Association of myeloid cells of triggering receptor-1 with left ventricular systolic dysfunction in BALB/c mice with sepsis

The role of TREM-1 in septic myocardial pyroptosis and septic cardiomyopathy in vitro and in vivo

Septic cardiomyopathy (SCM) is an acute cardiac dysfunction involving myocardial cell pyroptosis. TREM-1 is a known receptor on cell membrane that can amplify the inflammatory response. Our previous studies have shown that TREM-1 in cardiomyocytes is involved in the activation of NLRP3 through the SMC4/NEMO pathway. Here, we aimed to use Trem-1 and Nlrp3 knockout mice to verify the effect of TREM-1 through NLRP3 on cardiac function in septic mice. The results showed that TREM-1 knockout resulted in a decrease in the release of downstream cell signals, including SMC4 and NLRP3, resulting in a decrease in cytokine release and improvement of cardiac dysfunction. Knockout of NLRP3 also reduced cardiomyocyte pyroptosis and increased survival rate. The therapeutic targeting of TREM-1 activation of NLRP3 and its pathway may contribute to the treatment or prevention of SCM.

TREM-1 induces pyroptosis in cardiomyocytes by activating NLRP3 inflammasome through the SMC4/NEMO pathway

Sepsis often causes cell death via pyroptosis and hence results in septic cardiomyopathy. Triggering receptors expressed in myeloid cells-1 (TREM-1) may initiate cellular cascade pathways and, in turn, induce cell death and vital organ dysfunction in sepsis, but the evidence is limited. We set to investigate the role of TREM-1 on nucleotide-binding oligomerization domain-like receptors with pyrin domain-3 (NLRP3) inflammasome activation and cardiomyocyte pyroptosis in sepsis models using cardiac cell line (HL-1) and mice. In this study, TREM-1 was found to be significantly increased in HL-1 cells challenged with lipopolysaccharide (LPS). Pyroptosis was also significantly increased in the HL-1 cells challenged with lipopolysaccharide and an NLRP3 inflammasome activator, nigericin. The close interaction between TREM-1 and structural maintenance of chromosome 4 (SMC4) was also identified. Furthermore, inhibition of TREM-1 or SMC4 prevented the upregulation of NLRP3 and decreased Gasdermin-D, IL-1β and caspase-1 cleavage. In mice subjected to caecal ligation and puncture, the TREM-1 inhibitor LR12 decreased the expression of NLRP3 and attenuated cardiomyocyte pyroptosis, leading to improved cardiac function and prolonged survival of septic mice. Our work demonstrates that, under septic conditions, TREM-1 plays a critical role in cardiomyocyte pyroptosis. Targeting TREM-1 and its associated molecules may therefore lead to novel therapeutic treatments for septic cardiomyopathy.

Resveratrol ameliorates the behavioural and molecular changes in rats exposed to uninephrectomy: role of hippocampal SIRT1, BDNF and AChE

Subtle memory and cognitive changes may occur in uninephrectomized (Unix) patients long before the development of chronic kidney disease, such changes may be unnoticed. The dietary polyphenol, Resveratrol, displayed various neuroprotective effects, its role in chronic kidney disease is an area of intense studies. This work was designed to investigate the behavioural and molecular changes that may occur following 7 months of Unix in rats, and to determine whether Resveratrol intake can improve such pathology. Male Wistar rats were divided into three groups: sham operated, Unix and Unix group treated with Resveratrol (20 mg/kg/day). Rats were subjected to series of behavioural testing, different biochemical parameters along with RT-PCR and immunohistochemistry of the hippocampal tissue to track the development of functional or structural brain changes. Anxiety behaviour and reduced spatial memory performance were observed in rats 7 months post-nephrectomy; these deficits were remarkably reversed with Resveratrol. Among the species typical behaviour, burrowing was assessed; it showed significant impairment post-nephrectomy. Resveratrol intake was almost able to increase the burrowing behaviour. Decreased SIRT1 in immune-stained sections, oxidative stress, inflammatory changes, and increased AChE activity in hippocampal homogenates were found in Unix rats, and Resveratrol once more was capable to reverse such pathological changes. This work has investigated the occurrence of behavioural and structural brain changes 7 months following Unix and underlined the importance of Resveratrol to counterbalance the behavioural impairment, biochemical and brain pathological changes after uninephrectomy. These findings may raise the possible protective effects of Resveratrol intake in decreased kidney function.

Targeting the eCIRP/TREM-1 interaction with a small molecule inhibitor improves cardiac dysfunction in neonatal sepsis

Background

Neonatal sepsis and the associated myocardial dysfunction remain a leading cause of infant mortality. Extracellular cold-inducible RNA-binding protein (eCIRP) acts as a ligand of triggering receptor expressed on myeloid cells-1 (TREM-1). M3 is a small CIRP-derived peptide that inhibits the eCIRP/TREM-1 interaction. We hypothesize that the eCIRP/TREM-1 interaction in cardiomyocytes contributes to sepsis-induced cardiac dysfunction in neonatal sepsis, while M3 is cardioprotective.

Methods

Serum was collected from neonates in the Neonatal Intensive Care Unit (NICU). 5–7-day old C57BL/6 mouse pups were used in this study. Primary murine neonatal cardiomyocytes were stimulated with recombinant murine (rm) CIRP with M3. TREM-1 mRNA and supernatant cytokine levels were assayed. Mitochondrial oxidative stress, ROS, and membrane potential were assayed. Neonatal mice were injected with rmCIRP and speckle-tracking echocardiography was conducted to measure cardiac strain. Sepsis was induced by i.p. cecal slurry. Mouse pups were treated with M3 or vehicle. After 16 h, echocardiography was performed followed by euthanasia for tissue analysis. A 7-day survival study was conducted.

Results

Serum eCIRP levels were elevated in septic human neonates. rmCIRP stimulation of cardiomyocytes increased TREM-1 gene expression. Stimulation of cardiomyocytes with rmCIRP upregulated TNF-α and IL-6 in the supernatants, while this upregulation was inhibited by M3. Stimulation of cardiomyocytes with rmCIRP resulted in a reduction in mitochondrial membrane potential (MMP) while M3 treatment returned MMP to near baseline. rmCIRP caused mitochondrial calcium overload; this was inhibited by M3. rmCIRP injection impaired longitudinal and radial cardiac strain. Sepsis resulted in cardiac dysfunction with a reduction in cardiac output and left ventricular end diastolic diameter. Both were improved by M3 treatment. Treatment with M3 attenuated serum, cardiac, and pulmonary levels of pro-inflammatory cytokines compared to vehicle-treated septic neonates. M3 dramatically increased sepsis survival.

Conclusions

Inhibition of eCIRP/TREM-1 interaction with M3 is cardioprotective, decreases inflammation, and improves survival in neonatal sepsis.

Trial registration Retrospectively registered.

TREM-1; Is It a Pivotal Target for Cardiovascular Diseases?

Cardiovascular diseases (CVDs) are as menacing as ever and still continue to kill adults worldwide, notwithstanding tremendous efforts to decrease their consequent mortality and morbidity. Lately, a growing body of research indicated that inflammation plays a pivotal role in the pathogenesis and complications of CVDs. A receptor of the immunoglobulin superfamily, triggering receptors expressed on myeloid cells-1 (TREM-1) was shown to induce and amplify the inflammation in both acute and chronic disease’ pathogenesis and progression, which hence makes it one of the most important complication factors of CVDs. Thus, studies endeavored to investigate the role played by TREM-1 in CVDs with respect to their etiologies, complications, and possible therapeutics. We examined here, for the first time, the most relevant studies regarding TREM-1 involvement in CVDs. We critically analyzed and summarized our findings and made some suggestions for furtherance of the investigations with the aim to utilize TREM-1 and its pathways for diagnostic, management, and prognosis of CVDs. Overall, TREM-1 was found to be involved in the pathogenesis of acute and chronic cardiovascular conditions, such as acute myocardial infarction (AMI) and atherosclerosis. Although most therapeutic approaches are yet to be elucidated, our present research outcome displays a promising future to utilizing the TREM-1 pathway as a potential target for understanding and managing CVDs.

Soluble triggering receptor expressed on myeloid cell-1 (sTREM-1): a potential biomarker for the diagnosis of infectious diseases

Sensitive and useful biomarkers for the diagnosis and prognosis of infectious diseases have been widely developed. An example of these biomarkers is triggering receptor expressed on myeloid cell-1 (TREM-1), which is a cell surface receptor expressed on monocytes/macrophages and neutrophils. TREM-1 amplifies inflammation by activating the TREM-1/DAP12 pathway. This pathway is triggered by the interaction of TREM-1 with ligands or stimulation by bacterial lipopolysaccharide. Consequently, pro-inflammatory cytokines and chemokines are secreted. Soluble TREM-1 (sTREM-1) is a special form of TREM-1 that can be directly tested in human body fluids and well-known biomarker for infectious diseases. sTREM-1 level can be potentially used for the early diagnosis and prognosis prediction of some infectious diseases, including infectious pleural effusion, lung infections, sepsis, bacterial meningitis, viral infections (e.g., Crimean Congo hemorrhagic fever and dengue fever), fungal infections (e.g., Aspergillus infection), and burn-related infections. sTREM-1 is a more sensitive and specific biomarker than traditional indices, such as C-reactive protein and procalcitonin levels, for these infectious diseases. Therefore, sTREM-1 is a feasible biomarker for the targeted therapy and rapid and early diagnosis of infectious diseases.

The Triggering Receptor Expressed on Myeloid cells-1: A new player during acute myocardial infarction

Following myocardial ischemia, an intense activation of the immune system occurs that leads to inflammatory cytokines and chemokines production and to the recruitment of neutrophils and mononuclear cells in the infarcted area. Although pro-inflammatory signals initiate the cellular events necessary for scar formation, excessive and prolonged inflammation promotes deleterious cardiac remodeling and dysfunction. The triggering receptor expressed on myeloid cells-1 (TREM-1) is a highly conserved immune-receptor expressed by neutrophils and monocytes that acts as an amplifier of the innate immune response. Blockade of TREM-1 activation protects from hyper-responsiveness and death during severe infections. Here we review the role of TREM-1 in orchestrating the inflammatory response that follows MI. TREM-1 deletion (Trem-1-/-) or modulation by the use of a short inhibitory peptide (LR12) dampens myocardial inflammation, limits leukocyte recruitment, and improves heart function and survival in mice or pigs. Moreover, the soluble form of TREM-1 (sTREM-1) is found in the plasma of patients suffering from an acute MI and its concentration is an independent predictor of death. This suggests that TREM-1 may constitute a new therapeutic target during acute MI.