Alterations in neuronal gene expression profiles in response to experimental demyelination and axonal transection

New Efforts to Demonstrate the Successful Use of TRH as a Therapeutic Agent

Thyrotropin-releasing hormone (TRH) is a tripeptide that regulates the neuroendocrine thyroid axis. Moreover, its widespread brain distribution has indicated that it is a relevant neuromodulator of behaviors such as feeding, arousal, anxiety, and locomotion. Importantly, it is also a neurotrophic peptide, and thus may halt the development of neurodegenerative diseases and improve mood-related disorders. Its neuroprotective actions on those pathologies and behaviors have been limited due to its poor intestinal and blood-brain barrier permeability, and because it is rapidly degraded by a serum enzyme. As new strategies such as TRH intranasal delivery emerge, a renewed interest in the peptide has arisen. TRH analogs have proven to be safe in animals and humans, while not inducing alterations in thyroid hormones' levels. In this review, we integrate research from different approaches, aiming to demonstrate the therapeutic effects of TRH, and to summarize new efforts to prolong and facilitate the peptide's actions to improve symptoms and the progression of several pathologies.

Shared Molecular Signatures Across Zika Virus Infection and Multiple Sclerosis Highlight AP-1 Transcription Factor as a Potential Player in Post-ZIKV MS-Like Phenotypes

Zika virus (ZIKV) is an arbovirus of the Flaviviridae genus that has rapidly disseminated from across the Pacific to the Americas. Robust evidence has indicated a crucial role of ZIKV in congenital virus syndrome, including neonatal microcephaly. Moreover, emerging evidence suggests an association between ZIKV infection and the development of an extensive spectrum of central nervous system inflammatory demyelinating diseases (CNS IDD), such as multiple sclerosis-like clinical phenotypes. However, the underlying mechanisms of host-pathogen neuro-immune interactions remain to be elucidated. This study aimed to identify common transcriptional signatures between multiple sclerosis (MS) and ZIKV infection to generate molecular interaction networks, thereby leading to the identification of deregulated processes and pathways, which could give an insight of these underlying molecular mechanisms. Our investigation included publicly available transcriptomic data from MS patients in either relapse or remission (RR-MS) and datasets of subjects acutely infected by ZIKV for both immune peripheral cells and central nervous system cells. The protein-protein interaction (PPI) analysis showed upregulated AP-1 transcription factors (JUN and FOS) among the top hub and bottleneck genes in RR-MS and ZIKV data. Gene enrichment analysis retrieved a remarkable presence of ontologies and pathways linked to oxidative stress responses, immune cell function, inflammation, interleukin signaling, cell division, and transcriptional regulation commonly enriched in both scenarios. Considering the recent findings concerning AP-1 function in immunological tolerance breakdown, regulation of inflammation, and its function as an oxidative stress sensor, we postulate that the ZIKV trigger may contribute as a boost for the activation of such AP-1-regulated mechanisms that could favor the development of MS-like phenotypes following ZIKV infection in a genetically susceptible individual.

Neuron-Oligodendrocyte Interactions in the Structure and Integrity of Axons

The myelination of axons by oligodendrocytes is a highly complex cell-to-cell interaction. Oligodendrocytes and axons have a reciprocal signaling relationship in which oligodendrocytes receive cues from axons that direct their myelination, and oligodendrocytes subsequently shape axonal structure and conduction. Oligodendrocytes are necessary for the maturation of excitatory domains on the axon including nodes of Ranvier, help buffer potassium, and support neuronal energy metabolism. Disruption of the oligodendrocyte-axon unit in traumatic injuries, Alzheimer's disease and demyelinating diseases such as multiple sclerosis results in axonal dysfunction and can culminate in neurodegeneration. In this review, we discuss the mechanisms by which demyelination and loss of oligodendrocytes compromise axons. We highlight the intra-axonal cascades initiated by demyelination that can result in irreversible axonal damage. Both the restoration of oligodendrocyte myelination or neuroprotective therapies targeting these intra-axonal cascades are likely to have therapeutic potential in disorders in which oligodendrocyte support of axons is disrupted.

Activating transcription factor 3, an early cellular adaptive responder in ischemia/reperfusion-induced injury

Recent studies have reported that ischemia/reperfusion (I/R) may act in the immune system where an exaggerated inflammatory response is initiated. With the activation of the immune system, damage-associated molecular patterns migrate and adhere to the I/R region, consequently inducing multiorgan injury. Emerging data indicate that upon I/R, stress-inducible proteins, including activating transcription factor 3 (ATF3), play essential roles in signaling during antiapoptotic, antimigration, and anti-inflammatory processes. Accumulating data suggest that ATF3 may be a potential target in I/R- or inflammation-induced organ dysfunction. This minireview focuses on the emerging evidence of the roles of ATF3 in multiple organs including the kidney, myocardium, and brain following I/R injury. In addition, this review addresses the role of ATF3 in chronic inflammation-induced pathophysiologies such as diabetes and atherosclerosis.

Activating transcription factor 3 and the nervous system

Activating transcription factor 3 (ATF3) belongs to the ATF/cyclic AMP responsive element binding family of transcription factors and is often described as an adaptive response gene whose activity is usually regulated by stressful stimuli. Although expressed in a number of splice variants and generally recognized as a transcriptional repressor, ATF3 has the ability to interact with a number of other transcription factors including c-Jun to form complexes which not only repress, but can also activate various genes. ATF3 expression is modulated mainly at the transcriptional level and has markedly different effects in different types of cell. The levels of ATF3 mRNA and protein are normally very low in neurons and glia but their expression is rapidly upregulated in response to injury. ATF3 expression in neurons is closely linked to their survival and the regeneration of their axons following axotomy, and that in peripheral nerves correlates with the generation of a Schwann cell phenotype that is conducive to axonal regeneration. ATF3 is also induced by Toll-like receptor (TLR) ligands but acts as a negative regulator of TLR signaling, suppressing the innate immune response which is involved in immuno-surveillance and can enhance or reduce the survival of injured neurons and promote the regeneration of their axons.