In the course of our synthetic studies we

In the course of our synthetic studies, we also discovered an unprecedented application of Burgess reagent. Instead of generating an olefin by an intramolecular syn-elimination, the product resulting from the treatment of spirocyclic alcohols 11 and 12 with Burgess reagent led to the expansion of the cyclohexadiene ring. Our future plan is to examine whether this observation could be generalized to other systems containing an allylic hydrogen atom.
Experimental
Acknowledgments
Introduction The corticoid receptor system attracted new interest, especially since selective mineralcorticoid receptor (MR) antagonists were described to inhibit the development of pain (Dong et al., 2012, Li et al., 2018, Shaqura et al., 2016b). After experimental induction of local Chaetocin in the dorsal root ganglion, a single application of the MR antagonist eplerenone prevented mechanical hyperalgesia and allodynia over the following 14 days most likely due to genomic mechanisms interfering with gene transcription (Dong et al., 2012). Moreover, intrathecal application of the MR antagonist eplerenone elicited a very rapid (within minutes) attenuation of mechanical hyperalgesia and allodynia in rats with a localized hindpaw inflammation suggesting rather non-genomic mechanisms most likely through rapid intracellular signalling events (Li et al., 2018). In contrast, intrathecal application of the MR agonist seems to induce mechanical hyperalgesia and allodynia (Li et al., 2018). Thus, treatment targeting the MR outside the renal system may open a therapeutic option for several pain conditions like acute chemically-induced pain (Shaqura et al., 2016b), chronic neuropathic back pain (Dong et al., 2012) or chronic inflammatory pain (Li et al., 2018). On the other side, glucocorticoid receptor (GR) agonists are well known to inhibit acute postoperative (Pehora et al., 2017), chronic arthritic pain (Garg et al., 2014), and chronic low back pain (Lakemeier et al., 2013). This mainly occurs through delayed but long lasting genomic mechanisms triggered by activation of intracellular GR (McEwen et al., 1986). More recently it was shown that GR agonists can also elicit rapid non-genomic effects resulting in the attenuation of mechanical hyperalgesia and allodynia (Shaqura et al., 2016a). The question arises whether the described MR and GR effects on nociception are due to more indirect mechanisms through modulation of the immune system or whether they are due to more direct mechanisms modulating neuronal activity and excitation. For the latter GR and MR have to be identified on peripheral sensory neurons. Earlier binding studies had suggested two different corticoid receptors within the central nervous system and found evidence for type I (i.e. mineralocorticoid receptor) and type II corticosteroid receptor gene expression (McEwen et al., 1986). However, no data were available on the exact anatomical localization of MR or GR with regards to specific subpopulations of peripheral nerve fibers. First immunohistochemical studies stated that GR coexist with the neuropeptides substance P and CGRP in a specific subpopulation of DRG neurons (De Leon et al., 1994). More recently, the exact subpopulations of dorsal root ganglion neurons expressing GR and MR have been identified in rats and suggest their main role as modulators of nociception (Shaqura et al., 2016a).
Results Skin tissue samples were obtained from 10 patients of which age, gender and tissue origin are listed in Table 1. Five tissue samples were used as fresh frozen samples for PCR and western blot and five were used in fixative solution for immunohistochemistry.
Discussion Using PCR, we were able to isolate MR as well as GR specific transcripts from human skin similar to rat tissue such as spinal cord and DRG (Shaqura et al., 2016a). These findings are consistent with former in situ hybridization studies demonstrating GR hybridization products in the human brain, lung, heart and liver, but not skin (Oakley et al., 1996). To prove that MR as well as GR transcripts were indeed translated into receptor proteins, we performed western blot analysis that showed a single MR or GR specific protein band at the expected molecular weight, consistent with previous GR or MR protein demonstration in rat brain, DRG neurons and sciatic nerve (Han et al., 2005, Shaqura et al., 2016a). Since MR and GR specific transcripts and protein bands were demonstrated in skin tissue samples of patients suffering from dermatitis or lymphoma (tissue bank samples) the question arises whether MR and GR expression also occurs under normal nonpathological conditions?