Antinociceptive interaction of gabapentin with minocycline in murine diabetic neuropathy

Magnolol effectively ameliorates diabetic peripheral neuropathy in mice

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes lacking efficient treatment. Magnolol (MG), a peroxisome proliferator-activated receptor γ (PPARγ) agonist, is a natural product derived from Magnolia officinalis and widely used to treat a variety of diseases as a traditional Chinese medicine and Japanese Kampo medicine.

PURPOSE

Here, we aimed to investigate the potential of MG in ameliorating DPN-like pathology in mice and decipher the mechanism of MG in treating DPN.

MATERIALS AND METHODS

12-week-old male streptozotocin (STZ)-induced type 1 diabetic (T1DM) mice and 15-week-old male BKS Cg-m^+/+Lepr db/J (db/db) type 2 diabetic mice (T2DM) were used as DPN mice. MG was administrated (i.p) daily for 4 weeks. Peripheral nerve functions of mice were evaluated by measuring mechanical response latency, thermal response latency and motor nerve conduction velocity (MNCV). The mechanisms underlying the amelioration of MG on DPN-like pathology were examined by qRT-PCR, western blot and immunohistochemistry assays, and verified in the DPN mice with PPARγ-specific knockdown in dorsal root ganglia (DRG) neuron and sciatic nerve tissues by injecting adeno-associated virus (AAV)8-PPARγ-RNAi.

RESULTS

MG promoted DRG neuronal neurite outgrowth and effectively ameliorated neurological dysfunctions in both T1DM and T2DM diabetic mice, including improvement of paw withdrawal threshold, thermal response latency and MNCV. Additionally, MG promoted neurite outgrowth of DRG neurons, protected sciatic nerve myelin sheath structure, and ameliorated foot skin intraepidermal nerve fiber (IENF) density in DPN mice by targeting PPARγ. Mechanism research results indicated that MG improved mitochondrial dysfunction involving PPARγ/MKP-7/JNK/SIRT1/LKB1/AMPK/PGC-1α pathway in DRG neurons, repressed inflammation via PPARγ/NF-κB signaling and inhibited apoptosis through regulation of PPARγ-mediated Bcl-2 family proteins in DRG neurons and sciatic nerves.

CONCLUSIONS

Our work has detailed the mechanism underlying the amelioration of PPARγ agonist on DPN-like pathology in mice with MG as a probe, and highlighted the potential of MG in the treatment of DPN.

Elucidating the Neuroprotective Effect of Tecoma stans Leaf Extract in STZ-Induced Diabetic Neuropathy

Background

Diabetes is considered one of the most encyclopedic metabolic disorders owing to an alarming rise in the number of patients, which is increasing at an exponential rate. With the current therapeutics, which only aims to provide symptomatic and momentary relief, the scientists are shifting gears to explore alternative therapies which not only can target diabetes but can also help in limiting the progression of diabetic complications including diabetic neuropathy (DN).

Methods

Tecoma stans leaf methanolic extract was prepared using the Soxhlet method. A streptozotocin (STZ; 45 mg/kg)-induced diabetic animal model was used and treatment with oral dosing of T. stans leaf extract at the different doses of 200 mg/kg, 300 mg/kg, and highest dose, i.e., 400 mg/kg, was initiated on day 3 after STZ administration. The pharmacological response for general and biochemical (angiogenic, inflammatory, and oxidative) parameters and behavioral parameters were compared using Gabapentin as a standard drug with the results from the test drug.

Results

Parameters associated with the pathogenesis of diabetic neuropathy were evaluated. For general parameters, different doses of T. stans extract (TSE) on blood sugar showed significant effects as compared to the diabetic group. Also, the results from biochemical analysis and behavioral parameters showed significant positive effects in line with general parameters. The combination therapy of TSE at 400 mg/kg with a standard drug produced nonsignificant effects in comparison with the normal group.

Conclusion

The leaves of T. stans possess antidiabetic effects along with promising effects in the management of DN by producing significant effects by exhibiting antioxidative, antiangiogenic, and anti-inflammatory properties, which are prognostic markers for DN, and thus, T. stans can be considered as an emerging therapeutic option for DN.

SP6616 as a Kv2.1 inhibitor efficiently ameliorates peripheral neuropathy in diabetic mice

BACKGROUND

Diabetic peripheral neuropathy (DPN) is a common complication of diabetes severely afflicting the patients, while there is yet no effective medication against this disease. As Kv2.1 channel functions potently in regulating neurological disorders, the present work was to investigate the regulation of Kv2.1 channel against DPN-like pathology of DPN model mice by using selective Kv2.1 inhibitor SP6616 (ethyl 5-(3-ethoxy-4-methoxyphenyl)-2-(4-hydroxy-3-methoxybenzylidene)-7-methyl-3-oxo-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-6-carboxylate) as a probe.

METHODS

STZ-induced type 1 diabetic mice with DPN (STZ mice) were defined at 12 weeks of age (4 weeks after STZ injection) through behavioral tests, and db/db (BKS Cg-m+/+Leprdb/J) type 2 diabetic mice with DPN (db/db mice) were at 18 weeks of age. SP6616 was administered daily via intraperitoneal injection for 4 weeks. The mechanisms underlying the amelioration of SP6616 on DPN-like pathology were investigated by RT-PCR, western blot and immunohistochemistry technical approaches against diabetic mice, and verified against the STZ mice with Kv2.1 knockdown in dorsal root ganglion (DRG) tissue by injection of adeno associated virus AAV9-Kv2.1-RNAi. Amelioration of SP6616 on the pathological behaviors of diabetic mice was assessed against tactile allodynia, thermal sensitivity and motor nerve conduction velocity (MNCV).

FINDINGS

SP6616 treatment effectively ameliorated the threshold of mechanical stimuli, thermal sensitivity and MNCV of diabetic mice. Mechanism research results indicated that SP6616 suppressed Kv2.1 expression, increased the number of intraepidermal nerve fibers (IENFs), improved peripheral nerve structure and vascular function in DRG tissue. In addition, SP6616 improved mitochondrial dysfunction through Kv2.1/CaMKKβ/AMPK/PGC-1α pathway, repressed inflammatory response by inhibiting Kv2.1/NF-κB signaling and alleviated apoptosis of DRG neuron through Kv2.1-mediated regulation of Bcl-2 family proteins and Caspase-3 in diabetic mice.

INTERPRETATION

Our work has highly supported the beneficial of Kv2.1 inhibition in ameliorating DPN-like pathology and highlighted the potential of SP6616 in the treatment of DPN.

FUNDING

Please see funding sources.

Differential effects of minocycline on microvascular complications in murine models of type 1 and type 2 diabetes

Diabetes is a global healthcare problem associated with enormous healthcare and personal costs. Despite glucose lowering agents that control glycaemia, both type 1 (T1D) and type (T2D) diabetes patients often develop microvascular complications that increase morbidity and mortality. Current interventions rely on careful glycemic control and healthy lifestyle choices, but these are ineffective at reversing or completely preventing the major microvascular complications, diabetic peripheral neuropathy (DPN), diabetic retinopathy (DR), and diabetic kidney disease (DKD). Minocycline, a tetracycline antibiotic with anti-inflammatory and anti-apoptotic properties, has been proposed as a protective agent in diabetes. However, there are no reported studies evaluating the therapeutic efficacy of minocycline in T1D and T2D models for all microvascular complications (DPN, DR, and DKD). Therefore, we performed metabolic profiling in streptozotocin-induced T1D and db/db T2D models and compared the efficacy of minocycline in preventing complications to that of insulin and pioglitazone in both models. Minocycline partially ameliorated DR and DKD in T1D and T2D animals, but was less effective than insulin or pioglitazone, and failed to improve DPN in either model. These results suggest that minocycline is unlikely to improve outcomes beyond that achieved with current available therapies in patients with T1D or T2D associated microvascular complications.

Hesperidin as a Neuroprotective Agent: A Review of Animal and Clinical Evidence

Neuroprotection is the preservation of function and networks of neural tissues from damages caused by various agents, as well as neurodegenerative diseases such as Parkinson’s, Alzheimer’s, Huntington’s diseases, and multiple sclerosis. Hesperidin, a flavanone glycoside, is a natural phenolic compound with a wide range of biological effects. Mounting evidence has demonstrated that hesperidin possesses inhibitory effect against development of neurodegenerative diseases. Our review discusses neuropharmacological mechanisms for preventive and therapeutic effects of hesperidin in neurodegenerative diseases. In addition, the review examines clinical evidence confirming its neuroprotective function. Various cellular and animal models specific to neurodegenerative diseases have been conducted to evaluate the underlying neuropharmacological mechanisms of hesperidin. Neuroprotective potential of this flavonoid is mediated by improvement of neural growth factors and endogenous antioxidant defense functions, diminishing neuro-inflammatory and apoptotic pathways. Despite the various preclinical studies on the role of hesperidin in the neurodegenerative diseases, less is known about its definite effect on humans. A limited number of clinical trials showed that hesperidin-enriched dietary supplements can significantly improve cerebral blood flow, cognition, and memory performance. Further clinical trials are also required for confirming neuroprotective efficacy of this natural flavonoid and evaluating its safety profile.

KCNQ2/3/5 channels in dorsal root ganglion neurons can be therapeutic targets of neuropathic pain in diabetic rats

Background

Diabetic neuropathic pain is poorly controlled by analgesics, and the precise molecular mechanisms underlying hyperalgesia remain unclear. The KCNQ2/3/5 channels expressed in dorsal root ganglion neurons are important in pain transmission. The expression and activity of KCNQ2/3/5 channels in dorsal root ganglion neurons in rats with diabetic neuropathic pain were investigated in this study.

Methods

The mRNA levels of KCNQ2/3/5 channels were analyzed by real-time polymerase chain reaction. The protein levels of KCNQ2/3/5 channels were evaluated by Western blot assay. KCNQ2/3/5 channel expression in situ in dorsal root ganglion neurons was detected by double fluorescent labeling technique. M current (I_M) density and neuronal excitability were determined by whole-cell voltage and current clamp recordings. Mechanical allodynia and thermal hyperalgesia were assessed by von Frey filaments and plantar analgesia tester, respectively.

Results

The mRNA and protein levels of KCNQ2/3/5 channels significantly decreased, followed by the reduction of I_M density and elevation of neuronal excitability of dorsal root ganglion neurons from diabetic rats. Activation of KCNQ channels with retigabine reduced the hyperexcitability and inhibition of KCNQ channels with XE991 enhanced the hyperexcitability. Administration of retigabine alleviated both mechanical allodynia and thermal hyperalgesia, while XE991 augmented both mechanical allodynia and thermal hyperalgesia in diabetic neuropathic pain in rats.

Conclusion

The findings elucidate the mechanisms by which downregulation of the expression and reduction of the activity of KCNQ2/3/5 channels in diabetic rat dorsal root ganglion neurons contribute to neuronal hyperexcitability, which results in hyperalgesia. These data provide intriguing evidence that activation of KCNQ2/3/5 channels might be the potential new targets for alleviating diabetic neuropathic pain symptoms.

Minocycline as a promising therapeutic strategy for chronic pain

Chronic pain remains to be a clinical challenge due to insufficient therapeutic strategies. Minocycline is a member of the tetracycline class of antibiotics, which has been used in clinic for decades. It is frequently reported that minocycline may has many non-antibiotic properties, among which is its anti-nociceptive effect. The results from our lab and others suggest that minocycline exerts strong analgesic effect in animal models of chronic pain including visceral pain, chemotherapy-induced periphery neuropathy, periphery injury induced neuropathic pain, diabetic neuropathic pain, spinal cord injury, inflammatory pain and bone cancer pain. In this review, we summarize the mechanisms underlying the analgesic effect of minocycline in preclinical studies. Due to a good safety record when used chronically, minocycline may become a promising therapeutic strategy for chronic pain in clinic.

The efficacy of gabapentin in reducing pain intensity and postoperative nausea and vomiting following laparoscopic cholecystectomy: A meta-analysis

BACKGROUND

It is unknown whether gabapentin is effective in reducing acute pain following laparoscopic cholecystectomy. The purpose of the current meta-analysis was to evaluate the efficacy of gabapentin in reducing pain intensity and postoperative nausea and vomiting (PONV) after laparoscopic cholecystectomy.

METHODS

All randomized controlled trials (RCTs) evaluating the efficacy of gabapentin in reducing pain intensity and PONV after laparoscopic cholecystectomy were searched on the following databases: PubMed, EMBASE, the Cochrane Central Register of Controlled Trials (CENTRAL), the Google database, the Chinese Wanfang database, and the China National Knowledge Infrastructure (CNKI). The most recent literature search was conducted on March 21, 2017. Outcomes including visual analog scale (VAS) at 12 and 24 hours, total morphine consumption, and the occurrence of PONV. Continuous outcomes were expressed as the weighted mean difference (WMD) and 95% confidence interval (CI), and the one discontinuous outcome was expressed as risk ratio (RR) and 95% CI. Stata 12.0 software was used for meta-analysis.

RESULTS

A total of 9 studies involving 966 patients were identified. In total, there were 484 gabapentin subjects and 482 controls. Compared with the control group, gabapentin was associated with lower VAS at 12 hours (WMD = -10.18, 95% CI: -17.36 to -2.80, P = .007) and 24 hours (WMD = -6.33, 95% CI: -8.41 to -4.25, P = .000), which was equivalent on a 110-point VAS scale to 10.18 points at 12 hours and 6.33 points at 24 hours. Compared with the control group, gabapentin was associated with less total morphine consumption by approximately 110.83 mg (WMD = -110.83, 95% CI: -183.25 to -38.42, P = .003). In addition, the occurrence of nausea and vomiting in gabapentin was decreased (25.2% vs 47.6, RR = 0.53, 95% CI: 0.44-0.63, P = .000).

CONCLUSION

Gabapentin was efficacious in reducing postoperative pain, total morphine consumption, and morphine-related complications following laparoscopic cholecystectomy. In addition, there was a negative correlation between the gabapentin dosage and the occurrence of nausea and vomiting. The number of included studies is limited, and more studies are needed to verify the effects of gabapentin in laparoscopic cholecystectomy patients.