TRPA1/NOX in the soma of trigeminal ganglion neurons mediates migraine-related pain of glyceryl trinitrate in mice.

Glyceryl trinitrate is administered as a provocative test for migraine pain. Glyceryl trinitrate causes prolonged mechanical allodynia in rodents, which temporally correlates with delayed glyceryl trinitrate-evoked migraine attacks in patients. However, the underlying mechanism of the allodynia evoked by glyceryl trinitrate is unknown. The proalgesic transient receptor potential ankyrin 1 (TRPA1) channel, expressed by trigeminal nociceptors, is sensitive to oxidative stress and is targeted by nitric oxide or its by-products. Herein, we explored the role of TRPA1 in glyceryl trinitrate-evoked allodynia. Systemic administration of glyceryl trinitrate elicited in the mouse periorbital area an early and transient vasodilatation and a delayed and prolonged mechanical allodynia. The systemic, intrathecal or local administration of selective enzyme inhibitors revealed that nitric oxide, liberated from the parent drug by aldehyde dehydrogenase 2 (ALDH2), initiates but does not maintain allodynia. The central and the final phases of allodynia were respectively associated with generation of reactive oxygen and carbonyl species within the trigeminal ganglion. Allodynia was absent in TRPA1-deficient mice and was reversed by TRPA1 antagonists. Knockdown of neuronal TRPA1 by intrathecally administered antisense oligonucleotide and selective deletion of TRPA1 from sensory neurons in Advillin-Cre; Trpa1fl/fl mice revealed that nitric oxide-dependent oxidative and carbonylic stress generation is due to TRPA1 stimulation, and resultant NADPH oxidase 1 (NOX1) and NOX2 activation in the soma of trigeminal ganglion neurons. Early periorbital vasodilatation evoked by glyceryl trinitrate was attenuated by ALDH2 inhibition but was unaffected by TRPA1 blockade. Antagonists of the calcitonin gene-related peptide receptor did not affect the vasodilatation but partially inhibited allodynia. Thus, although both periorbital allodynia and vasodilatation evoked by glyceryl trinitrate are initiated by nitric oxide, they are temporally and mechanistically distinct. While vasodilatation is due to a direct nitric oxide action in the vascular smooth muscle, allodynia is a neuronal phenomenon mediated by TRPA1 activation and ensuing oxidative stress. The autocrine pathway, sustained by TRPA1 and NOX1/2 within neuronal cell bodies of trigeminal ganglia, may sensitize meningeal nociceptors and second order trigeminal neurons to elicit periorbital allodynia, and could be of relevance for migraine-like headaches evoked by glyceryl trinitrate in humans.

Potential therapeutic implications of ergogenic compounds on pathophysiology induced by traumatic brain injury: A narrative review.

Traumatic brain injury (TBI) is a devastating condition that often triggers a sequel of neurological disorders that can last throughout lifespan. From a metabolic viewpoint, the compromising of the energy metabolism of the brain has produced evidence linking the severity of brain injury to the extent of disturbances in the cerebral metabolism. The cerebral metabolic crisis, however, displays that regional heterogeneity varies temporally post-injury. It is important to note that energy generation and mitochondrial function are closely related and interconnected with delayed secondary manifestations of brain injury, including early neuromotor dysfunction, cognitive impairment, and post-traumatic epilepsy (PTE). Given the extent of post-traumatic changes in neuronal function and the possibility of amplifying secondary cascades, different therapies designed to minimize damage and retain/restore cellular function after TBI are currently being studied. One of the possible strategies may be the inclusion of ergogenic compounds, which is a class of supplements that typically includes ingredients used by athletes to enhance their performance. The combination of these compounds offers specific physiological advantages, which include enhanced energy availability/metabolism and improved buffering capacity. However, the literature on their effects in certain biological systems and neurological diseases, such as TBI, has yet to be determined. Thus, the present review aims to discuss the role of ergogenic compounds popularly used in secondary damage induced by this neurological injury. In this narrative review, we also discuss how the results from animal studies can be applied to TBI clinical settings.

Role of TRPA1 receptors in skin inflammation induced by volatile chemical irritants in mice.

Contact dermatitis is a very common inflammatory reaction in the skin, causing not only aesthetic problems but also loss functionality at work. The molecular mechanisms of contact dermatitis induced by chemical irritants are still unclear. Considering that transient receptor potential channels (TRP) may induce neurogenic inflammation and the exacerbation of inflammatory responses, here we investigated the role of transient receptor potential channel ankyrin type-1 (TRPA1) in skin inflammation evoked by chemical irritants. Ear oedema and nociceptive responses elicited by the topical application of xylene and toluene were measured in Swiss mice, wild type and TRPA1 knockout (Trpa1-/-) C57BL/6 mice. Histological analyses were performed in mice subjected to the ear oedema assay. Topical application of xylene and toluene in the mouse ear induced an edematogenic response (0.113 ±â€¯0.008 mm and 0.067 ±â€¯0.011 mm), compared to vehicle (0.008 ±â€¯0.008 mm), assessed by ear thickness measurements and histological analyses. These responses were prevented by topical pretreatment with a selective TRPA1 antagonist, HC-030031 (% inhibition: xylene 36.8 ±â€¯9.4% and toluene 50.7 ±â€¯11.0%), and by the genetic deletion of TRPA1 ((% inhibition: xylene 66.6 ±â€¯16.7% and toluene 75 ±â€¯0%). In addition, the topical application of xylene and toluene to the mouse paw elicited nociceptive responses, which were significantly reduced by oral treatment with HC-030031 ((% of inhibition: 84.9 ±â€¯1.3% and 27.1 ±â€¯8.0%, respectively); nociceptive responses were almost completely abolished in Trpa1-/-mice. Our data suggest that the activation of TRPA1 could be involved in some of the symptoms of irritant-mediated contact dermatitis, such as oedema, pain and neurogenic inflammation.