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Effects of long-term administration of vitamin D3 analogs to mice
E A Smith1, E P Frankenburg, S A Goldstein
1Orthopedic Research Laboratories, University of Michigan, Ann Arbor, Michigan 48109-0486, USA.
Abstract:
This study explores the effects of chronic administration of vitamin D(3) compounds on several biological functions in mice. Knowledge of long-term tolerability of vitamin D(3) analogs may be of interest in view of their potential clinical utility in the management of various pathologies such as malignancies, immunological disorders and bone diseases. Four unique vitamin D(3) analogs (code names, compounds V, EO, LH and LA) and 1,25-dihydroxyvitamin D(3) (1, 25(OH)(2)D(3)) were administered i.p. for 55 weeks to Balb/c mice. Each analog had previously been shown to have potent in vitro activities. After 55 weeks of administration, the mice had a profound decrease in their serum levels of interleukin-2 (IL-2). Likewise, several analogs depressed serum immunoglobulin G concentrations (compounds LH and LA), but levels of blood lymphocytes and splenic lymphocyte subsets (CD4, CD8 and CD19) were not remarkably depressed. The percent of committed myeloid hematopoietic stem cells was 4- to 5-fold elevated in the bone marrow of the mice that received analogs LH and V; nevertheless, their peripheral blood white and red cell counts and platelets were not significantly different in any of the groups. The mice that received 1,25(OH)(2)D(3) had a decrease in bone quantity and quality with a decrease in cross-sectional area and cortical thickness, and a 50% reduction in both stiffness and failure load compared with the control group. In contrast, the cohort that received a fluorinated analog (compound EO) developed bones with significantly larger cross-sectional area and cortical thickness as well as stronger mechanical properties compared with the control group. At the conclusion of the study, body weights were significantly decreased in all experimental mice. Their blood chemistries were normal. Extensive gross and microscopic autopsy analyses of the mice at the conclusion of the study were normal, including those of their kidneys. In conclusion, the vitamin D(3) analogs were fairly well tolerated. They did suppress immunity as measured by serum IL-2 and may provide a means to depress the immune response after organ transplantation and for autoimmune diseases. Use of these analogs prevented the detrimental effects of vitamin D(3) administration on mechanical and geometric properties of bone, while one analog (compound EO) actually enhanced bone properties. These results suggest that long-term clinical trials with the analogs are feasible.
Insights
This study shows vitamin D(3) analogs were well tolerated in mice over 55 weeks. Some analogs suppressed immunity but improved bone health, suggesting potential for clinical trials in organ transplantation and autoimmune diseases.
Area of Science:
- Immunology
- Endocrinology
- Pharmacology
Background:
- Vitamin D(3) analogs have potential clinical applications for malignancies, immunological disorders, and bone diseases.
- Long-term tolerability data for vitamin D(3) analogs is crucial for clinical utility.
- Previous in vitro studies indicated potent activities for the tested analogs.
Purpose of the Study:
- To evaluate the long-term biological effects and tolerability of chronic vitamin D(3) analog administration in mice.
- To assess the impact of vitamin D(3) analogs on immune function, bone properties, and general health markers.
- To determine the feasibility of future clinical trials based on long-term safety and efficacy.
Main Methods:
- Four novel vitamin D(3) analogs (V, EO, LH, LA) and 1,25-dihydroxyvitamin D(3) were administered intraperitoneally to Balb/c mice for 55 weeks.
- Immune markers (interleukin-2, immunoglobulin G, lymphocyte subsets) and hematopoietic stem cells were analyzed.
- Bone geometry, mechanical properties, body weight, blood chemistry, and gross/microscopic pathology were assessed.
Main Results:
- Chronic administration led to decreased serum interleukin-2 levels and, for some analogs, reduced immunoglobulin G.
- Myeloid hematopoietic stem cells increased with analogs LH and V, but peripheral blood cell counts remained normal.
- 1,25-dihydroxyvitamin D(3) impaired bone quality, while the fluorinated analog EO significantly enhanced bone geometry and mechanical strength.
- Body weights decreased in all experimental groups, but blood chemistry and autopsy findings were largely normal.
Conclusions:
- Vitamin D(3) analogs were generally well-tolerated, with notable immunosuppressive effects (reduced IL-2) and varied impacts on bone health.
- Specific analogs demonstrated potential for managing immune responses in transplantation and autoimmune diseases.
- One analog (EO) showed beneficial effects on bone properties, suggesting its therapeutic potential.
- The findings support the feasibility of long-term clinical trials with these vitamin D(3) analogs.
