Pamoic acid-induced peripheral GPR35 activation improves pruritus and dermatitis

Exosomes: A Promising Cell-Free Therapeutic Tool for Treating Cutaneous Nerve Injuries and Promoting Wound Healing

The skin is the body's largest organ. It serves various functions, including protection and metabolism. Due to its structure and location, it is more vulnerable to external physical and chemical damage than internal organs. Additionally, certain endogenous diseases can cause pathological changes to appear on the skin and nerves. When skin tissue breaks down or sustains severe trauma, the cells, blood vessels, and nerves across all layers can suffer varying degrees of damage. This often results in pain, itching, sensory disturbances, and other discomforts, causing significant distress to patients. Stem-cell-derived exosome therapy has emerged as a promising treatment for skin injuries due to its safety, non-toxicity, and precision medicine benefits. Research has shown that stem-cell-derived exosomes regulate nerve cells by mediating MicroRNA (miRNA) transport and expression between cells, promoting axon growth. This exosome-driven miRNA exchange serves as a vital mode of intercellular communication, playing a crucial role in nervous system repair. Nerves play a critical role in skin wound healing and tissue regeneration, with sensory and autonomic nerves influencing key skin functions such as inflammation, immune defense, apoptosis, proliferation, and wound repair. Exosomes may aid in treating cutaneous nerve injuries by directly or indirectly promoting axon regeneration, nerve cell proliferation, and the release of protective neurofactors.

GPR35 prevents drug-induced liver injury via the Gαs-cAMP-PKA axis in macrophages

Acetaminophen (APAP) overdose induces acute liver injury and represents the most frequent cause of drug-induced liver injury worldwide. Macrophage-mediated inflammation plays detrimental roles during the early stage of liver injury. However, the potential targets regulating inflammation to improve drug-induced liver injury remains undefined. In this study, we reported that G protein-coupled receptor 35 (GPR35) improves drug-induced liver injury by blocking macrophage-mediated inflammation via the Gαs-cyclic AMP-protein kinase A (Gαs-cAMP-PKA) pathway. The ablation of GPR35 exacerbates APAP-induced liver injury, characterized by higher levels of alanine aminotransferase and aspartate aminotransferase in sera, larger damaged areas, and increased levels of pro-inflammatory cytokines. More hepatic macrophages appeared in the inflamed liver of mice with GPR35 deficiency. In contrast, the agonists of GPR35 alleviated APAP-induced liver injury. The depletion of macrophages abolished GPR35-mediated protection. Mechanistically, GPR35 ablation facilitated the activation of pro-inflammatory AKT, MAPK, and NF-κB signaling pathways at the downstream of Toll-like receptors in macrophages. GPR35 agonists activated Gαs-cAMP-PKA signaling to inhibit the activation of these pro-inflammatory signaling pathways and then suppress the inflammatory response in macrophages. Thus, our findings demonstrate that GPR35 prevents drug-induced liver injury by blocking macrophage-mediated inflammation via the Gαs-cAMP-PKA pathway, indicating that GPR35 is a potential target for the development of novel medicines that control drug-induced liver injury.

GPR35 agonists inhibit TRPA1-mediated colonic nociception through suppression of substance P release

ABSTRACT

The development of nonopioid analgesics for the treatment of abdominal pain is a pressing clinical problem. To address this, we examined the expression of G i/o -coupled receptors, which typically inhibit nociceptor activation, in colonic sensory neurons. This led to the identification of the orphan receptor GPR35 as a visceral analgesic drug target because of its marked coexpression with transient receptor potential ankyrin 1 (TRPA1), a mediator of noxious mechanotransduction in the bowel. Building on in silico docking simulations, we confirmed that the mast cell stabiliser, cromolyn (CS), and phosphodiesterase inhibitor, zaprinast, are agonists at mouse GPR35, promoting the activation of different G i/o subunits. Pretreatment with either CS or zaprinast significantly attenuated TRPA1-mediated colonic nociceptor activation and prevented TRPA1-mediated mechanosensitisation. These effects were lost in tissue from GPR35 -/- mice and were shown to be mediated by inhibition of TRPA1-evoked substance P (SP) release. This observation highlights the pronociceptive effect of SP and its contribution to TRPA1-mediated colonic nociceptor activation and sensitisation. Consistent with this mechanism of action, we confirmed that TRPA1-mediated colonic contractions evoked by SP release were abolished by CS pretreatment in a GPR35-dependent manner. Our data demonstrate that GPR35 agonists prevent the activation and sensitisation of colonic nociceptors through the inhibition of TRPA1-mediated SP release. These findings highlight the potential of GPR35 agonists to deliver nonopioid analgesia for the treatment of abdominal pain.

Role of orphan G-protein coupled receptors in tissue ischemia: A comprehensive review

Ischemic events lead to many diseases and deaths worldwide. Ischemia/reperfusion (I/R) occurs due to reduced blood circulation in tissues followed by blood reflow. Reoxygenation of ischemic tissues is characterized by oxidative stress, inflammation, energy distress, and endoplasmic reticulum stress. There are still no adequate clinical protocols or pharmacological approaches to address the consequences of I/R damage. G protein-coupled receptors (GPCRs) are important therapeutic targets. They compose a large family of seven transmembrane-spanning proteins that are involved in many biological functions. Orphan GPCRs are a large subgroup of these receptors expressed in different organs. In the present review, we summarized the literature regarding the role of orphan GPCRs in I/R in different organs. We focused on the effect of these receptors on modulating cellular and molecular processes underlying ischemia including apoptosis, inflammation, and autophagy. The study showed that GPR3, GPR4, GPR17, GPR30, GPR31, GPR35, GPR37, GPR39, GPR55, GPR65, GPR68, GPR75, GPR81, and GPR91 are involved in ischemic events, mainly in the brain and heart. These receptors offer new possibilities for treating I/R injuries in the body.

GnRH peripherally modulates nociceptor functions, exacerbating mechanical pain

The function of peripheral nociceptors, the neurons that relay pain signals to the brain, are frequently tuned by local and systemic modulator substances. In this context, neurohormonal effects are emerging as an important modulatory mechanism, but many aspects remain to be elucidated. Here we report that gonadotropin-releasing hormone (GnRH), a brain-specific neurohormone, can aggravate pain by acting on nociceptors in mice. GnRH and GnRHR, the receptor for GnRH, are expressed in a nociceptor subpopulation. Administration of GnRH and its analogue, localized for selectively affecting the peripheral neurons, deteriorated mechanical pain, which was reproducible in neuropathic conditions. Nociceptor function was promoted by GnRH treatment in vitro, which appears to involve specific sensory transient receptor potential ion channels. These data suggest that peripheral GnRH can positively modulate nociceptor activities in its receptor-specific manner, contributing to pain exacerbation. Our study indicates that GnRH plays an important role in neurohormonal pain modulation via a peripheral mechanism.