Apoptosis a form of programmed cell death is a critical

Apoptosis, a form of programmed cell death, is a critical component in maintaining homeostasis and growth in all tissues and plays a significant role in immunity and cytotoxicity [54,55]. Although GR are expressed in all immune cells, the physiological outcomes of GR activation are highly cell type-specific: for example, glucocorticoids are anti-apoptotic in neutrophils, but pro-apoptotic in eosinophils, dendrites and some T-cells [56]. In addition, cortisol treatment could increase apoptosis of Fenoprofen Calcium and inhibit apoptosis of neutrophils in carp [57]. Previous studies have shown that apoptosis can be induced in fish by exposure to environmental stressors during different stages of the fish life cycle [58]. One of the interesting observations of this study is that cortisol treatment promoted apoptosis by PaGR activation under the condition of V. anguillarum infection, rather than in control MO/MΦ, while RU486 antagonized and nearly reversed the effects of cortisol. This result indicated that PaGR was also involved in MO/MΦ apoptosis. The main role of apoptosis is to prevent inflammation by removal of damaged cells [58]. Further investigations are needed on the regulation of apoptosis and PaGR activation, which together contribute to improving the understanding of the ayu immune system and help to elucidate the innate immune mechanisms of other teleosts.
Introduction A more recent concept postulated by Libert and coll. suggests that if the GR homodimer-mediated transactivation greatly overpasses the GR monomer transcriptional transrepression, a new therapeutic window could be exploited for unmet medical needs such as SIRS and sepsis [1]. Identifying new “super agonists” able to satisfy these demands could therefore be a new interesting approach to potential anti-inflammatory drugs. We recently designed a new class of potential ligands of glucocorticoid receptor [2] which are spirocyclic analogs of the compounds MK disclosed by Ali et al. [3] (Scheme 1). The spirocyclic substructure was expected to increase the conformational pool while keeping the key hydroxyl pharmacophore in the same environment, as indicated by the good superposition of the reference MK molecule on the spirocyclic target (Fig. 1). Earlier examples of spirocyclic corticoids did not imply a modification of the core scaffold but consisted in the replacement of a carbonyl group by a spirolactone aiming at producing potent aldosterone antagonists devoid of undesired endocrinological side effects. These derivatives were highly potent binders for the MR, AR and PR [4] but they bound weakly to the GR [5]. We have recently reported a detailed study of a practical synthetic route to this new class of spirocyclic ligands. The observation of an IC50 of 27 nM for a representative example in this series [2] prompted us to prepare more examples and study their biological activities in more detail.
Results and discussion
Conclusions Spirocyclic glucocorticoids were designed, synthesized and evaluated for their activity towards hGR. Pure diastereoisomers were tested for their binding to the hGR. This led to the identification of novel highly active glucocorticoid ligands. The best ligand identified so far in this series, compound 9b, had an excellent IC50 of 0.4 nM, 30-fold more potent than prednisolone, the classical reference GR ligand used in the same experiment (IC50 = 13 nM). Moreover, the same compound 9b revealed highly potent anti-inflammatory effects in in vitro and ex vivo cytokine release experiments. The corresponding diastereoisomer 8b was devoid of activity for hGR (IC50 = 1012 nM). Preliminary results also showed that this new class of hGR binders were selective over the PR. The dehydrated analogue (10a) of the most potent compound identified so far (9b) showed a 50-fold lower affinity for the hGR (10b, IC50 = 20 nM). This seems to indicate the importance of the H-bond generated by the hydroxyl moiety present on the ligand. However, as the affinity is still in the nM range, this could be an opportunity for the medicinal chemist to keep essential features for a nM potency, while removing the chemical complexity represented by an additional asymmetric center.