Effect of heme oxygenase–endogenous carbon monoxide on mortality during septic shock in rats

MicroRNA-203 Acts as a Potent Suppressor in Septic Shock by Alleviating Lung Injury via Inhibition of VNN1

BACKGROUND

Septic shock, the most serious complication of sepsis, is a life-threatening disease that is mainly characterized by hypoperfusion and multiple organ failure. Various aberrantly expressed microRNAs (miRNAs) have been reported to be related to septic shock. We explored the regulatory effect of microRNA-203 (miR-203) on lung injury in septic shock mice.

METHODS

Microarray-based gene expression profiling related to septic shock identified the differentially expressed gene vanin-1 (VNN1) and potential regulatory miR-203. miR-203 was predicted to mediate VNN1 expression, thus affecting septic shock, which was investigated by treatment with miR-203 mimic, miR-203 inhibitor, and siRNA-VNN1 in septic shock mouse models. Polymorphonuclear neutrophils (PMNs) and pulmonary alveolar macrophages in bronchoalveolar lavage fluid (BALF) as well as the wet/dry ratio of the lung were also measured to assess lung injury. Additionally, the effects of miR-203 on inflammatory cytokines, oxidative stress indexes, blood biochemical indexes, serine-threonine protein kinase (AKT) signaling pathway-related factors, and apoptosis-related factors were determined.

RESULTS

VNN1 was verified to be targeted and negatively regulated by miR-203. In mouse models of septic shock, weak expression of miR-203, high expression of VNN1, and inhibition of AKT signaling pathway were identified. In response to miR-203 mimic and VNN1 gene silencing, mouse models of septic shock displayed reduced apoptosis, MDA, ALT, and AST in lung tissues, decreased levels of TNF-α, IL-1β, IFN-γ, IL-10, and IL-6, in serum, and reduced PMN and PAM levels in BALF, in addition to elevated SOD activity. Notably, the presence of miR-203 mimic led to AKT signaling pathway activation.

CONCLUSION

This study shows that upregulating miR-203 can alleviate lung injury through activation of the AKT signaling pathway by downregulating VNN1 in septic shock.

Activation of protein kinase C-α/heme oxygenase-1 signaling pathway improves mitochondrial dynamics in lipopolysaccharide-activated NR8383 cells

Mitochondrial function and morphology are dynamically regulated by fusion and fission. Heme oxygenase-1 (HO-1), which may be upregulated by protein kinase C-α (PKC-α), improves mitochondrial dynamics by controlling the balance between fusion and fission in vivo and in vitro. However, whether the PKC-α/HO-1 signaling pathway is one of the underlying mechanisms in adjusting mitochondrial dynamics in lipopolysaccharide (LPS)-activated macrophages has remained elusive. To explore this, NR8383 cells were pre-treated with PKC-α inhibitor Go6976 or PKC-α activator phorbol-12-myristate-13-acetate for 30 min and then stimulated with LPS for 24 h. Next, the expression of PKC-α, HO-1, mitofusin 1 (Mfn1) and mitofusin 2 (Mfn2), optic atrophy 1 (OPA1), dynamin-related protein 1 (Drp1) and fission 1 (Fis1) was detected to evaluate the possible implication of the PKC-α/HO-1 signaling pathway in the LPS-induced NR8383 cells. The results indicated that activation of the PKC-α/HO-1 signaling pathway increased superoxide dismutase activities and the respiratory control ratio (RCR), decreased the levels of malondialdehyde, reactive oxygen species (ROS), Drp1 and Fis1, and simultaneously enhanced the levels of Mfn1, Mfn2 and OPA1. In contrast, the PKC-α inhibitor decreased the expression of RCR, Mfn1, Mfn2 and OPA1, and increased the expression of MDA and ROS in NR8383 cells. The results suggest that activation of the PKC-α/HO-1 signaling pathway is necessary for the balance of mitochondrial dynamics and oxidative stress in macrophages, which provides clues for probing novel strategies against the detrimental effects of sepsis and other disease states.

Effect of Heme Oxygenase-1 on Mitofusin-1 protein in LPS-induced ALI/ARDS in rats

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a common and important oxidative stress in the lung. Mitochondrial fusion responds to the normal morphology and function of cells and is finely regulated by mitochondrial fusion proteins, such as mitofusin-1 protein (Mfn1), mitofusin-2 protein (Mfn2) and optical atrophy 1 (OPA1). Additionally, Mfn1 has been identified as the most important protein in mitochondrial fusion. Heme oxygenase-1 (HO-1) is a stress-inducible protein that plays a critical role in protecting against oxidative stress. However, whether the protection of HO-1 is related to mitochondrial fusion is still a question. Thus, our in vitro and in vivo experiments aimed to identify the relationship between HO-1 and Mfn1. Here, we used Hemin and ZnPP-IX as treatments in an in vivo experiment. Then, HO-1 and Mfn1 were measured using RT-PCR and Western blotting. Supernatants were analyzed for MDA, SOD, and ROS. Our results implied that HO-1 upregulation suppressed oxidative stress induced by LPS, and the possible mechanism could be associated with Mfn1 and the PI3K/Akt pathway.

Effect of ERK1/2 signaling pathway in electro-acupuncture mediated up-regulation of heme oxygenase-1 in lungs of rabbits with endotoxic shock

Background

The anti-oxidative and anti-inflammatory activities of electro-acupuncture (EA), a traditional clinical method, are widely accepted, but its mechanisms are not yet well defined. In this study, we investigated the role of extracellular signal-regulated kinases1/2 (ERK1/2) pathways on electro-acupuncture – mediated up-regulation of heme oxygenase-1 (HO-1) in rabbit lungs injured by LPS-induced endotoxic shock.

Material/Methods

Seventy rabbits were randomly divided into 7 groups: group C, group M, group D, group SEAM, group EAM, group EAMPD, and group PD98059. Male New England white rabbits were given EA treatment on both sides once a day on days 1–5, and then received LPS to replicate the experimental model of injured lung induced by endotoxic shock. Then, they were killed by exsanguination at 6 h after LPS administration. The blood samples were collected for serum examination, and the lungs were removed for pathology examination, determination of wet-to-dry weight ratio, MDA content, SOD activity, serum tumor necrosis factor-α, determination of HO-1 protein and mRNA expression, and determination of ERK1/2 protein.

Results

The results revealed that after EA treatment, expression of HO-1and ERK1/2 was slightly increased compared to those in other groups, accompanied with less severe lung injury as indicated by lower index of lung injury score, lower wet-to-dry weight ratio, MDA content, and serum tumor necrosis factor-α levels, and greater SOD activity (p<0.05 for all). After pretreatment with ERK1/2 inhibitor PD98059, the effect of EA treatment and expression of HO-1 were suppressed (p<0.05 for all).

Conclusions

After electro-acupuncture stimulation at ST36 and BL13, severe lung injury during endotoxic shock was attenuated. The mechanism may be through up-regulation of HO-1, mediated by the signal transductions of ERK1/2 pathways. Thus, the regulation of ERK1/2 pathways via electro-acupuncture may be a therapeutic strategy for endotoxic shock.

Role of Nrf2/ARE pathway in protective effect of electroacupuncture against endotoxic shock-induced acute lung injury in rabbits

NF-E2 related factor 2 (Nrf2) is a major transcription factor and acts as a key regulator of antioxidant genes to exogenous stimulations. The aim of current study was to determine whether Nrf2/ARE pathway is involved in the protective effect of electroacupuncture on the injured lung in a rabbit model of endotoxic shock. A dose of lipopolysaccharide (LPS) 5 mg/kg was administered intravenously to replicate the model of acute lung injury induced by endotoxic shock. Electroacupuncture pretreatment was handled bilaterally at Zusanli and Feishu acupoints for five consecutive days while sham electroacupuncture punctured at non-acupoints. Fourty anesthetized New England male rabbits were randomized into normal control group (group C), LPS group (group L), electroacupuncture + LPS group (group EL) and sham electroacupuncture + LPS (group SEL). At 6 h after LPS administration, the animals were sacrificed and the blood samples were collected for biochemical measurements. The lungs were removed for calculation of wet-to-dry weight ratios (W/D), histopathologic examination, determination of heme oxygenase (HO)-1 protein and mRNA, Nrf2 total and nucleoprotein, as well as Nrf2 mRNA expression, and evaluation of the intracellular distribution of Nrf2 nucleoprotein. LPS caused extensive morphologic lung damage, which was lessened by electroacupuncture treatment. Besides, lung W/D ratios were significantly decreased, the level of malondialdehyde was inhibited, plasma levels of TNF-α and interleukin-6 were decreased, while the activities of superoxide dismutase, glutathione peroxidase and catalase were enhanced in the electroacupucnture treated animals. In addition, electroacupuncture stimulation distinctly increased the expressions of HO-1 and Nrf2 protein including Nrf2 total protein and nucleoprotein as well as mRNA in lung tissue, while these effects were blunted in the sham electroacupuncture group. We concluded that electroacupuncture treatment at ST36 and BL13 effectively attenuates lung injury in a rabbit model of endotoxic shock through activation of Nrf2/ARE pathway and following up-regulation of HO-1 expression.

Therapeutic applications of carbon monoxide

Heme oxygenase-1 (HO-1) is a regulated enzyme induced in multiple stress states. Carbon monoxide (CO) is a product of HO catalysis of heme. In many circumstances, CO appears to functionally replace HO-1, and CO is known to have endogenous anti-inflammatory, anti-apoptotic, and antiproliferative effects. CO is well studied in anoxia-reoxygenation and ischemia-reperfusion models and has advanced to phase II trials for treatment of several clinical entities. In alternative injury models, laboratories have used sepsis, acute lung injury, and systemic inflammatory challenges to assess the ability of CO to rescue cells, organs, and organisms. Hopefully, the research supporting the protective effects of CO in animal models will translate into therapeutic benefits for patients. Preclinical studies of CO are now moving towards more complex damage models that reflect polymicrobial sepsis or two-step injuries, such as sepsis complicated by acute respiratory distress syndrome. Furthermore, co-treatment and post-treatment with CO are being explored in which the insult occurs before there is an opportunity to intervene therapeutically. The aim of this review is to discuss the potential therapeutic implications of CO with a focus on lung injury and sepsis-related models.

Protective effects of polydatin on septic lung injury in mice via upregulation of HO-1

The present study was carried out to investigate the effects and mechanisms of polydatin (PD) in septic mice. The model of cecal ligation and puncture (CLP-)induced sepsis was employed. Pretreatment of mice with PD (15, 45, and 100 mg/kg) dose-dependently reduced sepsis-induced mortality and lung injury, as indicated by alleviated lung pathological changes and infiltration of proteins and leukocytes. In addition, PD inhibited CLP-induced serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) production, lung cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase isoform (iNOS) protein expressions and NF-κB activation. Notably, PD upregulated the expression and activity of heme oxygenase (HO-)1 in lung tissue of septic mice. Further, the protective effects of PD on sepsis were abrogated by ZnPP IX, a specific HO-1 inhibitor. These findings indicated that PD might be an effective antisepsis drug.