Functional interaction between N-methyl-D-aspartate receptor and ascorbic acid during neuropathic pain induced by chronic constriction injury of the sciatic nerve

Preclinical study in a postoperative pain model to investigate the action of ketamine, lidocaine, and ascorbic acid in reversing fentanyl-induced, non-glutamate-dependent hyperalgesia

Introduction

Opioid-induced hyperalgesia (OIH) is a paradoxical phenomenon in which exposure to opioids can increase sensitivity to painful stimuli. Currently, several drugs have been used in an attempt to prevent OIH. We design this study to address the effect of preemptive treatment with ketamine, lidocaine, and ascorbic acid in a rat preclinical model of perioperative opioid-induced hyperalgesia.

Methods

To reproduce OIH in a model of postoperative pain, rats received successive doses of fentanyl subcutaneously and underwent an incision in the paw. In an attempt to prevent OIH, ketamine, lidocaine, and ascorbic acid were administered before treatment with fentanyl. The von Frey test and the hot-plate test were used to evaluate mechanical allodynia and thermal hyperalgesia, respectively, with a follow-up period from 1 hour up to 7 days after surgery. Spinal cord nerve terminals (synaptosomes) were used to assess glutamate release under our experimental conditions.

Results

Consecutive fentanyl injections increased the postoperative pain as indicated by increased thermal hyperalgesia and allodynia 48 hours after incision. Ketamine, lidocaine, and the combination of ketamine + lidocaine were able to prevent thermal hyperalgesia but not mechanical allodynia. Ascorbic acid did not prevent the hyperalgesia induced by fentanyl. We found no correlation between spinal glutamate release and the pharmacological treatments.

Conclusion

Fentanyl induced a hyperalgesic effect that last few days in a postoperative model of pain. Hyperalgesic effect was not totally inhibited by ketamine and lidocaine in rats. Increased glutamate release was not the main molecular mechanism of fentanyl-induced hyperalgesia.

Comparative neuroprotective effects of Cerebrolysin, dexamethasone, and ascorbic acid on sciatic nerve injury model: Behavioral and histopathological study

Background

The majority of the suggested experimental modalities for peripheral nerve injury (PNI) result in varying degrees of recovery in animal models; however, there are not many reliable clinical pharmacological treatment models available. To alleviate PNI complications, research on approaches to accelerate peripheral nerve regeneration is encouraged. Cerebrolysin, dexamethasone, and ascorbic acid (vitamin C) drug models were selected in our study because of their reported curative effects of different mechanisms of action.

Methodology

A total of 40 adult male albino rats were used in this study. Sciatic nerve crush injury was induced in 32 rats, which were divided equally into four groups (model, Cerebrolysin, dexamethasone, and vitamin C groups) and compared to the sham group (n = 8). The sciatic nerve sensory and motor function regeneration after crushing together with gastrocnemius muscle histopathological changes were evaluated by the sciatic function index, the hot plate test, gastrocnemius muscle mass ratio, and immune expression of S100 and apoptosis cascade (BAX, BCL2, and BAX/BCL2 ratio).

Results

Significant improvement of the behavioral status and histopathological assessment scores occurred after the use of Cerebrolysin (as a neurotrophic factor), dexamethasone (as an anti-inflammatory), and vitamin C (as an antioxidant). Despite these seemingly concomitant, robust behavioral and pathological changes, vitamin C appeared to have the best results among the three main outcome measures. There was a positive correlation between motor and sensory improvement and also between behavioral and histopathological changes, boosting the effectiveness, and implication of the sciatic function index as a mirror for changes occurring on the tissue level.

Conclusion

Vitamin C is a promising therapeutic in the treatment of PNI. The sciatic function index (SFI) test is a reliable accurate method for assessing sciatic nerve integrity after both partial disruption and regrowth.

High-Dose Vitamin C in Advanced-Stage Cancer Patients

High-dose intravenously administered vitamin C (IVC) is widely used in cancer patients by complementary and alternative medicine practitioners. The most frequent indications for IVC therapy result from the belief in its effectiveness as a potent anti-cancer agent which additionally enhances chemosensitivity of cancer cells and reduces chemotherapy-related toxicities and fatigue intensity. In this narrative review, we decided to deal with this issue, trying to answer the question whether there is any scientific evidence supporting the rationale for application of high-dose IVC therapy in advanced-stage cancer patients. Although results obtained from preclinical studies demonstrated that millimolar ascorbate plasma concentrations achievable only after IVC administration were cytotoxic to fast-growing malignant cells and inhibited tumor growth as well as prolonged the survival of laboratory animals, such positive effects were not found in human studies with advanced-stage cancer patients. We also have not found the rationale for the use of IVC to increase the effectiveness of chemotherapy and to reduce the chemotherapy-induced toxicity in the above mentioned group. Nevertheless, in palliative care, high-dose IVC might be considered as a therapy improving the quality of life and reducing cancer-related symptoms, such as fatigue and bone pain. However, because of the absence of placebo-controlled randomized trials on IVC efficacy in advanced-stage cancer patients, the placebo effect cannot be excluded.

Ascorbic Acid Facilitates Neural Regeneration After Sciatic Nerve Crush Injury

Ascorbic acid (AA) is an essential micronutrient that has been safely used in the clinic for many years. The present study indicates that AA has an unexpected function in facilitating nerve regeneration. Using a mouse model of sciatic nerve crush injury, we found that AA can significantly accelerate axonal regrowth in the early stage [3 days post-injury (dpi)], a finding that was revealed by immunostaining and Western blotting for antibodies against GAP-43 and SCG10. On day 28 post-injury, histomorphometric assessments demonstrated that AA treatment increased the density, size, and remyelination of regenerated axons in the injured nerve and alleviated myoatrophy in the gastrocnemius. Moreover, the results from various behavioral tests and electrophysiological assays revealed that nerve injury-derived functional defects in motor and sensory behavior as well as in nerve conduction were significantly attenuated by treatment with AA. The potential mechanisms of AA in nerve regeneration were further explored by investigating the effects of AA on three types of cells involved in this process [neurons, Schwann cells (SCs) and macrophages] through a series of experiments. Overall, the data illustrated that AA treatment in cultured dorsal root ganglionic neurons resulted in increased neurite growth and lower expression of RhoA, which is an important inhibitory factor in neural regeneration. In SCs, proliferation, phagocytosis, and neurotrophin expression were all enhanced by AA. Meanwhile, AA treatment also improved proliferation, migration, phagocytosis, and anti-inflammatory polarization in macrophages. In conclusion, this study demonstrated that treatment with AA can promote the morphological and functional recovery of injured peripheral nerves and that this effect is potentially due to AA’s bioeffects on neurons, SCs and macrophages, three of most important types of cells involved in nerve injury and regeneration.

Vitamin D supplementation attenuates the behavioral scores of neuropathic pain in rats

Objective(s): Neuropathic pain due to lesion or dysfunction of the peripheral or central nervous system is often refractory to the conventional analgesics. Currently, there is no proven treatment to prevent or cure neuropathic pain. A recent surge of new data suggests the potential effects of vitamin D in the medical community. This study was designed to determine whether acute or chronic vitamin D administration was effective in alleviating symptoms of neuropathic pain in a rat model of neuropathic pain. Materials and Methods: Neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve in the rats that resulted in thermal hyperalgesia, mechanical, and cold allodynia. Results: Acute vitamin D injections (250, 500, and 1000 unit/kg i.p.) on the 7th, 14th, and 21st postoperative days could not attenuate mechanical and cold allodynia as well as heat hyperalgesia compared to CCI group. But when vitamin D (1000 unit/kg i.p.) administration was started on the first day after surgery and given daily until the 21st day, cold allodynia and heat hyperalgesia considerably were attenuated. However, no differences in paw withdrawal thresholds were observed. Conclusion: These results indicate that chronic vitamin D administrations can attenuate the behavioral scores of neuropathic pain in rats.

Prognostic implication of p27Kip1, Skp2 and Cks1 expression in renal cell carcinoma: a tissue microarray study

BACKGROUND

p27Kip1 plays a major role as a negative regulator of the cell cycle. The regulation of p27Kip1 degradation is mediated by its specific ubiquitin ligase subunits S-phase kinase protein (Skp) 2 and cyclin-dependent kinase subunit (Cks) 1. However, little is known regarding the prognostic utility of p27Kip1, Skp2 and Cks1 expression in renal cell carcinoma.

METHODS

Immunohistochemistry was performed for p27Kip1, Skp2 and Cks1 in tissue microarrays of 482 renal cell carcinomas with follow-up. The data were correlated with clinicopathological features. The univariate and multivariate survival analyses were also performed to determine their prognostic significance.

RESULTS

Immunoreactivity of p27Kip1, Skp2 and Cks1 was noted in 357, 71 and 82 patients, respectively. Skp2 and Cks1 expression were not noted in chromophobe cancers. A strong correlation was found between Skp2 and Cks1 expression (P < 0.001), both of which were inversely related to p27Kip1 levels (P = 0.006 and P < 0.001), especially in primary and clear-cell cancers. Low p27Kip1 expression and Skp2 expression were correlated with larger tumor size and higher stage, as well as tumor necrosis. Cks1 expression was only correlated with tumor size. In univariate analysis, low p27Kip1 expression, Skp2 and Cks1 expression were all associated with a poor prognosis, while in multivariate analysis, only low p27Kip1 expression were independent prognostic factors for both cancer specific survival and recurrence-free survival in patients with RCC.

CONCLUSION

Our results suggest that immunohistochemical expression levels of p27Kip1, Skp2 and Cks1 may serve as markers with prognostic value in renal cell carcinoma.