Effects of adrenergic agents on stress-induced brain microstructural and immunochemical changes in adult male Wistar rats

Preventive effects of melatonin on periodontal tissue destruction due to psychological stress in rats with experimentally induced periodontitis

OBJECTIVE AND BACKGROUND

Psychological stress is a potential modifiable environmental risk factor causally related to the exacerbation of periodontitis and other chronic inflammatory diseases. This animal study aimed to investigate comprehensively the preventive efficacy of systemic melatonin administration on the possible effects of restraint stress on the periodontal structures of rats with periodontitis.

METHODS

Forty-eight male Sprague Dawley rats were randomly divided into six groups: control, restraint stress (S), S-melatonin (S-Mel), experimental periodontitis (Ep), S-Ep, and S-Ep-Mel. Periodontitis was induced by placing a 3.0 silk suture in a sub-paramarginal position around the cervix of the right and left lower first molars of the rats and keeping the suture in place for 5 weeks. Restraint stress was applied simultaneously by ligation. Melatonin and carriers were administered to the control, S, Ep, and S-Ep groups intraperitoneally (10 mg/body weight/day, 14 days) starting on day 21 following ligation and subjection to restraint stress. An open field test was performed on all groups on day 35 of the study. Periodontal bone loss was measured via histological sections. Histomorphometric and immunohistochemical (RANKL and OPG) evaluations were performed on right mandibular tissue samples and biochemical (TOS (total oxidant status), TAS (total antioxidant status), OSI (oxidative stress index), IL-1β, IL-10, and IL-1β/IL-10) evaluations were performed on left mandibular tissue samples.

RESULTS

Melatonin significantly limited serum corticosterone elevation related to restraint stress (p < .05). Restraint stress aggravated alveolar bone loss in rats with periodontitis, while systemic melatonin administration significantly reduced stress-related periodontal bone loss. According to the biochemical analyses, melatonin significantly lowered IL-1β/IL-10, OSI (TOS/TAS), and RANKL/OPG rates, which were significantly elevated in the S-Ep group.

CONCLUSION

Melatonin can significantly prevent the limited destructive effects of stress on periodontal tissues by suppressing RANKL-related osteoclastogenesis and oxidative stress.

Dopamine receptors of the rodent fastigial nucleus support skilled reaching for goal-directed action

The dopaminergic (DA) system regulates both motor function, and learning and memory. The cerebellum supports motor control and the acquisition of procedural memories, including goal-directed behavior, and is subjected to DA control. Its fastigial nucleus (FN) controls and interprets body motion through space. The expression of dopamine receptors has been reported in the deep cerebellar nuclei of mice. However, the presence of dopamine D1-like (D1R) and D2-like (D2R) receptors in the rat FN has not yet been verified. In this study, we first confirmed that DA receptors are expressed in the FN of adult rats and then targeted these receptors to explore to what extent the FN modulates goal-directed behavior. Immunohistochemical assessment revealed expression of both D1R and D2R receptors in the FN, whereby the medial lateral FN exhibited higher receptor expression compared to the other FN subfields. Bilateral treatment of the FN with a D1R antagonist, prior to a goal-directed pellet-reaching task, significantly impaired task acquisition and decreased task engagement. D2R antagonism only reduced late performance post-acquisition. Once task acquisition had occurred, D1R antagonism had no effect on successful reaching, although it significantly decreased reaching speed, task engagement, and promoted errors. Motor coordination and ambulation were, however, unaffected as neither D1R nor D2R antagonism altered rotarod latencies or distance and velocity in an open field. Taken together, these results not only reveal a novel role for the FN in goal-directed skilled reaching, but also show that D1R expressed in FN regulate this process by modulating motivation for action.

Effect of propranolol on temporomandibular joint pain in repeatedly stressed rats

Stress substantially increases the risk of developing painful temporomandibular disorders (TMDs) by influencing the release of endogenous catecholamines. Propranolol, an antagonist of β-adrenergic receptors, has shown potential in alleviating TMD-associated pain, particularly when the level of catecholamines is elevated. The aim of this study was to explore whether intra-articular propranolol administration is effective in diminishing temporomandibular joint (TMJ) pain during repeated stress situations. Additionally, we investigated the effect of repeated stress on the expression of genes encoding β-adrenoceptors in the trigeminal ganglion. In the present study, rats were exposed to a stress protocol induced by sound, then to the administration of formalin in the TMJ (to elicit a nociceptive response), followed immediately afterward by different doses of propranolol, after which the analgesic response to propranolol was evaluated. We also assessed the levels of beta-1 and beta-2 adrenergic receptor mRNAs (Adrb1 and Adrb2, respectively) using reverse transcription-quantitative PCR (RT-qPCR). Our findings revealed that propranolol administration reduces formalin-induced TMJ nociception more effectively in stressed rats than in non-stressed rats. Furthermore, repeated stress decreases the expression of the Adrb2 gene within the trigeminal ganglion. The findings of this study are noteworthy as they suggest that individuals with a chronic stress history might find potential benefits from β-blockers in TMD treatment.

Low-frequency transcranial magnetic stimulation protects cognition in mice with chronic unpredictable mild stress through autophagy regulation

Although transcranial magnetic stimulation (TMS) has been approved for the treatment of major depression, few studies have analyzed the ability of low-frequency TMS (LF-TMS) to treat depressive symptoms. Our study confirmed that LF-TMS protects the cognitive function,which can play a certain reference role in the future clinical treatment. The effectiveness of high-frequency TMS therapy has been well documented. However, the use of low-frequency TMS (LF-TMS) in the treatment of depression is rarely reported. This study aims to evaluate whether LF-TMS can reverse depression-induced cognitive impairment. We created a mouse model of depression using the chronic unpredictable mild stress (CUMS) paradigm. Male C57BL/6J mice,6-8 weeks old,were randomly divided into four groups: a CON (control) group, a CUMS group, a CUMS+LF-TMS group, and a CUMS+LF-TMS+RAP (rapamycin) group. The CUMS was maintained for 28 days. LF-TMS (1 Hz) and Rap were administered for 28 days from the first day of CUMS. The mice in all groups except the control demonstrated evidence of anhedonia, anxiety, and cognitive decline on behavioral tests during the four weeks of CUMS.All the experiments were carried out under a 12-h light/dark cycle (lights on at 7 a.m.) except for the dark/light cycle reversal stimulation of CUMS. LF-TMS at 20 Mt, 1 Hz for 1 min alleviated damage to spatial cognition and synaptic plasticity in the hippocampus. Western blot analysis showed that LF-TMS reduced the down-regulation of autophagy signals in the CUMS+LF-TMS group, and enhanced the expression of synaptic plasticity-related factors, thereby improving the spatial cognitive impairment resulting from the CUMS. We concluded that LF-TMS can effectively relieve depressive behavior and cognitive dysfunction in mice subjected to CUMS by regulating autophagy signals and synaptic proteins.

The neuroprotective properties and therapeutic potential of epidermal neural crest stem cells transplantation in a rat model of vascular dementia

INTRODUCTION

The incidence rate of senile dementia is rising, and there is no definite cure for it yet. Cell therapy, as a new investigational approach, has shown promising results. Hair bulges with abundant easily accessible neural stem cells permit autologous implantation in irreversible neurodegenerative disorders.

METHODS

Fifty rats were randomly divided into 5 groups of control, sham-operation, two-common carotid vessel-occlusion rats that received vehicle (2VO + V), 2VO rats that received 1 × 10⁶ epidermal stem cells (2VO + ESC1), and 2VO rats that received 2.5 × 10⁶ epidermal stem cells (2VO + ESC2) in 300 µl PBS intravenously on days 4, 9, and 14 after surgery. The epidermal neural crest stem cells (EPI-NCSCs) were isolated from hair follicles of rat whiskers. The open-field, passive avoidance, and Morris water maze were used as behavioral tests. The basal-synaptic transmission, long-term potentiation (LTP), and short-term synaptic plasticity were evaluated by field-potential recording of the CA1 hippocampal area.

RESULTS

30 days after the first transplantation in the 2VO + ESC1 group, functional recovery was prominent in anxiety and fear memory compared to the 2VO + ESC2 group, while LTP induction was recovered in both groups of grafted animals without improvement in basal synaptic transmission. These positive recoveries may be related to the release of different neurotrophic factors from grafted cells that can stimulate endogenous neurogenesis and synaptic plasticity.

CONCLUSIONS

Our results showed that EPI-NCSCs implantation could rescue LTP and cognitive disability in 2VO rats, while transplantation of 1 million cells showed better performance relative to 2.5 million cells.

Effect of chronically electric foot shock stress on spatial memory and hippocampal blood brain barrier permeability

Maintaining blood-brain barrier (BBB) contributes critically to preserving normal brain functions. According to the available evidence, intense or chronic exposure to stress would potentially affect different brain structures, such as the hippocampus, negatively. The purpose of this study was to define the relationship between the BBB permeability of the hippocampus and the performance of spatial learning and memory under chronically electric foot shock stress. Sixteen rats were divided into the control and stress groups equally. Animals in the stress group were exposed to foot shock (1 mA, 1 Hz) for 10-s duration every 60 s (1 h/day) for 10 consecutive days. The anxiety-related behavior, spatial learning, and memory were assessed by an Open Field (OF) and the Morris Water Maze (MWM) respectively. The hippocampal BBB permeability was determined by Evans blue penetration assay. Our results demonstrated that the stress model not only increased locomotor activities in the OF test but reduced spatial learning and memory in MWM. Moreover, these effects coincided with a significant increase in hippocampal BBB permeability. In sum, the stress model can be used in future studies focusing on the relationship between stress and BBB permeability of the hippocampus.

Antinociceptive and anti-inflammatory activities of Copaifera pubiflora Benth oleoresin and its major metabolite ent-hardwickiic acid

ETHNOPHARMACOLOGICAL RELEVANCE

Copaifera species folkloric names are "copaíbas, copaibeiras, copaívas or oil stick", which are widely used in Brazilian folk medicine. Among all ethnopharmacological applications described for Copaifera spp oleoresins, their anti-inflammatory effect stands out. However, the knowledge of anti-inflammatory and antinociceptive properties of Copaifera pubiflora Benth is scarce.

AIM OF THE STUDY

To investigate the cytotoxic, anti-inflammatory, and antinociceptive activities of C. pubiflora oleoresin (CPO), and its major compound ent-hardwickiic acid (HA).

MATERIAL AND METHODS

The phosphatase assay was used to evaluate the cytotoxicity of CPO and HA in three different cell lines. CPO and HA doses of 1, 3, and 10 mg/kg were employed in the biological assays. The assessment of motor activity was performed using open-field and rotarod tests. Anti-inflammatory activity of CPO and HA was assessed through luciferase assay, measurement of INF-γ, IL-1β, IL-6, IL-10, and TNF-α in a multi-spot system with the immortalized cell line THP-1, zymosan-induced arthritis, and carrageenan-induced paw edema. Acetic acid-induced abdominal writhing and formalin tests were undertaken to evaluate the antinociceptive potential of CPO and HA. In addition, the evaluation using carrageenan was performed to investigate the effect of CPO in pain intensity to a mechanical stimulus (mechanical hyperalgesia), using the von Frey filaments. A tail-flick test was used to evaluate possible central CPO and HA actions.

RESULTS

In the cytotoxicity evaluation, CPO and HA were not cytotoxic to the cell lines tested. CPO and HA (10 mg/kg) did not affect animals' locomotor capacity in both open-field and rotarod tests. In the luciferase assay, CPO and HA significantly reduced luciferase activity (p < 0.05). This reduction indicates a decrease in NF-κB activity. HA and CPO decreased INF-γ, IL-1β, IL-6, IL-10, and TNF-α at 24 and 72 h in the multi-spot system. In zymosan-induced arthritis, CPO and HA decreased the number of neutrophils in the joint of arthritic mice and the number of total leukocytes (p < 0.05). In experimental arthritis HA significantly decreased joint swelling (p < 0.05). CPO and HA also increased the mechanical threshold during experimental arthritis. HA and CPO significantly inhibited the carrageenan-induced paw edema, being the doses of 10 mg/kg the most effective, registering maximum inhibitions of 58 ± 8% and 76 ± 6% respectively, p < 0.05. CPO and HA reduced the nociceptive behavior in both phases of formalin at all tested doses. The highest doses tested displayed inhibitions of 87 ± 1% and 72 ± 4%, respectively, p < 0.001, in the first phase, and 87 ± 1% and 81 ± 2%, respectively, p < 0.001, in the second phase. Oral treatment of CPO and HA (1, 3, 10 mg/kg) significantly reduced the nociceptive response in acetic acid-induced abdominal writhings, and the 10 mg/kg dose was the most effective with maximum inhibitions of 86 ± 2% and 82 ± 1%, respectively, p < 0.001. Both HA and CPO significantly decreased the intensity of mechanical inflammatory hyper-nociception on carrageenan-induced hyperalgesia at all tested doses, and 10 mg/kg was the most effective dose with maximum inhibitions of 73 ± 5% and 74 ± 7%, respectively, p < 0.05.CPO increased the tail-flick latencies in mice, and concomitant administration of naloxone partially reduced its effect.

CONCLUSIONS

CPO and HA may inhibit the production of inflammatory cytokines by suppressing the NF-κB signaling pathway, resulting in anti-inflammatory and antinociceptive activities.

Altered hippocampal function and cytokine levels in a rat model of Gulf War illness

AIMS

Gulf War illness (GWI) is a disorder affecting military personnel deployed in the Gulf War (GW) from 1990 to 1991. Here, we will use a rat model of GWI to evaluate hippocampal function and cytokine levels.

MATERIALS AND METHODS

Rats were exposed to diethyltoluamide and permethrin via dermal absorption and pyridostigmine bromide via gavage with or without a 5-min restraint for 28 days. Immediate and delayed effects of GW chemical exposure were evaluated using electrophysiology to quantitate hippocampal function, behavioral tests to assess cognitive effects and biochemical assays to measure neurotransmitter and cytokine levels.

KEY FINDINGS

Behavioral data revealed a statistically significant increase in motor activity at 3 months following completion of exposures, potentially indicating increased excitability, and/or restlessness. Electrophysiology data revealed statistically significant changes in paired pulse facilitation and input-output function of CA1 hippocampal neurons within 24 h and 3 months following completion of exposures. There was also a statistically significant reduction in the frequency of spontaneous firing activity of hippocampal neurons within 24 h following exposures. Naïve hippocampal slices directly incubated in GW chemicals also resulted in similar changes in electrophysiological parameters. Biochemical measurements revealed reduced hippocampal glutamate level at 3 months post-exposure. Furthermore, there was a statistically significant increase in plasma and hippocampal levels of IL-13, as well as decrease in plasma level of IL-1β.

SIGNIFICANCE

Our data support an effect on glutamate signaling within the hippocampus as indicated by changes in PPF and hippocampal level of glutamate, with some activation of T helper type 2 immune response.

Time-Restricted Feeding Improves Body Weight Gain, Lipid Profiles, and Atherogenic Indices in Cafeteria-Diet-Fed Rats: Role of Browning of Inguinal White Adipose Tissue

Time-restricted feeding (TRF) showed a potent effect in preventing obesity and improving metabolicoutcomes in several animal models of obesity. However, there is, as of yet, scarce evidence concerning its effectiveness against obesogenic challenges that more accurately mimic human Western diets, such as the cafeteria diet. Moreover, the mechanism for its efficacy is poorly understood. White adipose browning has been linked to body weight loss. Herein, we tested whether TRF has the potential to induce browning of inguinal white adipose tissue (iWAT) and to attenuate obesity and associated dyslipidemia in a cafeteria-diet-induced obesity model. Male Wistar rats were fed normal laboratory chow (NC) or cafeteria diet (CAF) for 16 weeks and were subdivided into two groups that were subjected to either ad libitum (ad lib, A) or TRF (R) for 8 h per day. Rats under the TRF regimen had a lower body weight gain and adiposity than the diet-matchedad lib rats, despite equivalent levels of food intake and locomotor activity. In addition, TRF improved the deranged lipid profile (total cholesterol (TC), triglycerides (TG), high-density lipoprotein (HDL-c), low-density lipoprotein (LDL-c)) and atherogenic indices (atherogenic index of plasma (AIP), atherogenic coefficient (AC), coronary risk index (CRI) in CAF-fed rats. Remarkably, TRF resulted in decreased size of adipocytes and induced emergence of multilocular brown-like adipocytes in iWAT of NC- and CAF-fed rats. Protein expression of browning markers, such as uncoupling protein-1 (UCP1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), were also up-regulated in the iWAToftime-restricted NC- or CAF-fed rats. These findings suggest that a TRF regimen is an effective strategy to improve CAF diet-induced obesity, probably via a mechanismthe involving WAT browning process.

Neuroprotective efficacy of different levels of high-frequency repetitive transcranial magnetic stimulation in mice with CUMS-induced depression: Involvement of the p11/BDNF/Homer1a signaling pathway

High-frequency repetitive transcranial magnetic stimulation (HF-rTMS) is widely used to treat depression. However, the underlying mechanism has not been identified, and there is uncertainty regarding the optimal choice of stimulus parameters, especially stimulus frequency. Our previous study in mice demonstrated that 10-Hz HF-rTMS ameliorated depression by inducing expression of Homer1a and reducing excitability of cortical pyramidal cells. The aims of this study were to compare the effects of 15-Hz and 25-Hz HF-rTMS in a model of chronic unpredictable mild stress (CUMS)-induced depression and investigate its possible molecular mechanism. Male C57BL/6J mice were treated with CUMS for 28 days followed by 15-Hz and 25-Hz rTMS for 4 weeks. The sucrose preference, open field, forced swimming, and tail suspension tests were used to evaluate depression-like behaviors. Immunostaining was performed to measure neuronal loss and neurogenesis. Apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining. Expression of synapse-related proteins and the effects of HF-rTMS on the signaling pathway were examined using Western blot. The results showed that both 15-Hz and 25-Hz rTMS had significant antidepressant effects; 15-Hz rTMS seemed to be more effective than 25-Hz rTMS in preventing neuronal loss and promoting neurogenesis, while 25-Hz rTMS was superior to 15-Hz rTMS in facilitating synaptic plasticity. We also found that 15-Hz and 25-Hz rTMS markedly increased expression of p11, BDNF, Homer1a, and p-trkB proteins. These findings suggest that 15-Hz and 25-Hz HF-rTMS could exert neuroprotective effects to different degrees via multiple perspectives, which at least in part involve the p11/BDNF/Homer1a pathway.

TLR4-NF-κB Signal Involved in Depressive-Like Behaviors and Cytokine Expression of Frontal Cortex and Hippocampus in Stressed C57BL/6 and ob/ob Mice

Studies found that elevated levels of cytokines such as interleukin- (IL-) 1β, IL-6, and tumor necrosis factor-α (TNF-α) are closely associated with the pathogenesis of depression. Obesity providing a low-grade inflammation state was proposed to be implicated in susceptibility to depression in obesity. However, the alterations of cytokines and the TLR4-NF-κB signal in the brain of normal-weight and obese mice under stress have not been fully elucidated. This study used chronic unpredictable mild stress (CUMS) to induce a depressive-like behavior in an animal model and examine depressive-like behaviors, memory changes, and serum corticosterone levels, as well as the expressions of cytokines and NF-κB in the frontal cortex and hippocampus. We aimed to observe the role of neuroinflammation in susceptibility to depression in obesity under CUMS. In addition, we investigated the protective effect of inhibiting the TLR4-NF-κB signal. Our results demonstrated that CUMS induced depressive-like behavior and spatial memory damage, higher level of serum corticosterone, and overexpression of cytokines and NF-κB in the frontal cortex and hippocampus in both C57BL/6 and ob/ob mice. ob/ob mice displayed serious behavioral disorder and higher levels of IL-1β, IL-6, TNF-α, and NF-κB. Our results concluded that a hyperactive TLR4-NF-κB signal and higher level of cytokines are involved in susceptibility to depression in stressed obese mice.

Nicotine alleviates chronic stress-induced anxiety and depressive-like behavior and hippocampal neuropathology via regulating autophagy signaling

Recently, we reported that chronic nicotine significantly improved chronic stress-induced impairments of cognition and the hippocampal synaptic plasticity in mice, however, the underlying mechanism still needs to be explored. In the present study, 32 male C57BL/6 mice were divided into four groups: control (CON), stress (CUS), stress with chronic nicotine administration (CUS + Nic) and chronic nicotine administration (Nic). The anxiety-like behavior and neuropathological alteration of DG neurons were examined. Moreover, PC12 cells were examined with corticosterone in the presence or absence of nicotine. Both cell viability and apoptosis were determined. When treated simultaneously with an unpredictable chronic mild stress (CUS), nicotine (0.2 mg/kg/d) attenuated behavioral deficits and neuropathological alterations of DG neurons. Moreover, Western blotting showed that chronic nicotine also elevated the level of autophagy makers including Beclin-1 and LC3 II triggered by CUS. In addition, concomitant treatment with nicotine (10 μM) significantly attenuated the loss of PC12 cell viability (p < .01) and apoptosis compared to that of corticosterone treatment alone. Besides, chronic nicotine also enhanced the protein and RNA expression levels of autophagy makers triggered by corticosterone, such as Beclin-1, LC3 II and p62/SQSTM1. However, the above improvements were significantly blocked by autophagy inhibitor 3-MA. Importantly, the activation of the PI3K/Akt/mTOR signaling was carefully tested to illuminate the effects of chronic nicotine. Consequently, chronic nicotine played a role of neuroprotection in either CUS mice or corticosterone cells associating with the enhancement of the autophagy signaling, which was involved in activating the PI3K/Akt/mTOR signaling.

Influence of Tanshinone IIa on heat shock protein 70, Bcl-2 and Bax expression in rats with spinal ischemia/reperfusion injury

Tanshinone IIa is an effective monomer component of Danshen, which is a traditional Chinese medicine for activating blood circulation to dissipate blood stasis. Tanshinone IIa can effectively improve brain tissue ischemia/hypoxia injury. The present study established a rat model of spinal cord ischemia/reperfusion injury and intraperitoneally injected Tanshinone IIa, 0.5 hour prior to model establishment. Results showed that Tanshinone IIa promoted heat shock protein 70 and Bcl-2 protein expression, but inhibited Bax protein expression in the injured spinal cord after ischemia/reperfusion injury. Furthermore, Nissl staining indicated a reduction in nerve cell apoptosis and fewer pathological lesions in the presence of Tanshinone IIa, compared with positive control Danshen injection.

Determination of motor activity and anxiety-related behaviour in rodents: methodological aspects and role of nitric oxide

In various areas of the bio-medical, pharmacological and psychological research a multitude of behavioural tests have been used to investigate the effects of environmental, genetic and epi-genetic factors as well as pharmacological substances or diseased states on behaviour and thus on the physiological and psycho-social status of experimental subjects. This article is reviewing the most frequently used behavioural tests in animal research (open field, elevated plus maze, zero maze, and black and white box). It provides a summary of common characteristics as well as differences in the methods used in various studies to determine motor activity, anxiety and emotionality. Additionally to methodological aspects, strain, sex and stress-related differences as well as the involvement of nitric oxide in modulation of motor activity and anxiety of rodents were briefly reviewed.