Presence of Small-Conductance Calcium-Activated Potassium (SK) Channels in the Central and Peripheral Nervous Systems and Their Role in Health and Disease.

Potassium (K+) channels establish and maintain the resting potential of most living cells. Their activity is predominantly regulated by the membrane voltage or the K+ gradient across the cell membrane. However, many cells also express small-conductance calcium-activated potassium (SK) channels, which have the unique ability to translate changes in the level of the intracellular second messenger, Ca2+ to changes in the membrane K+ conductance and, therefore, the resting membrane potential. This article reviews the structure, presence, distribution, and function of SK channels, their pharmacological modulation, and their role in health and disease, emphasizing nociception and pain.

Comparison between two viscosupplementation protocols for temporomandibular joint osteoarthritis.

OBJECTIVE: This clinical trial aimed to compare the efficacy of two protocols using high molecular weight hyaluronic acid (HA) intra-articular injection in patients with temporomandibular joint (TMJ) osteoarthritis and evaluate involvement of subchondral bone changes and psychosocial factors as predictors of HA treatment. METHODS: Twenty-one individuals were divided into two groups: (A) received three intra-articular HA injections, and (B) received one injection. Outcomes observed were pain intensity, functional limitation, maximum voluntary mouth opening, maximum assisted mouth opening, and treatment tolerability. Follow-ups were performed weekly for 21 days, and two months after the treatment started. RESULTS: No statistically significant intergroup differences were observed in any of the evaluated outcomes. However, Group A showed significant improvement in all outcomes, whereas Group B showed significant improvement only in pain intensity and functional limitation. CONCLUSION: This study demonstrated the effectiveness of both protocols in terms of pain intensity and functional limitation caused by osteoarthritis.

The role of aquaporins in hearing function and dysfunction.

The inner ear is composed by tiny and complex structures that, together with peripheral and central auditory pathways, are responsible for hearing processing. However, not only the anatomy of the cochlea, its compartments and related structures are complex. The mechanisms involved in the regulation of homeostasis in the inner ear fluid, which determines the ionic gradient necessary for hearing and balancing sensory excitability, is an intricate phenomenon that involves several molecules. Among them, Aquaporins (AQP) play a significant role in this process. AQP are part of a family of small, integral membrane proteins that regulate different processes, including bidirectional water and ionic flow in the inner ear. Changes in the expression of these proteins are essential to auditory physiology and several pathophysiological processes in the inner ear. This review focuses on the role of AQP in health and disease of the auditory system.

Action of Hyaluronic Acid as a Damage-Associated Molecular Pattern Molecule and Its Function on the Treatment of Temporomandibular Disorders.

The temporomandibular joint is responsible for fundamental functions. However, mechanical overload or microtraumas can cause temporomandibular disorders (TMD). In addition to external factors, it is known that these conditions are involved in complex biological mechanisms, such as activation of the immune system, activation of the inflammatory process, and degradation of extracellular matrix (ECM) components. The ECM is a non-cellular three-dimensional macromolecular network; its most studied components is hyaluronic acid (HA). HA is naturally found in many tissues, and most of it has a high molecular weight. HA has attributed an essential role in the viscoelastic properties of the synovial fluid and other tissues. Additionally, it has been shown that HA molecules can contribute to other mechanisms in the processes of injury and healing. It has been speculated that the degradation product of high molecular weight HA in healthy tissues during injury, a low molecular weight HA, may act as damage-associated molecular patterns (DAMPs). DAMPs are multifunctional and structurally diverse molecules that play critical intracellular roles in the absence of injury or infection. However, after cellular damage or stress, these molecules promote the activation of the immune response. Fragments from the degradation of HA can also act as immune response activators. Low molecular weight HA would have the ability to act as a pro-inflammatory marker, promoting the activation and maturation of dendritic cells, the release of pro-inflammatory cytokines such as interleukin 1 beta (IL-1ß), and tumor necrosis factor α (TNF-α). It also increases the expression of chemokines and cell proliferation. Many of the pro-inflammatory effects of low molecular weight HA are attributed to its interactions with the activation of toll-like receptors (TLRs 2 and 4). In contrast, the high molecular weight HA found in healthy tissues would act as an anti-inflammatory, inhibiting cell growth and differentiation, decreasing the production of inflammatory cytokines, and reducing phagocytosis by macrophages. These anti-inflammatory effects are mainly attributed to the interaction of high-weight HA with the CD44 receptor. In this study, we review the action of the HA as a DAMP and its functions on pain control, more specifically in orofacial origin (e.g., TMD).