Downregulation of PI3K-γ in a mouse model of sepsis-induced myocardial dysfunction

PIK3CG Regulates NLRP3/GSDMD-Mediated Pyroptosis in Septic Myocardial Injury

Cardiac insufficiency is a common complication of sepsis with high mortality. Inflammatory programmed cell death (pyroptosis) executed by NLRP3/gasdermin D (GSDMD) is intrinsically correlated with septic myocardial injury. However, it remains unclear whether PIK3CG, a classical target of septic myocardial injury, can affect pyroptosis by regulating NLRP3/GSDMD signaling. In this study, a series of experimental methods were used to observe the effect of PIK3CG on NLRP3/GSDMD-mediated pyroptosis in Cecal ligation and puncture (CLP)-injured BALB/c mice and lipopolysaccharide (LPS)-injured HL-1 cardiomyocytes. Transcriptome analysis of CLP-injured myocardium revealed a regulatory relationship between PIK3CG and NLRP3/GSDMD signaling, which was further verified in clinical myocardium samples from GEO database. Both in vitro and in vivo experiments showed that the protein and mRNA levels of PIK3CG, GSDMD, NLRP3, IL-1β, Caspase-1, and IL-18 were significantly increased. Importantly, PIK3CG siRNA was found to improve these changes, while PIK3CG overexpression worsened them. Notably, pyroptosis induced by CLP in the myocardium was reversed by the PIK3CG inhibitor (AS-604850). In conclusion, PIK3CG activates NLRP3 inflammasomes, thus promoting pyroptosis in septic myocardial injury.

Effects of the PI3K/Akt/HO-1 pathway on autophagy in a sepsis-induced acute lung injury mouse model

Sepsis-induced lung injury is an acute hypoxic respiratory insufficiency caused by systemic infectious factors that results in alveolar epithelial cell and capillary endothelial cell injury, diffuse pulmonary interstitial edema, and alveolar edema. Heme oxygenase (HO)-1 is usually associated with inflammation and has anti-inflammatory effects. Autophagy is a degradation pathway that eliminates cellular metabolic waste and plays an important protective role during stress. The phosphatidylinositol 3-kinase/ protein kinase B (PI3K/Akt) signaling pathway plays a key role in mediating cellular responses to inflammatory reactions. Therefore, we hypothesized that HO-1 is associated with autophagy and regulated by the PI3K/Akt signaling pathway in mice with sepsis-induced lung injury. Sepsis-induced lung injury was induced in mice using cecal ligation and puncture (CLP). Hemin or Sn-protoporphyrin IX (SnPP) was administered via intraperitoneal injection before surgery. Survival rates were observed during days 1-7 after the surgery; lung histology was discerned 24 h after the surgery; pro-inflammatory and anti-inflammatory factors in plasma and lung tissue were measured using enzyme-linked immunosorbent assay (ELISA); HO-1, Beclin-1, microtubule-associated protein 1 light chain 3B (LC3B)-II, p62 and lysosome associated membrane protein (LAMP)2 protein expression levels were measured 24 h after the surgery; HO-1 and LC3B-II protein expression levels were observed using immunofluorescence 24 h after the surgery; and autophagosomes were detected using electron microscopy 24 h after the surgery. Furthermore, when PI3K inhibitors LY294002, PI3K activators Recilisib and hemin were administered before the surgery, Akt, p-Akt, HO-1, and LC3-II levels were measured 24 h post-surgery. We found that HO-1 overexpression increased the survival rate and inhibited sepsis-induced lung injury. HO-1 overexpression attenuated the levels of proinflammatory cytokines (TNF-α, IL-1β) and increased the anti-inflammatory cytokine (IL-10, HO-1) overexpression. Moreover, HO-1 overexpression was also associated with increased expression of Beclin-1, LC3B-II and LAMP2 protein expression; decreased p62 protein expression; and significantly increased autophagosome formation. The results for HO-1-downregulated mice contrasted with those mentioned above. LY294002 inhibited p-Akt/Akt, HO-1, and LC3B-II protein expression; and hemin reversed the inhibitory effect of LY294002. The protective effect of HO-1 was involved in the mediation of autophagy, which may be regulated by the PI3K/Akt signaling pathway during sepsis-induced lung injury in mice.

Role of activating the nuclear factor kappa B signaling pathway in the development of septic cardiomyopathy in rats with sepsis

BACKGROUND

Despite advances in the treatment of sepsis over time, this condition remains both a serious threat and a cause of death among critical patients.

OBJECTIVE

This study aimed to explore the role of the nuclear factor kappa B (NF-κB) signaling pathway in the development of septic cardiomyopathy in rats with sepsis.

METHOD

A total of 32 Sprague Dawley rats were randomized into a sham operation group and three groups with sepsis, which were tested at one of the following time-points: 3, 6, or 12 h. Each group included eight rats. Sepsis models were created via cecal ligation and puncture procedures. All the study rats had the following cardiac parameters and serum levels measured at either 3, 6, or 12 h after the operation (according to their assigned group): heart rate, left ventricular systolic pressure (LVSP), maximum rate of left ventricular pressure rise (+dP/dtmax) and fall (-dP/dtmax), tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), interleukin 6 (IL-6), and cardiac troponin I (cTnI). The myocardium of the left ventricle was collected and subjected to hematoxylin and eosin staining to observe the changes in pathological morphology. The expression of toll-like receptor 4 (TLR4) and NF-κB in the myocardium were detected by western blot analysis.

RESULTS

Compared with the sham operation group, the rats in the sepsis subgroups exhibited significantly lower values for all the cardiac parameters measured, including the heart rate (sham operation group = 386.63 ± 18.62 beats per minute [bpm], sepsis 3-h group = 368.38 ± 12.55 bpm, sepsis 6-h group = 341.75 ± 17.05 bpm, sepsis 12-h group = 302.13 ± 21.15 bpm), LVSP (sham operation group = 125.50 ± 11.45 mmHg, sepsis 3-h group = 110.88 ± 7.51 mmHg, sepsis 6-h group = 100.00 ± 15.06 mmHg, sepsis 12-h group = 91.38 ± 14.73 mmHg), +dp/dtmax (sham operation group = 7137.50 ± 276.44 mm Hg/sec, sepsis 3-h group = 5745.00 ± 346.16 mm Hg/sec, sepsis 6-h group = 4360.00 ± 312.04 mm Hg/sec, sepsis 12-h group = 2871.25 ± 443.99 mm Hg/sec), and -dp/dtmax (sham operation group = 6363.75 ± 123.86 mm Hg/sec, sepsis 3-h group = 6018.75 ± 173.49 mm Hg/sec, sepsis 6-h group = 5350.00 ± 337.89 mm Hg/sec, sepsis 12-h group = 4085.00 ± 326.76 mm Hg/sec). They also displayed significantly higher levels of serum cytokines, including TNF-α (sham operation group = 14.72 ± 2.90 pg/mL, sepsis 3-h group = 34.90 ± 4.79 pg/mL, sepsis 6-h group = 24.91 ± 2.57 pg/mL, sepsis 12-h group 22.06 ± 3.11 pg/mL), IL-1β (sham operation group = 42.25 ± 16.91, 3-h group = 112.25 ± 13.77, sepsis 6-h group = 207.90 ± 22.64, sepsis 12-h group = 157.18 ± 23.06), IL-6 (sham operation group = 39.89 ± 5.74, sepsis 3-h group = 78.27 ± 9.31, sepsis 6-h group = 123.75 ± 13.11, sepsis 12-h group = 93.21 ± 8.96), and cTnI (sham operation group = 0.07 ± 0.03 ng/mL, sepsis 3-h group = 0.18 ± 0.06 ng/mL, sepsis 6-h group = 0.67 ± 0.19 ng/mL, sepsis = 12-h group 1.28 ± 0.10 ng/mL). The rats in the sepsis groups exhibited pathological changes in the myocardium, which deteriorated gradually over time. The animals in all the sepsis groups exhibited significantly higher levels of TLR4 and NF-κB protein expression compared with the sham group. The TLR4 protein expressions were 0.376 in the sham operation group, 0.534 in the sepsis 3-h group, 0.551 in the sepsis 6-h group, and 0.719 in the sepsis 12-h group. The NF-κB protein expressions were 0.299 in the sham operation group, 0.488 in the sepsis 3-h group, 0.516 in the sepsis 6-h group, and 0.636 in the sepsis 12-h group.

CONCLUSION

Sepsis can lead to myocardial injury and cardiac dysfunction. This may be related to the activation of the NF-κB intracellular signal transduction pathway and the release of inflammatory factors as a result of lipopolysaccharides acting on TLR4 during the onset of sepsis.

Time Series Transcriptomic Analysis by RNA Sequencing Reveals a Key Role of PI3K in Sepsis-Induced Myocardial Injury in Mice

Septic cardiomyopathy is the main complication and cause of death of severe sepsis with limited therapeutic strategy. However, the molecular mechanism of sepsis-induced cardiac injury remains unclear. The present study was designed to investigate differentially expressed genes (DEGs) involved in the pathogenesis of septic cardiomyopathy induced by cecal ligation and puncture (CLP) in mice. Male C57BL/6J mice (8-10 weeks old) were subjected to CLP with 21-gauge needles for 24, 48, and 72 h. Myocardial function was assessed by echocardiography. The pathological changes of the heart were evaluated by hematoxylin and eosin as well as immunohistochemical staining. Time series RNA sequencing was utilized to investigate the gene expression profiles. CLP surgery resulted in a significant decrease of animal survival rate and left ventricle contractile function, and an increase in cardiac dilation and infiltration of proinflammatory cells including Mac-2⁺ macrophages in a time-dependent manner. RNA sequencing identified 5,607 DEGs in septic myocardium at 24, 48, and 72 h after CLP operation. Moreover, gene ontology analysis revealed that these DEGs were mainly associated with the biological processes, including cell adhesion, immune system process, inflammatory response, and positive regulation of cell migration. KEGG pathway enrichment analysis indicated that Staphylococcus aureus infection, osteoclast differentiation, leishmaniasis, and ECM-receptor interaction were significantly altered in septic hearts. Notably, Pik3r1 and Pik3r5 were localized in the center of the gene co-expression network, and were markedly upregulated in CLP-induced septic myocardium. Further, blocking PI3Kγ by the specific inhibitor CZC24832 significantly protected against sepsis-induced cardiac impairment. The present study uncovers the gene expression signatures of CLP-induced myocardial injury and sheds light on the role of Pik3r5 in septic cardiomyopathy.

Regulatory role of the TLR4/JNK signaling pathway in sepsis‑induced myocardial dysfunction

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and is a leading cause of mortality worldwide. Myocardial dysfunction is associated with poor prognosis in patients with sepsis and contributes to a high risk of mortality. However, the pathophysiological mechanisms underlying sepsis-induced myocardial dysfunction are not completely understood. The aim of the present study was to investigate the role of toll-like receptor 4 (TLR4)/c-Jun N-terminal kinase (JNK) signaling in pro-inflammatory cytokine expression and cardiac dysfunction during lipopolysaccharide (LPS)-induced sepsis in mice. C57BL/6 mice were pretreated with TAK-242 or saline for 1 h and then subjected to LPS (12 mg/kg, intraperitoneal) treatment. Cardiac function was assessed using an echocardiogram. The morphological changes of the myocardium were examined by hematoxylin and eosin staining and transmission electron microscopy. The serum protein levels of cardiac troponin I (cTnI) and tumor necrosis factor-α (TNF-α) were determined by an enzyme-linked immunosorbent assay (ELISA). The TLR4 and JNK mRNA levels were analyzed via reverse transcription-quantitative PCR. TLR4, JNK and phosphorylated-JNK protein levels were measured by western blotting. In response to LPS, the activation of TLR4 and JNK in the myocardium was upregulated. There were significant increases in the serum levels of TNF-α and cTnI, as well as histopathological changes in the myocardium and suppressed cardiac function, following LPS stimulation. Inhibition of TLR4 activation using TAK-242 led to a decrease in the activation of JNK and reduced the protein expression of TNF-α in plasma, and alleviated histological myocardial injury and improved cardiac function during sepsis in mice. The present data suggested that the TLR4/JNK signaling pathway played a critical role in regulating the production of pro-inflammatory cytokines and myocardial dysfunction induced by LPS.

Profiles of differentially expressed long noncoding RNAs and messenger RNAs in the myocardium of septic mice

Background

Sepsis is the primary cause of mortality in the intensive care unit (ICU), mainly due to sepsis-induced dysfunction of essential organs such as the heart and lungs. This study investigated the myocardium's epigenetic characterization from septic mice to identify potential treatment targets for septic myocardial dysfunction.

Methods

Cecal ligation and puncture (CLP) was used to induce sepsis in male C57BL/6 mice. Hearts were collected 24 h after surgery to determine the expression profiles of long noncoding RNAs (lncRNAs) and messenger RNAs (mRNAs) by microarray. To validate the reliability of microarray results, we randomly chose six differentially expressed lncRNAs for qRT-PCR. Functional mapping of differentially expressed mRNAs was annotated with gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses; lncRNA-mRNA co-expression network was constructed to reveal connections between lncRNAs and mRNAs.

Results

Microarray analysis indicated that 1,568 lncRNAs and 2,166 mRNAs were differentially expressed in the myocardium from septic mice, which was further confirmed by qRT-PCR. KEGG pathway analysis showed that numerous differentially expressed mRNAs were relevant to tumor necrosis factor (TNF) and phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt) signaling pathways. Moreover, according to the lncRNA-mRNA co-expression network constructed by the above six lncRNAs and their interacting mRNAs, the co-expression network profiles had 57 network nodes and 134 connections, including 76 positive interactions and 58 negative interactions.

Conclusions

In mouse hearts, sepsis resulted in differential expression of lncRNAs and mRNAs related to TNF and PI3K-Akt signaling pathways, suggesting that lncRNAs and their interacting mRNAs may participate in the pathogenesis of septic myocardial dysfunction by regulating TNF and PI3K-Akt signaling pathways.

Altered function of the left ventricle and clinical significance of heart-type fatty acid-binding protein in cardiac dysfunction among patients with sepsis

The present study aimed to determine the clinical significance of heart-type fatty acid-binding protein (H-FABP) in patients with sepsis-induced cardiac dysfunction. A total of 30 healthy subjects served as the control group and 80 patients with sepsis were recruited for the present single-center prospective observational study for the final analysis. Among these patients, 50 developed cardiac dysfunction, while no cardiac dysfunction was detected in the remaining 30 patients. Echocardiography was performed on days 1, 3, 7 and 10 of hospitalization. Routine blood biochemistry, serum H-FABP, N-terminal pro-brain natriuretic peptide (NT-proBNP) and troponin I were also analyzed. Alterations in cardiac biomarkers and echocardiography results were compared between patients with sepsis who did and who did not develop any cardiac dysfunction to determine the time of the occurrence of sepsis-induced cardiac dysfunction. Furthermore, the significance of H-FABP in the prediction of the 28-day mortality rate was evaluated using binary logistic regression analysis for sepsis and receiver operating characteristic (ROC) curve analysis. In addition, the specificity and sensitivity of H-FABP in the prediction of sepsis-induced cardiac dysfunction were verified using ROC curve analysis. For patients with cardiac dysfunction, the levels of cardiac output (CO), stroke volume (SV), mitral early diastolic peak velocity to mitral atrial systolic peak velocity ratio (E/A) and left ventricle ejection fraction (LVEF) were relatively decreased, while the levels of H-FABP and NT-proBNP were markedly increased compared with patients with sepsis and without cardiac dysfunction. CO and SV initially increased and subsequently decreased. EF was elevated, and E/A initially decreased and subsequently increased. Furthermore, H-FABP and NT-proBNP decreased in sepsis patients with cardiac dysfunction. The results of the ROC curve and binary logistic regression analyses suggest that H-FABP was associated with the 28-day prognosis for patients with sepsis. An H-FABP level of >35.7 ng/ml was able to predict the 28-day mortality for patients with sepsis, with an area under the curve (AUC) of 0.680. Furthermore, >30.3 ng/ml was the threshold for the prediction of sepsis-induced cardiac dysfunction, and the sensitivity and specificity were 76.27 and 61.76%, respectively, with an AUC of 0.673. In summary, patients with sepsis had an increased risk of cardiac insufficiency on days 7-10 of hospitalization. In addition, H-FABP may serve as an indicator to predict the prognosis of patients with sepsis in the short term, which has a certain significance in the diagnosis of sepsis-induced cardiac dysfunction.

MG53 Protects against Sepsis-Induced Myocardial Dysfunction by Upregulating Peroxisome Proliferator-Activated Receptor-α

Background

The heart is one of the most commonly affected organs during sepsis. Mitsugumin-53 (MG53) has attracted attention in research due to its cardioprotective function. However, the role of MG53 in sepsis-induced myocardial dysfunction (SIMD) remains unknown. The purpose of this study was to explore the underlying mechanism of MG53 in SIMD and investigate its potential relationship with peroxisome proliferator-activated receptor-α (PPARα).

Methods

The cecal ligation and puncture (CLP) model was created to induce SIMD in rats. Protein levels of MG53 and PPARα, cardiac function, cardiomyocyte injury, myocardial oxidative stress and inflammatory indicators, and cardiomyocyte apoptosis were measured at 18 h after CLP. The effects of MG53 on PPARα in SIMD were investigated via preconditioning recombinant human MG53 (rhMG53) and PPARα antagonist GW6471.

Results

The expression of MG53 and PPARα sharply decreased in the myocardium at 18 h after CLP. Compared with the sham group, cardiac function was significantly depressed, which was associated with the destructed myocardium, upregulated oxidative stress indicators and proinflammatory cytokines, and excessive cardiomyocyte apoptosis in the CLP group. Supplementation with rhMG53 enhanced myocardial MG53, increased the survival rate with improved cardiac function, and reduced oxidative stress, inflammation, and myocardial apoptosis, which were associated with PPARα upregulation. Pretreatment with GW6471 abolished the abovementioned protective effects induced by MG53.

Conclusions

Both MG53 and PPARα were downregulated after sepsis shock. MG53 supplement protects the heart against SIMD by upregulating PPARα expression. Our results provide a new treatment strategy for SIMD.

High-throughput metabolic profiling, combined with chemometrics and bioinformatic analysis reveals functional alterations in myocardial dysfunction

High-throughput metabolic profiling technology has been used for biomarker discovery and to reveal underlying metabolic mechanisms.

L-Carnitine Attenuates Cardiac Dysfunction by Ischemic Insults Through Akt Signaling Pathway

We aim to investigate the cardioprotective effects of L-carnitine (LC) on cardiac function during ischemia and reperfusion (I/R) and contractile function of single cardiomyocyte. C57BL/6 J mice were randomly assigned to 5 groups: sham group; vehicle group, LC preconditioning group, LC preconditioning + LY294002 (a PI3K/Akt signaling pathway inhibitor) group (LC + LY), and LY294002 group (LY). The sham group was exposed to the open heart operation but not I/R, the other groups received 45 min ischemia/48 h reperfusion. At the end of reperfusion, echocardiography was performed on every mouse. In order to determine whether LC's cardioprotection could act directly at the level of cardiomyocytes, we also tested its effects on isolated cardiomyocytes under hypoxia condition. The expressions of p-PI3K, PI3K, Akt, p-Akt, Bax and Bcl-2 proteins were detected by immunoblotting. The results showed that LC preconditioning remarkably improved cardiac function after I/R, but the cardioprotective effect of LC was significantly weakened after the application of LY294002. We also found that LC could directly improve the contractile function of cardiomyocytes under hypoxia condition. The immunoblotting results showed that LC administration restrained myocardial apoptosis as evidenced by decreasing the level of Bax expression, increasing the levels of phosphorylation of Akt, PI3K, and Bcl-2 protein expression, but these were blocked by LYC94002. Thus, the cardioprotective effects of LC against myocardial ischemic damage and its effect on single cardiomyocyte under hypoxia may be associated with the PI3K/Akt signaling pathway.