Animal Studies, Pharmacology/Drug Development

Coordinated lipid metabolism contributes to maintaining skin homeostasis by regulating skin barrier formation, immune reactions, thermogenesis, and perception. Several reports have documented the changes in lipid composition in dermatitis, including in atopic dermatitis (AD); however, the specific mechanism by which these lipid profiles are altered during AD pathogenesis remains unknown. Here, we performed untargeted and targeted lipidomic analyses of an AD-like dermatitis model resulting from constitutive activation of Jak1 (Spade mice) to capture the comprehensive lipidome profile during dermatitis onset and progression. We successfully annotated over 700 skin lipids, including glycerophospholipids, ceramides, neutral lipids, and fatty acids, many of which were found to be present at significantly changed levels after dermatitis onset, as determined by the pruritus and erythema. Among them, we found the levels of ceramides composed of non-hydroxy fatty acids and dihydrosphingosines (Cer[NDS]) containing very long-chain (C22 or more) fatty acids were significantly downregulated before AD onset. Furthermore, in vitro enzyme assays using the skin of Spade mice demonstrated the enhancement of ceramide desaturation. Finally, we reveal topical application of Cer[NDS] before AD onset effectively ameliorated the progression of AD symptoms in Spade mice. Our results suggest that the disruption in epidermal ceramide composition is caused by boosting ceramide desaturation in the initiation phase of AD, which regulates AD pathogenesis.

Repeated skin contact to detergents causes chronic irritant contact dermatitis (ICD) associated with itch sensation and eczema. However, the mechanisms of detergent-induced ICD are poorly understood. Here, we established a new murine model of detergent-induced ICD with H1-antihistamine-refractory itch.

Assessment of pain responses and inflammation during animal surgery is difficult because traditional methods, such as visual analogue scores, are not applicable while under anaesthesia. Acute phase proteins (APPs), such as C-reactive protein and haptoglobin, that are typically monitored in veterinary research, do not show a significant change until at least 2 h post-surgery and therefore, immediate pathophysiological changes are uncertain. The current study used sequential window acquisition of all theoretical mass spectra (SWATH-MS) to investigate plasma proteome changes that occur immediately following surgery in dogs and also to assess the efficacy of a novel transdermal ketoprofen (TK) formulation. Castration was chosen as surgical model in this study. The procedure was performed on twelve dogs (n = 6 in two groups) and blood samples were collected at 0 h, 1 and 2 h after surgery for proteomic analysis. Following surgery, there was a general downregulation of proteins, including complement C- 3, complement factor B, complement factor D, transthyretin, and proteins associated with lipid, cholesterol, and glucose metabolisms, reflecting the systemic response to surgical trauma. Many of these changes were diminished in the transdermal group (TD) since ketoprofen, a non-steroidal anti-inflammatory drug (NSAID), inhibits prostanoids and the associated chemotactic neutrophil migration to site of tissue injury. SIGNIFICANCE: SWATH-MS Proteomic analysis revealed significant changes in plasma proteins, predominantly involved in early acute phase and inflammatory response at 1 & 2 h after surgery in castrated dogs. Pre-operative application of transdermal ketoprofen formulation had reduced systemic immune response, which was confirmed by negligible alteration of proteins in transdermal treated group. A key outcome of this experiment was studying the efficacy of a novel transdermal NSAID formulation in dogs.

Lesions or diseases of the somatosensory system can cause neuropathic pain (NP). Schwann cell (SC) autophagy plays an important role in NP. Uncoordinated gene 5 homolog B (UNC5B), the canonical dependent receptor of netrin-1, is known to be exclusively expressed in SCs and involved in NP; however, the underlying mechanisms were unclear. A rat model of sciatic nerve chronic constriction injury (CCI) was used to induce peripheral neuropathic pain. Adeno-associated virus (AAV) overexpressing UNC5B was applied to the injured nerve, and an autophagy inhibitor, 3-mechyladenine (3-MA), was intraperitoneally injected in some animals. Behavioral tests were performed to evaluate NP, the morphology of the injured nerves was analyzed, and autophagy-related proteins were detected. A rat SC line (RSC96) undergoing oxygen and glucose deprivation (OGD) was used to mimic an ischemic setting to examine the role of UNC5B in autophagy. Local UNC5B overexpression alleviated CCI-induced NP and rescued myelin degeneration. Meanwhile, UNC5B overexpression improved CCI-induced impairment of autophagic flux, while the autophagy inhibitor 3-MA reversed the analgesic effect of UNC5B. In cultured SCs, UNC5B helped recruit netrin-1 to the cell membrane. UNC5B overexpression promoted autophagic flux while inhibiting apoptosis, which was further augmented with exogenous netrin-1 and reversed by netrin-1 knockdown. The enhanced phosphorylation of AMP-activated protein kinase (AMPK) and Unc51-like autophagy activating kinase 1 (ULK1) by UNC5B overexpression was also correlated with netrin-1. Our results suggest that UNC5B facilitates autophagic flux in SCs via phosphorylation of AMPK and ULK1, dependent on its ligand netrin-1, protecting myelin and partly preventing injury-induced NP.

Sickle cell disease (SCD) is the most common inherited disease. Pain is a key morbidity of SCD and opioids are the main treatment but their side effects emphasize the need for new analgesic approaches. Humanized transgenic mouse models have been instructive in understanding the pathobiology of SCD and mechanisms of pain. Homozygous (HbSS) Berkley mice express >99% human sickle hemoglobin and several features of clinical SCD including hyperalgesia. Previously, we reported that the endocannabinoid 2-arachidonoylglycerol (2-AG) is a precursor of the pro-nociceptive mediator prostaglandin E2-glyceryl ester (PGE2-G) which contributes to hyperalgesia in SCD. We now demonstrate the causal role of 2-AG in hyperalgesia in sickle mice. Hyperalgesia in HbSS mice correlated with elevated levels of 2-AG in plasma, its synthesizing enzyme diacylglycerol lipase β (DAGLβ) in blood cells, and with elevated levels of PGE2 and PGE2-G, pro-nociceptive derivatives of 2-AG. A single intravenous injection of 2-AG produced hyperalgesia in non-hyperalgesic HbSS mice, but not in control (HbAA) mice expressing normal human HbA. JZL184, an inhibitor of 2-AG hydrolysis also produced hyperalgesia in non-hyperalgesic HbSS or hemizygous (HbAS) mice, but did not influence hyperalgesia in hyperalgesic HbSS mice. Systemic and intraplantar administration of KT109, an inhibitor of DAGLβ, decreased mechanical and heat hyperalgesia in HbSS mice. The decrease in hyperalgesia was accompanied by reductions in 2-AG, PGE2 and PGE2-G in the blood. These results indicate that maintaining the physiological level of 2-AG in the blood by targeting DAGLβ may be a novel and effective approach to treat pain in SCD.

Chronic neuropathic pain (CNP) can result from surgery or traumatic injury, but also from peripheral neuropathies caused by diseases, viral infections, or toxic treatments. Opioids, although very effective for acute pain, do not prevent the development of CNP, and are considered as insufficient treatment. Therefore, there is high need for effective and safe non-opioid options to treat, prevent and eventually reverse CNP. A more effective approach to alleviating CNP would constitute a treatment that acts concurrently on various mechanisms involved in relieving pain symptoms and preventing or reversing chronification by enhancing both neuroprotection and neuroregeneration. We have identified and characterized GRT-X (N-[(3-fluorophenyl)-methyl]-1-(2-methoxyethyl)-4-methyl-2-oxo-(7-trifluoromethyl)-1H-quinoline-3-caboxylic acid amide), a novel drug which is able to activate both voltage-gated potassium channels of the Kv7 family and the mitochondrial translocator protein 18 kDa (TSPO). The dual mode-of-action (MoA) of GRT-X was indicated in in vitro studies and in vivo in a rat model of diabetic neuropathy. In this model, mechanical hyperalgesia was dose-dependently inhibited. After severe crush lesion of cervical spinal nerves in rats, GRT-X promoted survival, speeded up regrowth of sensory and motor neurons, and accelerated recovery of behavioral and neuronal responses to heat, cold, mechanical and electrical stimuli. These properties may reduce the likelihood of chronification of acute pain, and even potentially relieve established CNP. The absence of a conditioned place preference in rats suggests lack of abuse potential. In conclusion, GRT-X offers a promising preclinical profile with a novel dual MoA.

C-shapes are stereotyped movements in planarians that are elicited by diverse stimuli (e.g. acidity, excitatory neurotransmitters, psychostimulants, and pro-convulsants). Muscle contraction and seizure contribute to the expression of C-shape movements, but a causative role for pain is understudied and unclear. Here, using nicotine-induced C-shapes as the endpoint, we tested the efficacy of three classes of antinociceptive compounds – an opioid, NSAID (non-steroidal anti-inflammatory drug), and transient receptor potential ankyrin 1 (TRPA1) channel antagonist. For comparison we also tested effects of a neuromuscular blocker. Nicotine (0.1-10 mM) concentration-dependently increased C-shapes. DAMGO (1-10 µM), a selective µ-opioid agonist, inhibited nicotine (5 mM)-induced C-shapes. Naloxone (0.1-10 µM), an opioid receptor antagonist, prevented the DAMGO (1 µM)-induced reduction of nicotine (5 mM)-evoked C-shapes, suggesting an opioid receptor mechanism. C-shapes induced by nicotine (5 mM) were also reduced by meloxicam (10-100 µM), a NSAID; HC 030031 (1-10 µM), a TRPA1 antagonist; and pancuronium (10-100 µM), a neuromuscular blocker. Evidence that nicotine-induced C-shapes are reduced by antinociceptive drugs from different classes, and require opioid receptor and TRPA1 channel activation, suggest C-shape etiology involves a pain component.

Previous studies have confirmed that the microglial activation and subsequent inflammatory responses in the trigeminal nucleus caudalis (TNC) are involved in the central sensitization of chronic migraine (CM). MicroRNA-155-5p has been shown to modulate the polarization of microglia and participate in inflammatory processes in a variety of neurological diseases. However, its role in CM remains unclear. The purpose of this study was to determine the precise role of miR-155-5p in CM.

Complex regional pain syndrome (CRPS) is caused by injuries from fracture after trauma and orthopaedic surgical procedures in the hind limbs. The symptoms of CRPS include warmth, pain, allodynia, and hyperalgesia. It is known that 5-hydroxytryptamine 3 (5-HT3) receptors contribute to hyperalgesia, but their role has not yet been fully elucidated. This study investigated the mechanism of pain relief when a 5-HT3 receptor antagonist was administered in a CRPS animal model.

The aim of this study was to examine the inhibitory effect of teriparatide (TPTD) on pain and on bone loss in ovariectomized (OVX) mice. The mechanism of osteoporotic pain in OVX mice was evaluated through an examination of pain-related behavior as well as immunohistochemical examinations.