Heparin attenuates HMGB1 expression in arterial tissue subjected to limb ischemia/reperfusion

6-O-desulfated heparin attenuates myocardial ischemia/reperfusion injury in mice through the regulation of miR-199a-5p/klotho axis

Heparin has been documented to reduce myocardial injury caused by ischemia/reperfusion (I/R), but its clinical application is limited due to its strong intrinsic anticoagulant property. Some desulfated derivatives of heparin display low anticoagulant activity and may have potential value as therapeutic agents for myocardial I/R injury. In this study, we observed that 6-O-desulfated heparin, a desulfated derivative of heparin, shortened the activated partial thromboplastin time and exhibited lower anticoagulant activity compared with heparin or 2-O-desulfated heparin (another desulfated derivative of heparin). Then, we explored whether 6-O-desulfated heparin could protect against myocardial I/R injury, and elucidated its possible mechanisms. Administration of 6-O-desulfated heparin significantly reduced creatine kinase activity, myocardial infarct size and cell apoptosis in mice subjected to 30 min of myocardial ischemia following 2 h of reperfusion, accompanied by a reverse in miR-199a-5p elevation, klotho downregulation and reactive oxygen species (ROS) accumulation. In cultured H9c2 cells, the mechanism of 6-O-desulfated heparin against myocardial I/R injury was further explored. Consistent with the results in vivo, 6-O-desulfated heparin significantly ameliorated hypoxia/reoxygenation-induced injury, upregulated klotho and decreased miR-199a-5p levels and ROS accumulation, and these effects were reversed by miR-199a-5p mimics. In conclusion, these results suggested that 6-O-desulfated heparin with lower anticoagulant activity attenuated myocardial I/R injury through miR-199a-5p/klotho and ROS signaling. Our study may also indicate that 6-O-desulfated heparin, as an excellent heparin derivative, is a potential therapeutic agent for myocardial I/R injury.

Protective Role of Sulodexide on Renal Injury Induced by Limb Ischemia-Reperfusion

Background

Though widely known as a potent antithrombin agent with protective effects on the kidney and other remote organs, it is currently ambiguous when it comes to sulodexide's function on ischemia-reperfusion (I/R) injury. With this research, we pursued to further explore how sulodexide exerts its influence on limb I/R injury, in which deleterious effects on the kidney were what we primarily focused on.

Methods

We randomized twenty-four C57BL/6 male rats into three groups, namely, sham operation group (control group), I/R group, and sulodexide pretreatment group. Hematoxylin and eosin staining was applied for discovery of renal histological changes. Serum creatinine (Cr) and serum urea nitrogen (BUN) were measured. Apoptotic parameters were detected by the TdT-mediated dUTP Nick-End Labeling method. To what extent and levels that antiapoptotic and proapoptotic proteins were expressed could be sensitively revealed by immunohistochemistry assay. Lipid peroxidation product propylene glycol and inflammatory factors were examined by enzyme-linked immunosorbent assay. Additionally, an extracorporeal hypoxia-reoxygenation (H/R) model of human renal proximal tubule epithelial HK2 cells was established. Our targets lay in cell proliferation and apoptosis, and we used western blotting to reflect apoptosis-related gene expression.

Results

The levels of serum BUN, Cr, and inflammatory factors in sulodexide-intervened rats manifested significant reduction when compared with the I/R group. Also, sulodexide could protect the kidney from histological changes and could effectively inhibit intraparenchymal apoptosis. Furthermore, adding 2 μl/mL or 5 μl/mL of sulodexide to H/R model cells in vitro gave rise to significant restoration of the degenerative proliferation capacity of the HK2 cells following H/R injury and late cellular apoptosis experienced dramatic reduction versus the H/R group. When treated with 5 μl/mL of sulodexide at a dose of 10 mg/kg, the levels of the antiapoptotic proteins were increased, while the proapoptotic proteins showed opposite trends. Notable escalation on antiapoptotic protein expression level, in contrast with the opposite trends exhibited in proapoptotic proteins, was observed with 5 μl/mL sulodexide pretreatment with the dosage being 10 mg/kg.

Conclusion

Sulodexide can protect against kidney damage caused by I/R injury of the lower limbs by enhancing cell proliferation, inhibiting apoptosis, reducing inflammatory reactions, and scavenging oxygen free radicals.

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.

Blockade of HMGB1 preserves vascular homeostasis and improves blood perfusion in rats of acute limb ischemia/reperfusion

Acute limb ischemia is one of the most common peripheral arterial disease, while surgical restoration of blood flow often results in ischemia/reperfusion (I/R) injury. Our previous study revealed the inflammation intensity in arterial tissue, characterized by expression of high mobility group box protein 1 (HMGB1), was contrary to the fluctuation of hemodynamics in reperfusion limbs in a rat model. This study meant to clarify the role of HMGB1 during this process. Laser Doppler perfusion imaging evaluated limb hemodynamics in mean and max perfusion unit (PU). Femoral arterial tissue was collected for molecular biology examination. The results revealed that HMGB1 promoted vascular structure remodeling and vasomotor dysfunction during acute I/R, characterized by degradation of collagenous fibers, disruption of elastic lamellae, intensive inflammation and phenotype transfer of smooth muscle cells. Blockade of HMGB1 preserved vascular homeostasis and improved PUs (P_meanPU<0.001, P_maxPU<0.001). The elevated expression of TNF-α, IL-6, ICAM, VCAM, MMP-2, MMP-9, α-SM actin correlated with HMGB1 positively. In conclusion, HMGB1 promoted vascular remodeling and dysfunction via initiating an inflammation cascade during I/R. Blockade of HMGB1 would preserve vascular homeostasis and facilitate the blood perfusion of ischemic limb.

Does enoxaparin interfere with HMGB1 signaling after TBI? A potential mechanism for reduced cerebral edema and neurologic recovery

BACKGROUND

Enoxaparin (ENX) has been shown to reduce cerebral edema and improve neurologic recovery after traumatic brain injury (TBI), through blunting of cerebral leukocyte (LEU) recruitment. High mobility group box 1 (HMGB1) protein may induce inflammation through LEU activation. We hypothesized that ENX after TBI reduces LEU-mediated edema through blockade of HMGB1 signaling.

METHODS

Twenty-three CD1 mice underwent severe TBI by controlled cortical impact and were randomized to one of four groups receiving either monoclonal antibody against HMGB1 (MAb) or isotype (Iso) and either ENX (1 mg/kg) or normal saline (NS): NS + Iso (n = 5), NS + MAb (n = 6), ENX + Iso (n = 6), ENX + MAb (n = 6). ENX or NS was administered 2, 8, 14, 23 and 32 hours after TBI. MAb or Iso (25 μg) was administered 2 hours after TBI. At 48 hours, cerebral intravital microscopy served to visualize live LEU interacting with endothelium and microvascular fluorescein isothiocyanate-albumin leakage. The Neurological Severity Score (NSS) graded neurologic recovery; wet-to-dry ratios determined cerebral/lung edema. Analysis of variance with Bonferroni correction was used for statistical analyses.

RESULTS

ENX and MAb similarly reduced in vivo pial LEU rolling without demonstrating additive effect. In vivo albumin leakage was greatest in vehicle-treated animals but decreased by 25% with either MAb or ENX but by 50% when both were combined. Controlled cortical impact-induced cerebral wet-to-dry ratios were reduced by MAb or ENX without additive effect. Postinjury lung water was reduced by ENX but not by MAb. Neurologic recovery at 24 hours and 48 hours was similarly improved with ENX, MAb, or both treatments combined.

CONCLUSION

Mirroring ENX, HMGB1 signaling blockade reduces LEU recruitment, cerebrovascular permeability, and cerebral edema following TBI. ENX further reduced lung edema indicating a multifaceted effect beyond HMGB1 blockade. Further study is needed to determine how ENX may play a role in blunting HMGB1 signaling in brain injury patients.