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Prolonged hyperglycemia-induced oxidative stress and endoplasmic reticulum stress have been demonstrated to play a key role in progression of diabetic peripheral neuropathy (DPN). PERK/ Nrf2 pathway plays a predominant role in oxidative and endoplasmic reticulum (ER) stress which is associated with cell survival. This study examined the modulation of the PERK/Nrf2 pathway and apoptosis by a traditional Chinese medicine Tangluoning (TLN) in streptozotocin-induced DPN rat models and the effects of serum TLN on the PERK/Nrf2 pathway, apoptosis, intracellular reactive oxygen species and mitochondrial membrane potential in Schwann cells cultured in 150 mM glucose. It is found that TLN attenuated oxidative and ER stress and apoptosis through the PERK/Nrf2 pathway by upregulating p-PERK, Nrf2/ARE pathways and downregulating the CHOP-related apoptosis pathways in the experimental DPN models both in vivo and in vitro.

BackgroundTang Bi Kang (TBK) is a traditional Chinese medicine granule. It has been shown to have effects on nerve conduction velocity deficits, blood-related factors and oxidative stress. This study was undertaken to evaluate proposed antioxidative and anti-inflammatory activity of Tang Bi Kang in rats with diabetic peripheral neuropathy (DPN).MethodsDPN was induced in male Wistar rats by intraperitoneal administration of streptozocin (STZ) (60 mg/kg.b.w) for 8 weeks. Fasting blood glucose (FBG) levels were measured in the blood obtained by clipping the tails of the rats. Tail-flick tests were conducted with a tail-flick analgesic meter. Motor and sensory nerve conduction velocities (MNCV and SNCV) of sciatic nerve were measured directly at two sites using a Functional Experiment System. Oxidative stress makers such as malondialdehyde (MDA), superoxide-dismutase (SOD) and glutathione peroxidase (GSH-Px), inflammatory cytokines such as interleukin (IL)-6, and tumour necrosis factor (TNF)-α were estimated. The statistical analysis of results was carried out using Student t-test and one-way analysis of variance (ANOVA), followed by least-significant difference post hoc with SPSS.ResultsThe administration of TBK for 4 weeks in DPN rats resulted in a significant decrease in FBG levels compared to untreated DPN rats. There was a significant increase in MNCV and SNCV in the DPN rats compared to untreated DPN rats. Serum level of MDA was significantly reduced while the activities of SOD and GSH-pX were significantly increased in the TBK treated DPN rats. TBK prevented DPN-induced increase in the serum levels of IL-6 and TNF-α.ConclusionThe results of this study demonstrate that the therapeutic effect of TBK on DPN rats may be associated with the antioxidative and anti-inflammatory responses.

Glomerular mesangial cells (GMCs) activation is implicated in the pathogenesis of diabetic nephropathy (DN). Our previous study revealed that high glucose (HG)-treated glomerular endothelial cells (GECs) produce an increased number of TGF-[Formula: see text]1-containing exosomes to activate GMCs through the TGF-[Formula: see text]1/Smad3 signaling pathway. We also identified that Tongxinluo (TXL), a traditional Chinese medicine, has beneficial effects on the treatment of DN in DN patients and type 2 diabetic mice. However, it remained elusive whether TXL could ameliorate renal structure and function through suppression of intercellular transfer of TGF-[Formula: see text]1-containing exosomes from GECs to GMCs. In this study, we demonstrate that TXL can inhibit the secretion of TGF-[Formula: see text]1-containing exosomes from HG-treated GECs. Furthermore, exosomes produced by HG induced-GECs treated with TXL cannot trigger GMC activation, proliferation and extracellular matrix (ECM) overproduction both in vitro and in vivo. These results suggest that TXL can prevent the transfer of TGF-[Formula: see text]1 from GECs to GMCs via exosomes, which may be one of the mechanisms of TXL in the treatment of DN.