A clinical evaluation of the pharmacokinetics and pharmacodynamics of intravenous alfaxalone in cyclodextrin in male and female rats following a loading dose and constant rate infusion

Objective: To characterise, as a clinical study, the pharmacokinetics and pharmacodynamics and describe the hypnotic effect of the neurosteroid alfaxalone (3α-hydroxy-5 α-pregnane-11, 20-dione) formulated with 2-hydroxypropyl-β-cyclodextrin in male and female rats. Study design: Prospective, experimental laboratory study. Animals: Twelve (six male and six female) adult, aged matched Sprague Dawley rats. Methods: Surgery and instrumentation was performed under isoflurane anaesthesia in an oxygen/nitrous oxide mixture (1:2) and local anaesthetic infiltration. All animals received a loading dose (1.67 mg kg -1 minute -1) for 2.5 minutes followed by a constant rate infusion (0.75 mg kg -1 minute -1) for 120 minutes of alfaxalone. Isoflurane and nitrous oxide was discontinued 2.5 minutes after the alfaxalone infusion started. Cardiorespiratory variables (heart rate, respiratory rate, arterial blood pressure, end tidal carbon dioxide tension) and clinical signs of anaesthetic depth were evaluated throughout anaesthesia. Carotid artery blood samples were collected at strategic time points for blood gas analysis, haematology and biochemistry and plasma concentrations of alfaxalone. Plasma samples were assayed using liquid chromatography-mass spectrometry (LC/MS). Results: There were significant differences between the sexes for plasma clearance (p = 0.0008), half-life (p = 0.0268) and mean residence time (p = 0.027). Mean arterial blood pressure was significantly higher in the male rats (p = 0.0255). Conclusions and clinical relevance: This study confirms alfaxalone solubilized in a 2-hydroxypropyl-β-cyclodextrin provides excellent total intravenous anaesthesia in rats. Sex-based differences in pharmacokinetics and pharmacodynamics were demonstrated and must be considered when designing biomedical research models using alfaxalone

Early CD30 signaling is critical for adoptively transferred CD4(+)CD25(+) regulatory T cells in prevention of acute graft-versus-host disease

Murine CD4(+)CD25(+) regulatory T cells (Treg cells) reduce acute graft-versus-host disease (aGvHD). However, surface molecules critical for suppression are unclear. Deficiency of CD30 (CD30(−/−)) leads to impaired thymic negative selection and augmented T-cell autoreactivity. Therefore, we investigated the role of CD30 signaling in Treg-cell function during aGvHD. Treg cells derived from CD30(−/−) animals were significantly less effective in preventing aGvHD lethality. Early blockade of the CD30/CD153 pathway with a neutralizing anti-CD153 mAb reduced Treg-mediated protection from proinflammatory cytokine accumulation and donor-type T-cell apoptosis. In vivo bioluminescence imaging demonstrated intact homing but reduced expansion of luciferase-expressing Treg cells when CD153 was blocked during the early phase after adoptive transfer. CD30 surface expression on Treg cells increased with alloantigen exposure, and CD153 expression on recipient-type dendritic cells increased in the presence of a proinflammatory environment. These data demonstrate that early CD30 signaling is critical for Treg-mediated aGvHD protection after major MHC-mismatch bone marrow transplantation

Donor-strain-derived immature dendritic cell pre-treatment induced hyporesponsiveness against allogeneic antigens

The maturation of antigen-presenting dendritic cells (DCs) serves as an important determinant for the regulation of immunity, and overall immune response. We hypothesized that a reduced immune response to donor alloantigens and improved allograft survival could be induced by pre-treating recipients with bone-marrow-derived donor-strain fixed immature DCs (FIDCs). Donor-strain-derived mature and immature DCs were fixed before grafting to ensure that they possessed a stable immunogenic phenotype. The fixed mature DCs effectively induced allogeneic T-cell proliferation in recipients, whereas FIDCs were unable to elicit an allogeneic T-cell response. T cells that had previously been exposed to FIDCs maintained naïve phenotypes and were unable to extensively divide after injection into lethally irradiated donor-strain mice. The pre-treatment of recipients with donor-strain FIDCs markedly prolonged the survival of islet as well as skin allografts. However, T-cell hyporesponsiveness induced by FIDC injection was abrogated by the depletion of CD4+ CD25+ T cells. Consequently, FIDC-induced T-cell hyporesponsiveness could reflect anergy rather than specific deletion. Our findings suggest that FIDCs of donor strain could be used to induce long-term graft survival