin D therapy may prolong survival in this patient population by mechanisms that are independent of calcium, phosphate and PTH. It is suggested that a re-evaluation of current treatment recommendations is needed and that future research should focus on mechanisms that distinguish potential tissue specific benefits of selective VDR activators in patients with CKD.

Vitamin D treatment in chronic kidney disease

Activated vitamin D continues to be the major treatment for suppressing parathyroid hormone (PTH) levels in dialysis patients who have secondary hyperparathyroidism. Active vitamin D compounds are distinguished by their ability to bind with high affinity to vitamin D receptors (VDRs) not only in the parathyroid glands, but in cells throughout the body. Because of recent data showing that pulsatile, intravenous vitamin D treatment (calcitriol or paricalcitol) confers a survival advantage in the dialysis population, there is new interest in understanding the systemic effects of VDR activation, particularly in the predialysis stages of chronic kidney disease (CKD), where high mortality rates from cardiovascular disease have recently been documented. Previous underutilization of calcitriol treatment to control PTH levels in stages 3 and 4 CKD was often due to concerns about its potential for accelerating the progression of CKD as a consequence of hypercalcemia, hypercalciuria, or hyperphosphatemia. Vitamin D analogs with selective VDR activity (such as paricalcitol) have great potential for preventing parathyroid hyperplasia and bone loss in early CKD without adversely affecting kidney function. Whether they also reduce cardiovascular morbidity and mortality in early CKD, as they appear to do in dialysis patients, remains to be determined.

The effects of calcitriol therapy on serum interleukin-1, interleukin-6 and tumour necrosis factor-alpha concentrations in post-menopausal patients with osteoporosis

Seventy post-menopausal women with osteoporosis were randomized into two groups: 40 patients received calcitriol (0.5 microg/day) and calcium (1000 mg/day); and 30 control patients received calcium (1000 mg/day) alone. Thirty healthy women formed the healthy control group. Bone mineral density (BMD) and serum interleukin (IL)-1, IL-6 and tumour necrosis factor-alpha (TNF-alpha) concentrations were measured at baseline and after 6 months of treatment. Calcitriol treatment for 6 months significantly increased BMD and reduced serum IL-1 and TNF-alpha concentrations compared with no significant changes in patients treated with calcium alone. Both treatments increased serum calcium and decreased parathyroid hormone concentrations. The healthy control group had a significantly lower IL-6 concentration than the post-menopausal women with osteoporosis. We have shown that calcitriol was an effective treatment for osteoporosis. Significant reductions in serum IL-1 and TNF-alpha concentrations suggest that, in addition to increasing the absorption of calcium, calcitriol may directly affect bone metabolism via cytokines.

Calcitriol Increases Burst-Forming Unit-Erythroid Proliferation in Chronic Renal Failure

BACKGROUND

Calcitriol (C) improves anemia in chronic renal failure. This effect may be related to the suppression of iPTH release, or to a direct effect on erythropoiesis.

METHODS

Thirty-three patients with chronic renal failure were enrolled; among them, 24 were on chronic hemodialysis and 9 on conservative management. None had other chronic or hematological disease, aluminum levels were below 20 microg/l and DFO testing was negative. The iPTH range was 250-480 pg/l. None were treated with C or r-HuEpo. In vitro study: Samples were drawn for a basal erythroid precursor (burst forming unit-erythroid BFU-E) study: Mononuclear cells were incubated for 14 days with r-HuEpo 3U/ml (A), r-HuEpo 3U/l + C 30 pg (B), r-HuEpo 3U/ml + C 300 pg (C), or r-HuEpo 30 U/ml + C 300 pg (D). In vivo study: After the basal evaluation, 10 patients on chronic dialysis were treated with C (Calcijex-Abbott) 1 microg three times a week, and 4 patients served as controls. BFU-E studies were performed after 1, 2 and 4 months.

RESULTS

In vitro, culture B showed increased BFU-E proliferation vs. A (41 +/- 23 vs. 27 +/- 15, p < 0.02); in cultures C and D, proliferation was 61 +/- 31 and 78 +/- 42, respectively, p < 0.01 vs. A. There was no difference among patients with predialysis renal failure and those on dialysis. BFU-E proliferation was inversely related to basal Hb (p < 0.04) and CRP levels (p < 0.05). During the in vivo study, all cultures showed a progressive increase in proliferation without a plateau level (basal, after 1, 2 and 4 months, respectively) In A: 17 +/- 8, 22 +/- 13, 30.9 +/- 14.9, 41.4 +/- 20; in B: 27.3 +/- 15, 35.6 +/- 20, 45.5 +/- 21, 57 +/- 26; in C: 48.2 +/- 20.6, 63.7 +/- 32, 75.7 +/- 37, 83 +/- 40; in D: 72 +/- 24, 91 +/- 42, 106 +/- 42, 110 +/- 42.3 (all p < 0.001). Hb and Hct showed a significant increase (p < 0.03) in the treatment group. The decrease in iPTH was not related to BFU-E proliferation.

CONCLUSIONS

In chronic uremia, C has a direct effect on erythroid precursors proliferation, as demonstrated both in vitro and in vivo, with a synergistic effect with r-HuEpo. C may be a useful adjuvant therapy to r-HuEpo treatment.

Effects of calcitriol on the immune system: new possibilities in the treatment of glomerulonephritis

1. 1,25-Dihydroxyvitamin D3 (1,25(OH)2D3), the hormonal form of vitamin D, is widely appreciated to play a central role in calcium and phosphate homeostasis. However, it is becoming increasingly clear that the sterol also play an important role in the regulation of cellular growth, haematopoietic tissues and the immune system, as well as in the modulation of hormone secretion by several endocrine glands. 2. In the present review, some of the mechanisms by which 1,25(OH)2D3 regulates immune function are highlighted. Moreover, a number of studies on the effects of calcitriol in several experimental animal models of renal disease are reported, suggesting new possibilities in the therapy of glomerulonephritis.

Modulation of TNF-alpha expression in bone marrow macrophages: involvement of vitamin D response element

The calcium-regulating hormone, 1,25(OH)(2)D(3), induces tumor necrosis factor-alpha (TNF-alpha) synthesis and release from bone marrow macrophages (BMMs). To investigate the mechanism of this regulation, we have examined the effects of 1,25(OH)(2)D(3) on the cytokine message. 1,25(OH)(2)D(3) increased TNF-alpha mRNA abundance in a dose- and time-dependent manner. The combined treatment of BMMs with LPS and 1,25(OH)(2)D(3) resulted in a synergistic increase of TNF-alpha. The steroid also increased the expression of CD14 (LPS receptor). Vitamin D receptors (VDRs) mediate 1,25(OH)(2)D(3) genomic effects by forming homodimers or heterodimers with retinoic acid receptors (RARs) or retinoic X receptors (RXRs). The RXR ligand, 9-cis retinoic acid (9cRA), reduced TNF-alpha mRNA abundance in BMMs, but increased CD14 mRNA levels. 1,25(OH)(2)D(3) or LPS did not affect TNF-alpha transcript stability. 9cRA, however, caused TNF-alpha mRNA destabilization. Next, we searched for potential vitamin D response elements (VDREs) in the promoter region (1.2 kb) of the TNF-alpha gene, and identified six such sequences. Using electrophoresis mobility shift assay (EMSA) we identified one of those sequences (-1008 to -994) as a likely candidate to be a VDRE (tnfVDRE). The binding of tnfVDRE to BMM-derived nuclear extract was increased following cell treatment with 1,25(OH)(2)D(3). No induction was observed with 9cRA treatment, but the retinoid enhanced the activity of 1,25(OH)(2)D(3) when added together. Previously characterized VDREs (mouse osteopontin and rat osteocalcin) competed effectively with tnfVDRE, demonstrating the nature of the TNF-alpha-derived sequence as a VDRE. We observed super-shift and block-shift of the complex in the presence of either anti-VDR or anti-RXR antibodies. Our data suggest that 1,25(OH)(2)D(3) increases TNF-alpha transcript abundance in BMMs via a transcriptional mechanism; 9cRA decreases TNF-alpha mRNA by destabilizing the transcript, and possibly also by forming transcriptionally inactive complex with 1,25(OH)(2)D(3) on the tnfVDRE. The receptor complex interacting with tnfVDRE found in the promoter of the cytokine gene is probably composed of VDR-RXR heterodimer.

The impact of vitamin D receptor genotype on the management of anemia in hemodialysis patients

BACKGROUND

Both in vitro and in vivo studies have shown that calcitriol, the active form of vitamin D, is involved in hematopoiesis. We hypothesized that the vitamin D receptor (VDR) genotype, which may differentiate response to endogenous or exogenous active vitamin D, has a role in the management of anemia in hemodialysis (HD) patients.

METHODS

The VDR BsmI gene polymorphism was determined in 91 HD patients and 85 healthy controls. In addition to well-known factors responsible for both anemia and inadequate response to erythropoietin (EPO), we examined the contribution of the VDR genotype to hematocrit (Hct), hemoglobin (Hb) level, total weekly dose of EPO, and EPO-Hb ratio as an index of patient EPO need.

RESULTS

Genotype distributions for the VDR gene were under the Hardy-Weinberg equilibrium and similar in patients and controls (genotypes BB, Bb, and bb: 22.0%, 38.5%, and 39.5% in patients versus 24.7%, 48.2%, and 27.1% in controls). There were statistically significant differences in Hct, Hb level, EPO dose, and EPO-Hb ratio in patients with the three BsmI genotypes, whereas the other parameters were the same. Comparison of patients with an Hb level less than versus greater than 11 g/dL showed that the former patients had lower albumin levels (P = 0.001), higher C-reactive protein levels (P = 0.014), and a greater frequency of BB genotype (P < 0.001). Similarly, comparison of patients with an EPO-Hb ratio in the highest quartile versus those in the lowest quartile showed that the former patients had lower albumin and transferrin levels (P = 0.013 for both) and greater frequencies of BB genotype (P = 0.016). In logistic regression analysis, both BB genotype and low serum albumin level were found to be the only independent predictors for an Hb level less than 11 g/dL (P < 0.001 and P = 0.046, respectively). Both parameters also predicted being in the highest quartile of EPO-Hb ratio (P = 0.004 for both).

CONCLUSION

The VDR BsmI gene polymorphism may predict both Hb level and EPO need in HD patients. However, because the underlying mechanisms have not been clarified in the present study, further research on this issue is needed.

A placebo-controlled trial to evaluate immunomodulatory effects of paricalcitol

Calcitriol has shown a benefit in various small uncontrolled studies of ex vivo immune function. We hypothesized that paricalcitol, a new vitamin D derivative, will have a positive effect on the immune system with minimal adverse effects on calcium homeostasis. Thirty-one hemodialysis patients not administered vitamin D because of low intact parathyroid hormone (PTH) levels were randomized to placebo or 4 microg of paricalcitol intravenously with the hemodialysis session three times weekly for 12 weeks. Effects on in vivo and ex vivo assessments of immune function were evaluated. All patients achieved the target dose of paricalcitol. Twenty patients were anergic at the start of the study; 4 of 11 patients in the paricalcitol group and 0 of 9 patients in the placebo group converted to reactive (P = 0.09). The in vivo response to standard hepatitis B booster vaccine and in vitro proliferation and release of interleukin-2 (IL-2), IL-6, tumor necrosis factor-alpha, and interferon-gamma from stimulated lymphocytes were not different between the groups. In contrast to clinical immune effects, paricalcitol increased serum calcium levels and decreased PTH and bone alkaline phosphatase levels (all P < 0.05). However, hypercalcemia was infrequent. In vitro experiments showed that paricalcitol led to greater dose-dependent thymidine uptake than calcitriol in lymphocytes isolated from either dialysis patients or control subjects. Paricalcitol has a tendency toward improving delayed hypersensitivity reactions, but did not have other proimmune effects. However, as expected, paricalcitol had significant effects on calcium homeostasis compared with placebo. Thus, patients with low PTH levels are unlikely to experience the proimmune effects of vitamin D therapy without more profound and potentially adverse oversuppression of PTH.

Effects of 1,25(OH)2D3 in experimental mesangial proliferative nephritis in rats

BACKGROUND

1,25-Dihydroxyvitamin D3 [1,25(OH)2D3], the active form of vitamin D3, is a potent immunomodulatory agent on several cell types such as monocytes and mesangial cells. Recruitment of inflammatory cells, as well as stimulation of resident cells and mesangial matrix accumulation are key features of various experimental and human glomerular diseases. Here we show that 1,25(OH)2D3 attenuates the morphologic and functional alterations in anti-Thy-1.1. nephritis, an experimental model of mesangial proliferative glomerulonephritis.

METHODS

The anti-Thy-1.1 group (group I) comprised 24 rats that at day 0 received 0.5 mL of saline containing 400 microg of monoclonal antibodies (mAb) anti-Thy-1.1 IgG. The anti-Thy-1.1 treated with 1,25(OH)2D3 group (group II) were 24 rats given 1,25(OH)2D3 at the dose of 25 ng/100 g body wt/day, from day -3 to day 14. At day 0, the rats received 400 microg of anti-Thy-1.1 monoclonal IgG. The control group (group III) comprised 12 rats injected with vehicle alone; the control group treated with 1,25(OH)2D3 (group IV)-12 rats were given 1,25(OH)2D3 as in group II without mAb administration. Proteinuria and urinary interleukin-6 excretion were measured daily. Blood urea nitrogen and creatinine, creatinine clearance, calcium, and phosphate were measured at days 0, 4, 7, and 14. In addition to conventional periodic acid-Schiff staining, binding of anti-Thy-1.1 IgG and C3b complement fraction, His48- and ED1-positive cells were studied by immunofluorescence. Mesangial proliferation was studied by the proliferating cell nuclear antigen (PCNA) technique. Apoptosis was evaluated by the TUNEL assay.

RESULTS

The anti-Thy-1.1 treated with 1,25(OH)2D3 group versus the anti-Thy-1.1 alone group showed a significant reduction in urinary protein (at day 7, 424 +/- 228 vs. 66 +/- 30 mg/mg urinary creatinine, P = 0.02) and interleukin-6 excretion (at day 3, 537 +/- 360 pg/mL vs. 110 +/- 34 pg/mg urinary creatinine, P = 0.015), reduced glomerular diameters (at day 7, 283 +/- 38 vs. 261 +/- 48 microm, P < 0.01), decreased neutrophil (at day 4, 20 +/- 12 His48-positive cells/glomerulus vs. 3.7 +/- 1.3 His48-positive cells/glomerulus, P < 0.001), and monocyte accumulation (day 7, 4.9 +/- 2.9 ED1-positive cells/glomerulus vs. 2.8 +/- 2.9 ED1-positive cells/glomerulus, P < 0.05), and attenuated glomerular cells proliferation (day 7, 13 +/- 3.2 PCNA-positive cells/glomerulus vs. 9.4 +/- 3 PCNA-positive cells/glomerulus, P < 0.01). Apoptosis showed a biphasic behavior with an early peak at day 4 in the anti-Thy-1.1 group (2.3 +/- 2.2 TUNEL-positive cells/glom) related to cellular lysis and a late peak at day 14 related to the recovery phase.

CONCLUSIONS

1,25(OH)2D3 can reduce glomerular hypercellularity, inflammatory infiltration in anti-Thy-1.1 nephritis, preserving the apoptotic response of the reparative phase.

The effects of 1alpha,24(S)-dihydroxyvitamin D(2) analog on cancer cell proliferation and cytokine expression

It is well established that 1alpha,25-dihydroxyvitamin D(3) (1alpha,25(OH)(2)D(3)), the active metabolite of vitamin D, plays a role in regulating proliferation and differentiation of cells, in addition to its classic function in mineral homeostasis. Recent studies have also provided evidence for the involvement of 1alpha,25(OH)(2)D(3) in regulating the immune system. However, therapeutic application of 1alpha,25(OH)(2)D(3) to hyperproliferative diseases such as cancer, or for immunologic purposes, is thwarted by its hypercalcemic activity. In order to overcome this obstacle, analogs of 1alpha,25(OH)(2)D(3) have been produced that exhibit decreased hypercalcemic activity while retaining the growth and immunologic regulating properties. In the present study, the efficacy of 1alpha,24(S)-dihydroxyvitamin D(2) (1alpha,24(S)(OH)(2)D(2)), a vitamin D(2) analog, in restraining cell proliferation was compared to that of 1alpha,25(OH)(2)D(3). In parallel studies, cancer cell lines were grown in increased concentrations (10(-10)-10(-7) M) of each compound for various incubation periods (1-4 days). Growth was assessed by measuring [(3)H]thymidine incorporation. The results revealed that 1alpha,24(S)(OH)(2)D(2) significantly inhibits proliferation to an extent similar to that observed for 1alpha,25(OH)(2)D(3). Moreover, incubating the human leukemia cell line, HL-60, with 1alpha,24(S)(OH)(2)D(2) resulted in an induction of differentiation of these promyelomonocyte cells into monocyte-macrophage-like cells, in a manner similar to that observed with 1alpha,25(OH)(2)D(3). Using a Western procedure, it was also shown that 1alpha,24(S)(OH)(2)D(2) like 1alpha,25(OH)(2)D(3) enhances the expression of vitamin D receptors (VDR) in the rat osteosarcoma cell line, ROS 17/2.8. The expression of tumor necrosis factor (TNF) alpha (TNF-alpha) in human peritoneal macrophages (HPM) obtained from uremic patients treated with continuous ambulatory peritoneal dialysis (CAPD) was found to be regulated by 1alpha,25(OH)(2)D(3) as well as by 1alpha,24(S)(OH)(2)D(2). Incubations of HPM with 1alpha,25(OH)(2)D(3) or 1alpha,24(S)(OH)(2)D(2), have inhibited the expression of TNF-alpha on both mRNA and protein levels. These results suggest that 1alpha,25(OH)(2)D(3) has a role in controlling the rate of inflammation in the peritoneal cavity of CAPD treated patients. Since 1alpha,24(S)(OH)(2)D(2) does not cause hypercalcemia, the present results encourage the possible use of this vitamin D(2) analog in the treatment of cancer and hyper-inflammatory diseases.

Regulation of TNF-alpha by 1alpha,25-dihydroxyvitamin D3 in human macrophages from CAPD patients

BACKGROUND

We have previously reported that 1alpha,25-dihydroxyvitamin D3 [1alpha,25(OH)2D3] accumulates in the dialysis fluid of uremic patients treated by continuous ambulatory peritoneal dialysis (CAPD). It has been reported that this metabolite regulates the production of cytokines by monocytes/macrophages. Since tumor necrosis factor-alpha (TNF-alpha) initiates an inflammatory cascade during peritonitis, the aim of the present study was to investigate the effect of 1alpha, 25(OH)2D3 on the production of TNF-alpha by human peritoneal macrophages (HPMs).

METHODS

HPMs were obtained from patients on CAPD. Cells were incubated with various concentrations of 1alpha, 25(OH)2D3, 1alpha,24(S) dihydroxyvitamin D2 [1alpha,24(S)(OH)2D2] or 25-hydroxyvitamin D3 (25-OH-D3) for 16 hours. This was followed by lipopolysaccharide (LPS; 1 microg/mL) incubation for 2.5 to 6 hours. TNF-alpha protein production was determined by enzyme-linked immunosorbent assay. TNF-alpha mRNA was assayed by the reverse transcriptase-polymerase chain reaction procedure, using internal synthetic mRNA standards for quantitative results.

RESULTS

Incubation of HPMs with 1alpha,25(OH)2D3 prior to stimulation with LPS dose dependently inhibited the expression of TNF-alpha on both mRNA and protein levels. Similar results were obtained with the less calcemic vitamin D2 analogue 1alpha,24(S)(OH)2D2. Incubation of HPMs with 25-OH-D3 also revealed a down-regulation of TNF-alpha expression. Since this down-regulatory effect was blocked by ketoconazole, it is likely that this effect was caused by the conversion of 25-OH-D3 into 1alpha,25(OH)2D3 by HPMs.

CONCLUSIONS

1alpha,25(OH)2D3 has a potent inhibitory effect on the production of TNF-alpha by LPS-activated HPMs. We hypothesize that 1alpha, 25(OH)2D3 may constitute a regulatory mechanism that, by controlling the intensity of the inflammatory response of the peritoneum, will moderate tissue damage during peritonitis.