Xuebijing Injection Ameliorates H2S-Induced Acute Respiratory Distress Syndrome by Promoting Claudin-5 Expression.

OBJECTIVE: To investigate the protective effects and underlying mechanisms of Xuebijing Injection (XBJ) on the lung endothelial barrier in hydrogen sulfide (H2S)-induced acute respiratory distress syndrome (ARDS). METHODS: Sprague-Dawley rats were exposed to H2S (300 ppm) to establish ARDS model, while human pulmonary microvascular endothelial cells (HPMECs) were incubated with NaHS (a H2S donor, 500 µmol/L) to establish cell model. H2S and XBJ were concurrently administered to the rat and cell models. Lung hematoxylin and eosin staining, immunohistochemistry, transmission electron microscopy and wet/dry ratio measurement were used to confirm ARDS induced by H2S in vivo. The expression levels of claudin-5, phosphorylated protein kinase B (p-AKT)/t-AKT and p-forkhead box transcription factor O1 (FoxO1)/t-FoxO1 in vivo and in vitro were also assessed. Paracellular permeability and transepithelial electrical resistance (TEER) were measured to evaluate endothelial barrier function in the cell model. RESULTS: The morphological investigation showed that XBJ attenuated H2S-induced ARDS in rats. XBJ significantly ameliorated both the reduction in TEER and the increased paracellular permeability observed in NaHS-treated HPMECs (P<0.05). The protective effects of XBJ were blocked by LY294002, a phosphatidylinositol 3-kinase (PI3K)/AKT/FoxO1 pathway antagonist (P<0.05). Furthermore, XBJ promoted the expression of claudin-5 and increased the levels of p-AKT and p-FoxO1 in vivo and in vitro (P<0.05). CONCLUSIONS: XBJ ameliorated H2S-induced ARDS by promoting claudin-5 expression via the PI3K/AKT/FoxO1 signaling pathway.

Spinal P2X7R contributes to streptozotocin-induced mechanical allodynia in mice.

Painful diabetic neuropathy (PDN) is a diabetes mellitus complication. Unfortunately, the mechanisms underlying PDN are still poorly understood. Adenosine triphosphate (ATP)-gated P2X7 receptor (P2X7R) plays a pivotal role in non-diabetic neuropathic pain, but little is known about its effects on streptozotocin (STZ)-induced peripheral neuropathy. Here, we explored whether spinal cord P2X7R was correlated with the generation of mechanical allodynia (MA) in STZ-induced type 1 diabetic neuropathy in mice. MA was assessed by measuring paw withdrawal thresholds and western blotting. Immunohistochemistry was applied to analyze the protein expression levels and localization of P2X7R. STZ-induced mice expressed increased P2X7R in the dorsal horn of the lumbar spinal cord during MA. Mice injected intrathecally with a selective antagonist of P2X7R and P2X7R knockout (KO) mice both presented attenuated progression of MA. Double-immunofluorescent labeling demonstrated that P2X7R-positive cells were mostly co-expressed with Iba1 (a microglia marker). Our results suggest that P2X7R plays an important role in the development of MA and could be used as a cellular target for treating PDN.

CX3CR1 contributes to streptozotocin-induced mechanical allodynia in the mouse spinal cord.

Patients with diabetic peripheral neuropathy experience debilitating pain that significantly affects their quality of life (Abbott et al., 2011), by causing sleeping disorders, anxiety, and depression (Dermanovic Dobrota et al., 2014). The primary clinical manifestation of painful diabetic neuropathy (PDN) is mechanical hypersensitivity, also known as mechanical allodynia (MA) (Callaghan et al., 2012). MA's underlying mechanism remains poorly understood, and so far, based on symptomatic treatment, it has no effective therapy (Moore et al., 2014).

Systemic dexmedetomidine attenuates mechanical allodynia through extracellular sign db type 2 diabetic mice.

Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus. However, the treatment for PDN is limited in clinical practice. In the present study, we investigated the effect of systemic administration dexmedetomidine (DEX), a selective alpha 2 adrenergic receptor (α2AR) agonist, on mechanical allodynia and its underlying mechanism in db/db mice, an animal model of type 2 diabetes mellitus. Our data demonstrated that db/db mice develop mechanical allodynia at the early stage of diabetes. During the period of mechanical allodynia, we detected increased release of norepinephrine (NE) and decreased levels of α2A-Adrenoceptors in db/db mice. Immunohistochemistry showed that the α2A-Adrenoceptor is predominantly expressed in neurons in the spinal cord. Acute injection of dexmedetomidine significantly decreased mechanical allodynia, which was blocked by its selective antagonist BRL44408. Furthermore, the upregulation of pERK1 and pERK2 in db/db mice were attenuated by preadministration of dexmedetomidine. We provide the first evidence that the functional alternation of spinal noradrenergic system might underlie exaggerated nociception in PDN. Systemic dexmedetomidine inhibits the mechanical allodynia which is related to ERK signaling pathway in type 2 diabetes, implying that the α2-Adrenoceptor might be a potential therapeutic strategy for PDN.

Extracellular signal-regulated protein kinase activation in spinal cord contributes to pain hypersensitivity in a mouse model of type 2 diabetes.

Painful peripheral neuropathy is a common complication of diabetes mellitus. The symptom of pain can become a major factor that decreases the quality of life of patients with diabetes, while effective treatment is lacking. In the present study, we aimed to investigate the changes of pain threshold in the early stage of diabetes in db/db mice, an animal model of type 2 diabetes mellitus, and the underlying molecular mechanisms. We found that (1) db/db mice (with a leptin receptor-null mutation and characterized by obesity and hyperglycemia) showed hypersensitivity to mechanical and thermal stimuli at the early stage of diabetes; (2) phosphorylated extracellular signal-regulated kinase (pERK), but not total ERK in the spinal cord and dorsal root ganglia in db/db mice significantly increased compared with wild-type mice. The increased pERK immunoreactivity occurred in both NeuN-expressing neurons and GFAP-expressing astrocytes, but not in Iba-1-expressing microglia; (3) both single and consecutive (for 5 days) intrathecal injections of U0126 (2 nmol per day), a selective MEK (an ERK kinase) inhibitor beginning at 8 weeks of age, attenuated the bilateral mechanical allodynia in the von-Frey test and heat hyperalgesia in Hargreave's test; and (4) db/db mice also displayed increased nocifensive behavior during the formalin test, and this was blocked by intrathecal injection of U0126. Also, the expression of pERK1 and pERK2 was upregulated following the formalin injection. Our results suggested that the activation of ERK in spinal neurons and astrocytes is correlated with pain hypersensitivity of the type 2 diabetes animal model. Inhibiting the ERK pathway may provide a new therapy for pain control in type 2 diabetes.