Effect of esaxerenone on ischaemia and reperfusion injury in rat hearts

OBJECTIVES

In myocardial infarction, the addition of mineralocorticoid receptor blockers to standard therapies, such as angiotensin-converting enzyme inhibitors or beta-blockers, reportedly reduces mortality and cardiac events. We investigated whether the non-steroidal mineralocorticoid receptor blocker esaxerenone has cardioprotective effects and its protective mechanisms.

METHODS

Isolated rat hearts were Langendorff-perfused (constant pressure, 80 mmHg) with oxygenated Krebs-Henseleit bicarbonate buffer and reperfused for 60 min; afterwards, recovery of function (left ventricular pressure, measured with an intraventricular balloon) and myocardial injury were measured. In a preliminary study, we determined the optimal concentration of esaxerenone required for myocardial protection. Next, esaxerenone was administered in the pre- and post-ischaemic phases to determine the optimal timing of administration. In addition, we assessed coronary flow response to acetylcholine with and without esaxerenone. We examined whether esaxerenone-induced cardioprotection was prevented by targeting putative components in the preconditioning manner (the mitochondrial ATP-sensitive potassium [KATP] channel).

RESULTS

Myocardial protection by esaxerenone was observed when esaxerenone was administered before ischaemia but not after ischaemia. The coronary flow response to acetylcholine was significantly better in the esaxerenone group than in the control group. The cardioprotective effect of esaxerenone was eliminated by the mitochondrial KATP channel blocker, 5-hydroxy decanoate.

CONCLUSIONS

This study confirmed the myocardial protective effect of the pre-ischaemic administration of esaxerenone. Esaxerenone may contribute to coronary endothelial protection and exert pharmacological preconditioning via the mitochondrial KATP channel.

Essential Involvement of Neutrophil Elastase in Acute Acetaminophen Hepatotoxicity Using BALB/c Mice

Intense neutrophil infiltration into the liver is a characteristic of acetaminophen-induced acute liver injury. Neutrophil elastase is released by neutrophils during inflammation. To elucidate the involvement of neutrophil elastase in acetaminophen-induced liver injury, we investigated the efficacy of a potent and specific neutrophil elastase inhibitor, sivelestat, in mice with acetaminophen-induced acute liver injury. Intraperitoneal administration of 750 mg/kg of acetaminophen caused severe liver damage, such as elevated serum transaminase levels, centrilobular hepatic necrosis, and neutrophil infiltration, with approximately 50% mortality in BALB/c mice within 48 h of administration. However, in mice treated with sivelestat 30 min after the acetaminophen challenge, all mice survived, with reduced serum transaminase elevation and diminished hepatic necrosis. In addition, mice treated with sivelestat had reduced NOS-II expression and hepatic neutrophil infiltration after the acetaminophen challenge. Furthermore, treatment with sivelestat at 3 h after the acetaminophen challenge significantly improved survival. These findings indicate a new clinical application for sivelestat in the treatment of acetaminophen-induced liver failure through mechanisms involving the regulation of neutrophil migration and NO production.

DNase I and Sivelestat Ameliorate Experimental Hindlimb Ischemia-Reperfusion Injury by Eliminating Neutrophil Extracellular Traps

Purpose

Neutrophil extracellular traps (NETs) play an important role in ischemia-reperfusion injury (IRI) of the hindlimb. The aim of this study was to investigate the effect of recombinant DNase I and sivelestat in eliminating NETs and their effects on IRI limbs.

Patients and Methods

An air pump was used to apply a pressure of 300 mmHg to the root of the right hindlimb of the rat for 2 h and then deflated to replicate the IRI model. The formation of NETs was determined by the detection of myeloperoxidase (MPO), neutrophil elastase (NE), and histone H3 in the skeletal muscles of the hindlimbs. Animals were administered 2.5 mg/kg bw/d DNase I, 15 or 60 mg/kg bw/d sivelestat by injection into the tail vein or intramuscularly into the ischemic area for 7d. Elimination of NETs, hindlimb perfusion, muscle fibrosis, angiogenesis and motor function were assessed.

Results

DNase I reduced NETs, attenuated muscle fibrosis, promoted angiogenesis in IRI area and improved limb motor function. Local administration of DNase I improved hindlimb perfusion more than intravenous administration. Sivelestat at a dose of 15 mg/kg bw/d increased perfusion, counteracted skeletal muscle fibrosis, promoted angiogenesis and enhanced motor function. However, sivelestat at a dosage of 60 mg/kg bw/d had an adverse effect on tissue repair, especially when injected locally.

Conclusion

Both DNase I and moderate doses of sivelestat can eliminate IRI-derived NETs. They improve hindlimb function by improving perfusion and angiogenesis, preventing muscle fibrosis. Appropriate administration mode and dosage is the key to prevent IRI by elimination of NETs. DNase I is more valid when administered topically and sivelestat is more effective when administered intravenously. These results will provide a better strategy for the treatment of IRI in clinical.

LncRNA FOXD3-AS1 aggravates myocardial ischemia/reperfusion injury by inactivating the Redd1/AKT/GSK3β/Nrf2 signaling pathway via the miR-128/TXNIP axis

Long noncoding RNA forkhead box D3-antisense RNA 1 (FOXD3-AS1) is associated with cardiovascular diseases, but its roles in myocardial ischemia/reperfusion (I/R) injury and the related signaling pathway have not been fully reported. We aimed to investigate the roles and mechanism of action of FOXD3-AS1 in myocardial I/R injury. An in vivo myocardial I/R injury mouse model and an in vitro hypoxia/reoxygenation (H/R) cardiomyocyte model was established. Quantitative reverse transcription-polymerase chain reaction, western blotting, and immunofluorescent assays were performed to examine the expression levels of FOXD3-AS1, microRNA (miR)-128, thioredoxin-interacting protein/regulation of development and DNA damage response 1/protein kinase B/glycogen synthase kinase 3β/nuclear factor erythroid 2-related factor 2 (TXNIP/Redd1/AKT/GSK3β/Nrf2) pathway-related proteins and apoptosis-related proteins. The interactions between FOXD3-AS1 and miR-128 and miR-128 and TXNIP were analyzed by Spearman's correlation test, predicted by ENCORI, and verified by dual-luciferase reporter assay. In addition, the levels of cardiac injury markers and oxidative stress markers were evaluated by corresponding kits. Cell Counting Kit-8 assays and flow cytometry were performed to assess cell viability and apoptosis. Hematoxylin and eosin staining was applied to observe the effect of FOXD3-AS1 on the morphology of myocardial I/R injured tissues. The results showed that the FOXD3-AS1 and TXNIP were highly expressed, whereas miR-128 was expressed at low levels in I/R myocardial tissues and H/R-induced H9c2 cells. FOXD3-AS1 directly targeted miR-128 to reduce its expression. TXNIP was confirmed as a downstream target of miR-128. Knockdown of FOXD3-AS1 led to the alleviation of I/R injury in vivo and in vitro. FOXD3-AS1 enhanced the expression of TXNIP by sponging miR-128, which inhibited the Redd1/AKT/GSK3β/Nrf2 pathway. Both inhibition of miR-128 and overexpression of TXNIP reversed the cardioprotective effect of FOXD3-AS1 small interfering RNA in H/R-induced H9c2 cells.

Carbon Monoxide-Releasing Molecule-3 Ameliorates Acute Lung Injury in a Model of Hemorrhagic Shock and Resuscitation: Roles of p38MAPK Signaling Pathway

OBJECTIVE

It was reported that carbon monoxide-releasing molecule-3 (CORM-3) administration immediately after hemorrhagic shock and resuscitation (HSR) ameliorates the HSR-induced acute lung injury (ALI); however, the specific mechanism of the protective effects against HSR-induced ALI remains unclear.

METHODS

To induce hemorrhagic shock, rats were bled to a mean arterial blood pressure of 30 mm Hg for 45 min and then resuscitated with shed blood via the left vein. CORM-3 (4 mg/kg or 8 mg/kg) was respectively administrated after HSR. Twelve  hours post-HSR, lung injury was assessed by wet/dry (W/D) ratio, hematoxylin-eosin staining staining, and lung ultrasound; the apoptotic and pyroptotic macrophages were measured by immunofluorescence staining; and the expression of phosphorylated p38 mitogen activated protein kinase (p-p38MAPK) and total p38MAPK was measured by western blotting. SB203580 (5 mg/kg), a special inhibitor of p-p38MAPK, was administrated by abdominal cavity to assess the roles of p38MAPK in HSR-induced ALI.

RESULTS

Increased B-line score, lung injury score, and W/D ratio indicated the fact of ALI after HSR. Twelve hours post-HSR, CORM-3 administration significantly decreased the B-line score, lung injury score, W/D ratio, apoptotic and pyroptotic macrophages, and the expressions of p-p38MAPK. Further, SB203580 not only reduced HSR-induced ALI, but also enhanced the protective effects of CORM-3 against ALI.

CONCLUSION

We identified the protective effects of CORM-3 against HSR-induced ALI. The mechanism might be related to the inhibition of p38MAPK signaling pathway in lung macrophages.

Neutrophil Elastase Inhibitor Sivelestat Attenuates Myocardial Injury after Cardioplegic Arrest in Rat Hearts

Purpose: Sivelestat, a neutrophil elastase inhibitor, attenuates global ischemia-induced myocardial damage and coronary endothelial dysfunction. Here, we investigated whether sivelestat exerts the cardioprotective effects against cardioplegic arrest in rat hearts.

Methods: Isolated Langendorff-perfused rat hearts were randomly allocated to three groups and subjected to 2-min infusions with St. Thomas’ Hospital cardioplegic solution No. 2 (STH2) and 30-min global ischemia followed by 60-min reperfusion as follows: (i) control (STH2 treatment only), (ii) sivelestat (19 μmol/L) infusion for the first 10 min of reperfusion, and (iii) sivelestat (19 μmol/L) infusion for 10 min before ischemia and for the first 10 min of reperfusion. Left ventricular developed pressure (LVDP) recovery and troponin T leakage were measured at the end of reperfusion. Coronary flow response to acetylcholine (ACh) was assessed.

Results: Single and multiple doses of sivelestat significantly improved LVDP recovery (69 ± 15 and 69 ± 14 vs 48 ± 15 [control]; p <0.05) and decreased troponin T leakage (0.4 ± 0.3 and 0.7 ± 0.5 vs 1.7 ± 0.6 [control]; p <0.05). Multiple doses of sivelestat significantly improved coronary flow response to ACh (121 ± 9 vs 105 ± 4; p <0.05).

Conclusions: Addition of sivelestat to STH2 attenuates myocardial injury after cardioplegic arrest in rat hearts. This cardioprotective effect was achieved even when sivelestat was administered during early reperfusion.

Gerontoxanthone I and Macluraxanthone Induce Mitophagy and Attenuate Ischemia/Reperfusion Injury

Mitophagy is a crucial process in controlling mitochondrial biogenesis. Balancing mitophagy and mitochondrial functions is required for maintaining cellular homeostasis. In this study, we found that Gerontoxanthone I (GeX1) and Macluraxanthone (McX), xanthone derivatives isolated from Garcinia bracteata C. Y. Wu ex Y. H. Li, induced Parkin puncta accumulation and promoted mitophagy. GeX1 and McX treatment induced the degradation of mitophagy-related proteins such as Tom20 and Tim23. GeX1 and McX directly stabilized PTEN-induced putative kinase 1 (PINK1) on the outer membrane of the mitochondria, and then recruited Parkin to mitochondria. This significantly induced phosphorylation and ubiquitination of Parkin, suggesting that GeX1 and McX mediate mitophagy through the PINK1-Parkin pathway. Transfecting ParkinS65A or pretreated MG132 abolished the induction effects of GeX1 and McX on mitophagy. Furthermore, GeX1 and McX treatment decreased cell death and the level of ROS in an ischemia/reperfusion (IR) injury model in H9c2 cells compared to a control group. Taken together, our data suggested that GeX1 and McX induce PINK1-Parkin–mediated mitophagy and attenuate myocardial IR injury in vitro.

Inhibition of miR-148b ameliorates myocardial ischemia/reperfusion injury via regulation of Wnt/β-catenin signaling pathway

Our work aims to elucidate the effect how microRNA-148b (miR-148b) participated in myocardial ischemia/reperfusion (I/R) injury via regulation of Wnt/β-catenin signaling pathway. The in vivo myocardial I/R models of SD rats and in vitro hypoxia/reoxygenation (H/R) models of H9C2 cells were established. The heart function and infarction area of rats and lactic dehydrogenase (LDH), creatine kinase (CK), malondialdehyde (MDA), and superoxide dismutase (SOD) levels were evaluated. Myocardial cell viability was measured using positron emission tomography combined with computer tomography and (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, and the apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated nick-end labeling method and flow cytometry; quantitative reverse-transcription polymerase chain reaction and western blot were used to detect the related molecules expressions. The myocardial infarction area of rats was significantly increased with reductions in LVSP, + dp/dtmax, - dp/dtmax, LVFS%, LVEF% and standardized uptake value and elevation in left ventricular developed pressure after ischemia/reperfusion (I/R), and the LDH, CK, and MDA levels were enhanced with the decreased SOD. The apoptotic rates were higher in I/R rats and H/R H9C2 cells with upregulated miR-148b and cleaved caspase-3, but decreased Bcl-2/Bax ratio; and meanwhile, the Wnt/β-catenin pathway was inhibited. Additionally, the H/R-induced H9C2 cells also exhibited decreased cell viability. MiR-148b overexpression further aggravated I/R injury of rats, whereas inhibition of miR-148b reduced I/R and H/R injury through activation of Wnt/β-catenin pathway. In addition, Wnt-1 small interfering RNA exposure abolished the effect of miR-148b inhibitor on H/R injury of H9C2 cells. Inhibition of miR-148b improved the antioxidative ability and myocardial cell survival to suppress its apoptosis by activating Wnt/β-catenin signaling pathway, thus ameliorating the myocardial I/R injury.

Prevention of Pulmonary Edema after Minimally Invasive Cardiac Surgery with Mini-Thoracotomy Using Neutrophil Elastase Inhibitor

PURPOSE

Unilateral re-expansion pulmonary edema (RPE) is a rare but one of the most critical complications that may occur after re-expansion of a collapsed lung after minimally invasive cardiac surgery (MICS) with mini-thoracotomy.

METHODS

We performed a total of 40 consecutive patients with MICS by right mini-thoracotomy with single-lung ventilation between January 2013 and June 2016. We divided the patients into control group (n = 13) and neutrophil elastase inhibitor group (n = 27). Neutrophil elastase inhibitor group received continuous intravenous infusion of neutrophil elastase inhibitor at 0.2-0.25 mg/kg per hour from the start of anesthesia until extubation during the perioperative period.

RESULTS

There were no relations with operative time, cardiopulmonary bypass (CPB) time, aortic clamp time, and intraoperative water valances for postoperative mechanical ventilation support time. Compared with the neutrophil elastase inhibitor group, the control group had significantly higher initial alveolar-arterial oxygen gradient and significantly lower initial ratio of partial pressure of arterial oxygen to fraction of inspired oxygen at the intensive care unit (ICU). The control group had significantly longer postoperative mechanical ventilation support time and hospital stay compared with the neutrophil elastase inhibitor group.

CONCLUSIONS

Neutrophil elastase inhibitor may have beneficial effects against RPE after MICS with mini-thoracotomy.

Proresolving Actions of Synthetic and Natural Protease Inhibitors Are Mediated by Annexin A1

Annexin A1 (AnxA1) is a glucocorticoid-regulated protein endowed with anti-inflammatory and proresolving properties. Intact AnxA1 is a 37-kDa protein that may be cleaved in vivo at the N-terminal region by neutrophil proteases including elastase and proteinase-3, generating the 33-kDa isoform that is largely inactive. In this study, we investigated the dynamics of AnxA1 expression and the effects of synthetic (sivelestat [SIV]; Eglin) and natural (secretory leukocyte protease inhibitor [SLPI]; Elafin) protease inhibitors on the resolution of LPS-induced inflammation. During the settings of LPS inflammation AnxA1 cleavage associated closely with the peak of neutrophil and elastase expression and activity. SLPI expression increased during resolving phase of the pleurisy. Therapeutic treatment of LPS-challenge mice with recombinant human SLPI or Elafin accelerated resolution, an effect associated with increased numbers of apoptotic neutrophils in the pleural exudates, inhibition of elastase, and modulation of the survival-controlling proteins NF-κB and Mcl-1. Similar effects were observed with SIV, which dose-dependently inhibited neutrophil elastase and shortened resolution intervals. Mechanistically, SIV-induced resolution was caspase-dependent, associated to increased levels of intact AnxA1 and decreased expression of NF-κB and Mcl-1. The proresolving effect of antiproteases was also observed in a model of monosodium urate crystals-induced inflammation. SIV skewed macrophages toward resolving phenotypes and enhanced efferocytosis of apoptotic neutrophils. A neutralizing antiserum against AnxA1 and a nonselective antagonist of AnxA1 receptor abolished the accelerated resolution promoted by SIV. Collectively, these results show that elastase inhibition not only inhibits inflammation but actually promotes resolution, and this response is mediated by protection of endogenous intact AnxA1 with ensuing augmentation of neutrophil apoptosis.

Neutrophil Elastase Inhibitor Following Liver Resection: A Matched Cohort Study

BACKGROUND

Sivelestat is a neutrophil elastase inhibitor (NEI) with positive impact on the respiratory complications in thoracic surgery. Based on the findings of a recent study, NEI may have a good response for avoiding ischemia reperfusion injury in liver resection.

OBJECTIVES

The current study aimed to examine the impact of NEI on the postoperative outcomes after liver resection.

PATIENTS AND METHODS

The data were collected from 374 consecutive patients scheduled to undergo liver resection. Seven perioperative variables were matched on the basis of the patients' background. Then, the NEI (n = 61) and control (n = 61) groups were compared. NEI was administered at a dose of 0.2 mg/kg/h for three days from the postoperative day 0 (POD0). The liver function, coagulation activity, inflammatory response, respiratory complications, and overall complications were compared.

RESULTS

The levels of serum interleukin-6 (NEI group: 113 pg/mL [26.9 - 522.0] vs. control group: 174 [28.6 - 1040.6], P < 0.01) and C-reactive protein (CRP) (2.9 IU/L [range: 0.1 - 8.6] vs. 4.11 [0.3 - 13.8], P = 0.01) on the first postoperative day (POD1) and the alveolar-arterial oxygen tension difference (32.3 Torr [-28.6 - 132.3] vs. 46.6 [-11.2 - 251.6], P = 0.04) on the third postoperative day (POD3) were significantly lower in the NEI group than the control group. The rate of pleural effusion was significantly lower in the NEI group compared to that of the control group [13 patients (21.3%) vs. 23 (37.7%), P = 0.04]. However, the coagulation activities (P = 0.68), liver function (P = 0.69), non-respiratory complications (P = 0.84), and overall complications (P = 0.71) did not differ significantly between the groups.

CONCLUSIONS

Intravenous NEI administration had positive impact on the postoperative inflammatory response and oxygenation while it did not affect either coagulation or the liver function, as well as severe grade complications following resection.

Protective Effect and Mechanism of Total Flavones from Rhododendron simsii Planch Flower on Cultured Rat Cardiomyocytes with Anoxia and Reoxygenation

Many flavonoids have cardioprotection against myocardial ischemia/reperfusion (I/R) injury. Total flavones from Rhododendron simsii Planch flower (TFR) can protect myocardial ischemic injuries. However, its protective mechanism is still unknown. The present study was designed to investigate the mechanism of TFR on myocardial I/R and anoxia/reoxygenation (A/R) injuries. Rat model of myocardial I/R injury was made, and myocardial infarction was determined. A/R injury was induced in cultured rat cardiomyocytes; cellular damage was evaluated by measuring cell viability, LDH and cTnT releases, and MDA content. Expressions of ROCK₁ and ROCK₂ protein were examined by Western blot analysis, and K⁺ currents were recorded by using whole-cell patch clamp technique. TFR 20~80 mg/kg markedly reduced I/R-induced myocardial infarction. TFR 3.7~300 mg/L significantly inhibited A/R-induced reduction of cell viability, LDH and cTnT releases, and MDA production. Exposure to A/R significantly increased ROCK₁ and ROCK₂ expressions in rat cardiomyocytes, but TFR 33.3~300 mg/L obviously inhibited this increase. 300 mg/L TFR significantly augmented inward rectifier K⁺ current and other K⁺ currents in rat cardiomyocytes. These results indicate that TFR has a protective effect on rat cardiomyocytes A/R damage, and the protective mechanism may be engaged with the inhibition of ROCK₁ and ROCK₂ and activation of K⁺ channels.

Heart protective effects and mechanism of quercetin preconditioning on anti-myocardial ischemia reperfusion (IR) injuries in rats

In this study, we investigated the effects and mechanism of quercetin preconditioning on anti-myocardial ischemia reperfusion (IR) injuries in vivo. Meanwhile, their potential anti-oxidative stress and anti-inflammation effect were assessed. SD rats were orally given quercetin 250 mg/kg. Myocardium apoptosis was determined with TUNEL staining. The biomarkers related to myocardial ischemia injury were determined. Simultaneously, hemodynamic parameters were monitored as left ventricular systolic pressure (LVSP), LV end-diastolic pressure (LVEDP) and maximal rate of increase and decrease of left ventricular pressure (dP/dtmax). The oxidative stress indicators and inflammatory factors were also evaluated. Western blot method was used for analysis of PI3K, Akt, p-Akt, Bax and Bcl-2 protein expressions. The results showed that quercetin significantly reduced apoptosis rate, improved cardiac function, decreased levels of creatine kinase (CK), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH). Quercetin also restrained the oxidative stress related to myocardial ischemia injury as evidenced by decreased malondialdehyde (MDA), and elevated GSH, superoxide dismutase (SOD), catalase (CAT), glutathione-peroxidase (GSH-Px), glutathione reductase (GR) activity. Meanwhile, the inflammatory cascade was inhibited as evidenced by decreased cytokines such as tumor necrosis factor-α (TNF-α), C-reactive protein (CRP) and interleukin-1β (IL-1β). Our results still showed that quercetin pretreatment significantly inhibited the apoptosis by decreasing the number of apoptotic cells, decreasing the level of cleaved Bax, and increasing the level of Bcl-2 in rats subjected to I/R injury. Simultaneously, quercetin pretreatment markedly increased the phosphorylation of Akt. Blockade of PI3K activity by LY294002, dramatically abolished its anti-apoptotic effect and lowered Akt phosphorylation level. It can be concluded that quercetin pretreatment was protected against myocardium IR injury by decreasing oxidative stress, repressing inflammatory cascade, inhibiting apoptosis in vivo and PI3K/Akt pathway involved in the anti-apoptotic effect.

Sivelestat attenuates myocardial reperfusion injury during brief low flow postischemic infusion

The neutrophil elastase inhibitor sivelestat (ONO-5046) possesses unknown mechanisms of cardioprotection when infused following global ischemia, even in the absence of neutrophils. Since myocardial ischemia-reperfusion injury is strongly associated with endothelial dysfunction and reactive oxygen species (ROS) generation during reperfusion, we have tested the hypothesis that infusion of sivelestat during postischemic low flow would preserve endothelial and contractile function and reduce infarct size through an ROS-mediated mechanism. Isolated male rat hearts, subjected to global ischemia of 25 minutes, were reperfused with low flow with or without sivelestat followed by a full flow reperfusion. Hearts treated with sivelestat showed a significant improvement of LV contractile function and a reduction in infarct size. Infusion of L-NAME (nonspecific blocker of endothelial nitric oxide synthase (eNOS)) along with sivelestat during reperfusion reversed the preservation of contractile function and infarct size. In vitro EPR spin trapping experiments showed that sivelestat treatment decreased superoxide adduct formation in bovine aortic endothelial cells (BAECs) subjected to hypoxia-reoxygenation. Similarly, dihydroethidine (DHE) staining showed decreased superoxide production in LV sections from sivelestat-treated hearts. Taken together, these results indicate that sivelestat infusion during postischemic low flow reduces infarct size and preserves vasoreactivity in association with decreased ROS formation and the preservation of nitric oxide.

How immune complexes from certain IgG NAbs and any F(ab')₂ can mediate excessive complement activation

In sepsis death follows an excessive inflammatory response involving cytokines and complement that is activated primarily via the amplifying C3/C5 convertase. Excessive stimulation of complement amplification requires IgG-containing or F(ab')₂-containing immune complexes (IC) that capture dimeric C3b on one of their heavy chains or heavy chain fragments. The ability of IgG-IC to capture dimeric C3b by the Fab portion is dependent on an affinity for C3 within the Fab portion, but outside the antigen-binding region. This property is rare among IgG NAbs. In contrast to this, the lack of the Fc portion renders the Fab regions of any F(ab')(2)-IC accessible to nascent C3b, but dimeric C3b deposits only if F(ab')₂-IC form secondary IC with anti-hinge NAbs that rigidify the complex and thereby promote deposition of dimeric C3b. Both types of complexes, C3b₂-IgG-IC and C3b₂-F(ab')₂-IC/anti-hinge NAbs, are potent precursors of alternative C3 convertases and stimulate complement amplification along with properdin up to 750 times more effectively than C3b and properdin. F(ab')₂ fragments are not normally generated, but are formed from NAbs by enzymes from pathogens and neutrophils in sepsis. Unlike IgG-IC F(ab')₂-IC are not cleared by Fc-receptor dependent processes and circulate long enough to form secondary IC with anti-hinge NAbs that rigidify the complexes such that they capture dimeric C3b and gain the potency to stimulate complement amplification.

The effects of hydroxysafflor yellow A on blood pressure and cardiac function

AIM OF THE STUDY

This work aims to investigate the effects of HSYA on cardiac function and blood pressure.

MATERIALS AND METHODS

To evaluate changes in mean arterial pressure (MAP) and heart rate (HR), different groups of pentobarbitone-anesthetized normotensive and spontaneously hypertensive rats (SHR) were treated with intravenous HSYA (0.1-3 mg/kg). Isolated WKY rat hearts in Langendorff system were employed for examining the effect of HSYA on hemodynamic. After 30 min equilibration time the isolated hearts were perfused with HSYA (30 μmol/L) in a stepwise fashion. Potassium channel inhibitors were used to determine the role of potassium channel activation in HSYA effect.

RESULTS

Intravenous injection of the HSYA significantly reduced MAP and HR in both normotensive rats and SHR in a dose-dependent manner. HSYA reduced left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), the maximum rate of increase of left ventricular pressure (+dp/dt(max)) and heart rate (HR) in a dose-dependent manner. HSYA had no remarkable effect on the maximum rate of decrease of left ventricular pressure (-dp/dt(max)); BK(Ca) and K(ATP) blocker can weakened the inhibitory effect of HSYA on heart function and HR, but K(V) and K(ACh) blocker did not significantly weaken the HSYA effects.

CONCLUSION

Our results show that HSYA could significantly reduce blood pressure and heart rate, which may be related to activation of BK(Ca) and K(ATP) channels.

Vitexin protects against myocardial ischemia/reperfusion injury in Langendorff-perfused rat hearts by attenuating inflammatory response and apoptosis

The aim of the present study is to investigate the effects and its possible underlying mechanisms of vitexin on myocardial ischemia/reperfusion (I/R) injury in isolated rat hearts. Isolated rat hearts were perfused with Langendorff apparatus, which subjected to 30 min ischemia and then followed by 60 min reperfusion. In the isolated rat heart subjected to I/R injury, treatment of vitexin (50, 100, 200 μmol/L) significantly enhanced coronary flow, and decreased the pathological scores of myocardium. 50, 100, 200 μmol/L vitexin significantly attenuated I/R-induced increases of myocardial TNF-α and IL-1β, and 25, 50, 100, 200 μmol/L vitexin significantly reduced apoptosis index of cardiac muscle cell of rat isolated heart subjected to I/R injury. Vitexin significantly inhibited I/R-induced increase of myocardial Bax protein expression; however, 100, 200 μmol/L vitexin markedly increased myocardial Bcl-2 protein expression. Furthermore, vitexin at concentrations of 50, 100, 200 μmol/L significantly reduced expression of myocardial NF-κBp65 protein. Therefore, these results demonstrate that vitexin exhibits significant protective effect against myocardial I/R injury in isolated rat heart, which is related to inhibition of the release of inflammatory cytokines and the apoptosis of cardiac muscle cell via up-regulating protein expression of Bcl-2 as well as down-regulating Bax and NF-κBp65.