Tannins in the Treatment of Diabetic Neuropathic Pain: Research Progress and Future Challenges

Diabetes mellitus and its consequences continue to put a significant demand on medical resources across the world. Diabetic neuropathic pain (DNP) is a frequent diabetes mellitus chronic microvascular outcome. Allodynia, hyperalgesia, and aberrant or lack of nerve fibre sensation are all symptoms of DNP. These clinical characteristics will lead to worse quality of life, sleep disruption, depression, and increased mortality. Although the availability of numerous medications that alleviate the symptoms of DNP, the lack of long-term efficacy and unfavourable side effects highlight the urgent need for novel treatment strategies. This review paper systematically analysed the preclinical research on the treatment of DNP using plant phytochemicals that contain only tannins. A total of 10 original articles involved in in-vivo and in-vitro experiments addressing the promising benefits of phytochemical tannins on DNP were examined between 2008 and 2021. The information given implies that these phytochemicals may have relevant pharmacological effects on DNP symptoms through their antihyperalgesic, anti-inflammatory, and antioxidant properties; however, because of the limited sample size and limitations of the studies conducted so far, we were unable to make definitive conclusions. Before tannins may be employed as therapeutic agents for DNP, more study is needed to establish the specific molecular mechanism for all of these activities along the pain pathway and examine the side effects of tannins in the treatment of DNP.

LncRNA-UC.25+ ShRNA Alleviates P2Y14 Receptor Mediated Diabetic Neuropathic Pain Via STAT1

Diabetic neuropathic pain (DNP) is a common complication of diabetes, and its complicated pathogenesis as well as clinical manifestations has brought great troubles to clinical treatment. The spinal cord is an important part of regulating the occurrence and development of DNP. Spinal microglia can regulate the activity of spinal cord neurons and have a regulatory effect on chronic pain. P2Y12 receptor is involved in DNP. P2Y14 and P2Y12 receptor belong to the Gi subtype of P2Y receptors, but there is no report that P2Y14 receptor is involved in DNP. Closely related to many human diseases, the dysregulation of lncRNA has the effect of promoting or inhibiting the occurrence and development of diseases. The aim of this research is to investigate the function of spinal cord P2Y14 receptor in type 2 DNP and to understand the function as well as the possible mechanism of lncRNA-UC.25+ (UC.25+) in rat spinal cord P2Y14 receptor-mediated DNP. Our results showed that P2Y14 shRNA can reduce the expression of P2Y14 in DNP rats, thereby restraining the activation of microglia, decreasing the expression of inflammatory factors and the level of p38 MAPK phosphorylation. At the same time, UC.25+ shRNA can down-regulate the expression of P2Y14 receptor, reduce the release of inflammatory factors, and diminish the p38 MAPK phosphorylation, indicating that UC.25+ can alleviate spinal cord P2Y14 receptor-mediated DNP. The RNA immunoprecipitation result showed that UC.25+ enriched STAT1 and positively regulated its expression. The chromatin immunoprecipitation result indicated that STAT1 combined to the promoter region of P2Y14 receptor and positively regulated the expression of P2Y14 receptor. Therefore, we infer that UC.25+ may alleviate DNP in rats by regulating the expression of P2Y14 receptor in spinal microglia via STAT1.

Inhibition of phosphorylated calcium/calmodulin-dependent protein kinase IIα relieves streptozotocin-induced diabetic neuropathic pain through regulation of P2X3 receptor in dorsal root ganglia

Diabetic neuropathic pain (DNP) is frequent among patients with diabetes. We previously showed that P2X3 upregulation in dorsal root ganglia (DRG) plays a role in streptozotocin (STZ)-induced DNP but the underlying mechanism is unclear. Here, a rat model of DNP was established by a single injection of STZ (65 mg/kg). Fasting blood glucose was significantly elevated from the 1st to 3rd week. Paw withdrawal thresholds (PWTs) and paw withdrawal latencies (PWLs) in diabetic rats significantly reduced from the 2nd to 3rd week. Western blot analysis revealed that elevated p-CaMKIIα levels in the DRG of DNP rats were accompanied by pain-associated behaviors while CaMKIIα levels were unchanged. Immunofluorescence revealed significant increase in the proportion of p-CaMKIIα immune positive DRG neurons (stained with NeuN) in the 2nd and 3rd week and p-CaMKIIα was co-expressed with P2X3 in DNP rats. KN93, a CaMKII antagonist, significantly reduce mechanical hyperalgesia and thermal hyperalgesia and these effects varied dose-dependently, and suppressed p-CaMKIIα and P2X3 upregulation in the DRGs of DNP rats. These results revealed that the p-CaMKIIα upregulation in DRG is involved in DNP, which possibly mediated P2X3 upregulation, indicating CaMKIIα may be an effective pharmacological target for DNP management.

Transdermal electroneurostimulation in patients with diabetic neuropathy

BACKGROUND: The dynamics of pain syndrome determined using various algic tests in the treatment of patients with diabetic neuropathic pain syndrome using tansdermal electroneurostimulation has been little studied. AIMS: To study the dynamics of projection zones of neuropathic pain syndrome in patients with diabetic polyneuropathy while using TENS. MATERIAL AND METHODS: 75 patients with diabetic polyneuropathy were examined. The control group (n=25; 33.3%) received a course of standard pharmacotherapy. The main group consisted of 2 groups. The first group (n=25; 33.3%) underwent a course of high-frequency low-amplitude (HL TENS) transdermal electroneurostimulation, and the second group (n=25; 33.3%) underwent a course of low-frequency high-amplitude (LH TENS) therapy. Pain syndrome was determined using a visual analogue scale (VAS) and a body diagram before, after treatment and in the long-term period. RESULTS: Using a visual analogue scale (VAS), the dynamics of pain syndrome after the use of LF TENS was lower than after the use of HFTENS by an average of 35% (p 0.05). The data obtained indicate that the regression of pain syndrome after physiotherapeutic treatment of TENS in patients from the main comparison groups exceeds similar indicators in patients from the control group by an average of 63% (p 0.05) both immediately after the course of exposure and in the distant the observation period by 23%. Against the background of TENS, the area of pain syndrome according to the body pattern significantly decreased by 53% after treatment (p 0.05) and by 65.6% in the long-term period (p 0.05), compared with a decrease in the area of pain syndrome in the control group. CONCLUSION: There were revealed significant differences between the quantitative and projection forms of pain measurement. The use of TENS enhances the analgesic effect of drug therapy in the treatment of diabetic neuropathic pain syndrome by 1.37 times while maintaining this effect without negative dynamics for 2 months after the end of the course of non-drug therapy. The developed technique for assessing pain syndrome using a body diagram in combination with a visual analogue scale (VAS) in patients with diabetic polyneuropathy provides a more reliable assessment of pain syndrome.

Jinmaitong Alleviates Diabetic Neuropathic Pain Through Modulation of NLRP3 Inflammasome and Gasdermin D in Dorsal Root Ganglia of Diabetic Rats

Jinmaitong (JMT) is a compound prescription of traditional Chinese medicine that has been used to treat diabetic neuropathic pain (DNP) for many years. Here, we investigated the effects of JMT on the activation of NOD-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome and pyroptosis in Dorsal root ganglia (DRG) of diabetic rats. Streptozotocin (STZ)-induced diabetic rats were gavaged with JMT (0.88 g/kg/d) or alpha-lipoic acid (ALA, positive control, 0.48 mmol/kg/d) for 12 weeks. Distilled water was administered as a vehicle control to both diabetic and non-affected control rats. Blood glucose levels and body weights were measured. Behavioral changes were tested with mechanical withdrawal threshold (MWT) and tail-flick latency (TFL) tests. Morphological injury associated with DRG was observed with hematoxylin and eosin (H&E) and Nissl’s staining. mRNA and protein levels of NLRP3 inflammasome components (NLRP3, ASC, caspase-1), downstream IL-1β and gasdermin D (GSDMD) were evaluated by immunohistochemistry, quantitative real time-PCR and western blot. The results showed that JMT had no effect on blood glucose levels and body weights, but significantly improved MWT and TFL behavior in diabetic rats, and attenuated morphological damage in the DRG tissues. Importantly, JMT decreased the mRNA and protein levels of components of NLRP3 inflammasome, including NLRP3, ASC and caspase-1. JMT also down-regulated the expression of IL-1β and GSDMD in the DRG of DNP rats. In addition, ALA treatment did not perform better than JMT. In conclusion, JMT effectively relieved DNP by decreasing NLRP3 inflammasome activation and pyroptosis, providing new evidence supporting JMT as an alternative treatment for DNP.

Effect of Pentoxifylline on Diabetic Neuropathic Pain in Rats

Background and Aim Diabetic neuropathy (DN) is the most common diabetic complication, which has a lifetime prevalence of about 50%. About 20 to 30% of patients with DN suffer from neuropathic pain. This study was designed to investigate the role of early and late treatment of pentoxifylline (PTX) in management of diabetic neuropathic pain (DNP). Method Diabetic rats were administered PTX (50 and 200 mg/kg/day, in drinking water) either one week after STZ injection and for 7 weeks or 6 weeks after STZ injection and for 2 weeks. Mechanical allodynia were assessed weekly, Iba-1 and GFAP immunorectivity, spinal NFκB & spinal sciatic TNF-α were estimated at the end of the study. Epidermal thickness of the food pad and Na+/K+-ATPase activity in sciatic nerve were measured as an outcome measure for predegenerative markers of DN. Results The results of the present study suggest that activated microglia and not astrocytes are involved in the development of experimental diabetic neuropathy. PTX inhibit neuroimmune activation of microglia, reduce the levels of proinflammatory cytokines and improve epidermal thickness of the food pad and Na+/K+-ATPase activity in sciatic nerve. Only PTX 200 mg/kg/day when administered early and late treatment in diabetic rats produced antiallodynic effect. Conclusion PTX is a fundamental drug whose antiallodynic effect depends on the pathogenetic mechanisms and has the ability to halt or inhibit the progression of the disease. The earlier the use of PTX in the developmental phase of mechanical hyperalgesia the more the antiallodynic effect of the drug.

Diabetic Neuropathic Pain has Endogenous Modulation Depending on the Intensity of Physical Exercise: A Brief Communication

The opioidergic systems play a key role in endogenous modulation of neuropathic pain, given that Naloxone, a nonselective opioid receptors antagonist at a dose of 100 µg, reverted the antihyperalgesia caused by physical exercise demonstrated in our previous study. Due to the lack of relates regarding the control variables of physical exercise and endogenous modulation in neuropathic diabetic pain, we investigated if such modulation is exercise intensity dependent.