Astroglial Connexins in Neurological and Neuropsychological Disorders and Radiation Exposure

Microglia in radiation-induced brain injury: Cellular and molecular mechanisms and therapeutic potential

BACKGROUND

Radiation-induced brain injury is a neurological condition resulting from radiotherapy for malignant tumors, with its underlying pathogenesis still not fully understood. Current hypotheses suggest that immune cells, particularly the excessive activation of microglia in the central nervous system and the migration of peripheral immune cells into the brain, play a critical role in initiating and progressing the injury. This review aimed to summarize the latest advances in the cellular and molecular mechanisms and the therapeutic potential of microglia in radiation-induced brain injury.

METHODS

This article critically examines recent developments in understanding the role of microglia activation in radiation-induced brain injury. It elucidates associated mechanisms and explores novel research pathways and therapeutic options for managing this condition.

RESULTS

Post-irradiation, activated microglia release numerous inflammatory factors, exacerbating neuroinflammation and facilitating the onset and progression of radiation-induced damage. Therefore, controlling microglial activation and suppressing the secretion of related inflammatory factors is crucial for preventing radiation-induced brain injury. While microglial activation is a primary factor in neuroinflammation, the precise mechanisms by which radiation prompts this activation remain elusive. Multiple signaling pathways likely contribute to microglial activation and the progression of radiation-induced brain injury.

CONCLUSIONS

The intricate microenvironment and molecular mechanisms associated with radiation-induced brain injury underscore the crucial roles of immune cells in its onset and progression. By investigating the interplay among microglia, neurons, astrocytes, and peripheral immune cells, potential strategies emerge to mitigate microglial activation, reduce the release of inflammatory agents, and impede the entry of peripheral immune cells into the brain.

Gap Junctions or Hemichannel-Dependent and Independent Roles of Connexins in Fibrosis, Epithelial-Mesenchymal Transitions, and Wound Healing

Fibrosis initially appears as a normal response to damage, where activated fibroblasts produce large amounts of the extracellular matrix (ECM) during the wound healing process to assist in the repair of injured tissue. However, the excessive accumulation of the ECM, unresolved by remodeling mechanisms, leads to organ dysfunction. Connexins, a family of transmembrane channel proteins, are widely recognized for their major roles in fibrosis, the epithelial-mesenchymal transition (EMT), and wound healing. Efforts have been made in recent years to identify novel mediators and targets for this regulation. Connexins form gap junctions and hemichannels, mediating communications between neighboring cells and inside and outside of cells, respectively. Recent evidence suggests that connexins, beyond forming channels, possess channel-independent functions in fibrosis, the EMT, and wound healing. One crucial channel-independent function is their role as the primary functional component for cell adhesion. Other channel-independent functions of connexins involve their roles in mitochondria and exosomes. This review summarizes the latest advances in the channel-dependent and independent roles of connexins in fibrosis, the EMT, and wound healing, with a particular focus on eye diseases, emphasizing their potential as novel, promising therapeutic targets.

Connexins Signatures of the Neurovascular Unit and Their Physio-Pathological Functions

Central nervous system (CNS) homeostasis is closely linked to the delicate balance of the microenvironment in which different cellular components of the neurovascular unit (NVU) coexist. Intercellular communication plays a pivotal role in exchanges of signaling molecules and mediators essential for survival functions, as well as in the removal of disturbing elements that can lead to related pathologies. The specific signatures of connexins (Cxs), proteins which form either gap junctions (GJs) or hemichannels (HCs), represent the biological substrate of the pathophysiological balance. Connexin 43 (Cx43) is undoubtedly one of the most important factors in glia–neuro–vascular crosstalk. Herein, Cxs signatures of every NVU component are highlighted and their critical influence on functional processes in healthy and pathological conditions of nervous microenvironment is reviewed.

Height, weight, and cardiovascular effects of stimulants on children with brain tumors

INTRODUCTION

Children with brain tumors may develop inattention, slow processing, and hypersomnia. Stimulant medications improve these problems, but their effect on growth, heart rate, and blood pressure (BP) are inadequately explored.

PROCEDURE

We retrospectively studied children with brain tumors treated at our institution that had data available for 1 year pre and 2 years on stimulant treatment. Tumor location, gender, radiation treatment (RT), age at RT, drug type, and hormone therapy were variables of interest.

RESULTS

We identified 65 children (35 males) that fulfilled eligibility criteria. Focal RT was utilized in 58; 11 additionally had whole brain RT; and seven received no RT. Thirty were treated for hypersomnia and inattention, eight for hypersomnia alone, and rest for inattention. Modafinil was the first drug in 18 (27.7%), and methylphenidate in the others. Forty-seven (72.3%), 45 (69.2%), and 49 (75.4%) were on thyroxine, cortisone, and growth hormones, respectively. There was no difference in pre- and post-stimulant body mass index (BMI), heart rate, and BP. There was also no difference between modafinil and methylphenidate groups. Rate of height acquisition slowed on stimulants (P = .0096). Thyroxine treatment correlated with increase in BMI after stimulants (P = .04). Younger age (P = .0003) and higher prestimulant BMI (P = .0063) correlated with increased heart rate on stimulants, while higher age at RT (P =.016) correlated with elevated systolic BP on stimulants. No associations were found with height acquisition and diastolic BP.

CONCLUSION

Stimulants are well tolerated by children with brain tumors that are appropriately managed for endocrine deficiencies, but may reduce the trajectory of height attainment.