It had been indicated in the previous studies that acupuncture relieved the excessive excitation of hypothalamic-pituitary-adrenal cortex axis (HPAA) function induced by stress stimulation. But the changes in glucocorticoid receptor (GR) induced by acupuncture have not been detected clearly. The objective of the study was to observe the impacts of acupuncture on the protein expressions of corticotrophin releasing hormone (CRH), adrenocorticotropic hormone receptor (ACTHR), and GR under the physiological and stress states. The results showed that under the stress state, acupuncture upregulated the protein expression of GR in the hippocampus, hypothalamic paraventricular nucleus (PVN), and pituitary gland, downregulated the protein expression of GR in the adrenal cortex, and obviously reduced the protein expressions of CRH and ACTHR. Under the physiological state, acupuncture promoted GR protein expression in the hippocampus and CRH protein expression in the hippocampus and PVN. The results explained that acupuncture regulated the stress reaction via promoting the combination of glucocorticoids (GC) with GR, and GR protein expression. The increase of GR protein expression induced feedback inhibition on the overexpression of CRH and ACTHR, likely decreased GC level, and caused the reduction of GR protein expression in the adrenal cortex.
The normal expression of glucocorticoid receptor (GR) plays an important role in maintaining the normal physiological condition in the body [
When the stressors arrive to the paraventricular nucleus of the hypothalamic paraventricular nucleus (PVN), corticotrophin releasing hormone (CRH) neurons synthesize and release CRH and transport it to the adenohypophysis. Afterward, CRH enables the adenohypophysis to secrete adrenocorticotropic hormone (ACTH). In blood circulation, ACTH acts on the adrenal cortex and accelerates the synthesis and the secretion of GC in the adrenal cortex. Being the negative feedback regulator, the ectogenic GC adjusts CRH secretion in the PVN through hypothalamic-pituitary-adrenal cortex axis (HPAA), inhibits the stress reaction, modifies the structure of the hippocampus and other limbic systems, and impacts awakening, cognitive, and emotional functions [
Acupuncture is a procedure in which fine needles are inserted into an individual at discrete points and then manipulated, with the intent of regulating HPAA function [
In this study, we discussed the impacts of acupuncture at different acupoints on GR expressions in the hippocampus, PVN, pituitary gland, and adrenal cortex of the rats induced by unpredictable chronic mild stress (UCMS) stimulation as well as the associated changes in the expressions of CRH and ACTHR so as to explore the acupoint specificity and the mechanism of acupuncture on the regulation of HPAA function.
Male Sprague-Dawley rats in 150–170 g were obtained from the Laboratory Animal Resources Center, National Institute for the Control of Pharmaceutical and Biological Products, Beijing (Certificate no. SCXK (jing) 2009–0017). These animals were individually caged on a 12 h light/dark cycle (lights on at 8:00 am, lights off at 8:00 pm) under controlled temperature (22 ± 1°C) and humidity (50% ± 5%) conditions. Standard rat chow and water were given ad libitum. Animals were allowed to acclimatize for seven days before the study. All experiment procedures comply with the guidelines of the “Principles of Laboratory Animal Care” (NIH publication no. 80-23, revised 1996) and the legislation of the People’s Republic of China for the use and care of laboratory animals. The experimental protocols were approved by the Animal Experimentation Ethics Committee of the Institute of Acupuncture and Moxibustion, China Academy of Chinese Medical Sciences. Efforts were made to minimize the number of animals used and the suffering of the experimental animals.
Fifty-eight of one hundred rats were recruited with the total score of 60~120 in the open field test [
Experimental protocol. There were 5 groups. N: the normal group, no acupuncture; NEA: the normal acupuncture group, acupuncture at Qimen (LR14) and Shenshu (BL23); M: UCMS group, no acupuncture; MNEA: the group of UCMS acupuncture at Sanyinjiao (SP6) and Zhubin (KI9); MEA: the group of UCMS acupuncture at Qimen (LR14) and Shenshu (BL23) group.
The open field test on all rats was conducted on the day before the study (−1st day) , the 21st day (after UCMS), and the 29th day (after treatment) in the study course. After the models of UCMS were established on the 21st day, the electroacupuncture (EA) treatment of 8 days was applied to bilateral SP6 and KI9 of rats in the MNEA group once daily for 30 min. For the MEA group, EA was applied to bilateral BL23 and LR14 following the same procedure and EA parameters as the MNEA group. For the NEA group, EA was applied to the same procedure as the MEA group. M group and N group in the EA groups with the inhaled anesthesia accepted during the treatment (Figure
Western blot analysis was performed as follows [
The antibodies used included the following: anti-CRH (Datashect, #10944-1-AP) (1 : 500), anti-ACTHR and anti-GR (Santa Cruz, #H-70 and #H-300) (1 : 1000), anti-
The statistical analysis was performed by using one-way analysis of variance (ANOVA) with software GraphPad Prism (California), and the data were expressed as means ± SEM. All results with
The open field test score and sucrose consumption. (a, b, and c) showed the normalized data of the horizontal, vertical, and along-the-line movement test on the −1st day, 21st day, and 29th day. (d) showed the normalized data of sucrose consumption detected on the 0th day, 22nd day, and 30th day. Normalized data [
The activity of the animals in the five groups was gradually decreased on the 21st day (after modeling) and on the 29th day (after treatment) as compared with that before modeling (on −1st day). After modeling, the horizontal, vertical, and the along-the-line activities in the open field test in M, MNEA, and MEA groups were all reduced obviously as compared with N and NEA groups (
The sucrose consumption was done on the 0th day (before modeling), on the 22nd day (after modeling), and on the 30th day (after acupuncture). After modeling, the results in M, MNEA, and MEA groups were different significantly as compared with N and NEA groups. After acupuncture, it was significantly reduced in M group, indicating the extremely significant differences as compared with N and NEA groups (
There are results that showed that the stress reduced sucrose consumption (a symptom of anhedonia and considered a depressive-like behavior in rats) and 8 days of acupuncture, especially the MEA treatment, reduced anhedonia and restored the sucrose consumption of M animals to the levels of control animals. This is a very significant behavioral finding and should be discussed and properly emphasized.
Effect of acupuncture on GR protein expression. GR protein expression was reduced obviously in the hippocampus, PVN, and pituitary gland and was dramatically increased in the adrenal cortex in M group as compared with N group. Compared with M group, GR protein expression was upregulated in the hippocampus, PVN, and pituitary gland and was downregulated in the adrenal cortex to different extents in MEAN and MNEA groups, but the results in MEA group were superior to MNEA group. The corresponding protein expression was increased obviously in the hippocampus in NEA group, which was significantly different as compared with N group. *
Western blot analysis showed that there was a protein expression of GR detected in the hippocampus, PVN, pituitary gland, and adrenal cortex. GR protein expression was increased or inhibited in response to acupuncture in NEA group. And it was decreased obviously in the hippocampus, PVN, and pituitary gland and increased obviously in the adrenal cortex in M group. Compared with the results in N group, GR protein expressions were either increased or decreased in the hippocampus, PVN, pituitary gland, and adrenal cortex by 95.99%, −23.61%, −5.2%, and 80.76% separately in NEA group. And the results were reduced significantly by 75.85%, 62.23%, and 28.04%, respectively, in the hippocampus, PVN, and pituitary gland, and the result was increased significantly by 265.01% in adrenal cortex in M group. Acupuncture induced the dual-directional regulation of GR protein expression in the hippocampus, PVN, pituitary gland, and adrenal cortex. Compared with M group, in MNEA and MEA groups, GR protein expressions were increased by 22.61% and 109.57%, 180.06% and 362.6%, and 52.9% and 246.38% separately in the hippocampus, PVN, and pituitary gland, but they were decreased by 34.82% and 88.34% in the adrenal cortex in MNEA and MEA groups. These data suggested that acupuncture promoted GR protein expression in the hippocampus, PVN, and pituitary gland but inhibited the expression in the adrenal cortex. The results in MEA were superior to MNEA group.
Effect of acupuncture on CRH protein expression. In M group, CRH protein expression was increased obviously in the hippocampus, PVN, and pituitary gland, which was significantly different as compared with N group. In MEA and MNEA groups, CRH protein expression was downregulated in hippocampus, PVN, and pituitary gland to different extents as compared with M group, but the results in MEA group were superior to MNEA group. The protein expression was increased significantly in the hippocampus and PVN in NEA group, which was different significantly as compared with N group. *
Western blot analysis showed that there was a detectable signal of CRH in the hippocampus, PVN, and pituitary gland. CRH protein expression was slightly increased in response to acupuncture in NEA group. And the remarkable increase of CRH protein expression was discovered in M group. Obviously, acupuncture downregulated CRH protein overexpression induced by UCMS stimulation. Compared with N group, CRH protein expressions were increased or inhibited in NEA group in the hippocampus, PVN, and pituitary gland by 109.03%, 67.31%, and −23.15% separately. And the results were increased significantly in the hippocampus, PVN, and pituitary gland in M group by 543.81%, 307.66%, and 89.18%. The UCMS-induced overexpression of CRH protein could be inhibited by acupuncture. Compared with M group, CRH protein expression was reduced remarkably in the hippocampus, PVN, and pituitary gland in MNEA and MEA groups by 36.91% and 86.95%, 20.86% and 53.67%, 24.64% and 65.03% successively. Those data indicated that acupuncture inhibited CRH protein expression in the hippocampus, PVN, and pituitary gland. The results in MEA group were superior to MNEA group.
Effect of acupuncture on ACTHR protein expression. ACTHR protein expression was increased obviously in the pituitary gland and adrenal cortex in M group as compared with N group. ACTHR protein expression was downregulated in the pituitary gland and adrenal cortex in MEA and MNEA groups to different extents as compared with M group, but the results in MEA group were superior to MNEA group. The difference was not significant in comparison between NEA and N groups. *
ACTHR is ACTH receptor. Western blot analysis showed that there was a detectable signal of ACTHR in the pituitary gland and adrenal cortex. ACTHR protein expression was slightly inhibited in response to acupuncture in NEA group. The remarkable increase of ACTHR protein expression was discovered in M group, and acupuncture downregulated obviously ACTHR protein overexpression induced by UCMS stimulation. Compared with N group, ACTHR protein expression was slightly inhibited in NEA group in the pituitary gland and adrenal cortex by 10.6% and 29.61% separately; ACTHR expression was increased significantly in the pituitary gland and adrenal cortex in M group by 95.78% and 123.79%. Compared with M group, ACTHR protein expression was reduced remarkably in pituitary gland and adrenal cortex in MNEA and MEA groups by 32.9% and 69.38% and 51.52% and 71.58% successively. Those data indicated that acupuncture inhibited ACTHR expression in the pituitary gland and adrenal cortex. The results in MEA group were superior to MNEA group.
The main results of the study were as follows.
After modeling, the horizontal, vertical, and along-the-line movements of the UCMS model rats were decreased apparently as compared with the normal model rats and the sucrose consumption was reduced significantly. These results were similar to the behavior changes of the chronic stress model rats in the previous studies [
The chronic stress induced the decrease of GR expression in many organs of the body and the increase of adrenal weight. Acupuncture relieved the overexcitation of HPAA function induced by chronic stress [
The adrenal cortex is the target organ of the synthesis and secretion of GC. The long-term chronic stress stimulation can cause the excessive secretion of GC in the adrenal cortex of the rat. This study observed that UCMS induced the significant decrease of GR protein expression in the hippocampus, PVN, and pituitary gland. Acupuncture upregulated GR protein expression in the hippocampus, PVN, and pituitary gland. Perhaps, through promoting the connection of high concentration GC with GR in the hippocampus, PVN, and pituitary gland, the function of GR was activated and the negative feedback regulation of GR was intensified on HPAA. The decrease of GC level caused the decrease of HPAA excitability. The decrease of GC level lowered the combination with GR in adrenal cortex; as a result, GR activity as well as its protein expression was decreased. The results above were caused by the inhibition of acupuncture on GR protein expression induced by UCMS stimulation in the adrenal cortex. It was indicated that acupuncture presented the dual-directional regulation on GR protein expression induced by UCMS stimulation, which was achieved via HPAA. Our preliminary work had observed the impacts of acupuncture on the peripheral blood CORT in the rats with the spinal cord injury [
Being the most superior hormone in HPAA, CRH launches the response of HPAA to the corresponding stressor. Simultaneously, CRH is also involved in the activation in the sympathetic-adrenal-medullary system. Therefore, it is recognized generally that CRH is one of the important initiating factors in the stress process. The increase of CRH secretion may be used as an objective index to reflect the body’s stress state [
Lian et al. had made the model fitting to explain the stress reaction impact on the interaction of GR and ACTHR gene with stress factors. The results indicated that GR and ACTHR gene variants were the contributing factors of the decline of psychological stress reaction, physiological stress reaction, and work ability. It showed that ACTHR expression was closely related to the stress reaction [
This study had detected the protein expression of ACTHR in the pituitary gland and adrenal cortex and observed that UCMS induced the increase of ACTHR protein expression in the pituitary gland and adrenal cortex, which was downregulated by acupuncture. Additionally, the effects were different on the different acupoints, which was likely related to the downregulation of acupuncture on CRH protein expression and the inhibition of ACTHR protein expression via HPAA.
This study observed that acupuncture impacts the protein expressions of CRH, ACTHR, and GR in the normal model rats. Except for the significant differences in the protein expressions of GR and CRH in the hippocampus and the protein expression of CRH in the PVN between the N group and NEA group, the differences in the rest aspects were not significant. The stress is the comprehensive reaction of the body to the stressor [
Acupuncture improved the behavior changes induced by UCMS stimulation, which was related to the promotion of acupuncture on the combination of GC and GR in the hippocampus, PVN, and pituitary gland, the activation of GR, and promotion of GR protein expression. The increase of GR protein expression induced the negative feedback inhibition on CRH protein expression, downregulated ACTHR overexpression in the pituitary gland and adrenal cortex, decreased GC level, and reduced GR activity in the adrenal cortex and the protein expression. Molecularly, it had been verified that the regulation of acupuncture on stress reaction was achieved via the regulation of HPAA function, and the effects were different at different acupoints.
Electroacupuncture
Hypothalamic paraventricular nucleus
Hypothalamic-pituitary-adrenal cortex axis
Unpredictable chronic mild stress
Glucocorticoid receptor
Corticotrophin releasing hormone
Adrenocorticotropic hormone receptor.
The authors declared that there is no conflict of interests regarding the publication of this paper.
Shao-Jun Wang conceived the whole procedure of the study, wrote the paper, and conducted the statistical analysis. Jiao-Jiao Zhang, Shao-Jun Wang, and Li-Li Qie carried out the experiment. All authors discussed and approved the final paper.
The authors hereby thank Lian-hong Tan for assistance with the experiment. The authors also thank Fang Wang for assistance in the paper preparation. This work was supported by Grant from the National Nature Science Foundation of China (81072856/H2718 and 81373724/H2718) to Shao-Jun Wang.