Intranasal CEPO-FC prevents attention deficits in streptozotocin-induced rat model of Alzheimer's disease: Focus on synaptic plasticity-related factors.

Alzheimer's disease remains an issue of great controversy due to its pathology. It is characterized by cognitive impairments and neuropsychiatric symptoms. The FDA approved medications for this disease, can only mitigate the symptoms. One reason for the lack of effective medications is the inaccessibility of the brain which is encompassed by the blood-brain barrier, making intranasal (IN) route of administration potentially advantageous. Male Wistar rats underwent stereotaxic surgery to induce an Alzheimer's disease model via intracerebroventricular (ICV) streptozotocin injection, and Carbamylated Erythropoietin-Fc (CEPO-FC), a derivative of Erythropoietin without its harmful characteristics, was administered intranasally for ten consecutive days. Cognition performance for memory and attention was assessed using the Novel Object Recognition Test and the Object-Based Attention Test respectively. Depression like behavior was evaluated using the Forced Swim Test. Western blotting was done on the extracted hippocampus to quantify STIM proteins. Calbindin, PSD-95, Neuroplastin, Synaptophysin and GAP-43 genes were assessed by Realtime PCR. Behavioral tests demonstrated that IN CEPO-FC could halt cognition deficits and molecular investigations showed that, STIM proteins were decreased in Alzheimer's model, and increased after IN CEPO-FC treatment. Calbindin and PSD-95 were downregulated in our disease model and upregulated when treated with IN CEPO-FC. While Neuroplastin, and GAP-43 expressions remained unchanged. This study suggests that IN CEPO-FC in low doses could be promising for improving cognition and synaptic plasticity deficits in Alzheimer's disease and since IN route of administration is a convenient way, choosing IN CEPO-FC for clinical trial might worth consideration. See also the graphical abstract(Fig. 1).

Dipeptide mimetic of BDNF ameliorates motor dysfunction and striatal apoptosis in 6-OHDA-induced Parkinson's rat model: Considering Akt and MAPKs signaling.

Parkinson's disease (PD) is a progressive and debilitating neurodegenerative disorder associated with motor and non-motor complaints. Dysregulation of neurotrophic factors and related signaling cascades have been reported to be common events in PD which is accompanied by dopaminergic (DA) neuron demise. However, the restoration of neurotrophic factors has several limitations. Bis-(N-monosuccinyl-L-methionyl-L-serine) heptamethylenediamide (BHME) is a dipeptide mimetic of brain-derived neurotrophic factor (BDNF) with reported anti-oxidant and neuroprotective effects in several experimental models. The current study has investigated the effect of BHME on 6-hydroxydopamine (6-OHDA)-caused motor anomalies in Wistar rats. In this regard, rats were treated daily with BHME (0.1 or 1 mg/kg) 1 h after 6-OHDA-caused damage until the twelfth day. Afterwards, motor behavior and DA neuron survival were evaluated via behavioral tests and immunohistochemistry (IHC) staining, respectively. Moreover, the activity of Akt, mitogen-activated protein kinases (MAPKs) family, and Bax/Bcl-2 ratio were evaluated by Western blotting. Our results indicated that BHME prevents motor dysfunction and DA cell death following 6-OHDA injection, and this improvement was in parallel with an enhancement in Akt activity, decrement of P38 phosphorylation, along with a reduction in Bax/Bcl-2 ratio. In conclusion, our findings indicated that BHME, as a mimetic of BDNF, can be considered for further research and is a promising therapeutic agent for PD therapy.

Evaluation of the GABAA Receptor Expression and the Effects of Muscimol on the Activity of Wide Dynamic Range Neurons Following Chronic Constriction Injury of Sciatic Nerve in Rats.

INTRODUCTION: The modality of γ-aminobutyric acid type a receptors (GABAA) controls dorsal horn neuronal excitability and inhibits sensory information. This study aimed to investigate the expression of the GABAA receptor and the effects of its agonist muscimol on Wide Dynamic Range (WDR) neuronal activity in the Chronic Constriction Injury (CCI) model of neuropathic pain. METHODS: Adult male Wistar rats weighing 200 to 250 g were used to induce CCI neuropathy. Fourteen days after surgery, muscimol (0.5, 1, and 2 mg/kg IP) was injected. Then, the behavioral tests were performed. After that, the animals were killed, and the lumbar segments of the spinal cords were collected for Western blot analysis of the GABAA receptor α1 subunit expression. The electrophysiological properties of WDR neurons were studied by single-unit recordings in separate groups 14 days after CCI. RESULTS: The outcomes indicated the development of thermal hyperalgesia and mechanical allodynia after neuropathy; nonetheless, the expression of the GABAA receptor α1 subunit did not change significantly. Moreover, the evoked responses of the WDR neurons to electrical, mechanical, and thermal stimuli increased considerably. Fourteen days after CCI, muscimol administration decreased thermal hyperalgesia, mechanical allodynia, and hyper-responsiveness of the WDR neurons in CCI rats. CONCLUSION: The modulation of the spinal GABAA receptors after nerve injury can offer further insights to design new therapeutic agents to reduce neuropathic pain symptoms.

Recovery of inferior alveolar nerve by photobiomodulation therapy using two laser wavelengths: A behavioral and immunological study in rat.

Postoperative sensory disturbances of inferior alveolar nerve (IAN) are major challenges in dental procedures. We aimed to investigate the effect of photobiomodulation therapy (PBMT) with 810 nm and 980 nm diode lasers on behavioral and immunological factors in a rat IAN crush model. Seventy-two rats were randomly assigned to the four groups of 810 nm laser (crush injury+810 nm laser; 6 J/cm2, 15 sessions, every 48 h), 980 nm laser (crush injury+980 nm laser; same protocol), control (crush injury without irradiation), and sham surgery (no crush injury and no irradiation). The neurosensory response of IAN was evaluated by Von Frey behavioral test before (baseline) and post-surgery in a period of one month. Changes of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), nuclear factor-kappa B (NF-κB), TNF-α, and IL-1ß, were assessed on days 2 and 30 post injury. Data were analyzed for significant differences by repeated measures and one-way ANOVA (p < .05). One day after surgery, all rats subjected to nerve injury showed significant increase in the withdrawal threshold of von Frey test compared to the baseline (p = .02 for control and p = .03 for laser groups). The threshold gradually returned to the baseline scores in 810 nm, 980 nm, and control groups from days 11, 17, and 29, respectively. There was a significant lower withdrawal threshold in 810 nm and 980 nm laser groups compared to the control group in days 11 to 19 and 9 to 23, respectively. At both time points, the levels of NGF and BDNF were significantly higher in 810 nm laser group compared to the control group. There was a significant difference between laser and control groups regarding NF-κB expression (all p values<.001). TNF-α and IL-1ß were significantly lower in laser groups compared to the control group (all p values < .001). PBMT with 810 and 980 nm diode laser protocol used in this study, promoted the neurosensory recovery of IAN after crush injury in rats. In addition, application of 810 nm diode laser was associated with more improvement in immunological responses compared to that of 980 nm laser.

Microglial-induced apoptosis is potentially responsible for hyperalgesia variations during CFA-induced inflammation.

AIMS: Activated microglia is known as a main mediator of inflammatory pain, but the possible mechanisms of its operation are poorly understood. Microglial cells have considered as one of the main sources of pro-inflammatory cytokines in the CNS. PTEN is one of the important targets of pro-inflammatory cytokines and the main mediator of apoptotic cell death. In this study, we investigated the possible effect of microglial activation on PTEN/PI3K/Akt signaling pathway and apoptosis in an inflammatory rat model of Complete Freund's adjuvant (CFA). METHODS: Persistent peripheral inflammation was induced by a subcutaneous injection of CFA into the rats' right hind paw on day 0. Minocycline (a potent selective inhibitor of microglial) was administered intraperitoneally during days 1-21 after CFA injection. Hyperalgesia was assessed on days 0, 7, and 21 using plantar test, then lumbar spinal cord segments were isolated, and the amount of spinal Iba1 (microglial marker), PTEN, P.Akt, and cleaved caspase-3 (a marker of apoptosis activation) were analyzed using Western blot. The spinal TNF-α levels were assayed by ELISA and the microglia numbers were determined using immunohistochemical technique. RESULTS: Results revealed that increased hyperalgesia was concurrent with an increment of Iba1 (P < 0.001), TNF-α (P < 0.001), PTEN (P < 0.01), cleaved caspase-3 (P < 0.001), and a decrement of P.Akt (P < 0.01) during the acute phase of CFA-induced inflammation, while, at the same time as decreasing hyperalgesia during the chronic phase of study, Iba1 and TNF-α expression significantly decreased and PTEN, cleaved caspase-3, and P.Akt restored to baseline on day 0. Minocycline administration reduced the elevation of spinal Iba1 (P < 0.001), TNF-α (0.001), PTEN (P < 0.01), and cleaved caspase-3 (P < 0.001) expression induced by CFA injection, and also restored Akt activity to the baseline on day 0 (P < 0.001). CONCLUSIONS: These results suggest that microglial-mediated pain following CFA injection might be related in part to increased spinal cell apoptosis which probably is mediated by PTEN/PI3K/Akt deregulation.

Thymulin treatment attenuates inflammatory pain by modulating spinal cellular and molecular signaling pathways.

Thymulin is a peptide hormone which is mainly produced by thymic epithelial cells and it has immune-modulatory and anti-inflammatory effects. In this study, we investigated the effects of different doses and various timings of thymulin intraperitoneal administration on spinal microglial activity and intracellular pathways in an inflammatory rat model of Complete Freund's adjuvant (CFA). Thymulin treatment was implemented following CFA-induced inflammation for 21 days. After conducting behavioral tests (edema and hyperalgesia), the cellular and molecular aspects were examined to detect the thymulin effect on inflammatory factors and microglial activity. We demonstrated that thymulin treatment notably reduced thermal hyperalgesia and paw edema induced by CFA. Furthermore, molecular investigations showed that thymulin reduced CFA-induced activation of microglia cells, phosphorylation of p38 MAPK and the production of spinal pro-inflammatory cytokines (TNF-α, IL-6) during the study. Our results suggest that thymulin treatment attenuates CFA-induced inflammation. This effect may be mediated by inhibition of spinal microglia and production of central inflammatory mediators which seems to be associated with the ability of thymulin to reduce p38 MAPK phosphorylation. These data provide evidence of the anti-hyperalgesic effect of thymulin on inflammatory pain and characterize some of the underlying spinal mechanisms.

Anti-hyperalgesia effect of nanchelating based nano particle, RAc1, can be mediated via liver hepcidin expression modulation during persistent inflammation.

OBJECTIVE: Rheumatoid arthritis (RA) is a chronic systemic inflammatory disorder accompanied with hyperalgesia, edema and pain. At least 30% of the patients failed to respond to the available treatments and medications, which yet have a lot of serious adverse effects on patients. So, using novel technologies to produce more efficient medications is needed. According to the role of iron manipulation in inflammatory process, we have synthetized RAc1 nano particle, which contains zinc and has iron chelating property. In the present study, we evaluated RAc1 nano particle effects on hyperalgesia and liver hepcidin and serum IL-1ß and TNF-α expression levels during acute and chronic phases of adjuvant-induced inflammation in male rats and compared its effects with Deferoxamine. METHODS AND MATERIALS: Complete Freund's adjuvant (CFA)-induced arthritis was caused by single subcutaneous injection of CFA into the rat's hind paw on day zero. RAc1 with 100, 200 and 400 ng/kg doses and deferoxamin with doses of 200 mg/kg after diluting in vehicles were administered daily (i.p.) during the 21 days of the study after CFA injection. Hyperalgesia, Edema, liver hepcidin and serum IL-1ß and TNF-α expression levels were assessed on days 0, 7, 14 and 21 of the study. RESULTS: The results of this study indicated the role of RAc1 nano particle administration in reducing paw edema, thermal hyperalgesia, and liver hepcidin and serum IL-1ß and TNF-α expression even in comparison with Deferoxamine during different phases of inflammation caused by CFA. CONCLUSION: It seems that RAc1 nano particle exerts its immune modulatory effects by decreasing liver hepcidin expression and serum IL-1ß and TNF-α levels.

CEPO-Fc (An EPO Derivative) Protects Hippocampus Against Aß-induced Memory Deterioration: A Behavioral and Molecular Study in a Rat Model of Aß Toxicity.

Alzheimer's disease (AD) is a debilitating neurodegenerative disease, characterized by extracellular deposition of senile plaques, mostly amyloid ß-protein (Aß) and neuronal loss. The neuroprotective effects of erythropoietin (EPO) have been reported in some models of neurodegenerative disease, but because of its hematopoietic side effects, its derivatives lacking hematopoietic bioactivity is recommended. In this study, the neuroprotective effects of carbamylated erythropoietin-Fc (CEPO-Fc) against beta amyloid-induced memory deficit were evaluated. Adult male Wistar rats weighing 250-300 g were bilaterally cannulated into CA1. Aß25-35 was administered intrahippocampally for 4 consecutive days (5 µg/2.5 µL/each side/day). CEPO-Fc (500 or 5000 IU) was injected intraperitoneally during days 4-9. Learning and memory performance of rats was assessed on days 10-13 using Morris Water Maze, then hippocampi were isolated and the amount of activated forms of hippocampal MAPKs' subfamily, Akt/GSK-3ß and MMP-2 were analyzed using Western blot. From the behavioral results, it was revealed that CEPO-Fc treatment in both 500 and 5000 IU significantly reversed Aß-induced learning and memory deterioration. From the molecular analysis, an increment of MAPKs and MMP-2 activity and an imbalance in Akt/GSK-3ß signaling after Aß25-35 administration was observed. CEPO-Fc treatment prevented the elevation of hippocampal of P38, ERK, MMP-2 activity and also Akt/GSK-3ß signaling impairment induced by Aß25-35 but it had no effect on JNK. It seems that CEPO-Fc prevents Aß-induced learning and memory deterioration, and also modulates hippocampal MAPKs, Akt/GSK-3ß and MMP-2 activity. This study suggests that CEPO-Fc can be considered as a potential therapeutic strategy for memory deficits like AD.

Long term treatment by mesenchymal stem cells conditioned medium modulates cellular, molecular and behavioral aspects of adjuvant-induced arthritis.

Neuroinflammation plays a crucial role in expression of symptoms of numerous autoimmune and neurodegenerative diseases such as pain during rheumatoid arthritis. Overproduction of pro-inflammatory cytokines and activation of intracellular signaling pathways have been strongly implicated in the generation of pathological pain states, particularly at central nervous system sites and induction of spinal neuroinflammatory symptoms. The wide ranges of research to define new therapeutic approaches, including neuroimmune-modulators like stem cells are in progress. Mesenchymal stem cells conditioned medium (MSC-CM) has anti-inflammatory factors which can regulate the immune responses. The aim of this study was to investigate the effect of administration of MSC-CM on behavioral, cellular and molecular aspects of adjuvant-induced arthritis in male Wistar rats. Complete Freund's adjuvant (CFA)-induced arthritis (AA) was caused by single subcutaneous injection of CFA into the rat's hind paw on day 0. MSC-CM was administered daily (i.p.) and during the 21 days of the study after injection. Hyperalgesia, Edema, Serum TNF-α levels and p38MAPK and NF-κB activities were assessed on days 0,7,14 and 21 of the study. The results of this study indicated the role of MSC-CM in reducing inflammatory symptoms, serum TNF-α levels and activity of intracellular signaling pathway factors during different phases of inflammation caused by CFA. It seems that MSC-CM treatment due to its direct effects on inhibition of intracellular signaling pathways and pro-inflammatory cytokines can alleviate inflammatory symptoms and pain during CFA-induced arthritis.

CB1 Cannabinoid Agonist (WIN55,212-2) Within the Basolateral Amygdala Induced Sensitization to Morphine and Increased the Level of µ-Opioid Receptor and c-fos in the Nucleus Accumbens.

The basolateral amygdala (BLA) is rich of CB1 cannabinoid receptors (CB1R) and has reciprocal connections with the nucleus accumbens (NAc) which is involved in opioid sensitization. In this study, effects of intra-BLA administration of CB1R agonist on sensitization to antinociceptive effect of morphine and changes in the levels of µ-opioid receptor (MOR), p-CREB, and c-fos in the NAc were investigated. Animals received intra-BLA microinjection of CB1R agonist (WIN55,212-2) once daily for 3 days consecutively (sensitization period). After 5 days free of drug, tail-flick test was performed before and after the administration of an ineffective dose of morphine. Afterward, the levels of MOR, p-CREB, and c-fos proteins were measured in the NAc by Western blot analysis. The results indicated that intra-BLA injection of WIN55,212-2 during sensitization period resulted in the induction of antinociceptive responses by ineffective dose of morphine and caused a significant increase in the MOR and c-fos levels but not p-CREB/CREB ratio in the NAc. These finding revealed that CB1 receptor agonist in the BLA induces development of morphine sensitization and increases expression of MOR in the NAc. It seems that c-fos is one of the important factors involved in the induction of sensitization to antinociceptive effect of morphine.

Inhibition of microglial activity alters spinal wide dynamic range neuron discharge and reduces microglial Toll-like receptor 4 expression in neuropathic rats.

It is believed that neuropathic pain results from aberrant neuronal discharges although some evidence suggests that the activation of glia cells contributes to pain after an injury to the nervous system. This study aimed to evaluate the role of microglial activation on the hyper-responsiveness of wide dynamic range neurons (WDR) and Toll-like receptor 4 (TLR4) expressions in a chronic constriction injury (CCI) model of neuropathic pain in rats. Adult male Wistar rats (230 ± 30 g) underwent surgery for induction of CCI neuropathy. Six days after surgery, administration of minocycline (10, 20, and 40 mg/kg, i.p.) was initiated and continued until day 14. After administration of the last dose of minocycline or saline, a behavioral test was conducted, then animals were sacrificed and lumbar segments of the spinal cord were collected for Western blot analysis of TLR4 expression. The electrophysiological properties of WDR neurons were investigated by single unit recordings in separate groups. The findings showed that after CCI, in parallel with thermal hyperalgesia, the expression of TLR4 in the spinal cord and the evoked response of the WDR neurons to electrical, mechanical, and thermal stimulation significantly increased. Post-injury administration of minocycline effectively decreased thermal hyperalgesia, TLR4 expression, and hyper-responsiveness of WDR neurons in CCI rats. The results of this study indicate that post-injury, repeated administration of minocycline attenuated neuropathic pain by suppressing microglia activation and reducing WDR neuron hyper-responsiveness. This study confirms that post-injury modulation of microglial activity is a new strategy for treating neuropathic pain.

Cellular events during arthritis-induced hyperalgesia are mediated by interleukin-6 and p38 MAPK and their effects on the expression of spinal mu-opioid receptors.

Activation of mitogen-activated protein kinase (MAPK) enzymes in nociceptive plasticity has been extensively studied. P38 MAPK enzyme, which can be activated by cytokines, acts as a crucial intracellular regulator of environmental changes. The aim of this study was to elucidate the cellular events during arthritis-induced hyperalgesia that are mediated by interleukin-6 and p38 MAPK, and their effects on the expression of spinal mu-opioid receptors (MORs), in different stages of arthritis in male Wistar rats. Complete Freund's adjuvant (CFA)-induced arthritis (AA) was caused by subcutaneous injection of CFA into the rats' hindpaw. Anti-IL-6 antibody and p38 MAPK phosphorylation inhibitor were administered during 21 days of study. Spinal MOR, p38, and phosphorylated-p38 (pp38) proteins expressions were detected by Western blotting. Daily treatment with anti-IL-6 antibody and p38 MAPK phosphorylation inhibitor, SB203580, significantly decreased paw edema in AA group. Daily anti-IL-6 and SB203580 administration caused a significant reduction in hyperalgesia in the first week of the study, but increased hyperalgesia in the next 2 weeks in experimental groups compared to the AA control group. Expression of pp38 MAPK protein significantly decreased on the 3, 7, 14, and 21 days in AA+SB203580 and AA+anti-IL6 groups compared to AA group. Additionally, daily treatment with anti-IL6 antibody and SB203580 in AA group caused significantly decrease in spinal MOR expression compared to AA control group. The results of our study can confirm that activated spinal p38 MAPK enzyme may play an important role in cellular IL-6 signaling pathways in hyperalgesia variation during different stages of AA inflammation. Also, it can be suggested that at least a part of p38 MAPK effects on hyperalgesia is mediated by spinal MOR expression variation.

Post-injury repeated administrations of minocycline improve the antinociceptive effect of morphine in chronic constriction injury model of neuropathic pain in rat.

It is confirmed that pharmacological attenuation of glial cells can alleviate neuropathic pain by lowering proinflammatory cytokine expression. The present study tries to confirm that post-injury administration of glia inhibitor, minocycline, can attenuate the neuropathic pain symptoms and improves the efficacy of morphine anti-nociception in chronic constriction injury (CCI). Male Wistar rats (230-270 g) underwent surgery for induction CCI model of neuropathy. For assessment of the thermal hyperalgesia and mechanical allodynia after CCI induction, morphine (2.5, 5, 7.5, 10 and 15 mg/kg; s.c.) and saline were administered on post-operative days (PODs) 0, 6 and 14. Hargreaves and Von-Frey tests were performed before and 30 min after morphine administration, respectively. The results showed significant decrease in antinociceptive effect of morphine on POD 6 compared to POD 0 only at the dose of 5 mg/kg. On the other hand, on POD 14 the antinociceptive effect of morphine (5, 7.5, 10 and 15 mg/kg) significantly decreased in comparison with POD 0. In another set of experiments, animals received minocycline (10, 20 and 40 mg/kg; i.p.) for eight days from POD 6 to 13 and then the antinociceptive effect of single dose of morphine 5 mg/kg was tested on POD 14. Behavioral tests showed that minocycline (40 mg/kg) could effectively attenuate the thermal hyperalgesia and mechanical allodynia on POD 13. Moreover, minocycline (40, 20 mg/kg) improved the anti-hyperalgesic, and minocycline (40 mg/kg) improved the anti-allodynic effects of morphine 5 mg/kg on POD 14. It seems that the reduction of antinociceptive effect of morphine after CCI may be mediated through glia activation. Modulation of glial activity by minocycline can attenuate CCI-induced neuropathic pain. It is also shown that repeated post-injury administration of minocycline improves the antinociceptive effect of morphine in neuropathic pain.

Achillea santolina reduces serum interleukin-6 level and hyperalgesia during complete Freund's adjuvant-induced inflammation in male Wistar rats.

OBJECTIVE: Immune system is involved in the etiology and pathophysiologic mechanisms of inflammation. Medicinal plants are an important source of substances which are claimed to induce non-specific immunomodulatory effects. In view of this and on account of the interleukin (IL)-6's role in inflammation and pain induction, this study investigated the effects of Achillea santolina extracts on inflammation which was induced by complete Freund's adjuvant (CFA) in male Wistar rats. METHODS: Both methanolic and defatted extracts prepared from aerial parts of the plant were examined. Inflammatory symptoms such as hyperalgesia and paw edema in CFA-injected rats' paw were measured by radiant heat and plethysmometer during different stages of study respectively. Serum IL-6 level was checked by rat standard enzyme-linked immunosorbent assay specific kit. RESULTS: The results indicated dose-related effects of methanolic extract on paw edema, hyperalgesia and serum IL-6 level reduction in rats. Methanolic extract of A. santolina exhibited significant antihyperalgesic and anti-inflammatory effects during pretreatment and short-term treatment at dose of 200 mg/kg and there was no significant difference between 200 and 400 mg/kg doses of this extract. Defatted extract did not show significant effect on CFA-induced inflammation during different stages of treatment (P>0.05). Short-term treatment with methanolic extract at dose of 200 mg/kg was more effective than indomethacin in edema, hyperalgesia and serum IL-6 level reduction (P<0.01, P<0.01 and P<0.05 respectively). CONCLUSION: These results suggest that methanolic extract of A. santolina possesses potent anti-inflammatory and immunomodulatory activities during pretreatment and short-term administration.