Analgesic and Anti-Inflammatory Effects of the Synthetic Neurosteroid Analogue BNN27 during CFA-Induced Hyperalgesia

Corticotropin-releasing hormone deficiency results in impaired analgesic response during CFA-induced inflammation

PURPOSE

Corticotropin-releasing hormone (CRH) plays an important role in relief of pain by releasing analgesia-associated molecules in several inflammatory states. During inflammation, peripheral CRH acts on cells of the immune system to stimulate the local expression of proopiomelanocortin (POMC) and the production of β-endorphin, which in turn binds to opioid receptors on sensory neurons to produce antinociception. In the present study, we further investigated the role of endogenous CRH in inflammatory pain by determining the effects of Crh-deficiency on this process.

METHODS

For this purpose, we used Crh-deficient (Crh-/-) mice and their wildtype (Crh + / +) littermates in the CFA (Complete Freund's Adjuvant)-induced inflammatory pain model. Pain thresholds were evaluated with the Hargreaves apparatus.

RESULTS

Our experiments showed that Crh deficiency led to increased pain response, which was associated with decreased POMC mRNA levels in locally inflamed paws of these mice. Furthermore, Crh-/- mice had higher paw edema than Crh + / + mice. Histological evaluation of inflamed paw tissues revealed increased inflammatory response in Crh-/- mice. Protein levels of proinflammatory cytokines, such as IL-6, TNF-α, and IL-1β, were higher in inflamed tissue of Crh-/- mice compared to wildtype mice. Corticosterone replacement increased the pain threshold of Crh-/- mice, restored their paw volume to the levels of wildtype mice, and significantly reduced their proinflammatory cytokine levels. Furthermore, glucocorticoid administration significantly increased POMC mRNA expression in the inflamed paw.

CONCLUSION

Our data suggest that genetic deficiency of CRH is associated with increased pain. This effect is likely attributable to the accompanying glucocorticoid insufficiency and is in part mediated by opioids expressed locally.

The role of androgens in migraine pathophysiology

Migraine affects ∼12 % of the worldwide population and is more prevalent in females, which suggests a role of sex hormones in migraine pathophysiology. Most studies have focused on estrogen and progesterone, and the involvement of androgens has been less studied. However, due to the recent advances in androgen interventions, which could advance new androgen-based migraine treatments, it is critical to better understand the role of androgens in migraine. Testosterone, the most studied androgen, was found to have an antinociceptive effect in various animal and human pain studies. Thus, it could also have a protective effect related to lower migraine severity and prevalence. In this review, we discuss studies examining the role of androgens on migraine-related symptoms in migraine animal models. Additionally, we summarize the results of human studies comparing androgen levels between patients with migraine and healthy controls, studies assessing the relationships between androgen levels and migraine severity, and intervention studies examining the impact of testosterone treatment on migraine severity. Many of the studies have limitations, however, the results suggest that androgens may have a minor effect on migraine. Still, it is possible that androgens are involved in migraine pathophysiology in a sub-group of patients such as in adolescents or postmenopausal women. We discuss potential mechanisms in which testosterone, as the main androgen tested, can impact migraine. These mechanisms range from the cellular level to systems and behavior and include the effect of testosterone on sensory neurons, the immune and vascular systems, the stress response, brain function, and mood. Lastly, we suggest future directions to advance this line of research.

mRNA expression of CRF family members in urothelial bladder cancer

The corticotropin-releasing factor (CRF) gene family includes the three urocortins (UCN1, 2 and 3) and the two receptors (CRFR1 and 2), which play a significant role in the physiology of various organs. The expression of the CRF family of genes and its receptors are shown to participate in the pathogenesis of inflammation and even tumorigenesis. However, data regarding the human urinary tract, especially the bladder, are scarce. To the best of our knowledge, no studies are currently available on the CRF system and bladder cancer. The primary goal of the present study was to investigate the mRNA expression of the CRF family members in bladder cancer. The secondary aim was to analyze the differences with the expression of the same mRNAs in normal bladders. From August 2018 to July 2021, 43 recruited patients were divided into three groups. Group A included healthy patients, group B included patients with bladder cancer and group C included patients with a history of cancer from whom samples were taken from the normal bladder mucosa. Detection of mRNA of the CRF family of genes was performed using reverse transcription-quantitative PCR. The mRNA of the three urocortins, CRF and the two receptors were predominantly expressed in all three groups of patients. Statistical analysis using the Kruskal-Wallis test showed that UCN1 was downregulated in patients with bladder cancer and those with possible cancer compared with the healthy group (mean rank group A=24.3 vs. mean rank group B=12.58; P=0.006) and (mean rank group A=24.3 vs. mean rank group C=8.88; P=0.001). The present experiments showed that mRNA of the CRF family of genes was amplified in normal and cancer bladder tissues. Downregulation of the UCN1 gene may be associated with bladder cancer, contributing to the prognosis, diagnosis or therapy of urothelial malignancies.

Endogenous opiates and behavior: 2021

This paper is the forty-fourth consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2021 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonizts and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Optogenetic modulation of electroacupuncture analgesia in a mouse inflammatory pain model

Peripheral tissue damage and associated inflammation can trigger neuroplastic changes in somatic pain pathways, such as reduced neuronal firing thresholds and synaptic potentiation, that ultimately lead to peripheral sensitization and chronic pain. Electroacupuncture (EA) can relieve chronic inflammatory pain, but the underlying mechanisms are unknown, including the contributions of higher pain centers such as somatosensory cortex (SSC). We investigated these mechanisms using optogenetic modulation of SSC activity in a mouse inflammatory pain model. Injection of Complete Freund's Adjuvant into the hind paw reliably induced inflammation accompanied by reduced mechanical and thermal pain thresholds (hyperalgesia) within three days (mechanical: 1.54 ± 0.13 g; thermal: 3.94 ± 0.43 s). Application of EA produced significant thermal and mechanical analgesia, but these responses were reversed by optogenetic activation of SSC neurons, suggesting that EA-induced analgesia involves modulation of central pain pathways. Western blot and immunostaining revealed that EA also attenuated CaMKIIα signaling in the dorsal root ganglion, central spinal cord, SSC, and anterior cingulate cortex (ACC). In contrast, optogenetic activation of the SSC induced CaMKIIα signaling in SSC and ACC. These findings suggest that AE can relieve inflammatory pain by suppressing CaMKIIα-dependent plasticity in cortical pain pathways. The SSC and ACC CaMKIIα signaling pathways may be valuable therapeutic targets for chronic inflammatory pain treatment.