High-turnover osteoporosis is induced by cyclosporin A in rats

Advances in the interaction between endoplasmic reticulum stress and osteoporosis

The endoplasmic reticulum (ER) is the main site for protein synthesis, folding, and secretion, and accumulation of the unfolded/misfolded proteins in the ER may induce ER stress. ER stress is an important participant in various intracellular signaling pathways. Prolonged- or high-intensity ER stress may induce cell apoptosis. Osteoporosis, characterized by imbalanced bone remodeling, is a global disease caused by many factors, such as ER stress. ER stress stimulates osteoblast apoptosis, increases bone loss, and promotes osteoporosis development. Many factors, such as the drug's adverse effects, metabolic disorders, calcium ion imbalance, bad habits, and aging, have been reported to activate ER stress, resulting in the pathological development of osteoporosis. Increasing evidence shows that ER stress regulates osteogenic differentiation, osteoblast activity, and osteoclast formation and function. Various therapeutic agents have been developed to counteract ER stress and thereby suppress osteoporosis development. Thus, inhibition of ER stress has become a potential target for the therapeutic management of osteoporosis. However, the in-depth understanding of ER stress in the pathogenesis of osteoporosis still needs more effort.

The association between psoriasis and psoriatic arthritis with the risk of osteoporosis, osteopenia and bone fractures: A systematic review and meta-analysis

BACKGROUND AND AIMS

The possible association between psoriatic/psoriatic arthritis (PsA) and bone loss has been observed; however, studies have yielded inconclusive results. This meta-analysis aimed to assess whether there is an increase in the risk of osteoporosis, osteopenia and fractures in patients with psoriasis/PsA, compared with healthy individuals.

METHODS

PubMed and Scopus were systematically searched from their inception to September 2020 to identify relevant studies. Relative risk, hazard ratio or odds ratio (OR), with their corresponding 95% confidence intervals (95% CI) were calculated and pooled using a random-effects model.

RESULTS

A total of 12 different studies, with a total of 199 389 296 participants, were included. Overall, no significant relationship was observed between psoriasis/PsA and the risk of osteoporosis (psoriasis: OR = 1.28, 95%CI = 0.86-1.90; PsA: OR = 1.32, 95%CI = 0.79-2.19) and osteopenia (psoriasis: OR = 1.50, 95%CI = 0.75-3.02; PsA: OR = 1.61, 95%CI = 0.67-3.85). However, in the subgroup analysis, psoriasis was significantly associated with an increased risk of osteoporosis in men (OR = 1.27, 95%CI = 1.02-1.59) and studies with cohort design (OR = 1.04, 95%CI = 1.003-1.09). Psoriasis was also related to the risk of osteopenia in studies on a combination of both genders (OR = 2.86, 95%CI = 2.70-3.02). The pooled analysis demonstrated a significantly higher risk of fractures among patients with psoriasis (OR = 1.29, 95%CI = 1.02-1.63) and PsA (OR = 2.88, 95%CI = 1.51-5.48), compared with participants without psoriasis/PsA.

CONCLUSIONS

Patients with psoriasis/PsA have an increased risk of fractures. There is little evidence supporting the relation of psoriasis to osteoporosis/osteopenia.

Systemic evaluation of the relationship between psoriasis, psoriatic arthritis and osteoporosis: observational and Mendelian randomisation study

OBJECTIVES AND METHODS

With 432 513 samples from UK Biobank dataset, multivariable linear/logistic regression were used to estimate the relationship between psoriasis/psoriatic arthritis (PsA) and estimated bone mineral density (eBMD)/osteoporosis, controlling for potential confounders. Here, confounders were set in three ways: model0 (including age, height, weight, smoking and drinking), model1 (model0 +regular physical activity) and model2 (model1 +medication treatments). The eBMD was derived from heel ultrasound measurement. And 4904 patients with psoriasis and 847 patients with PsA were included in final analysis. Mendelian randomisation (MR) approach was used to evaluate the causal effect between them.

RESULTS

Lower eBMD were observed in patients with PsA than in controls in both model0 (β-coefficient=-0.014, p=0.0006) and model1 (β-coefficient=-0.013, p=0.002); however, the association disappeared when conditioning on treatment with methotrexate or ciclosporin (model2) (β-coefficient=-0.005, p=0.28), mediation analysis showed that 63% of the intermediary effect on eBMD was mediated by medication treatment (p<2E-16). Patients with psoriasis without arthritis showed no difference of eBMD compared with controls. Similarly, the significance of higher risk of osteopenia in patients with PsA (OR=1.27, p=0.002 in model0) could be eliminated by conditioning on medication treatment (p=0.244 in model2). Psoriasis without arthritis was not related to osteopenia and osteoporosis. The weighted Genetic Risk Score analysis found that genetically determined psoriasis/PsA were not associated with eBMD (p=0.24 and p=0.88). Finally, MR analysis showed that psoriasis/PsA had no causal effect on eBMD, osteoporosis and fracture.

CONCLUSIONS

The effect of PsA on osteoporosis was secondary (eg, medication) but not causal. Under this hypothesis, psoriasis without arthritis was not a risk factor for osteoporosis.

Psoriasis and bone mineral density: implications for long-term patients

Psoriasis is a chronic inflammatory disease associated with several comorbidities. Osteoporosis is defined as a reduction in bone mineral density with impaired bone microarchitecture. Several mechanisms may be implicated as a possible cause for the association between psoriasis and osteoporosis, such as systemic inflammation, anti-psoriatic drug intake and joint dysfunction for psoriatic arthritis (PsA). The aim of the present study was to assess bone mineral density (BMD) in patients with psoriasis, correlating the prevalence of osteopenia/osteoporosis with Psoriasis Area and Severity Index (PASI) score, mean duration of psoriatic disease, PsA and previous treatments for psoriasis. Forty-three consecutive patients with psoriasis, 19 of whom were affected by the arthropathic form, were enrolled. We evaluated the severity of psoriasis as measured by PASI score, the CASPAR criteria and ultrasounds of the joints to verify the diagnosis of PsA and the age of psoriasis onset to estimate mean disease duration. Patients underwent a bone density scan of the lumbar spine and femoral neck by dual-energy X-ray absorptiometry to measure BMD. Patients with osteopenia/osteoporosis showed a statistically significant longer average duration of psoriatic disease (17 years), compared to patients affected by psoriasis with normal T-score (8.8 years) (P = 0.04). The linear logistic regression confirms a significant relation between mean psoriatic disease duration and BMD alterations (P = 0.04). Our results suggest the necessity of an early diagnostic evaluation of bone metabolism in patients with psoriasis, especially if characterized by longer disease duration.

The role of carnitine on ovariectomy and inflammation-induced osteoporosis in rats

This study was carried out to assess the protective bone-sparing effect of carnitine with anti-inflammatory properties on chronic inflammation-induced bone loss in ovariectomised (OVX) rats. A total of 64 rats were divided into eight groups. Sixteen rats were sham-operated (SH) while the others were ovariectomised (OVX). (1) SH, (2) sham + inflammation (SHinf), (3) OVX, (4) ovariectomy + inflammation (OVXinf), (5) OVX + CAR1, (6) OVX + CAR2, (7) OVXinf + CAR1, (8) OVXinf + CAR2. After the ovariectomy surgery, all the groups (3, 4, 5, 6, 7, and 8) were allowed to recover for two months. Sixty days after the OVX, inflammation was induced by subcutaneous injections of talc in groups 2, 4, 7, and 8. Group 5 and 7 were given 50 mg/kg CAR; Group 6 and 8 were given 100 mg/kg CAR from the 60th to the 80th day. Serum levels of TNF-α, IL-1, IL-6, OP, and OC were assessed to determine inflammation and to evaluate osteoblastic activity. Bone mineral density (BMD) was assessed by dual energy X-ray absorptiometry in femur bones of rats. Carnitine administration was able to restore BMD up to values measured in both the OVX and the SH animals. The serum levels of TNF-α, IL-1β, and IL-6 were increased significantly in the OVXinf rats compared with the SH group. In OVX rats, inflammation which is evaluated by serum cytokine levels exacerbated this bone loss, as supported by values of BMD of the total femur. The two different doses of carnitine reduced bone loss and improved inflammatory biomarkers.

The effect of alpha-lipoic acid in ovariectomy and inflammation-mediated osteoporosis on the skeletal status of rat bone

Osteoporosis is a high mortality and morbidity ranged skeletal disease and results in high costs of medical care in the European Union. We evaluated the possible protective effect of alpha-lipoic acid (ALA) on rat bone metabolism in ovariectomy and inflammation-mediated osteoporosis models. Groups were designed as: (1) sham; (2) sham+inflammation; (3) ovariectomy (OVX); (4) ovariectomy+ALA-25mg/kg; (5) ovariectomy+ALA-50mg/kg; (6) ovariectomy+inflammation; (7) ovariectomy+inflammation+ALA-25mg/kg; and (8) ovariectomy+inflammation+ALA-50mg/kg groups. OVX groups were allowed to recover for two months. Then, inflammation was induced in inflammation groups by subcutaneous talc injection. ALA-25mg/kg and 50mg/kg were administered to drug groups chronically. The skeletal response was assessed by bone mineral density (BMD), osteopontin and osteocalcin measurements. Pro-inflammatory cytokine measurements (interleukin (IL)-1 beta, interleukin-6, and tumor necrosis factor-alpha) were performed to observe inflammatory process. In OVX, INF and OVX+INF groups, BMD levels were lowest and osteocalcin, osteopontin, IL-1 beta, IL-6, and TNF-alpha levels were highest when compared to sham group. ALA administration increased BMD levels and decreased osteocalcin, osteopontin, IL-1 beta, IL-6, and TNF-alpha levels versus OVX and OVX+INF control groups. Both in senile and postmenopausal osteoporosis, the balance in coupling were destroyed on behalf of bone resorption. ALA had a protective effect on both senile and postmenopausal osteoporosis. The positive effect of this drug in these osteoporosis models might originate from its positive effects on bone turnover markers and cytokine levels. From this perspective, ALA may be a candidate for radical osteoporosis treatment both in senile and postmenopausal types clinically at the end of advanced studies.

Ciclosporin therapy is associated with minimal changes in calcium metabolism in dogs with atopic dermatitis

BACKGROUND

Ciclosporin is widely used in the management of canine atopic dermatitis. In humans, ciclosporin therapy has been linked to disturbances in calcium metabolism and resultant skeletal disorders.

OBJECTIVES

The objective of this study was to assess calcium homeostasis in dogs before and after a 6 week course of once daily oral ciclosporin at the licensed dose (5 mg/kg).

ANIMALS

Sixteen client-owned dogs with spontaneous atopic dermatitis.

METHODS

Serum concentrations of calcium, phosphate, creatinine, 25-hydroxyvitamin D, 1,25-dihyroxyvitamin D and plasma concentrations of ionized calcium and parathyroid hormone (PTH) were measured, together with the urinary fractional excretion of calcium and phosphate. The extent of skin lesions was scored using the Canine Atopic Dermatitis Extent and Severity Index (CADESI)-03 and the degree of pruritus by the Edinburgh Pruritus Scale prior to and at the end of the study.

RESULTS

The CADESI-03 and the Edinburgh Pruritus Scale scores decreased satisfactorily in all dogs by the end of the study. Plasma PTH concentrations were significantly increased (P = 0.02) following ciclosporin treatment, whereas all other biochemical parameters were not significantly different from their starting values. The increase in PTH was mild in most cases and the proportion of dogs that had a PTH concentration above the reference range was not significantly different following treatment.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study indicates that ciclosporin has minimal impact on calcium metabolism in dogs with atopic dermatitis when used at the licensed and clinically effective dosage for 6 weeks.

Influence of mast cells in drug-induced gingival overgrowth

Mast cells (MCs) are multifunctional effector cells that were originally thought to be involved in allergic disorders. Now it is known that they contain an array of mediators with a multitude of effects on many other cells. MCs have become a recent concern in drug-induced gingival overgrowth (DIGO), an unwanted outcome of systemic medication. Most of the studies have confirmed the significant presence of inflammation as a prerequisite for the overgrowth to occur. The inflammatory changes within the gingival tissue appear to influence the interaction between the inducing drug and the fibroblast activity. The development of antibodies to MC-specific enzymes, tryptase and chymase, has facilitated the study of mast cells in DIGO. Many immunohistochemical studies involving MCs have been conducted; as a result, DIGO tissues are found to have increased the number of MCs in the gingiva, especially in the area of fibrosis. At the cellular level, gingival fibrogenesis is initiated by several mediators which induce the recruitment of a large number of inflammatory cells, including MCs. The purpose of this paper is to access the roles played by MCs in gingival overgrowth to hypothesize a relationship between these highly specialized cells in the pathogenesis of DIGO.

Bone Loss after Heart Transplant: Effect of Alendronate, Etidronate, Calcitonin, and Calcium plus Vitamin D3

Objective

To compare the effects of calcitonin, etidronate, and alendronate in preventing bone loss during the first 2 years after heart transplant.

Methods

A total of 222 heart transplant recipients (mean [SD] age, 52.4 [10] years, 85% male) were evaluated. Patients with normal bone mineral density (reference group, n = 102) received 1000 mg/d calcium plus 800 IU/d vitamin D3. The rest were assigned to 200 IU/d of calcitonin (n = 42), 400 mg/d etidronate orally for 14 days quarterly (n = 33), or 10 mg/d alendronate (n = 45). All patients received calcium and vitamin D. Bone mineral density was assessed by dual-energy x-ray absorptiometry in the lumbar spine, the entire femur, and the femoral neck at baseline and 6, 12, and 24 months after transplant.

Results

At 2 years after transplant, bone mineral density in the lumbar spine had decreased in the reference group (−3.07%), calcitonin group (−0.93%), and etidronate group (−1.87%) but not in the alendronate group (+4.9%; P < .001). After 2 years, bone mineral density in the entire femur decreased in all groups (−3.2% in the reference group, −3.6% in the calcitonin group, −4.6% in the etidronate group, and −0.5% in the alendronate group) but bone loss was significantly lower in the alendronate group ( P < .001). Bone mineral density in the femoral neck also decreased in all groups. The incidence of vertebral fractures did not differ among groups. Adverse events were similar between groups.

Conclusions

Alendronate therapy in heart transplant recipients was associated with a significant increase in bone mineral density in the lumbar spine and less bone loss at the hip.

Effect of cyclosporine-A on orthodontic tooth movement in rats

OBJECTIVE

The objective of this study is to examine the effect of cyclosporine-A (CsA) on the rate of orthodontic tooth movement in rats.

SETTING AND SAMPLE POPULATION

This is a randomized controlled trial with a split-mouth design in Sprague-Dawley rats.

MATERIAL AND METHODS

Eighteen rats, divided at random in two groups, were fed with 8 mg/kg CsA (experiment) or mineral oil (control) daily after initial healing of bilateral maxillary second molar removal. All rats received orthodontic coil springs (10 cN) secured to the maxillary incisors and first molars at the rights side, while no springs were placed at the left. Distances between first and third molars were measured on days 0, 3, 6, and 12. After sacrificing on day 12, the alveolar ridges of the maxillae were sectioned and blood samples were collected for serum tartrate-resistant acid phosphatase (TRAP)-5b level detection and for histology, respectively.

RESULTS

Significantly larger changes in intermolar distances were found after orthodontic force application in the CsA group at days 3 and 12 when compared with the control group. The inter-radicular dental alveolus of CSA-fed rats was osteopenic. Significantly increased TRAP-5b serum level was noted in the CsA group when compared with the control group.

CONCLUSIONS

We suggest that CsA enhanced the rate of orthodontic tooth movement. The osteopenia and the increased osteoclastic activity could be the underlying factors.

Effects of cyclosporin-a on rat skeletal biomechanical properties

Background

Cyclosprin A (CsA) has been widely used clinically to treat the patients who have undergone organ transplantation or acquired autoimmune disease. The purpose of this study is to determine the effects of three different doses of CsA (1.5, 7.5, 15 mg/kg body weight) on the skeletal biomechanical proprieties at different anatomic sites in rats.

Methods

Fifty-six male 3-month-old Wistar rats were divided into five groups. Eight rats were randomly chosen as the basal group, while the others were randomly distributed into four groups of 12 animals each. One group was used as controls and received daily subcutaneous injection of 1 ml of saline solution; another three experimental groups were injected subcutaneously with CsA in a daily dose of 1.5, 7.5, and 15 mg/kg body weight respectively for 60 days. The bone biomechanical proprieties, the bone mineral density, as well as the trabecular bone architecture were measured at different anatomic sites, i.e. the lumbar vertebra, the middle femur shaft, and the proximal femur.

Results

CsA therapy at 7.5 and 1.5 mg/kg can significantly reduce the ultimate force, the ultimate stress and the energy absorption per unit of bone volume of the lumbar vertebra, with no effect on the middle femur. CsA therapy at 7.5 mg/kg can significantly reduce the ultimate force, the ultimate stress and the Young's modulus of the femoral neck, but not CsA at 1.5 mg/kg. Furthermore, CsA therapy at 7.5 and 1.5 mg/kg can significantly reduce the bone mineral density of the lumber vertebra and the proximal femur, but have no effect on the middle femur. CsA therapy at 7.5 and 1.5 mg/kg can also significantly reduce the bone volume fraction of the proximal tibia and the lumber vertebra, but has no effect on the cortical thickness of the middle femoral shaft. In the 15 mg/kg CsA group only one rat survived, and the kidney and liver histology of the survived rat showed extensive tissue necrosis.

Conclusion

Long-term use of CsA can weaken the biomechanical properties and thus increase the fracture rate of the lumbar vertebra and the proximal femur. However, CsA therapy has less effect on the middle femur shaft. The effects of CsA on skeleton are site-specific.

Intermittent therapy with 1,25 vitamin D and calcitonin prevents cyclosporin-induced alveolar bone loss in rats

Bone loss associated with cyclosporin A (CsA) therapy can result in serious morbidity to patients. Intermittent administration of 1,25 Vitamin D and calcitonin reduces osteopenia in a murine model of postmenopausal osteoporosis. The purpose of this study was to evaluate the effects of this therapeutic approach on CsA-induced alveolar bone loss in rats. Forty male Wistar rats were allocated to four experimental groups according to the treatment received during 8 weeks: (1) CsA (10 mg/kg/day, s.c.); (2) 1,25 Vitamin D (2 microg/kg, p.o.; in weeks 1, 3, 5, and 7) plus calcitonin (2 microg/kg, i.p.; in weeks 2, 4, 6, and 8); (3) CsA concurrently with intermittent 1,25 Vitamin D and calcitonin administration; and (4) the control treatment group (vehicle). At the end of the 8-week treatment period, serum concentrations of bone-specific alkaline phosphatase, tartrate-resistant acid phosphatase (TRAP-5b), osteocalcin, interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) were measured and an analysis of bone volume, bone surface, number of osteoblasts, and osteoclasts was performed. CsA administration resulted in significant alveolar bone resorption, as assessed by a lower bone volume and an increased number of osteoclasts, and increased serum bone-specific alkaline phosphatase, TRAP-5b, IL-1 beta, IL-6, and TNF-alpha concentrations. The intermittent administration of calcitriol and calcitonin prevented the CsA-induced osteopenic changes and the increased serum concentrations of TRAP-5b and inflammatory cytokines. Intermittent calcitriol/calcitonin therapy prevents CsA-induced alveolar bone loss in rats and normalizes the production of associated inflammatory mediators.

Short-term induction of thrombocytopenia delays periodontal healing in rats with periodontal disease: participation of endostatin and vascular endothelial growth factor

BACKGROUND AND OBJECTIVE

Platelets contain factors, including VEGF and endostatin, that can modulate the healing process. We evaluated the effects of severe thrombocytopenia on periodontal healing in rats and determined the contribution of VEGF and endostatin to the healing process.

MATERIAL AND METHODS

Rats were distributed into three test groups and two control groups. Cotton ligatures were placed at the gingival margin level of the lower first molar in the test groups. Sham-operated rats and rats in one of the periodontitis groups were killed 15 days later. Rats in the remaining two periodontitis groups had the ligatures removed in order to study the spontaneous recovery from the periodontal disease 15 days later, and these rats were treated with rabbit antiplatelet serum, in order to induce thrombocytopenia, or normal rabbit serum. An additional group without ligatures received antiplatet serum in the same period.

RESULTS

After ligature removal, rats treated with normal rabbit serum showed reduced myeloperoxidase activity, decreased alveolar bone loss and increased numbers of blood vessels. Thrombocytopenia caused a delay in alveolar bone regeneration, a decrease in the number of vessels and a modest decrease in myeloperoxidase activity. In the rats with periodontitis, serum endostatin concentrations were slightly decreased and serum VEGF remained unchanged compared with sham-operated animals. After ligature removal, a significant VEGF increase and endostatin decrease were observed in the rats treated with normal rabbit serum. Thrombocytopenia led to a dramatic fall in both VEGF and endostatin concentrations.

CONCLUSION

Thrombocytopenia leads to a delay of periodontal healing in the situation of experimental periodontitis, which might be mediated in part by a decrease in the serum concentration of VEGF and endostatin derived from the platelets. However, other factors derived from the platelets may also have contributed to a delay of periodontal healing in the rats with thrombocytopenia.

Oral administration of vitamin C prevents alveolar bone resorption induced by high dietary cholesterol in rats

BACKGROUND

A high-cholesterol diet stimulates alveolar bone resorption, which may be induced via tissue oxidative damage. Vitamin C reduces tissue oxidative damage by neutralizing free radicals and scavenging hydroxyl radicals, and its antioxidant effect may offer the clinical benefit of preventing alveolar bone resorption in cases of hyperlipidemia. We examined whether vitamin C could suppress alveolar bone resorption in rats fed a high-cholesterol diet.

METHODS

In this 12-week study, rats were divided into four groups: a control group (fed a regular diet) and three experimental groups (fed a high-cholesterol diet supplemented with 0, 1, or 2 g/l vitamin C). Vitamin C was provided by adding it to the drinking water. The bone mineral density of the alveolar bone was analyzed by microcomputerized tomography. As an index of tissue oxidative damage, the 8-hydroxydeoxyguanosine level in the periodontal tissue was determined using a competitive enzyme-linked immunosorbent assay.

RESULTS

Hyperlipidemia, induced by a high-cholesterol diet, decreased rat alveolar bone density and increased the number of tartrate-resistant acid phosphatase-positive osteoclasts. The expression of 8-hydroxydeoxyguanosine was upregulated in the periodontal tissues. Intake of vitamin C reduced the effect of a high-cholesterol diet on alveolar bone density and osteoclast differentiation and decreased periodontal 8-hydroxydeoxyguanosine expression.

CONCLUSION

In the rat model, vitamin C suppressed alveolar bone resorption, induced by high dietary cholesterol, by decreasing the oxidative damage of periodontal tissue.

Alendronate therapy in cyclosporine-induced alveolar bone loss in rats

BACKGROUND AND OBJECTIVE

Cyclosporine A is an immunosuppressive drug that is widely used in organ transplant patients as well as to treat a number of autoimmune conditions. Bone loss is reported as a significant side-effect of cyclosporine A use because this can result in serious morbidity of the patients. As we have shown that cyclosporine A-associated bone loss can also affect the alveolar bone, the purpose of this study was to evaluate the effect of the concomitant administration of alendronate on alveolar bone loss in a rat model.

MATERIAL AND METHODS

Forty Wistar rats (10 per group) were given cyclosporine A (10 mg/kg, daily), alendronate (0.3 mg/kg, weekly), or both cyclosporine A and alendronate, for 60 d. The control group received daily injections of sterile saline. The expression of proteins associated with bone turnover, including osteocalcin, alkaline phosphatase and tartrate-resistant acid phosphatase (TRAP), and also the calcium levels, were evaluated in the serum. Analysis of the bone volume, alveolar bone surface, the number of osteoblasts per bone surface and the number of osteoclasts per bone surface around the lower first molars was also performed.

RESULTS

The results indicate that cyclosporine A treatment was associated with bone resorption, represented by a decrease in the bone volume, alveolar bone surface and the number of osteoblasts per bone surface and by an increase in the number of osteoclasts per bone surface and TRAP-5b. These effects were effectively counteracted by concomitant alendronate administration.

CONCLUSION

It is concluded that concomitant administration of alendronate can prevent cyclosporine A-associated alveolar bone loss.

Conversion of immunosuppressive monotherapy from cyclosporin a to tacrolimus reverses bone loss in rats

Tacrolimus is used for transplant patients with refractory graft rejection and those with intolerance to cyclosporin (CsA), without the disfiguring adverse effects frequently attributed to CsA therapy. Since we have shown that CsA-associated bone loss can also affect alveolar bone, the purpose of this study was to evaluate the effects of conversion of monotherapy from CsA to tacrolimus on alveolar bone loss in rats. Groups of rats were treated with either CsA (10 mg/kg/day, s.c.), tacrolimus (1 mg/kg/day, s.c.), or drug vehicle for 60 and 120 days, and an additional group received CsA for 60 days followed by conversion to tacrolimus for a further 60-day period. Bone-specific alkaline phosphatase (BALP), tartrate-resistent acid phosphatase (TRAP-5b), calcium (Ca(2+)), interleukin (IL)-1beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) concentrations were evaluated in the serum. Analyses of bone volume, bone surface, number of osteblasts, and osteoclasts were performed. Treatment with CsA for either 60 or 120 days was associated with bone resorption, represented by lower bone volume and increased number of osteoclasts; serum BALP, TRAP-5b, IL-1beta, IL-6, and TNF-alpha were also higher in these animals. After conversion from CsA to tacrolimus, all the altered serum markers returned to control values in addition to a significant increase of bone volume and a lower number of osteoclasts. This study shows that conversion from CsA to tacrolimus therapy leads to a reversal of the CsA-induced bone loss, which can probably be mediated by downregulation of IL-1beta, IL-6, and TNF-alpha production.