Calcitriol Indeed our immunohistochemical analysis of skin t

Indeed, our immunohistochemical analysis of skin tissue samples without any pathology confirmed the expression of MR and GR. Extending earlier findings in rats (Shaqura et al., 2016a, Shaqura et al., 2016b), we demonstrate here that MR mainly colocalize with the nociceptive neuronal marker CGRP suggesting a crucial role for MR in the modulation of nociceptive stimuli. This finding is consistent with functional evidence of MR antagonists that reverse the mechanical hyperalgesia under painful conditions such as inflammatory (Li et al., 2018) or neuropathic pain (Cha et al., 2005, Dong et al., 2012). In addition, GR do not only colocalize with peptidergic CGRP-IR nociceptive nerve terminals but also with numerous myelinated peripheral nerves in human skin. Apart from its role in nociception (Huynh et al., 2015, Pehora et al., 2017), earlier reports have suggested a functional role of GR in glucocorticoid-induced neuronal myelination (Morisaki et al., 2010), regeneration (Morisaki et al., 2010) and gene expression (Girard et al., 2010). In the skin, we also identified GR-IR Calcitriol in keratinocytes within the basal layer of the epidermis consistent with the long history of glucocorticoids as therapeutic agents for numerous skin diseases (Stojadinovic et al., 2007). Moreover, recent evidence is accumulating that glucocorticoids produced by skin cells may bind their local receptors and may play an important role in the maintenance of local homeostasis (Hannen et al., 2017). There is considerable clinical evidence supporting the beneficial role of corticoids in postoperative pain. Numerous clinical trials have demonstrated that the intravenous administration of dexamethasone (8 mg) significantly prolonged the sensory and motor block in regional anesthesia (Pehora et al., 2017). A recent meta-analysis showed that an even lower dose of perineural dexamethasone (4 mg) extended the neuronal local anesthetic block more effectively than systemically applied dexamethasone suggesting a local effect on sensory neurons (Chong et al., 2017). While these clinical data showed a clear benefit in patient care, there remained some uncertainty regarding the biological mechanisms of this effect which our current data now clarifies.
Conclusion
Materials and methods
Introduction Glucocorticoids are steroid hormones that regulate metabolic, immunological, and neurological processes [1], [2], [3] through transcriptional regulation of a multitude of genes [4]. Glucocorticoids are lipophilic hormones that can pass through the plasma membrane to bind to their cognate nuclear receptor, the glucocorticoid receptor (GR), which leads to nuclear translocation and dimerization of the receptor [5]. The cellular actions of glucocorticoids have been expanded recently to encompass rapid, transcription-independent effects on cellular function, including, for example, endocannabinoid and nitric oxide production [6] and regulation of ion channels [7]. The rapid nature and transcription independence of these glucocorticoid effects suggest actions at a plasma membrane-associated receptor. As with other steroid hormones, a membrane-impermeant GR ligand, dexamethasone (Dex) conjugated to bovine serum albumin (Dex-BSA), is often used to determine if glucocorticoids can act at a binding site constrained to the membrane. Dex-BSA was used in a companion study to test whether glucocorticoid restricted to the membrane signals to the intracellular GR to induce nuclear translocation and gene transcription in hypothalamic neurons (Rainville et al.). The Dex-BSA available from a commercial source is synthesized with between 8 and 40 molecules of Dex per BSA molecule, which raises the possibility that relatively high levels of free Dex may be present if the purity and/or the stability of the compound are not assured. There has been little direct testing of the purity and stability of the Dex-BSA compound to date. Due to the fluorine atom in the Dex molecule, we were able to use 19F nuclear magnetic resonance (NMR) to detect non-covalently bound Dex [8] in a commercially available Dex-BSA compound. Additionally, we determined the biological relevance of a Dex contamination detected in the Dex-BSA in an assay of rapid glucocorticoid actions, and we describe a simple method for robust purification of the steroid-BSA conjugate via denaturing and dialysis. The purification methods discussed here can also be applied to other commonly used steroid conjugates, such as corticosterone-, estradiol- and testosterone-BSA.