Cardiac GR Mediates the Diurnal Rhythm in Ventricular Arrhythmia Susceptibility.

BACKGROUND: Ventricular arrhythmias (VAs) demonstrate a prominent day-night rhythm, commonly presenting in the morning. Transcriptional rhythms in cardiac ion channels accompany this phenomenon, but their role in the morning vulnerability to VAs and the underlying mechanisms are not understood. We investigated the recruitment of transcription factors that underpins transcriptional rhythms in ion channels and assessed whether this mechanism was pertinent to the heart's intrinsic diurnal susceptibility to VA. METHODS AND RESULTS: Assay for transposase-accessible chromatin with sequencing performed in mouse ventricular myocyte nuclei at the beginning of the animals' inactive (ZT0) and active (ZT12) periods revealed differentially accessible chromatin sites annotating to rhythmically transcribed ion channels and distinct transcription factor binding motifs in these regions. Notably, motif enrichment for the glucocorticoid receptor (GR; transcriptional effector of corticosteroid signaling) in open chromatin profiles at ZT12 was observed, in line with the well-recognized ZT12 peak in circulating corticosteroids. Molecular, electrophysiological, and in silico biophysically-detailed modeling approaches demonstrated GR-mediated transcriptional control of ion channels (including Scn5a underlying the cardiac Na+ current, Kcnh2 underlying the rapid delayed rectifier K+ current, and Gja1 responsible for electrical coupling) and their contribution to the day-night rhythm in the vulnerability to VA. Strikingly, both pharmacological block of GR and cardiomyocyte-specific genetic knockout of GR blunted or abolished ion channel expression rhythms and abolished the ZT12 susceptibility to pacing-induced VA in isolated hearts. CONCLUSIONS: Our study registers a day-night rhythm in chromatin accessibility that accompanies diurnal cycles in ventricular myocytes. Our approaches directly implicate the cardiac GR in the myocyte excitability rhythm and mechanistically link the ZT12 surge in glucocorticoids to intrinsic VA propensity at this time.

Increased Hippocampal Glucocorticoid Receptor Expression and Reduced Anxiety-Like Behavior Following Tuina in a Rat Model With Allergic Airway Inflammation.

OBJECTIVE: This study aimed to explore the influence mechanism of Tuina on anxiety-like behavior in immature rats with allergic airway inflammation (AAI). METHODS: A total of 27 Sprague-Dawley male rats (aged ∼5 weeks) were divided randomly into control, AAI, and AAI with Tuina groups (9 rats per group). The anxiety-like behavior was assessed by an open field test and elevated plus-maze test. Allergic airway inflammation was assessed based on the pathological score of the lung, plasma ovalbumin-specific immunoglobulin E, interleukin 4, interleukin 5, and tumor necrosis factor-alpha levels. Glucocorticoid receptor (GR) messenger RNA and protein expression in the hippocampus and lung were detected by polymerase chain reaction and immunohistochemistry, respectively. Meanwhile, corticotropin-releasing hormone (CRH) messenger RNA in the hypothalamus, the plasma levels of adrenocorticotropic hormone and corticosterone were also determined respectively by polymerase chain reaction and enzyme-linked immunosorbent assay for hypothalamic-pituitary-adrenal axis (HPA) function. RESULTS: The AAI group had obvious anxiety-like behavior and hyperactive HPA axis, along with decreased GR expression in the hippocampus and lung. Following Tuina, AAI and the anxiety-like behavior were efficiently reduced, and the hyperactivity of HPA axis was efficiently inhibited, along with enhanced GR expression in the hippocampus and lung. CONCLUSION: Glucocorticoid receptor expression in the hippocampus and lung was enhanced, and anxiety-like behavior was reduced following Tuina in rats with AAI.

[The regulative effects of Aspergillus fumigatus on expression of glucocorticoid receptor in asthmatic rats].

Objective: To study the regulative effects of Aspergillus fumigatus (A.fumigatus) on expression of glucocorticoid receptor (GCR) in asthmatic rats. Methods: Wistar rats were randomly divided into 4 groups: a normal control group (UC), a normal control with A. fumigatus group (UC+ AF), an OVA group (OVA), and an OVA with A. fumigatus group (OVA+ AF). OVA and OVA+ AF groups were sensitized and challenged with OVA to establish asthmatic models. UC and UC+ AF groups were given normal saline as controls. After the last challenge, OVA+ AF and UC+ AF groups were given A. fumigatus spores intranasally. Airway hyper-responsiveness, eosinophil percentage (Eos%) and serum IgE level were measured to confirm the establishment of asthmatic models. Sections of pulmonary tissue were stained with hematoxylin-eosin (HE) and the expression of GCR mRNA and protein in lung tissues were measured by qRT-PCR and Western blot. Lung tissues and blood were plated on the potato dextrose agar(PDA)medium and cultured for 24 h to measure the number of colony. Results: The Penh value, Eos% in BALF and serum IgE level in UC+ AF group were slightly higher than those in the UC group (all the P>0.05). The Penh value, Eos% in BALF and serum IgE level in OVA group were significantly higher than those in the UC group (all the P<0.05). The Penh value in OVA+ AF group was significantly increased compared with the OVA group at the concentration of 25 g/L and 50 g/L of methacholine (all the P>0.05). Pulmonary histology revealed that both OVA group and OVA+ AF group showed high levels of inflammatory cell infiltration of bronchus and lung vessels, interstitial edema and smooth muscle thickening, while the UC and UC + AF groups were normal. Compared with the UC group, the expressions of GCR mRNA and protein in UC+ AF group and OVA group were decreased significantly (GCR mRNA in UC, UC+ AF and OVA group were 0.93±0.15, 0.65±0.10, 0.72±0.22, respectively, F=10.744, P<0.01; GCR protein in UC, UC+ AF and OVA group were 100±0, 89±8, 82±15, respectively, F=18.939, P<0.01). The expressions of GCR mRNA and protein in OVA+ AF group were further decreased than those in OVA group (GCR mRNA: OVA group: 0.72±0.22 vs OVA+ AF group: 0.52±0.08, t=2.462, P<0.05; GCR protein: OVA group: 81.88±15.41 vs OVA+ AF group: 59.09±7.60, t=2.997, P<0.05). The ratio of A. fumigatus colonization in lung tissues in OVA+ AF group (4/8) was higher than the UC+ AF group (0/8). Conclusion:A. fumigatus exposure can down-regulate the expression of GCR in the lung, which maybe an important mechanism of steroid-resistant asthma.

Efficacy of suspended moxibustion stimulating Shenshu (BL23) and Guanyuan (CV4) on the amygdala-HPA axis in rats with kidney-deficiency symptom pattern induced by hydrocortisone.

OBJECTIVE: To investigated the effects of suspended moxibustion stimulating Shenshu (BL23) and Guanyuan (CV4) acupoints on the amygdala and HPA axis in our rat model and elucidated the possible molecular mechanisms of moxibustion on kidney- deficiency symptom pattern (KYDS). METHODS: Sixty male Sprague Dawley rats were randomly divided into a control group ( 12) and an experimental group ( 48). Rats in the experimental group were given intramuscular injections of hydrocortisone to establish a KYDS model. The 48 rats successfully modeled were then randomly divided into a model group (model, 12), a carbenoxolone intraperitoneal injection group (CBX, 12), a moxibustion group (moxi, 12), and a moxi + CBX group ( 12). In the moxi, the Shenshu (BL23) and Guanyuan (CV 4) acupoints were treated with moxibustion for 14 d. After treatment, measures were taken of serum levels of corticosterone (CORT), adrenocorticotropic hormone (ACTH), and corticotropin-releasing hormone (CRH). The expression of mineralocorticoid receptors (MRs), glucocorticoid receptors (GRs), 11beta-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), CRH, and ACTH in the rats' amygdala, hypothalamus, or pituitary (as appropriate) was detected. Data were analyzed using one-way analysis of variance. RESULTS: Compared with those of the control group, the serum levels of CRH, ACTH, and CORT; the mRNA and protein expressions of MR, GR, and 11ß-HSD1 in the amygdala; the mRNA and protein expressions of 11ß-HSD1 in the hypothalamus; the CRH mRNA expression in the amygdala and hypothalamus; and the ACTH mRNA expression in the pituitary of the rats in the model group were all significantly decreased (0.05 or 0.01). After treatment with moxibustion, all the aforementioned observation indices except for 11ß-HSD1 mRNA expression were ameliorated compared with those in the model group (0.05 or 0.01). CONCLUSIONS: Suspended moxibustion can effectively improve the serum levels of ACTH, CRH, and CORT and can up-regulate the mRNA and protein expressions of MR, GR, 11ß-HSD1, CRH, and ACTH in the amygdala and hypothalamus of KYDS rats. This may be one of the molecular mechanisms with which moxibustion alleviates KYDS.

Glucocorticoids in the Treatment of Glomerular Diseases: Pitfalls and Pearls.

Glucocorticoids exert anti-inflammatory and immunosuppressive activities by genomic and nongenomic effects. The classic genomic effects are mediated by cytosolic glucocorticoid receptors that can upregulate the expression of anti-inflammatory proteins in the nucleus (transactivation) or repress the translocation of proinflammatory transcription factors from the cytosol into the nucleus (transrepression). The nongenomic effects are probably mediated by membrane glucocorticoid receptors. Glucocorticoid receptors are expressed also in podocytes and experimental data suggest that glucocorticoids may protect from podocyte injury. Glucocorticoids have a low therapeutic index and may exert a number of time-dependent and dose-dependent side effects. Measures to prevent or attenuate side effects include single-morning administration of short-acting glucocorticoids, dietetic counseling, increasing physical activity, frequent monitoring, and adapting the doses to the clinical conditions of the patient. Synthetic glucocorticoids, either given alone or in combination with other immunosuppressive drugs, are still the cornerstone therapy in multiple glomerular disorders. However, glucocorticoids are of little benefit in C3 glomerulopathy and may be potentially deleterious in patients with maladaptive focal glomerulosclerosis. Their efficacy depends not only on the type and severity of glomerular disease, but also on the timeliness of administration, the dosage, and the duration of treatment. Whereas an excessive use of glucocorticoids can be responsible for severe toxicity, too low a dosage and too short duration of glucocorticoid treatment can result in false steroid resistance.