Infiltrating T helper 17 cells in the paraventricular nucleus are pathogenic for stress-induced hypertension

Stress while lacking of control induces ventral hippocampal autophagic flux hyperactivity and a depression-like behavior

BACKGROUND

Stressed animals may perform depression-like behavior insomuch as stress-provoking blood-brain barrier (BBB) disruption, central immune activation, and autophagic flux changes. This study was undertaken to assess whether adult mice having (executive) vs. lacking (yoke) of behavioral control in otherwise equivalent stress magnitude condition, may display differences in their BBB integrity, ventral hippocampal (VH) interleukin-6 (IL-6) and autophagic flux level and VH-related depression-like behavior. To further understand the causative relation of enhanced autophagic flux and stress-primed depression-like behavior, we assessed the effects of bilateral intra-VH 3-methyladenine (3-MA), an autophagic flux inhibitor, infusion in stressed mice.

METHODS

Adult mice used had comparable genetic background and housing condition. Executive/yoke pairs of mice received a 10-day (1 h/day) footshock stressor regimen. Throughout the regimen, the ongoing footshock was terminated immediately contingent on the executive mouse', while irrelevant to the respective yoke mouse' voluntary behavior, or lasting for 7 s. Each dyad's cage-mate receiving no such regimen served as no stressor controls.

RESULTS

Yoke mice displayed disrupted BBB integrity (escalated Evans blue extravasation and decreased VH ZO-1, claudin-5 expression), increases in VH autophagic flux (increased LC3II/LC3I and decreased p62) and immobility duration in forced swimming test. Most of these indices remained unaltered in executive mice. Administration of 3-MA did not affect immobility duration in control mice, while prevented the increases in immobility duration in yoke mice.

CONCLUSIONS

(1) stress susceptibility may be determined by their differences in stress-coping results; (2) VH autophagic flux increase plays a permissive role in priming the stressed animals susceptible to exhibit depression-like behavior.

The timeline of neuronal and glial alterations in experimental obesity

In experimental models, hypothalamic dysfunction is a key component of the pathophysiology of diet-induced obesity. Early after the introduction of a high-fat diet, neurons, microglia, astrocytes and tanycytes of the mediobasal hypothalamus undergo structural and functional changes that impact caloric intake, energy expenditure and systemic glucose tolerance. Inflammation has emerged as a central component of this response, and as in other inflammatory conditions, there is a time course of events that determine the fate of distinct cells involved in the central regulation of whole-body energy homeostasis. Here, we review the work that identified key mechanisms, cellular players and temporal features of diet-induced hypothalamic abnormalities.

IL (Interleukin)-17A Acts in the Brain to Drive Neuroinflammation, Sympathetic Activation, and Hypertension

[Figure: see text].

Upregulation of Chemokines in the Paraventricular Nucleus of the Hypothalamus in Rats with Stress-Induced Hypertension

Background

The neuroinflammation of paraventricular nucleus (PVN) of the hypothalamus has been implicated in the development of hypertension. The promoted invasion of peripheral immune cells into PVN may be attributed to the upregulation of chemokines, then exacerbating neuroinflammation. We studied the expressions of chemokines, activation of microglial cells, and inflammatory mediators in PVN of rats with stress-induced hypertension (SIH).

Material/Methods

SIH was induced by electrical foot shock combined with noise for 2 h twice a day, at an interval of 4 h for 14 consecutive days. At the end of the 14th day, fresh PVN tissues were collected to measure the expressions of chemokines using the RayBiotech antibody array.

Results

We are the first to report that the expression of CXCL7 was extremely high in PVN of control rats, and was significantly lower in SIH rats. The expressions of CCL2 and CX3CL1 in PVN of SIH rats significantly exceeded those of control rats. The numbers of CX3CR1 (receptor of CX3CL1)-immunostained cells and oxycocin-42 (OX-42, marker of microglia)-positive cells increased in PVN of the SIH rats. The stress enhanced the protein expressions of proinflammatory cytokines IL-6 and IL-17 and reduced those of anti-inflammatory cytokines TGF-β and IL-10 in PVN.

Conclusions

In PVN of SIH rats, chronic stress induced neuroinflammation characterized by the activated microglia and upregulated proinflammatory cytokines. Expressions of chemokines CXCL7, CX3CL1, and CCL2 were altered. The causal link of chemokines to PVN neuroinflammation and hypertension remain to be determined.

Gut microbiota modulates stress-induced hypertension through the HPA axis

Stress is associated with an increased risk of hypertension, and the incidence of stress-related hypertension has risen rapidly in recent years; however, the underlying mechanisms remain elusive. Gut dysbiosis has been demonstrated to contribute to hypertension and hyperactivation of the hypothalamus-pituitary-adrenal (HPA) axis. Based on our previous findings showing the altered gut microbiota in the rats of stress-induced hypertension (SIH), the present study aims to investigate whether the stress-induced alteration in gut microbiota can lead to the dysfunction of the HPA axis which contributes to the development of SIH. SIH was developed in rats subjected to electric foot-shock combined with buzzer noise stressors. The gut microbiota of rats were deleted by administering an antibiotic cocktail containing ampicillin (1 g/L), vancomycin (500 mg/L), neomycin (1 g/L), and metronidazole (1 g/L) in drinking water. The serum levels of adrenocorticotropic hormone (ACTH) and corticosterone (CORT) were tested using enzyme-linked immunosorbent assay (ELISA). The mRNA expression of glucocorticoid receptor (GR) and corticotropin-releasing factor (CRF), CRFR1 and CRFR2 was detected by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The cellular protein expressions of corticotropin-releasing hormone (CRH), c-fos, and GR were examined by immunohistochemical staining. In the present study, SIH rats showed a hyperactive HPA axis as indicated by the increased CRH expression in the paraventricular nucleus (PVN) of the hypothalamus, the elevated serum ACTH or CORT concentrations, and increased adrenal gland index. The decreased GR expression and increased CRFR1 in the hypothalamus might underlie the hyperactivation of the HPA axis. The microbial deletion by antibiotics mitigated the hyperactivation of the HPA axis and attenuated the stress-induced elevation of blood pressure, indicating that the causal link of gut microbiota to SIH is mediated, at least in part, by the HPA axis activity. Our findings shed new light on the mechanisms underlying SIH.