Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by thunderclap headache and intracranial segmental vasoconstriction with or without signs of neurological deficit with a variable course that requires extensive study to prevent complications. The evidence shows RCVS is characterized by being multi-etiological; both the cause and the specific symptoms must be treated to reduce the chance of complications and recurrence. The timely identification of the RCVS and its etiology is the cornerstone of success in managing the disease. New data must be generated to have more efficient resources for the approach to this disease.

Late-onset Alzheimer’s disease (LOAD) is the most common form of Alzheimer’s disease (AD) and its risk increases exponentially with aging. The incidence of LOAD is reported to increase from 1 in every 1,000 people aged 37 to 65 in every 100 people aged 80 years and older. LOAD is extensively associated with aging and cognition decline. Several risk factors, including lifestyle choices, environmental factors, and medical ailments, affect cellular stress. The cellular stress can bring upon epigenetic alterations that affect cellular aging making the individual more susceptible to LOAD development. In due course the cellular stress resulting into epigenetic deregulation, oxidative burden, and genomic mutations leads to increased disease risk. Role of epigenetic and non-epigenetic mechanisms in accelerated cellular aging that are reported to increase the risk of LOAD development are summarized in this review. The underlying biological mechanism of cellular aging and the risk factors that could predispose cellular aging and LOAD development are also discussed in the upcoming sections.

Alzheimer’s disease (AD), which affects around twenty-seven million people globally, is an aging-related neurodegenerative condition characterized by the extracellular deposition of misfolded amyloid-β (Aβ) peptides and the intracellular production of neurofibrillary tangles (NFTs) AD results from the death of certain groups of neurons in the brain while appearing to have no impact on neighboring neurons. It is progressive and incurable. Therefore, the pathophysiology of afflicted populations and the development of intervention measures to stop neuronal cell death have been the main areas of attention for delineating therapeutic options. Proinflammatory cytokines are responsible for the stimulation of inflammatory responses and are mostly generated by activated macrophages in the brain. This review discusses how glial cells and innate and adaptive immune responses have a critical role in AD. It also provides information about microglial activation through the cluster of differentiation 40 (CD40) ligation and CD40L. CD40L ligation of microglial CD40 results in a large increase in tumor necrosis factor-α (TNF-α) production. Cultured cortical neuronal injury is caused when microglia are activated by CD40 ligation in the presence of interferon-γ (IFN-γ). This injury is significantly reduced by blocking the CD40 pathway or neutralising TNF-α. The management of AD would require integrating all available information about the innate and adaptive immune response affecting AD-related neuronal death.

The enteric nervous system (ENS) is considered by some authors as the second human brain, given its fundamental role in the regulation process of the central nervous system (CNS). Recent data from scientific literature have shown the existence of close bidirectional communication between the gut microbiota and the CNS, influencing physiological and biochemical changes related to cognition, emotion, behavior, anxiety, depressive symptoms, and stress. Furthermore, the existence of mediators in the connection between intestinal microorganisms and the CNS is evident, which includes neural networks, signaling, immune, and endocrine responses. However, the mechanisms underlying the effects of gut microbiota on brain processes still need to be determined. Therefore, understanding the relationship between the gut and neurodegenerative diseases (NDs) is essential for developing effective prophylactic alternatives and disease-modifying drugs that can prevent or slow the progression of such diseases. Herein, this short review aimed to present the most recent data from the scientific literature associated with the physiological, biochemical, and cellular aspects involved in the interrelationship between the gut-brain axis and NDs, discussing the role of the intestinal microbiota, and its relationship with CNS disorders.