Oral bioavailability of DN101, a concentrated formulation of calcitriol, in tumor-bearing dogs

Effects of calcitriol on phagocytic function, toll-like receptor 4 expression, and cytokine production of canine leukocytes

OBJECTIVE To determine the in vitro effects of calcitriol on indicators of immune system function in blood samples collected from healthy dogs. SAMPLE Blood samples from 8 healthy adult dogs. PROCEDURES Blood samples were incubated with calcitriol (10^-7M) or control substance for 24 hours. Afterward, lipopolysaccharide (LPS)-, lipoteichoic acid (LTA)-, and N-acetylmuramyl-l-alanyl-d-isoglutamine hydrate (MDP)-stimulated leukocyte production of tumor necrosis factor (TNF) and interleukin-10 (IL10) were measured with a canine-specific multiplex assay. Phagocytosis of opsonized Escherichia coli and leukocyte expression of constitutive toll-like receptor 4 (TLR4) were evaluated via flow cytometry. Blood samples from 3 dogs were used to create a concentration-response curve to evaluate whether the observed cytokine modulation was concentration dependent. RESULTS Incubation of canine blood samples with calcitriol resulted in significant decreases in LPS-, LTA-, and MDP-stimulated leukocyte production of TNF but not IL10. Blunting of TNF production was concentration dependent. Leukocyte calcitriol exposure had no significant effect on phagocytosis and TLR4 expression. CONCLUSIONS AND CLINICAL RELEVANCE These data indicated that calcitriol induced an anti-inflammatory shift in canine leukocytes exposed to LPS, LTA, and MDP in vitro, without altering phagocytosis or TLR4 expression. Thus, calcitriol could represent a novel candidate immunomodulatory treatment for dogs.

Presumptive Glucocorticoid-Induced Refractory Hypocalcemia in a Dog with Idiopathic Immune-Mediated Hypoparathyroidism, Thrombocytopenia, and Hemolytic Anemia

Clinically relevant hypocalcemia is a well-documented complication of glucocorticoid administration in people with hypoparathyroidism. The current report describes the phenomenon in a dog. A 7 yr old neutered male Pomeranian was diagnosed with immune-mediated thrombocytopenia, immune-mediated hemolytic anemia, and primary hypoparathyroidism. This dog required long-term parenteral calcium gluconate to prevent clinical hypocalcemia despite appropriate doses of oral calcitriol and calcium carbonate. This is the first description of clinically significant presumptive glucocorticoid induced hypocalcemia in a dog with primary hypoparathyroidism.

Effect of calcitriol on in vitro whole blood cytokine production in critically ill dogs

Hypovitaminosis D has been identified as a predictor of mortality in human beings, dogs, cats and foals. However, the immunomodulatory effects of vitamin D in critically ill dogs has not been evaluated. The aim of this study was to evaluate the effect of calcitriol on cytokine production from whole blood collected from critically ill dogs in vitro. Twelve critically ill dogs admitted to a veterinary intensive care unit (ICU) were enrolled in a prospective cohort study. Whole blood from these dogs was incubated with calcitriol (2×10^-7M) or ethanol (control) for 24h. Subsequent to this incubation, lipopolysaccharide (LPS)-stimulated whole blood production of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 were measured using a canine-specific multiplex assay. Calcitriol significantly increased LPS-stimulated whole blood production of IL-10 and decreased TNF-α production without significantly altering IL-6 production. There was no significant difference in whole blood cytokine production capacity between survivors and non-survivors at the time of discharge from the ICU or 30days after discharge. These data suggests that calcitriol induces an anti-inflammatory phenotype in vitro in whole blood from critically ill dogs.

A novel multi-tiered experimental approach unfolding the mechanisms behind cyclodextrin-vitamin inclusion complexes for enhanced vitamin solubility and stability

This study was conducted to provide a mechanistic account for understanding the synthesis, characterization and solubility phenomena of vitamin complexes with cyclodextrins (CD) for enhanced solubility and stability employing experimental and in silico molecular modeling strategies. New geometric, molecular and energetic analyses were pursued to explicate experimentally derived cholecalciferol complexes. Various CD molecules (α-, β-, γ-, and hydroxypropyl β-) were complexed with three vitamins: cholecalciferol, ascorbic acid and α-tocopherol. The Inclusion Efficiency (IE%) was computed for each CD-vitamin complex. The highest IE% achieved for a cholecalciferol complex was for 'βCDD₃-8', after utilizing a unique CD:cholecalciferol molar synthesis ratio of 2.5:1, never before reported as successful. 2HPβCD-cholecalciferol, γCD-cholecalciferol and α-tocopherol inclusion complexes (IC's) reached maximal IE% with a CD:vitamin molar ratio of 5:1. The results demonstrate that IE%, thermal stability, concentration, carrier solubility, molecular mechanics and intended release profile are key factors to consider when synthesizing vitamin-CD complexes. Phase-solubility data provided insights into the design of formulations with IC's that may provide analogous oral vitamin release profiles even when hydrophobic and hydrophilic vitamins are co-incorporated. Static lattice atomistic simulations were able to validate experimentally derived cholecalciferol IE phenomena and are invaluable parameters when approaching formulation strategies using CD's for improved solubility and efficacy of vitamins.