Prenatal urban traffic noise exposure impairs spatial learning and memory and reduces glucocorticoid receptor expression in the hippocampus of male rat offspring

Noise exposure-induced the cerebral alterations: From emerging evidence to antioxidant-mediated prevention and treatment

It's well acknowledged that noise exposure has become a major environmental risk factor of public health. The previous standpoint holds that the main harm of noise exposure is to cause hearing loss of human. However, in the past two decades a large number of studies have linked the noise exposure to various cerebral changes. In this review, we summarized that noise exposure led to cerebral changes through breaking the redox balance, inducing neuroinflammation and neuronal apoptosis and altering the neurotransmission in numerous brain areas, including cortex, thalamus, hippocampus, amygdala, striatum and cerebellum. Those cerebral changes finally result in a variety of disorders, such as tinnitus, anxiety, depression, cognitive impairment and motor dysfunction. Furthermore, we reviewed several antioxidants, such as resveratrol, vitamin C, curcumin, N-acetylcysteine and α-asarone, and highlighted their protective mechanisms against noise exposure, aiming to provide a promising strategy to prevent and treat noise exposure-induced diseases. Taken together, noise exposure induces various cerebral changes and further leads to disorders in the central nervous system, which can be ameliorated by the treatment with antioxidants.

Early-life noise exposure causes cognitive impairment in a sex-dependent manner by disrupting homeostasis of the microbiota-gut-brain axis

Epidemiological investigations show that noise exposure in early life is associated with health and cognitive impairment. The gut microbiome established in early life plays a crucial role in modulating developmental processes that subsequently affect brain function and behavior. Here, we examined the impact of early-life exposure to noise on cognitive function in adolescent rats by analyzing the gut microbiome and metabolome to elucidate the underlying mechanisms. Chronic noise exposure during early life led to cognitive deficits, hippocampal injury, and neuroinflammation. Early-life noise exposure showed significant difference on the composition and function of the gut microbiome throughout adolescence, subsequently causing axis-series changes in fecal short-chain fatty acid (SCFA) metabolism and serum metabolome profiles, as well as dysregulation of endothelial tight junction proteins, in both intestine and brain. We also observed sex-dependent effects of microbiota depletion on SCFA-related beneficial bacteria in adolescence. Experiments on microbiota transplantation and SCFA supplementation further confirmed the role of intestinal bacteria and related SCFAs in early-life noise-exposure-induced impairments in cognition, epithelial integrity, and neuroinflammation. Overall, these results highlight the homeostatic imbalance of microbiota-gut-brain axis as an important physiological response toward environmental noise during early life and reveals subtle differences in molecular signaling processes between male and female rats.

Sex differences in the vulnerability of the hippocampus to prenatal stress

Distressing events during pregnancy that engage activity of the body's endocrine stress response have been linked with later life cognitive deficits in offspring and associated with developmental changes in cognitive-controlling neural regions. Interestingly, prenatal stress (PS)-induced alterations have shown some sex specificity. Here, we review the literature of animal studies examining sex-specific effect of physical PS on the function and structure of the hippocampus as hippocampal impairments likely underlie PS-associated deficits in learning and memory. Furthermore, the connectivity between the hypothalamic-pituitary-adrenal (HPA) axis and the hippocampus as well as the heavy presence of glucocorticoid receptors (GRs) in the hippocampus suggests this structure plays an important role in modulation of activity within stress circuitry in a sex-specific pattern. We hope that better understanding of sex-specific, PS-related hippocampal impairment will assist in uncovering the molecular mechanisms behind sex-based risk factors in PS populations across development, and perhaps contribute to greater precision in management of cognitive disturbances in this vulnerable population.

Relationship Between Chronic Noise Exposure, Cognitive Impairment, and Degenerative Dementia: Update on the Experimental and Epidemiological Evidence and Prospects for Further Research

Degenerative dementia, of which Alzheimer's disease is the most common form, is characterized by the gradual deterioration of cognitive function. The events that trigger and promote degenerative dementia are not clear, and treatment options are limited. Experimental and epidemiological studies have revealed chronic noise exposure (CNE) as a potential risk factor for cognitive impairment and degenerative dementia. Experimental studies have indicated that long-term exposure to noise might accelerate cognitive dysfunction, amyloid-β deposition, and tau hyperphosphorylation in different brain regions such as the hippocampus and cortex. Epidemiological studies are increasingly examining the possible association between external noise exposure and dementia. In this review, we sought to construct a comprehensive summary of the relationship between CNE, cognitive dysfunction, and degenerative dementia. We also present the limitations of existing evidence as a guide regarding important prospects for future research.