ABSTRACT
The inner ear, the organ of equilibrium and hearing, has an extraordinarily complex and intricate arrangement. It contains highly specialized structures meticulously tailored to permit auditory processing. However, hearing also relies on both peripheral and central pathways responsible for the neuronal transmission of auditory information from the cochlea to the corresponding cortical regions. Understanding the anatomy and physiology of all components forming the auditory system is key to better comprehending the pathophysiology of each disease that causes hearing impairment. In this narrative review, the authors focus on the pathophysiology as well as on cellular and molecular mechanisms that lead to hearing loss in different neonatal infectious diseases. To accomplish this objective, the morphology and function of the main structures responsible for auditory processing and the immune response leading to hearing loss were explored. Altogether, this information permits the proper understanding of each infectious disease discussed.
ABSTRACT
Zika virus (ZIKV) is a strongly neurotropic flavivirus whose infection has been associated with microcephaly in neonates. However, clinical and experimental evidence indicate that ZIKV also affects the adult nervous system. In this regard, in vitro and in vivo studies have shown the ability of ZIKV to infect glial cells. In the central nervous system (CNS), glial cells are represented by astrocytes, microglia, and oligodendrocytes. In contrast, the peripheral nervous system (PNS) constitutes a highly heterogeneous group of cells (Schwann cells, satellite glial cells, and enteric glial cells) spread through the body. These cells are critical in both physiological and pathological conditions; as such, ZIKV-induced glial dysfunctions can be associated with the development and progression of neurological complications, including those related to the adult and aging brain. This review will address the effects of ZIKV infection on CNS and PNS glial cells, focusing on cellular and molecular mechanisms, including changes in the inflammatory response, oxidative stress, mitochondrial dysfunction, Ca2+ and glutamate homeostasis, neural metabolism, and neuron-glia communication. Of note, preventive and therapeutic strategies that focus on glial cells may emerge to delay and/or prevent the development of ZIKV-induced neurodegeneration and its consequences.
Subject(s)
Zika Virus Infection , Zika Virus , Humans , Zika Virus/physiology , Zika Virus Infection/complications , Zika Virus Infection/drug therapy , Zika Virus Infection/pathology , Neuroglia/metabolism , Central Nervous System/metabolism , Brain/metabolismABSTRACT
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.
Subject(s)
Aquaporins , Ear, Inner , Aquaporins/metabolism , Cochlea/metabolism , Ear, Inner/metabolism , Hearing/physiologyABSTRACT
Recent studies have suggested the neuroinvasive potential of severe acute respiratory coronavirus 2 (SARS-CoV-2). Notably, neuroinvasiveness might be involved in the pathophysiology of coronavirus disease 2019 (COVID-19). Some studies have demonstrated that synapse-connected routes may enable coronaviruses to access the central nervous system (CNS). However, evidence related to the presence of SARS-CoV-2 in the CNS, its direct impact on the CNS, and the contribution to symptoms suffered, remain sparse. Here, we review the current literature that indicates that SARS-CoV-2 can invade the nervous system. We also describe the neural circuits that are potentially affected by the virus and their possible role in the progress of COVID-19. In addition, we propose several strategies to understand, diagnose, and treat the neurological symptoms of COVID-19.
