1α,25(OH)2-3-Epi-Vitamin D3, a Natural Physiological Metabolite of Vitamin D3: Its Synthesis, Biological Activity and Crystal Structure with Its Receptor

Background: The 1 alpha,25-dihydroxy-3-epi-vitamin-D(3) (1 alpha,25(OH)(2)-3-epi-D(3)), a natural metabolite of the seco-steroid vitamin D(3), exerts its biological activity through binding to its cognate vitamin D nuclear receptor (VDR), a ligand dependent transcription regulator. In vivo action of 1 alpha,25(OH)(2)-3-epi-D(3) is tissue-specific and exhibits lowest calcemic effect compared to that induced by 1 alpha,25(OH)(2)D(3). To further unveil the structural mechanism and structure-activity relationships of 1 alpha,25(OH)(2)-3-epi-D3 and its receptor complex, we characterized some of its in vitro biological properties and solved its crystal structure complexed with human VDR ligand-binding domain (LBD). Methodology/Principal Findings: In the present study, we report the more effective synthesis with fewer steps that provides higher yield of the 3-epimer of the 1 alpha,25(OH)(2)D(3). We solved the crystal structure of its complex with the human VDR-LBD and found that this natural metabolite displays specific adaptation of the ligand-binding pocket, as the 3-epimer maintains the number of hydrogen bonds by an alternative water-mediated interaction to compensate the abolished interaction with Ser278. In addition, the biological activity of the 1 alpha,25(OH)(2)-3-epi-D(3) in primary human keratinocytes and biochemical properties are comparable to 1 alpha,25(OH)(2)D(3). Conclusions/Significance: The physiological role of this pathway as the specific biological action of the 3-epimer remains unclear. However, its high metabolic stability together with its significant biologic activity makes this natural metabolite an interesting ligand for clinical applications. Our new findings contribute to a better understanding at molecular level how natural metabolites of 1 alpha,25(OH)(2)D(3) lead to significant activity in biological systems and we conclude that the C3-epimerization pathway produces an active metabolite with similar biochemical and biological properties to those of the 1 alpha,25(OH)(2)D(3)

The combined treatment of human peripheral blood mononuclear cells with thymolymphotropin and interleukin 2 increases PPD-driven T-cell proliferation and IL-2 induced cellular cytotoxicity against HIV-infected cells.

Two in vitro systems (the DNA synthetic response to mycobacterial antigens and cytotoxicity against lymphoid cells) were used to analyse the effect of thymolymphotropin (TLT) on peripheral blood mononuclear cells (PBMC). Purified protein derivative of mycobacteria (PPD)-driven T-cell proliferation in low-responder donors was increased by the combined treatment with TLT and suboptimal doses of recombinant interleukin 2 (IL-2). Similarly, the activities of natural killer (NK) cells and lymphokine-activated killer (LAK) cells have been enhanced in PBMC cultures pretreated with TLT. Also, TLT showed an enhancing effect on the development of LAK cells capable of lysing Epstein-Barr virus (EBV)-transformed B-lymphocytes infected or uninfected with the human immunodeficiency virus (HIV)

Biomechanics of Vibration Exercise

This biomechanistic approach of vibration exercise discusses the human body as a group of segments (foot, shank, thigh, trunk, head) balanced on top of each other. These segments are interlinked by joints, the stiffness of which is generated by the surrounding muscles. Reflexes and pre-tension of the muscles are important factors that modulate the apparent joint stiffness and leg stiffness. In addition, leg stiffness is also affected by posture, with greater leg stiffness occurring in erect posture than in a crouched posture. To ensure comfort and to reduce the possible risk, vibration transmission to the head should be attenuated. This can be achieved by adjusting the pre-tension and posture. In addition, raising the heel from the vibration platform reduces vibration transmissibility. For similar reasons, side-alternating platforms have lower transmissibility to trunk and head than side-synchronous platforms, as they allow an additional degree of freedom in the lumbo-sacral joint. Finally, vibration elicits stretch-shortening cycles within the tendon and skeletal muscle, at a minimum of 6 Hz. These mechanical stretch-shortening cycles provide a solid rationale for the activation of mono-synaptic stretch reflexes

The Histone Deacetylase Inhibitor ITF2357 Reduces Production of Pro-Inflammatory Cytokines In Vitro and Systemic Inflammation In Vivo

We studied inhibition of histone deacetylases (HDACs), which results in the unraveling of chromatin, facilitating increased gene expression. ITF2357, an orally active, synthetic inhibitor of HDACs, was evaluated as an anti-inflammatory agent. In lipopolysaccharide (LPS)-stimulated cultured human peripheral blood mononuclear cells (PBMCs), ITF2357 reduced by 50% the release of tumor necrosis factor-α (TNFα) at 10 to 22 nM, the release of intracellular interleukin (IL)-1α at 12 nM, the secretion of IL-1β at 12.5 to 25 nM, and the production of interferon-γ (IFNγ) at 25 nM. There was no reduction in IL-8 in these same cultures. Using the combination of IL-12 plus IL-18, IFNγ and IL-6 production was reduced by 50% at 12.5 to 25 nM, independent of decreased IL-1 or TNFα. There was no evidence of cell death in LPS-stimulated PBMCs at 100 nM ITF2357, using assays for DNA degradation, annexin V, and caspase-3/7. By Northern blotting of PBMCs, there was a 50% to 90% reduction in LPS-induced steady-state levels of TNFα and IFNγ mRNA but no effect on IL-1β or IL-8 levels. Real-time PCR confirmed the reduction in TNFα RNA by ITF2357. Oral administration of 1.0 to 10 mg/kg ITF2357 to mice reduced LPS-induced serum TNFα and IFNγ by more than 50%. Anti-CD3–induced cytokines were not suppressed by ITF2357 in PBMCs either in vitro or in the circulation in mice. In concanavalin-A–induced hepatitis, 1 or 5 mg/kg of oral ITF2357 significantly reduced liver damage. Thus, low, nonapoptotic concentrations of the HDAC inhibitor ITF2357 reduce pro-inflammatory cytokine production in primary cells in vitro and exhibit anti-inflammatory effects in vivo