The effect of a nitroxide antioxidant on ischemia-reperfusion injury in the ratin vivohind limb model

Low-molecular-weight heparin calcium attenuates the tourniquet-induced ischemia-reperfusion injury in rats

Ischemia-reperfusion injury (IRI) is a common postoperative complication of the tourniquet used surgery; low-molecular-weight heparin calcium (LMWH) is frequently used postoperatively to prevent the formation of deep venous thrombosis. However, subcutaneous hemorrhage can usually be seen in patients who underwent lower limb surgery, especially in total knee arthroplasty, the influence of LMWH on IRI remains controversial. In this experiment, we designed an animal model to observe the influence of LMWH on the skeletal muscle injury induced by tourniquets. Sprague-Dawley (SD) rats underwent either 2 h of unilateral hindlimb ischemia or anesthesia alone, at different time points of reperfusion interval, animals received either 4mg/kg LMWH or normal saline subcutaneously twice a day. The levels of inflammatory markers in serum, the expression of apoptosis proteins, as well as histological examination of skeletal muscles, were detected at 48-h reperfusion. We found that the injury of skeletal muscle and the systemic inflammatory response was less severe in LMWH-treated animals, indicating that LMWH could attenuate the tourniquet-induced IRI. In conclusion, LMWH given postoperatively after limb surgery may be clinically beneficial.

HMGB1/RAGE pro-inflammatory axis promotes vascular endothelial cell apoptosis in limb ischemia/reperfusion injury

OBJECTIVE

High-Mobility Group Box 1 (HMGB1) promotes vascular injuries induced by limb Ischemia and Reperfusion (IR), but the molecular mechanisms are not well understood. This study aimed to investigate the role of Receptor for Advanced-Glycation End products (RAGE) in HMGB1-regulated inflammatory response and vascular injury in limb IR using the rat IR and cellular Hypoxia and Reoxygenation (HR) models.

METHODS

We analyzed the vascular structure and elastic fiber deposition in rat femoral arteries by histological staining. We determined gene expression in vascular tissues and cells by quantitative RT-PCR, Western blotting and immunofluorescence; analyzed the protein levels in rat serum or cell supernatant by ELISA; and assessed protein interaction by co-immunoprecipitation. We used CCK-8 for analyzing cell viability, and assessed apoptosis by Hoechst staining and flow cytometry.

RESULTS

RAGE inhibition by FPS-ZM1 significantly repressed rat vascular injury that was induced by limb IR treatment. HMGB1 and RAGE expression, P38, ERK1/2, P65 and IKBa phosphorylation, as well as HIF-1a, NLRP3, Caspase-1, TNF-a and IL-6 expression and P65 in nucleus, increased in femoral arteries of a rat IR model and HUVEC undergoing HR treatment, whereas all the factors except HMGB1 and RAGE were inhibited by FPS-ZM1 treatment. In addition, we found that HMGB1 binds with RAGE in HUVEC undergoing HR treatment, which was suppressed by FPS-ZM1. Finally, the apoptosis of HUVEC also increased by HR treatment, but repressed under FPS-ZM1 treatment.

CONCLUSION

HMGB1 binds with RAGE to promote vascular inflammation and endothelial cell apoptosis, which mediates vascular injury during acute limb IR.

Unique Superparamagnetic-like Behavior Observed in Non-π-delocalized Nitroxide Diradical Compounds Showing Discotic Liquid Crystalline Phase

A unique superparamagnetic-like behavior and a large "positive magneto-LC effect" were observed in the solid phases and the hexagonal columnar (Col_h ) liquid crystalline (LC) phase, respectively, of novel achiral non-π-delocalized nitroxide diradical compounds (R,S)-1, which showed polymorphism in the solid phases (solids I and II). The SQUID magnetization measurement revealed that (1) (R,S)-1 containing a small amount of racemic diastereomers (R*,R*)-1 possessed an unusual and large temperature-independent magnetic susceptibility (χ_TIM >0) component in the original nanocrystalline solid I that was responsible for the observed superparamagnetic-like behavior under low magnetic fields and did not arise from the contamination by extrinsic magnetic metal or metal ion impurities, besides ordinary temperature-dependent paramagnetic susceptibility (χ_para >0) and temperature-independent diamagnetic susceptibility (χ_dia <0) components, (2) a large increase in molar magnetic susceptibility (χ_M ) (positive magneto-LC effect) that occurred at the solid I-to-liquid crystal transition upon heating was preserved as an additional χ_TIM increase in the resulting polymorphic nanocrystalline solid II by cooling, and (3) such unique magnetic phenomena were induced by thermal processing for (R,S)-1 or by adding a small amount of (R*,R*)-1 to (R,S)-1 as the impurity.

Chiral all-organic nitroxide biradical liquid crystals showing remarkably large positive magneto-LC effects

The liquid crystalline chiral nitroxide biradical (S,S,S,S)-3 synthesized has shown much larger ‘positive magneto-LC effects’ in the chiral nematic (N*) phase than the monoradical (S,S)-1.

Total hip and knee replacement surgery results in changes in leukocyte and endothelial markers

BACKGROUND

It is estimated that over 8 million people in the United Kingdom suffer from osteoarthritis. These patients may require orthopaedic surgical intervention to help alleviate their clinical condition. Investigations presented here was to test the hypothesis that total hip replacement (THR) and total knee replacement (TKR) orthopaedic surgery result in changes to leukocyte and endothelial markers thus increasing inflammatory reactions postoperatively.

METHODS

During this 'pilot study', ten test subjects were all scheduled for THR or TKR elective surgery due to osteoarthritis. Leukocyte concentrations were measured using an automated full blood count analyser. Leukocyte CD11b (Mac-1) and CD62L cell surface expression, intracellular production of H(2)O(2 )and elastase were measured as markers of leukocyte function. Von Willebrand factor (vWF) and soluble intercellular adhesion molecule-1 (sICAM-1) were measured as markers of endothelial activation.

RESULTS

The results obtained during this study demonstrate that THR and TKR orthopaedic surgery result in similar changes of leukocyte and endothelial markers, suggestive of increased inflammatory reactions postoperatively. Specifically, THR and TKR surgery resulted in a leukocytosis, this being demonstrated by an increase in the total leukocyte concentration following surgery. Evidence of leukocyte activation was demonstrated by a decrease in CD62L expression and an increase in CD11b expression by neutrophils and monocytes respectively. An increase in the intracellular H(2)O(2 )production by neutrophils and monocytes and in the leukocyte elastase concentrations was also evident of leukocyte activation following orthopaedic surgery. With respect to endothelial activation, increases in vWF and sICAM-1 concentrations were demonstrated following surgery.

CONCLUSION

In general it appeared that most of the leukocyte and endothelial markers measured during these studies peaked between days 1-3 postoperatively. It is proposed that by allowing orthopaedic surgeons access to alternative laboratory markers such as CD11b, H(2)O(2 )and elastase, CD62L, vWF and sICAM-1, an accurate assessment of the extent of inflammation due to surgery per se could be made. Ultimately, the leukocyte and endothelial markers assessed during this investigation may have a role in monitoring potential infectious complications that can occur during the postoperative period.