Tumor necrosis factor (TNF)-a and interleukin (IL)-1b stimulate tissue non-specific alkaline phosphatase (TNAP) activity and mineralization in cultures of vascular smooth muscle cells (VSMCs). They are, therefore, considered as stimulators of vascular calcification in the context of atherosclerosis and diabetes type 2. In contrast, although ankylosing spondylitis (AS) leads to the formation of syndesmophytes, which are ectopic ossifications from entheses (where ligaments, tendons and capsules are attached to bone), anti-TNF-a therapies fail to block bone formation in this disease. In this context, our aims were to compare the effects of TNF-a and IL-1b on TNAP activity and mineralization in entheseal cells and VSMCs. Organotypic cultures of mouse ankle entheses were treated or not with TNF-a and IL-1b for 5 days. Micro-computed tomography was performed to determine trabecular bone parameters, and histology to assess TNAP activity and mineralization. Human mesenchymal stem cells cultured in pellets in chondrogenic conditions and human VSMCs were also used to determine the effects of cytokines on TNAP activity and expression, measured by quantitative PCR. In organotypic cultures, TNF-a and IL-1b significantly reduced the tibia BV/TV ratio. They also inhibited TNAP activity in entheseal chondrocytes in situ, and in mouse and human chondrocytes in vitro. In contrast, TNF-a stimulated TNAP expression and activity in human VSMCs. These differences were likely due to cell-specific effects of peroxisome proliferator-activated receptor g (PPARg), which is inhibited by TNF-a. Indeed, in human chondrocytes and VSMCs, the PPARg inhibitor GW-9662 displayed the same opposite effects as TNF-a on TNAP expression. In conclusion, whereas TNF-a and IL-1b stimulate TNAP activity in VSMCs, they inhibit it in entheseal cells in situ and on chondrocytes in vitro. The identification of PPARg as a likely mediator of cytokine effects deserves consideration for future research on the mechanisms of ectopic ossification.

1 IL-33 is expressed in human osteoblasts, but has no direct effect on bone remodelingsuggested that expression of IL-33, in contrast to that of IL-1β, is not repressed by PPARγ, likely explaining why IL-33, but not IL-1β, is expressed in adipocytes. The IL-33 receptor ST2L is not constitutively expressed in human bone marrow stromal cells, osteoblasts or CD14-positive monocytes, and IL-33 has no effect on these cells. In addition, although ST2L mRNA is induced by TNF-α and IL-1β in bone marrow stromal cells, IL-33 has the same effects as TNF-α and IL-1β, and, therefore, the biological activity of IL-33 may be redundant in this system. In agreement with this hypothesis, MC3T3-E1 osteoblast-like cells constitutively express ST2L mRNA, and in these cells IL-33 and TNF-α/IL-1β similarly decrease osteocalcin RNA levels in these cells. In conclusion, our results suggest that IL-33 has no direct effects on normal bone remodeling.

BackgroundAnorexia nervosa is a primary psychiatric disorder, with non-negligible rates of mortality and morbidity. Some of the related alterations could participate in a vicious cycle limiting the recovery. Animal models mimicking various physiological alterations related to anorexia nervosa are necessary to provide better strategies of treatment.AimTo explore physiological alterations and recovery in a long-term mouse model mimicking numerous consequences of severe anorexia nervosa.MethodsC57Bl/6 female mice were submitted to a separation-based anorexia protocol combining separation and time-restricted feeding for 10 weeks. Thereafter, mice were housed in standard conditions for 10 weeks. Body weight, food intake, body composition, plasma levels of leptin, adiponectin, IGF-1, blood levels of GH, reproductive function and glucose tolerance were followed. Gene expression of several markers of lipid and energy metabolism was assayed in adipose tissues.ResultsMimicking what is observed in anorexia nervosa patients, and despite a food intake close to that of control mice, separation-based anorexia mice displayed marked alterations in body weight, fat mass, lean mass, bone mass acquisition, reproductive function, GH/IGF-1 axis, and leptinemia. mRNA levels of markers of lipogenesis, lipolysis, and the brown-like adipocyte lineage in subcutaneous adipose tissue were also changed. All these alterations were corrected during the recovery phase, except for the hypoleptinemia that persisted despite the full recovery of fat mass.ConclusionThis study strongly supports the separation-based anorexia protocol as a valuable model of long-term negative energy balance state that closely mimics various symptoms observed in anorexia nervosa, including metabolic adaptations. Interestingly, during a recovery phase, mice showed a high capacity to normalize these parameters with the exception of plasma leptin levels. It will be interesting therefore to explore further the central and peripheral effects of the uncorrected hypoleptinemia during recovery from separation-based anorexia.

No abstract