TRPA1 activation in non-sensory supporting cells contributes to regulation of cochlear sensitivity after acoustic trauma

A Baicalin-Based Functional Polymer in Dynamic Reversible Networks Alleviates Osteoarthritis by Cellular Interactions

Osteoarthritis (OA) is increasingly recognized as a whole-organ disease predominantly affecting the elderly, characterized by typical alterations in subchondral bone and cartilage, along with recurrent synovial inflammation. Despite the availability of various therapeutics and medications, a complete resolution of OA remains elusive. In this study, novel functional hydrogels are developed by integrating natural bioactive molecules for OA treatment. Specifically, baicalin (Bai) is combined with 2-hydroxyethyl acrylate (HEA) to form a polymerizable monomer (HEA-Bai) through esterification, which is subjected to reversible addition-fragmentation chain transfer (RAFT) polymerization to produce Bai-based polymer (Pm). These macromolecules are incorporated into Schiff-base hydrogels, which demonstrate excellent mechanical properties and self-healing performance. Notably, the Bai-based formulations are taken up by fibroblast-like synoviocytes (FLSs), where they regulate glycolysis. Mechanistically, inhibition of yes-associated protein 1 (YAP1) by the formulations suppressed the FLSs glycolysis and reduced the secretion of inflammatory factors, including interleukin 1β (IL-1β), IL-6, and IL-8. Furthermore, the functional hydrogel (AG-Pm)-OC, severing as a lubricant and nutrient, prolonged joint retention of Bai, thereby reducing cartilage degradation and synovial inflammation. Meanwhile, (AG-Pm)-OC alleviated joint pain by targeting the YAP1 signaling and inhibiting macrophage recruitment and polarization. Taken together, this flavonoid-based injectable hydrogel exhibits enhanced biocompatibility and efficacy against OA.

Pannexin-1 regulation of ATP release promotes the invasion of pituitary adenoma

PURPOSE

Pannexin-1 (PANX1) channel participates in the development and progression of many tumor types, however, its role of PANX1 in invasive pituitary adenoma (PA) remains unknown. The current study was designed to investigate the role of PANX1 in invasion of PA.

METHODS

We examined the expression of PANX1 in 116 surgical invasion and non-invasion PA samples (60 for bulk transcriptome and 56 for immunohistochemistry). The effects of PANX1 on PA growth were assessed in vitro and xenograft models. Meanwhile, the metabolism changes of PA cells are explored via transcriptomics and metabolomics using integration strategy.

RESULTS

PANX1 is significantly upregulated in invasive PA compared with noninvasive PA and pituitary gland, and have a potential diagnostic signature for invasive PA. Accordingly, overexpression of PANX1 could promote the proliferation and invasion of GH3 and MMQ cell lines in vitro and in vivo. Further metabolomics results confirme that overexpression of PANX1 could trigger changes in several metabolic pathways of GH3 cells. Among the dysregulated cellular metabolites, decreased intracellular ATP suggeste that PANX1 may promote the invasion of PA through impacting extracellular ATP concentration. Mechanistically, extracellular ATP might promote Ca2+ influx and upregulated the expression of MMP2/9 by activating P2X7R. Additionally, PANX1-ATP-P2 X7R signaling pathway might enhance GH3 cell invasion by remodeling the actin cytoskeleton.

CONCLUSION

Our findings point to a pivotal role of PANX1 in promoting PA invasion, which indicated a potential therapeutic target for invasive PA.

Role of TRP Channels in Cancer-Induced Bone Pain

The burden of cancer is growing in almost every country. Bone metastases significantly affect the prognosis and lead to an increase in mortality and morbidity. The management of cancer-induced bone pain (CIBP) still shows various unmet needs. Opioid use is burdened by a number of possible side effects. Moreover, recent progresses in cancer treatment significantly increased the life expectancy of cancer patients, even those with metastatic disease. In this narrative review, we reported the main findings regarding TRP channel function in cancer pain models. TRP cation channels play a key role in different functions of cancer cells, including the regulation of their potential for metastasization, and are the main channels involved in the pathways of pain perception, through peripheral and central effects. Genetic deletion decreased pain sensitivity following tumour cell inoculation. Preclinical data suggest a potential role for modulators of some TRP channels, such as TRPV1, TRPA1, TRPM7 and TRPM8. Clinical results are still scarce; however, the physiological role in modulating bone remodelling and the involvement of TRP channels in preclinical models of bone cancer pain have garnered interest as areas of research in the last few years, as innovative analgesic strategies that may overcome the long-term side effects of opioids.

Transient Receptor Potential (TRP) Channels in Cochlear Function: Looking Beyond Mechanotransduction

Transient receptor potential (TRP) channels play key roles in sensory biology as transducers of various stimuli. Although these ion channels are expressed in the cochlea, their functions remain poorly understood. Recent studies by Vélez-Ortega and colleagues indicate that their expression by non-sensory supporting cells helps limit damage from acoustic trauma.

TRPA1, TRPV1, and Caffeine: Pain and Analgesia

Caffeine (1,3,7-trimethylxanthine) is a naturally occurring methylxanthine that acts as a potent central nervous system stimulant found in more than 60 different plants and fruits. Although caffeinated beverages are widely and casually consumed, the application of caffeine beyond dietary levels as pharmacologic therapy has been recognized since the beginning of its recorded use. The analgesic and vasoactive properties of caffeine are well known, but the extent of their molecular basis remains an area of active research. There is existing evidence in the literature as to caffeine's effect on TRP channels, the role of caffeine in pain management and analgesia, as well as the role of TRP in pain and analgesia; however, there has yet to be a review focused on the interaction between caffeine and TRP channels. Although the influence of caffeine on TRP has been demonstrated in the lab and in animal models, there is a scarcity of data collected on a large scale as to the clinical utility of caffeine as a regulator of TRP. This review aims to prompt further molecular research to elucidate the specific ligand-host interaction between caffeine and TRP by validating caffeine as a regulator of transient receptor potential (TRP) channels-focusing on the transient receptor potential vanilloid 1 (TRPV1) receptor and transient receptor potential ankyrin 1 (TRPA1) receptor subtypes-and its application in areas of pain.

Optogenetics Reveals Roles for Supporting Cells in Force Transmission to and From Outer Hair Cells in the Mouse Cochlea

Outer hair cells (OHCs) of the organ of Corti (OoC), acting as bidirectional cellular mechanoelectrical transducers, generate, receive, and exchange forces with other major elements of the cochlear partition, including the sensory inner hair cells (IHCs). Force exchange is mediated via a supporting cell scaffold, including Deiters' (DC) and outer pillar cells (OPC), to enable the sensitivity and exquisite frequency selectivity of the mammalian cochlea and to transmit its responses to the auditory nerve. To selectively activate DCs and OPCs in male and female mice, we conditionally expressed in them a hyperpolarizing halorhodopsin (HOP), a light-gated inward chloride ion pump, and measured extracellular receptor potentials (ERPs) and their DC component (ERPDCs) from the cortilymph, which fills the OoC fluid spaces, and compared the responses with similar potentials from HOP-/- littermates. The compound action potentials (CAP) of the auditory nerve were measured as an indication of IHC activity and transmission of cochlear responses to the CNS. HOP light-activated hyperpolarization of DCs and OPCs suppressed cochlear amplification through changing the timing of its feedback, altered basilar membrane (BM) responses to tones at all measured levels and frequencies, and reduced IHC excitation. HOP activation findings reported here complement recent studies that revealed channelrhodopsin activation depolarized DCs and OPCs and effectively bypassed, rather than blocked, the control of OHC mechanical and electrical responses to sound and their contribution to timed and directed electromechanical feedback to the mammalian cochlea. Moreover, our findings identify DCs and OPCs as potential targets for the treatment of noise-induced hearing loss.

Localization of Cadherins in the postnatal cochlear epithelium and their relation to space formation

The sensory epithelium of the cochlea, the organ of Corti, has complex cytoarchitecture consisting of mechanosensory hair cells intercalated by epithelial support cells. The support cells provide important trophic and structural support to the hair cells. Thus, the support cells must be stiff yet compliant enough to withstand and modulate vibrations to the hair cells. Once the sensory cells are properly patterned, the support cells undergo significant remodeling from a simple epithelium into a structurally rigid epithelium with fluid-filled spaces in the murine cochlea. Cell adhesion molecules such as cadherins are necessary for sorting and connecting cells in an intact epithelium. To create the fluid-filled spaces, cell adhesion properties of adjoining cell membranes between cells must change to allow the formation of spaces within an epithelium. However, the dynamic localization of cadherins has not been properly analyzed as these spaces are formed. There are three cadherins that are reported to be expressed during the first postnatal week of development when the tunnel of Corti forms in the cochlea. In this study, we characterize the dynamic localization of cadherins that are associated with cytoskeletal remodeling at the contacting membranes of the inner and outer pillar cells flanking the tunnel of Corti.

Key findings

F-actin remodeling occurs between E18.5 to P7 in the cochlear sensory epithelium.Transient changes of F-actin cytoskeleton drives epithelial morphogenesis.Fluid-filled spaces in epithelium is driven by changes in cell adhesion.

A Novel Flp Reporter Mouse Shows That TRPA1 Expression Is Largely Limited to Sensory Neuron Subsets

Transient receptor potential ankyrin 1 (TRPA1) is a polymodal cation channel that is activated by electrophilic irritants, oxidative stress, cold temperature, and GPCR signaling. TRPA1 expression has been primarily identified in subsets of nociceptive sensory afferents and is considered a target for future analgesics. Nevertheless, TRPA1 has been implicated in other cell types including keratinocytes, epithelium, enterochromaffin cells, endothelium, astrocytes, and CNS neurons. Here, we developed a knock-in mouse that expresses the recombinase FlpO in TRPA1-expressing cells. We crossed the TRPA1Flp mouse with the R26ai65f mouse that expresses tdTomato in a Flp-sensitive manner. We found tdTomato expression correlated well with TRPA1 mRNA expression and sensitivity to TRPA1 agonists in subsets of TRPV1 (transient receptor potential vanilloid receptor type 1)-expressing neurons in the vagal ganglia and dorsal root ganglia (DRGs), although tdTomato expression efficiency was limited in DRG. We observed tdTomato-expressing afferent fibers centrally (in the medulla and spinal cord) and peripherally in the esophagus, gut, airways, bladder, and skin. Furthermore, chemogenetic activation of TRPA1-expressing nerves in the paw evoked flinching behavior. tdTomato expression was very limited in other cell types. We found tdTomato in subepithelial cells in the gut mucosa but not in enterochromaffin cells. tdTomato was also observed in supporting cells within the cochlea, but not in hair cells. Lastly, tdTomato was occasionally observed in neurons in the somatomotor cortex and the piriform area, but not in astrocytes or vascular endothelium. Thus, this novel mouse strain may be useful for mapping and manipulating TRPA1-expressing cells and deciphering the role of TRPA1 in physiological and pathophysiological processes.

The Relevance of Autophagy within Inner Ear in Baseline Conditions and Tinnitus-Related Syndromes

Tinnitus is the perception of noise in the absence of acoustic stimulation (phantom noise). In most patients suffering from chronic peripheral tinnitus, an alteration of outer hair cells (OHC) starting from the stereocilia (SC) occurs. This is common following ototoxic drugs, sound-induced ototoxicity, and acoustic degeneration. In all these conditions, altered coupling between the tectorial membrane (TM) and OHC SC is described. The present review analyzes the complex interactions involving OHC and TM. These need to be clarified to understand which mechanisms may underlie the onset of tinnitus and why the neuropathology of chronic degenerative tinnitus is similar, independent of early triggers. In fact, the fine neuropathology of tinnitus features altered mechanisms of mechanic-electrical transduction (MET) at the level of OHC SC. The appropriate coupling between OHC SC and TM strongly depends on autophagy. The involvement of autophagy may encompass degenerative and genetic tinnitus, as well as ototoxic drugs and acoustic trauma. Defective autophagy explains mitochondrial alterations and altered protein handling within OHC and TM. This is relevant for developing novel treatments that stimulate autophagy without carrying the burden of severe side effects. Specific phytochemicals, such as curcumin and berberin, acting as autophagy activators, may mitigate the neuropathology of tinnitus.