Dexmedetomidine protects against lung injury induced by limb ischemia-reperfusion via the TLR4/MyD88/NF-κB pathway.

Dexmedetomidine (DEX) can protect the lung from ischemia-reperfusion (I/R) injury, but the underlying mechanisms are not fully understood. The aims of this study were to determine whether DEX attenuates lung injury following lower extremity I/R and to investigate the related toll-like receptor 4 (TLR4) signaling pathway. Twenty-eight SD rats were divided into four groups (n = 7): Sham, I/R, I/R + DEX (25 µg/kg prior to ischemia), and I/R + DEX + Atip (250 µg/kg atipamezole before DEX treatment). Lower extremity I/R was induced by left femoral artery clamping for 3 hours and followed by 2 hours reperfusion. Quantitative alveolar damage and the wet/dry (W/D) ratio were calculated. Interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF)-α in the bronchoalveolar lavage fluid (BALF) and serum and myeloperoxidase (MPO) in the lung were measured. The TLR4 and MyD88 mRNA expression levels were measured by RT-PCR, nuclear factor (NF)-κB, and phosphorylated NF-κB by western blot, respectively. Quantitative alveolar damage, W/D ratio, MPO, BALF and serum IL-1, IL-6, and TNF-α, and TLR4, MyD88, NF-κB, and p-NF-κB expression significantly increased in the I/R group relative to the Sham group. DEX preconditioning significantly reduced lung edema, and histological injury relative to the I/R group. Serum and BALF IL-1, IL-6, and TNF-α levels, MPO activity and TLR4, MyD88, NF-κB, and p-NF-κB expression were also significantly reduced in the I/R + DEX group compared with the I/R group. Atipamezole partially reversed all the aforementioned effects. DEX preconditioning protects the lungs against lower extremity I/R injury via α2-adrenoceptor-dependent and α2-adrenoceptor-independent mechanisms. It also suppresses the TLR4 pathway and reduces inflammation.

[Nrf2/ARE pathway mediates the reducing effect of Dexmedeto-midine on ischemia/reperfusion injury in skeletal muscle].

OBJECTIVE: To explore the role of Nrf2/ARE pathway in skeletal muscle ischemia/reperfusion(I/R) injury preconditioning by dexmedetomidine(DEX). METHODS: Twenty-eight SD rats were randomly divided into sham-operated(Sham group)、I/R group、I/R+ DEX(DEX group) and I/R+DEX +Atipamezole (Atip group). In the Atip group, Atip(250 µg/kg) and DEX(25 µg/kg) were injected together after anesthesia; In the Sham and I/R groups, the homologous saline was also injected at the same time; In the DEX group, the homologous DEX and saline were coinjected. After 30 minutes, the hind limb ischemia was induced by clamping the common femoral artery and ligaturing collateral circulation. After 3 h of ischemia, the clamp and tourniquet were removed and the rats underwent 2 h of reperfusion. We measured plasma concentrations of lactate dehydrogenase (LDH) and creatine kinase(CK). The gastrocnemius muscle was harvested and immediately stored at -80℃ for the assessment of malondialdehyde(MDA)、superoxide dismutase(SOD) and Nrf2/HO-1 protein detected by Western blot. The other section muscle was stored in triformol for immunohistochemical and HE staining. The wet/dry was also immediately detecting. RESULTS: The levels of wet/dry、MDA、LDH、CK、Nrf2 and HO-1 were higher(P<0.05) while the level of SOD was lower(P<0.05) in the I/R group than those in sham group. The levels of wet/dry、MDA、LDH、CK were significantly lower(P<0.05) yet the levels of SOD and Nrf2/HO-1 were significantly higher(P<0.05) in DEX group than those in I/R group. However, Atip reversed the effect of DEX in Atip group, each of indicators had significant changes compared with those in the DEX group(P<0.05). CONCLUSIONS: Nrf2 protein was expressed in skeletal muscle of rat and DEX could promote its level in nucleus by α-adrenergic receptor. The down-stream products of Nrf2 have the effect of antioxidant.

Identification of major compounds in rat bile after oral administration of total triterpenoids of Ganoderma lucidum by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry.

Triterpenoids are the main bioactive components of Ganoderma lucidum, a famous traditional Chinese medicine. After oral administration of total triterpenoids of G. lucidum (TTGL), the rat bile was analyzed by high-performance liquid chromatography coupled with diode array detection and electrospray ion trap tandem mass spectrometry (HPLC-DAD-ESI-MS(n)) and liquid chromatography coupled with electrospray ionization hybrid ion trap and time-of-flight mass spectrometry (LC-ESI-IT-TOF/MS). From rat bile and TTGL samples, a total of 31 triterpenoids, including seven new compounds, were identified or tentatively characterized based on their fragmentation behaviors. Among them, 22 triterpenoids were identified from TTGL and 29 triterpenoids were detected from rat bile after oral administration of TTGL. The results indicated that the majority of triterpenoids detected in TTGL extract could be excreted through rat bile. It is the first report on excretion of total triterpenoids of G. lucidum in rat bile.