Icariin Improves Glucocorticoid Resistance in a Murine Model of Asthma with Depression Associated with Enhancement of GR Expression and Function.

Icariin, a flavonoid glycoside isolated from Epimedium brevicornum, exerts a variety of biological activities. However, its effects on depression-induced glucocorticoid resistance in asthma and the underlying mechanisms have not been elucidated. In this study, a murine model of asthma with depression was established by exposure to ovalbumin combined with chronic unpredictable mild stress, and icariin was given orally during ovalbumin challenge and chronic unpredictable mild stress exposure. Depression-like behaviors were assessed by the open field test, forced swim test, and tail suspension test. The characteristic features of allergic asthma, including airway hyperreactivity, histopathology, inflammatory cytokine levels in bronchoalveolar lavage fluid, and immunoglobulin E and corticosterone levels in serum, were examined. Following splenocyte isolation in vitro, the inhibitory effects of corticosterone on the proliferation and cytokine secretion of splenocytes, glucocorticoid receptor DNA-binding activity, and expression of p-glucocorticoid receptor s226, glucocorticoid receptor α, and p-p38 mitogen-activated protein kinase in splenocytes were determined. We found that icariin had limited effects on depression-like behaviors, however, it markedly suppressed airway hyperresponsiveness, inflammatory infiltration in lung tissues, levels of interleukin-4, interleukin-5, and interleukin-6 in bronchoalveolar lavage fluid, and immunoglobulin E in serum. Furthermore, icariin improved the inhibitory effects of corticosterone on lipopolysaccharide-stimulated splenocytes, increased the glucocorticoid receptor expression and glucocorticoid receptor DNA-binding activity, and inhibited the phosphorylation of glucocorticoid receptors S226 and p38 mitogen-activated protein kinase. Taken together, icariin improved glucocorticoid resistance in a murine model of asthma with depression associated with enhancement of glucocorticoid receptor function and glucocorticoid receptor expression, and its effects on the glucocorticoid receptor function were related to decreased phosphorylation of glucocorticoid receptors S226 and p38 mitogen-activated protein kinase.

Modified Si-Jun-Zi-Tang Attenuates Airway Inflammation in a Murine Model of Chronic Asthma by Inhibiting Teff Cells via the mTORC1 Pathway.

Background: Modified Si-Jun-Zi-Tang (MSJZT), a multi-herb formulation, is frequently used in traditional Chinese medicine for patients during the remission stage of asthma. However, the pharmacological basis underlying the effects of MSJZT on asthma has yet to be elucidated. This study aims at evaluating the anti-asthmatic effects of MSJZT and investigating its possible mechanism. Methods: A chronic murine model of asthma was established by sensitization and repeated challenge with ovalbumin (OVA) in female BALB/c mice, followed with oral administration of MSJZT during remission, and then mouse were re-challenged by OVA. The chemical profile of MSJZT was analyzed by high-performance liquid chromatography. The characteristic features of allergic asthma, including airway hyperreactivity, histopathology, cytokine levels (IL-4, -5, -13, -17, and INF-γ), T regulatory (Treg) lymphocytes (Foxp3+CD4+CD25+), and T effector (Teff) lymphocytes (Foxp3-CD25+CD4+) in bronchoalveolar lavage fluid (BALF), and downstream proteins of mTORC1/2 signaling pathway were examined. Results: MSJZT markedly suppressed airway hyper-responsiveness to aerosolized methacholine, and reduced levels of IL-4, IL-5, and IL-13 in the BALF. Histological studies showed that MSJZT significantly reduced inflammatory infiltration in lung tissues. The percentage and absolute number of Teff cells were suppressed to a remarkable level by MSJZT without affecting Treg cells. Furthermore, MSJZT effectively inhibited the mTORC1 activity, but exerted limited effects on mTORC2, as assessed by the phosphorylation of the mTORC1 and mTORC2 substrates, S6 ribosomal protein, p70 S6 kinase, mTOR S2481, and Akt, respectively. Conclusion: MSJZT attenuated chronic airway inflammation in a mouse model of asthma by inhibiting Teff cells, which occurred, at least in part, via modulation of the mTORC1 signaling pathway.

Effects of electroacupuncture at Zusanli (ST36) on inflammatory cytokines in a rat model of smoke-induced chronic obstructive pulmonary disease.

OBJECTIVE: Improvement in lung function was reported after acupuncture treatment of chronic obstructive pulmonary disease (COPD), but little is known about the underlying mechanisms. Because an immune response imbalance could be seen in COPD, we hypothesize that electroacupuncture (EA) may play a role in regulating inflammatory cytokines and contribute to lung protection in a rat model of smoke-induced COPD. METHODS: A COPD model using male Sprague-Dawley rats exposed to cigarette smoke was established. The rats were randomly divided into four groups (control, sham, COPD, and COPD plus EA), and COPD model was evaluated by measuring pulmonary pathological changes and lung function. EA was applied to the acupuncture point Zusanli (ST36) for 30 min/d for 14 d in sham and COPD rats. Bronchoalveolar lavage fluid (BALF) was used to measure levels of tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and malonaldehyde (MDA). RESULTS: Compared with the control rats, COPD rats had significant changes in lung resistance (RL) and lung compliance (CL) (both P<0.01), bronchi and bronchiole airway obstruction (P<0.01), and levels of MDA, TNF-α, and IL-1ß (P<0.01). There were no significant differences between the control and the sham groups. Compared with the COPD rats, the COPD plus EA rats had decreased RL and increased CL (both P<0.05), and reduced bronchi and bronchiole airway obstruction (P<0.05, P<0.01, respectively), while levels of TNF-α, IL-1ß, and MDA in BALF were lowered (P<0.05 and P<0.01, respectively). However, TNF-α and IL-1ß levels of the EA group rats remained higher than those of the control group (P<0.05). CONCLUSION: EA at ST36 can reduce lung injury in a COPD rat model, and beneficial effects may be related to down-regulation of inflammatory cytokines. The anti-inflammatory and antioxidant effects may prolong the clinical benefit of EA.

Acid sensing ion channel 1 in lateral hypothalamus contributes to breathing control.

Acid-sensing ion channels (ASICs) are present in neurons and may contribute to chemoreception. Among six subunits of ASICs, ASIC1 is mainly expressed in the central nervous system. Recently, multiple sites in the brain including the lateral hypothalamus (LH) have been found to be sensitive to extracellular acidification. Since LH contains orexin neurons and innervates the medulla respiratory center, we hypothesize that ASIC1 is expressed on the orexin neuron and contributes to acid-induced increase in respiratory drive. To test this hypothesis, we used double immunofluorescence to determine whether ASIC1 is expressed on orexin neurons in the LH, and assessed integrated phrenic nerve discharge (iPND) in intact rats in response to acidification of the LH. We found that ASIC1 was co-localized with orexinA in the LH. Microinjection of acidified artificial cerebrospinal fluid increased the amplitude of iPND by 70% (pH 7.4 v.s. pH 6.5:1.05±0.12 v.s. 1.70±0.10, n = 6, P<0.001) and increased the respiratory drive (peak amplitude of iPND/inspiratory time, PA/Ti) by 40% (1.10±0.23 v.s. 1.50±0.38, P<0.05). This stimulatory effect was abolished by blocking ASIC1 with a nonselective inhibitor (amiloride 10 mM), a selective inhibitor (PcTX1, 10 nM) or by damaging orexin neurons in the LH. Current results support our hypothesis that the orexin neuron in the LH can exert an excitation on respiration via ASIC1 during local acidosis. Since central acidification is involved in breathing dysfunction in a variety of pulmonary diseases, understanding its underlying mechanism may improve patient management.

Orexin-A and respiration in a rat model of smoke-induced chronic obstructive pulmonary disease.

1. Orexins are neuropeptides synthesized in the hypothalamus that regulate many physiological functions, including energy homeostasis, stress responses, sleep/wake states etc. It is now emerging that orexins may also regulate breathing, but little is known as to how they do this, particularly in chronic obstructive pulmonary disease (COPD). In the present study, we used a rat model of cigarette smoke-induced COPD to investigate orexin-A expression in the hypothalamus and medulla and its effect on respiration. 2. Sprague-Dawley rats were exposed to cigarette smoke (1 h twice daily) for 12 weeks. Lung function and pathological changes associated with inflammation and emphysema were determined to confirm the validity of the COPD model. 3. Hypothalamic and medullary orexin-A levels, as determined by radioimmunoassay, were higher in smoke-exposed than control rats. Furthermore, the expression of prepro-orexin (PPO) mRNA in the hypothalamus and orexin OX(1) receptor mRNA in the medulla, as determined by real-time quantitative polymerase chain reaction, was higher in smoke-exposed than control rats. 4. The number of orexin-A-positive neurons in the hypothalamus and OX(1) and OX(2) receptor-positive neurons in the ventrolateral medulla was higher in smoke-exposed than control rats. 5. Microinjection of orexin-A (1 µmol/L, 0.1 µL) into the pre-Bötzinger complex enhanced phrenic nerve discharge to a greater extent in smoke-exposed compared with control rats (61% vs 36%, respectively). 6. The findings of the present study demonstrate that the increased respiratory activity in smoke-exposed rats is due to an increase in orexin-A as well as upregulation of orexin receptors in the ventrolateral medulla.