Spontaneous Akt2 deficiency in a colony of NOD mice exhibiting early diabetes.

Diabetes constitutes a major public health problem, with dramatic consequences for patients. Both genetic and environmental factors were shown to contribute to the different forms of the disease. The monogenic forms, found both in humans and in animal models, specially help to decipher the role of key genes in the physiopathology of the disease. Here, we describe the phenotype of early diabetes in a colony of NOD mice, with spontaneous invalidation of Akt2, that we called HYP. The HYP mice were characterised by a strong and chronic hyperglycaemia, beginning around the age of one month, especially in male mice. The phenotype was not the consequence of the acceleration of the autoimmune response, inherent to the NOD background. Interestingly, in HYP mice, we observed hyperinsulinemia before hyperglycaemia occurred. We did not find any difference in the pancreas' architecture of the NOD and HYP mice (islets' size and staining for insulin and glucagon) but we detected a lower insulin content in the pancreas of HYP mice compared to NOD mice. These results give new insights about the role played by Akt2 in glucose homeostasis and argue for the ß cell failure being the primary event in the course of diabetes.

Effects of divergent selection upon adrenocortical activity on immune traits in pig.

BACKGROUND: The sustainability of farming and animal welfare requires the reconsideration of current selection schemes. In particular, implementation of new selection criteria related to animal health and welfare should help to produce more robust animals and to reduce anti-microbial use. The hypothalamo-pituitary-adrenocortical (HPA) axis plays a major role in metabolic regulation and adaptation processes and its activity is strongly influenced by genetic factors. A positive association between HPA axis activity and robustness was recently described. To explore whether selecting pigs upon HPA axis activity could increase their robustness, a divergent selection experiment was carried out in the Large White pig breed. This allowed the generation of low (HPAlo) and high (HPAhi) responders to adrenocorticotropic hormone administration. RESULTS: In this study, we compared 23 hematologic and immune parameters of 6-week-old, HPAlo and HPAhi piglets and analysed their response to a low dose of lipopolysaccharide (LPS) two weeks later. At six weeks of age, HPAhi piglets displayed greater red blood cell and leucocyte number including CD8α+ γδ cells, cytotoxic T lymphocytes, naive T helper (Th) cells and B lymphocytes as compared to HPAlo individuals. The ability of blood cells to secrete TNFα in response to LPS ex vivo was higher for HPAhi pigs. At week eight, the inflammatory response to the LPS in vivo challenge was poorly affected by the HPA axis activity. CONCLUSIONS: Divergent selection upon HPA axis activity modulated hematologic and immune parameters in 6-week-old pigs, which may confer an advantage to HPAhi pigs at weaning. However, HPAlo and HPAhi piglets did not exhibit major differences in the parameters analysed two weeks later, i. e. in 8-week-old pigs. In conclusion, chronic exposure to high cortisol levels in HPAhi pigs does not negatively impact immunity.

ß2-adrenergic stimulation of dendritic cells favors IL-10 secretion by CD4+ T cells.

Adrenergic receptor agonists and antagonists are extensively used as drugs in medicine for a broad spectrum of indications. We examined the consequences of ß2-adrenergic stimulation of murine dendritic cells (DCs) on CD4+ T cell activation. We demonstrated in vitro that treatment of LPS-matured DCs with the ß2-agonist salbutamol reduced their ability to trigger OT-II T cell proliferation specific for ovalbumin antigen. Salbutamol also induced a decrease in MHC class II molecule expression by DC through Gi protein activation. Co-culture of CD4+ T cells with salbutamol-conditioned mature DC impaired TNFα and IL-6 secretion while preserving IL-10 production by T cells. Using a vaccination protocol in mice, we showed that salbutamol favored IL-10-producing CD4+ T cells. None of these effects was observed when working with ß2-adrenoreceptor deficient mice. Finally, we suggest that ß2-adrenergic stimulation of DC could be an interesting way to shape CD4+ T cell responses for the purposes of immunotherapy.

ß2-adrenoreceptor stimulation dampens the LPS-induced M1 polarization in pig macrophages.

The cross-talk between sympatho-adreno-medullar axis and innate immunity players was mainly studied in rodents. In intensive husbandry, pigs are exposed to multiple stressors inducing repeated releases of catecholamines that bind to adrenoreceptors (AR) on target cells. Among adrenoreceptors, the ß2-AR is largely expressed by immune cells including macrophages. We report herein on the effects of catecholamines, through ß2-AR stimulation, on pig macrophage functions activated by LPS. ß2-AR stimulation of porcine macrophages prevented the LPS-induced increase in TNFα and IL-8 secretion while increasing IL-10 secretion. In contrast, treatment with a ß2-agonist had no effect on anti-microbial functions. Lastly, ß2-AR stimulation of macrophages reduced the expression of genes up-regulated by LPS. Altogether, we demonstrated that ß2-AR stimulation of porcine macrophages prevented polarization towards a pro-inflammatory phenotype. Since porcine macrophages are a suitable model for human macrophages, our results might be relevant to appreciate catecholamine effects on human macrophages.

Ankyrin-B mutation causes type 4 long-QT cardiac arrhythmia and sudden cardiac death.

Mutations in ion channels involved in the generation and termination of action potentials constitute a family of molecular defects that underlie fatal cardiac arrhythmias in inherited long-QT syndrome. We report here that a loss-of-function (E1425G) mutation in ankyrin-B (also known as ankyrin 2), a member of a family of versatile membrane adapters, causes dominantly inherited type 4 long-QT cardiac arrhythmia in humans. Mice heterozygous for a null mutation in ankyrin-B are haploinsufficient and display arrhythmia similar to humans. Mutation of ankyrin-B results in disruption in the cellular organization of the sodium pump, the sodium/calcium exchanger, and inositol-1,4,5-trisphosphate receptors (all ankyrin-B-binding proteins), which reduces the targeting of these proteins to the transverse tubules as well as reducing overall protein level. Ankyrin-B mutation also leads to altered Ca2+ signalling in adult cardiomyocytes that results in extrasystoles, and provides a rationale for the arrhythmia. Thus, we identify a new mechanism for cardiac arrhythmia due to abnormal coordination of multiple functionally related ion channels and transporters.