Cold-inducible RNA-binding protein (CIRP) triggers inflammatory responses in hemorrhagic shock and sepsis

RNA-binding proteins in vascular inflammation and atherosclerosis

Atherosclerotic cardiovascular disease (ASCVD) remains the major cause of premature death and disability worldwide, even when patients with an established manifestation of atherosclerotic heart disease are optimally treated according to the clinical guidelines. Apart from the epigenetic control of transcription of the genetic information to messenger RNAs (mRNAs), gene expression is tightly controlled at the post-transcriptional level before the initiation of translation. Although mRNAs are traditionally perceived as the messenger molecules that bring genetic information from the nuclear DNA to the cytoplasmic ribosomes for protein synthesis, emerging evidence suggests that processes controlling RNA metabolism, driven by RNA-binding proteins (RBPs), affect cellular function in health and disease. Over the recent years, vascular endothelial cell, smooth muscle cell and immune cell RBPs have emerged as key co- or post-transcriptional regulators of several genes related to vascular inflammation and atherosclerosis. In this review, we provide an overview of cell-specific function of RNA-binding proteins involved in all stages of ASCVD and how this knowledge may be used for the development of novel precision medicine therapeutics.

The protective effect of H151, a novel STING inhibitor, in renal ischemia-reperfusion-induced acute kidney injury

Renal ischemia-reperfusion (RIR)-induced acute kidney injury (AKI) is a common renal functional disorder with high morbidity and mortality. Stimulator of interferon (IFN) genes (STING) is the cytosolic DNA-activated signaling pathway that mediates inflammation and injury. Our recent study showed that extracellular cold-inducible RNA-binding protein (eCIRP), a newly identified damage-associated molecular pattern, activates STING and exacerbates hemorrhagic shock. H151 is a small molecule that selectively binds to STING and inhibits STING-mediated activity. We hypothesized that H151 attenuates eCIRP-induced STING activation in vitro and inhibits RIR-induced AKI in vivo. In vitro, renal tubular epithelial cells incubated with eCIRP showed increased levels of IFN-β, STING pathway downstream cytokine, IL-6, tumor necrosis factor-α, and neutrophil gelatinase-associated lipocalin, whereas coincubation with eCIRP and H151 diminished those increases in a dose-dependent manner. In vivo, 24 h after bilateral renal ischemia-reperfusion, glomerular filtration rate was decreased in RIR-vehicle-treated mice, whereas glomerular filtration rate was unchanged in RIR-H151-treated mice. In contrast to sham, serum blood urea nitrogen, creatinine, and neutrophil gelatinase-associated lipocalin were increased in RIR-vehicle, but in RIR-H151, these levels were significantly decreased from RIR-vehicle. In contrast to sham, kidney IFN-β mRNA, histological injury score, and TUNEL staining were also increased in RIR-vehicle, but in RIR-H151, these levels were significantly decreased from RIR-vehicle. Importantly, in contrast to sham, in a 10-day survival study, survival decreased to 25% in RIR-vehicle, but RIR-H151 had a survival of 63%. In conclusion, H151 inhibits eCIRP-induced STING activation in renal tubular epithelial cells. Therefore, STING inhibition by H151 can be a promising therapeutic intervention for RIR-induced AKI.NEW & NOTEWORTHY Renal ischemia-reperfusion (RIR)-induced acute kidney injury (AKI) is a common renal functional disorder with a high morbidity and mortality rate. Stimulator of interferon genes (STING) is the cytosolic DNA-activated signaling pathway responsible for mediating inflammation and injury. Extracellular cold-inducible RNA-binding protein (eCIRP) activates STING and exacerbates hemorrhagic shock. H151, a novel STING inhibitor, attenuated eCIRP-induced STING activation in vitro and inhibited RIR-induced AKI. H151 shows promise as a therapeutic intervention for RIR-induced AKI.

THE PROTECTIVE EFFECT OF C23 IN A RAT MODEL OF CARDIAC ARREST AND RESUSCITATION

ABSTRACT

Background : Systemic inflammation acts as a contributor to neurologic deficits after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). Extracellular cold-inducible RNA-binding, protein (CIRP) has been demonstrated to be responsible in part for the inflammation through binding to toll-like receptor 4 (TLR4) after cerebral ischemia. The short peptide C23 derived from CIRP has a high affinity for TLR4, we hypothesize that C23 reduces systemic inflammation after CA/CPR by blocking the binding of CIRP to TLR4. Methods : Adult male SD rats in experimental groups were subjected to 5 min of CA followed by resuscitation. C23 peptide (8 mg/kg) or normal saline was injected intraperitoneally at the beginning of the return of spontaneous circulation (ROSC). Results : The expressions of CIRP, TNF-α, IL-6, and IL-1β in serum and brain tissues were significantly increased at 24 h after ROSC ( P < 0.05). C23 treatment could markedly decrease the expressions of TNF-α, IL-6, and IL-1β in serum ( P < 0.05). Besides, it can decrease the expressions of TLR4, TNF-α, IL-6, and IL-1β in the cortex and hippocampus and inhibit the colocalization of CIRP and TLR4 ( P < 0.05). In addition, C23 treatment can reduce the apoptosis of hippocampus neurons ( P < 0.05). Finally, the rats in the C23 group have improved survival rate and neurological prognosis ( P < 0.05). Conclusions: These findings suggest that C23 can reduce systemic inflammation and it has the potential to be developed into a possible therapy for post-CA syndrome.

Acute cold stress induces intestinal injury via CIRP-TLR4-IRE1 signaling pathway in pre-starter broilers

BACKGROUND

Cold stress is a common environmental stress in broiler chicks. Cold-inducible RNA-binding protein (CIRP) is a conserved cold shock protein that can regulate inflammatory response through Toll-like receptor 4 (TLR4). The mechanism that how CIRP involves in the regulation of cold stress in broilers remains unclear.

METHODS AND RESULTS

In this study, 360 7-day-old healthy male SZ901 chicks were selected and randomly allocated to four groups, and then subjected to acute cold exposure at the ambient temperature of 12 ± 1 °C for 0 h, 4 h, 8 h, and 12 h, respectively. After cold exposure, abdominall skin temperature, gene expression of CIRP-TLR4-IRE1 signaling pathway in ileum mucosa, and small intestinal structure were measured. The results showed that cold exposure decreased abdominall skin temperature, upregulated the gene expression of endoplasmic reticulum stress (ERS) markers IRE1, inflammatory factors IL-1β, IL-6, IL-10, TNF-α, and tight junction proteins ZO-1 and Occludin in ileum of chicks compared with the control group with no (0 h) cold exposure. Compared with the control group, a long time cold exposure upregulated the gene expression of CIRP, TLR4, GRP78, NF-κB in ileum mucosa, and decreased the villus height and V/C of small intestine.

CONCLUSIONS

The above results suggest that acute cold stress induces endoplasmic reticulum stress via upregulating the gene expression of CIRP-TLR4-IRE1 signaling pathway, and results in the structural damage of chick intestine.

Maternal sepsis in pregnancy and the puerperal periods: a cross-sectional study

Maternal sepsis is a life-threatening condition and ranks among the top five causes of maternal death in pregnancy and the postpartum period. Herein, we conducted a retrospective study on sepsis cases to explain the related risk factors by comparing them with bloodstream infection (BSI) and control maternities. In total, 76 sepsis cases were enrolled, and 31 BSI and 57 maternal cases of the same age but with neither sepsis nor BSI were set as controls. Genital tract infection (GTI) and pneumonia were the two most common infection sources in both sepsis (22 cases, 29% and 29 cases, 38%) and BSI cases (18 cases, 58% and 8 cases, 26%). Urinary tract infection (UTI)/pyelonephritis (9 cases, 12%) and digestive infection cases (11 cases, 14%) only existed in the sepsis group. Significantly different infection sources were discovered between the sepsis-death and sepsis-cure groups. A higher proportion of pneumonia and a lower proportion of GTI cases were present in the sepsis-death group (17 cases, 45% pneumonia and 9 cases, 24% GTI) than in the sepsis-cure group (12 cases, 32% pneumonia and 13 cases, 34% GTI). In addition, although gram-negative bacteria were the dominant infectious microorganisms as previously reported, lower proportion of gram-negative bacteria infectious cases in sepsis (30 cases, 50%) and even lower in sepsis-death group (14 cases, 41%) was shown in this study than previous studies. As expected, significantly greater adverse maternal and fetal outcomes, such as higher maternal mortality (26.3% vs. 0% vs. 0%), higher fetal mortality (42.2% vs. 20.8% vs. 0%), earlier gestational age at delivery (26.4 ± 9.5 vs. 32.3 ± 8.1 vs. 37.7 ± 4.0) and lower newborn weight (1,590 ± 1287.8 vs. 2859.2 ± 966.0 vs. 3214.2 ± 506.4), were observed in the sepsis group. This study offered some potential pathogenesis and mortality risk factors for sepsis, which may inspire the treatment of sepsis in the future.

CIRP attenuates acute kidney injury after hypothermic cardiovascular surgery by inhibiting PHD3/HIF-1α-mediated ROS-TGF-β1/p38 MAPK activation and mitochondrial apoptotic pathways

BACKGROUND

The ischemia-reperfusion (IR) environment during deep hypothermic circulatory arrest (DHCA) cardiovascular surgery is a major cause of acute kidney injury (AKI), which lacks preventive measure and treatment. It was reported that cold inducible RNA-binding protein (CIRP) can be induced under hypoxic and hypothermic stress and may have a protective effect on multiple organs. The purpose of this study was to investigate whether CIRP could exert renoprotective effect during hypothermic IR and the potential mechanisms.

METHODS

Utilizing RNA-sequencing, we compared the differences in gene expression between Cirp knockout rats and wild-type rats after DHCA and screened the possible mechanisms. Then, we established the hypothermic oxygen-glucose deprivation (OGD) model using HK-2 cells transfected with siRNA to verify the downstream pathways and explore potential pharmacological approach. The effects of CIRP and enarodustat (JTZ-951) on renal IR injury (IRI) were investigated in vivo and in vitro using multiple levels of pathological and molecular biological experiments.

RESULTS

We discovered that Cirp knockout significantly upregulated rat Phd3 expression, which is the key regulator of HIF-1α, thereby inhibiting HIF-1α after DHCA. In addition, deletion of Cirp in rat model promoted apoptosis and aggravated renal injury by reactive oxygen species (ROS) accumulation and significant activation of the TGF-β1/p38 MAPK inflammatory pathway. Then, based on the HK-2 cell model of hypothermic OGD, we found that CIRP silencing significantly stimulated the expression of the TGF-β1/p38 MAPK inflammatory pathway by activating the PHD3/HIF-1α axis, and induced more severe apoptosis through the mitochondrial cytochrome c-Apaf-1-caspase 9 and FADD-caspase 8 death receptor pathways compared with untransfected cells. However, silencing PHD3 remarkably activated the expression of HIF-1α and alleviated the apoptosis of HK-2 cells in hypothermic OGD. On this basis, by pretreating HK-2 and rats with enarodustat, a novel HIF-1α stabilizer, we found that enarodustat significantly mitigated renal cellular apoptosis under hypothermic IR and reversed the aggravated IRI induced by CIRP defect, both in vitro and in vivo.

CONCLUSION

Our findings indicated that CIRP may confer renoprotection against hypothermic IRI by suppressing PHD3/HIF-1α-mediated apoptosis. PHD3 inhibitors and HIF-1α stabilizers may have clinical value in renal IRI.

A novel miRNA mimic attenuates organ injury after hepatic ischemia/reperfusion

INTRODUCTION

Extracellular cold-inducible RNA-binding protein (eCIRP) is a novel mediator of inflammation and tissue injury. It has been shown that miRNA 130b-3p acts as an endogenous inhibitor of eCIRP. Because RNA mimics are unstable after in vivo administration, we have chemically engineered miRNA 130b-3p mimic (named PS-OMe miR130) to improve its stability by protection from nuclease activity. We hypothesize that PS-OMe miR130 reduces eCIRP-mediated injury and inflammation in a murine model of hepatic ischemia/reperfusion (I/R), a model of sterile inflammation.

METHODS

Adult male mice underwent 70% hepatic ischemia for 60 minutes and 24-hour reperfusion. At the start of reperfusion, mice were treated intravenously with vehicle (phosphate-buffered saline) or PS-OMe miR130. Blood and liver tissue were collected after 24 hours for biochemical analysis. Apoptosis in the liver tissue was determined by transferase dUTP nick-end labeling assay.

RESULTS

After hepatic I/R, organ injury markers including aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase significantly decreased after PS-OMe miR130 treatment. Furthermore, histological analysis of liver sections demonstrated significantly less injury in PS-OMe miR130 treatment mice versus vehicle mice. In addition, tumor necrosis factor α mRNA, interleukin-1β mRNA, and neutrophil infiltration (myeloperoxidase activity and granulocyte receptor 1 immunohistochemistry) were significantly attenuated after PS-OMe miR130 treatment. Finally, apoptosis significantly decreased in liver tissue after treatment.

CONCLUSION

PS-OMe miR130 decreases eCIRP-mediated injury and inflammation in a murine model of hepatic I/R.

Radiation upregulates macrophage TREM-1 expression to exacerbate injury in mice

Introduction

Exposure to high-dose ionizing radiation causes tissue injury, infections and even death due to immune dysfunction. The triggering receptor expressed on myeloid cells-1 (TREM-1) has been demonstrated to critically amplify and dysregulate immune responses. However, the role of TREM-1 in radiation injury remains unknown. Extracellular cold-inducible RNA-binding protein (eCIRP), a new damage-associated molecular pattern, is released from activated or stressed cells during inflammation. We hypothesized that ionizing radiation upregulates TREM-1 expression via eCIRP release to worsen survival.

Methods

RAW264.7 cells and peritoneal macrophages collected from C57BL/6 wild-type (WT) mice were exposed to 5- and 10-Gray (Gy) radiation. C57BL/6 WT and CIRP-/- mice underwent 10-Gy total body irradiation (TBI). TREM-1 expression on RAW264.7 cells and peritoneal macrophages in vitro and in vivo were evaluated by flow cytometry. eCIRP levels in cell culture supernatants and in peritoneal lavage isolated from irradiated mice were evaluated by Western blotting. We also evaluated 30-day survival in C57BL/6 WT, CIRP-/- and TREM-1-/- mice after 6.5-Gy TBI.

Results

The surface protein and mRNA levels of TREM-1 in RAW264.7 cells were significantly increased at 24 h after 5- and 10-Gy radiation exposure. TREM-1 expression on peritoneal macrophages was significantly increased after radiation exposure in vitro and in vivo. eCIRP levels were significantly increased after radiation exposure in cell culture supernatants of peritoneal macrophages in vitro and in peritoneal lavage in vivo. Moreover, CIRP-/- mice exhibited increased survival after 6.5-Gy TBI compared to WT mice. Interestingly, TREM-1 expression on peritoneal macrophages in CIRP-/- mice was significantly decreased compared to that in WT mice at 24 h after 10-Gy TBI. Furthermore, 30-day survival in TREM-1-/- mice was significantly increased to 64% compared to 20% in WT mice after 6.5-Gy TBI.

Conclusion

Our data indicate that ionizing radiation increases TREM-1 expression in macrophages via the release of eCIRP, and TREM-1 contributes to worse survival after total body irradiation. Thus, targeting TREM-1 could have the potential to be developed as a novel medical countermeasure for radiation injury.

RNA-binding proteins in degenerative joint diseases: A systematic review

RNA-binding proteins (RBPs), which are conserved proteins comprising multiple intermediate sequences, can interact with proteins, messenger RNA (mRNA) of coding genes, and non-coding RNAs to perform different biological functions, such as the regulation of mRNA stability, selective polyadenylation, and the management of non-coding microRNA (miRNA) synthesis to affect downstream targets. This article will highlight the functions of RBPs, in degenerative joint diseases (intervertebral disc degeneration [IVDD] and osteoarthritis [OA]). It will reviews the latest advancements on the regulatory mechanism of RBPs in degenerative joint diseases, in order to understand the pathophysiology, early diagnosis and treatment of OA and IVDD from a new perspective.

Identification of potential biomarkers and pathways for sepsis using RNA sequencing technology and bioinformatic analysis

Long non-coding RNAs (lncRNAs) has been proven by many to play a crucial part in the process of sepsis. To obtain a better understanding of sepsis, the molecular biomarkers associated with it, and its possible pathogenesis, we obtained data from RNA-sequencing analysis using serum from three sepsis patients and three healthy controls (HCs). Using edgeR (one of the Bioconductor software package), we identified 1118 differentially expressed mRNAs (DEmRNAs) and 1394 differentially expressed long noncoding RNAs (DElncRNAs) between sepsis patients and HCs. We identified the biological functions of these disordered genes using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway analyses. The GO analysis showed that the homophilic cell adhesion via plasma membrane adhesion molecules was the most significantly enriched category. The KEGG signaling pathway analysis indicated that the differentially expressed genes (DEGs) were most significantly enriched in retrograde endocannabinoid signaling. Using STRING, a protein-protein interaction network was also created, and Cytohubba was used to determine the top 10 hub genes. To examine the relationship between the hub genes and sepsis, we examined three datasets relevant to sepsis that were found in the gene expression omnibus (GEO) database. PTEN and HIST2H2BE were recognized as hub gene in both GSE4607, GSE26378, and GSE9692 datasets. The receiver operating characteristic (ROC) curves indicate that PTEN and HIST2H2BE have good diagnostic value for sepsis. In conclusion, this two hub genes may be biomarkers for the early diagnosis of sepsis, our findings should deepen our understanding of the pathogenesis of sepsis.

Serum cold-inducible RNA-binding protein levels as a potential biomarker for systemic sclerosis-associated interstitial lung disease

Systemic sclerosis (SSc) is a complex autoimmune disease characterized by fibrotic, inflammatory, and vascular dysfunction. Danger-associated molecular patterns (DAMPs)-mediated inflammasome activation has been reported to be involved in the pathogenesis of SSc. Cold-inducible RNA-binding protein (CIRP) is newly identified as a DAMP. Here we examined the clinical significance of serum levels of CIRP in 60 patients with SSc and 20 healthy control patients (HCs) using an enzyme-linked immunosorbent assay. Serum CIRP levels in diffuse cutaneous SSc (dcSSc) patients were significantly increased compared with limited cutaneous SSc (lcSSc) patients or HCs. When examining the relationship with SSc-specific parameters, serum CIRP levels with the presence of interstitial lung disease (ILD) were higher than those without ILD. In detail, serum CIRP levels correlated negatively with the percent predicted diffusing capacity for carbon monoxide and positively with levels of Krebs von den Lungen-6. In addition, elevated serum CIRP levels declined along with decreased SSc-ILD activity in patients who received immunosuppressive therapy. These results suggest that CIRP may play a role in the development of ILD in SSc. Moreover, CIRP could serve as a useful serological marker of SSc-ILD in terms of disease activity and therapeutic effects.

ASO targeting RBM3 temperature-controlled poison exon splicing prevents neurodegeneration in vivo

Neurodegenerative diseases are increasingly prevalent in the aging population, yet no disease-modifying treatments are currently available. Increasing the expression of the cold-shock protein RBM3 through therapeutic hypothermia is remarkably neuroprotective. However, systemic cooling poses a health risk, strongly limiting its clinical application. Selective upregulation of RBM3 at normothermia thus holds immense therapeutic potential. Here we identify a poison exon within the RBM3 gene that is solely responsible for its cold-induced expression. Genetic removal or antisense oligonucleotide (ASO)-mediated manipulation of this exon yields high RBM3 levels independent of cooling. Notably, a single administration of ASO to exclude the poison exon, using FDA-approved chemistry, results in long-lasting increased RBM3 expression in mouse brains. In prion-diseased mice, this treatment leads to remarkable neuroprotection, with prevention of neuronal loss and spongiosis despite high levels of disease-associated prion protein. Our promising results in mice support the possibility that RBM3-inducing ASOs might also deliver neuroprotection in humans in conditions ranging from acute brain injury to Alzheimer's disease.

Activation of immune signals during organ transplantation

The activation of host's innate and adaptive immune systems can lead to acute and chronic graft rejection, which seriously impacts graft survival. Thus, it is particularly significant to clarify the immune signals, which are critical to the initiation and maintenance of rejection generated after transplantation. The initiation of response to graft is dependent on sensing of danger and stranger molecules. The ischemia and reperfusion of grafts lead to cell stress or death, followed by releasing a variety of damage-associated molecular patterns (DAMPs), which are recognized by pattern recognition receptors (PRRs) of host immune cells to activate intracellular immune signals and induce sterile inflammation. In addition to DAMPs, the graft exposed to 'non-self' antigens (stranger molecules) are recognized by the host immune system, stimulating a more intense immune response and further aggravating the graft damage. The polymorphism of MHC genes between different individuals is the key for host or donor immune cells to identify heterologous 'non-self' components in allogeneic and xenogeneic organ transplantation. The recognition of 'non-self' antigen by immune cells mediates the activation of immune signals between donor and host, resulting in adaptive memory immunity and innate trained immunity to the graft, which poses a challenge to the long-term survival of the graft. This review focuses on innate and adaptive immune cells receptor recognition of damage-associated molecular patterns, alloantigens and xenoantigens, which is described as danger model and stranger model. In this review, we also discuss the innate trained immunity in organ transplantation.

A comparison of bilateral and unilateral cerebral perfusion for total arch replacement surgery for non-marfan, type A aortic dissection

OBJECTIVES

Acknowledging lacking of consensus exist in total aortic arch (TAA) surgery for acute type A aortic dissection (AAD), this study aimed to investigate the neurologic injury rate between bilateral and unilateral cerebrum perfusion on the specific population.

METHODS

A total of 595 AAD patients other than Marfan syndrome receiving TAA surgery since March 2013 to March 2022 were included. Among them, 276 received unilateral cerebral perfusion (via right axillary artery, RCP) and 319 for bilateral cerebral perfusion (BCP). The primary outcome was neurologic injury rate. Secondary outcomes were 30-day mortality, serum inflammation response (high sensitivity C reaction protein, hs-CRP; Interleukin-6, IL-6; cold-inducible RNA binding protein, CIRBP) and neuroprotection (RNA-binding motif 3, RBM3) indexes.

RESULTS

The BCP group reported a significantly lower permanent neurologic deficits [odds ratio: 0.481, Confidence interval (CI): 0.296-0.782, p = 0.003] and 30-day mortality (odds ratio: 0.353, CI: 0.194-0.640, p < 0.001) than those received RCP treatment. There were also lower inflammation cytokines (hr-CRP: 114 ± 17 vs. 101 ± 16 mg/L; IL-6: 130 [103,170] vs. 81 [69,99] pg/ml; CIRBP: 1076 [889, 1296] vs. 854 [774, 991] pg/ml, all p < 0.001), but a higher neuroprotective cytokine (RBM3: 4381 ± 1362 vs 2445 ± 1008 pg/mL, p < 0.001) at 24 h after procedure in BCP group. Meanwhile, BCP resulted in a significantly lower Acute Physiology, Age and Chronic Health Evaluation (APACHE) Ⅱscore (18 ± 6 vs 17 ± 6, p < 0.001) and short stay in intensive care unit (4 [3,5] vs. 3 [2,3] days, p < 0.001) and hospital (16 ± 4 vs 14 ± 3 days, p < 0.001).

CONCLUSIONS

This present study indicated that BCP compared with RCP was associated with lower permanent neurologic deficits and 30-day mortality in AAD patients other than Marfan syndrome receiving TAA surgery.

An engineered miRNA PS-OMe miR130 inhibits acute lung injury by targeting eCIRP in sepsis

BACKGROUND

Sepsis is caused by the dysregulated immune response due to an initial infection and results in significant morbidity and mortality in humans. Extracellular cold inducible RNA binding protein (eCIRP) is a novel mediator identified in sepsis. We have previously discovered that microRNA 130b-3p inhibits eCIRP mediated inflammation. As RNA mimics are very unstable in vivo, we hypothesize that an engineered miRNA 130b-3p mimic named PS-OMe miR130, improves stability of the miRNA by protection from nuclease activity. We further hypothesize that PS-OMe miR130 reduces not only eCIRP-mediated inflammation and but also acute lung injury in a murine model of polymicrobial sepsis.

METHODS

Single stranded PS-OMe miR130 was synthesized and the binding affinity to eCIRP was evaluated using surface plasmon resonance (SPR) and computational modeling. Macrophages were treated with PS-OMe miR130 with and without eCIRP and cell supernatant analyzed for cytokines. In vitro stability and the in vivo half-life of PS-OMe miR130 were also assessed. The effect of PS-Ome miR130 on eCIRP's binding to TLR4 was evaluated by SPR analysis and modeling. Finally, the effect of PS-OMe miR130 on inflammation and injury was assessed in a murine model of sepsis.

RESULTS

We demonstrate via SPR and computational modeling that PS-OMe miR130 has a strong binding affinity to eCIRP. This engineered miRNA decreases eCIRP induced TNF-α and IL-6 proteins, and it is highly stable in vitro and has a long in vivo half-life. We further demonstrate that PS-OMe miR130 blocks eCIRP binding to its receptor TLR4. Finally, we show that PS-OMe miR130 inhibits inflammation and lung injury, and improves survival in murine sepsis.

CONCLUSION

PS-OMe miR130 can be developed as a novel therapeutic by inhibiting eCIRP-mediated inflammation and acute lung injury in sepsis.

RBM3 is associated with acute lung injury in septic mice and patients via the NF-κB/NLRP3 pathway

Sepsis refers to host response disorders caused by infection, leading to life-threatening organ dysfunction. RNA-binding motif protein 3 (RBM3) is an important cold-shock protein that is upregulated in response to mild hypothermia or hypoxia. In this study, we aimed to investigate whether RBM3 is involved in sepsis-associated acute lung injury (ALI). Intraperitoneal injection of LPS (10 mg/kg) was performed in wild type (WT) and RBM3 knockout (KO, RBM3^-/^-) mice to establish an in vivo sepsis model. An NLRP3 inflammasome inhibitor, MCC950 (50 mg/kg), was injected intraperitoneally 30 min before LPS treatment. Serum, lung tissues, and BALF were collected 24 h later for further analysis. In addition, we also collected serum from sepsis patients and healthy volunteers to detect their RBM3 expression. The results showed that the expression of RBM3 in the lung tissues of LPS-induced sepsis mice and the serum of patients with sepsis was significantly increased and positively correlated with disease severity. In addition, RBM3 knockout (KO) mice had a low survival rate, and RBM3 KO mice had more severe lung damage, inflammation, lung cell apoptosis, and oxidative stress than WT mice. LPS treatment significantly increased the levels of nucleotide binding and oligomerization domain-like receptor family 3 (NLRP3) inflammasomes and mononuclear cell nuclear factor-κB (NF-κB) in the lung tissues of RBM3 KO mice. However, these levels were only slightly elevated in WT mice. Interestingly, MCC950 improved LPS-induced acute lung injury in WT and RBM3 KO mice but inhibited the expression of NLRP3, caspase-1, and IL-1β. In conclusion, RBM3 was overexpressed in sepsis patients and LPS-induced mice. RBM3 gene deficiency aggravated sepsis-associated ALI through the NF-κB/NLRP3 pathway.

NEUTROPHIL HETEROGENEITY IN SEPSIS: THE ROLE OF DAMAGE-ASSOCIATED MOLECULAR PATTERNS

ABSTRACT

Sepsis is a severe inflammatory disease syndrome caused by the dysregulated host response to infection. Neutrophils act as the first line of defense against pathogens by releasing effector molecules such as reactive oxygen species, myeloperoxidase, and neutrophil extracellular traps. However, uncontrolled activation of neutrophils and extensive release of effector molecules often cause a "friendly fire" to damage organ systems. Although neutrophils are considered a short-lived, terminally differentiated homogeneous population, recent studies have revealed its heterogeneity comprising different subsets or states implicated in sepsis pathophysiology. Besides the well-known N1 and N2 subsets of neutrophils, several new subsets including aged, antigen-presenting, reverse-migrated, intercellular adhesion molecule-1 + , low-density, olfactomedin 4 + , and Siglec-F + neutrophils have been reported. These neutrophils potentially contribute to the pathogenesis of sepsis based on their proinflammatory and immunosuppressive functions. Damage-associated molecular patterns (DAMPs) are endogenous molecules to induce inflammation by stimulating pattern recognition receptors on immune cells. Different kinds of DAMPs have been shown to contribute to sepsis pathophysiology, including extracellular cold-inducible RNA-binding protein, high-mobility group box 1, extracellular histones, and heat shock proteins. In this review, we summarize the different subsets of neutrophils and their association with sepsis and discuss the novel roles of DAMPs on neutrophil heterogeneity.

Extracellular CIRP Induces Novel Nectin-2+ (CD112+) Neutrophils to Promote Th1 Differentiation in Sepsis

Neutrophil heterogeneity represents different subtypes, states, phenotypes, and functionality of neutrophils implicated in sepsis pathobiology. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern that promotes inflammation and alters neutrophil phenotype and function through TLR4. Nectin-2 or CD112 is an Ig-like superfamily member. CD112 serves as the ligand for DNAM-1 (CD226), which induces Th1 differentiation in naive CD4+ T cells. Th1 cells produce IFN-γ to fuel inflammation. CD112 is expressed mainly on APCs, but its expression in neutrophils is unknown. We hypothesize that eCIRP induces CD112 expression in neutrophils, promoting Th1 differentiation in sepsis. Incubation of neutrophils with recombinant murine (rm)CIRP significantly increased the gene and protein expression of CD112 in neutrophils. Anti-TLR4 Ab-treated neutrophils significantly decreased CD112+ neutrophils compared with controls upon rmCIRP stimulation. After 4 h of rmCIRP injection in mice, CD112+ neutrophils were significantly increased in the blood and spleen. At 20 h after cecal ligation and puncture-induced sepsis, CD112+ neutrophils were also significantly increased. Blood and splenic CD112+ neutrophils in septic CIRP-/- mice were much lower than in septic wild-type mice. Coculture of naive CD4 T cells with rmCIRP-treated (CD112+) neutrophils significantly increased IFN-γ-producing Th1 cells compared with coculture with PBS-treated neutrophils. CD112 Ab significantly attenuated Th1 differentiation induced by rmCIRP-treated neutrophils. Thus, eCIRP increases CD112 expression in neutrophils via TLR4 to promote Th1 differentiation in sepsis. Targeting eCIRP may attenuate sepsis by reducing Th1-promoting CD112+ neutrophils.

Demethyleneberberine alleviated the inflammatory response by targeting MD-2 to inhibit the TLR4 signaling

Introduction

The colitis induced by trinitrobenzenesulfonic acid (TNBS) is a chronic and systemic inflammatory disease that leads to intestinal barrier dysfunction and autoimmunedisorders. However, the existing treatments of colitis are associated with poor outcomes, and the current strategies remain deep and long-time remission and the prevention of complications. Recently, demethyleneberberine (DMB) has been reported to be a potential candidate for the treatment of inflammatory response that relied on multiple pharmacological activities, including anti-oxidation and antiinflammation. However, the target and potential mechanism of DMB in inflammatory response have not been fully elucidated.

Methods

This study employed a TNBS-induced colitis model and acute sepsis mice to screen and identify the potential targets and molecular mechanisms of DMB in vitro and in vivo. The purity and structure of DMB were quantitatively analyzed by high-performance liquid chromatography (HPLC), mass spectrometry (MS), Hydrogen nuclear magnetic resonance spectroscopy (¹H-NMR), and infrared spectroscopy (IR), respectively. The rats were induced by a rubber hose inserted approximately 8 cm through their anus to be injected with TNBS. Acute sepsis was induced by injection with LPS via the tail vein for 60 h. These animals with inflammation were orally administrated with DMB, berberine (BBR), or curcumin (Curc), respectively. The eukaryotic and prokaryotic expression system of myeloid differentiation protein-2 (MD-2) and its mutants were used to evaluate the target of DMB in inflammatory response.

Resluts

DMB had two free phenolic hydroxyl groups, and the purity exceeded 99% in HPLC. DMB alleviated colitis and suppressed the activation of TLR4 signaling in TNBS-induced colitis rats and LPS-induced RAW264.7 cells. DMB significantly blocked TLR4 signaling in both an MyD88-dependent and an MyD88-independent manner by embedding into the hydrophobic pocket of the MD-2 protein with non-covalent bonding to phenylalanine at position 76 in a pi-pi T-shaped interaction. DMB rescued mice from sepsis shock induced by LPS through targeting the TLR4-MD-2 complex.

Conclusion

Taken together, DMB is a promising inhibitor of the MD-2 protein to suppress the hyperactivated TLR4 signaling in inflammatory response.

Exosome-derived CIRP: An amplifier of inflammatory diseases

Cold-inducible RNA-binding protein (CIRP) is an intracellular stress-response protein and a type of damage-associated molecular pattern (DAMP) that responds to various stress stimulus by altering its expression and mRNA stability. Upon exposure to ultraviolet (UV) light or low temperature, CIRP get translocated from the nucleus to the cytoplasm through methylation modification and stored in stress granules (SG). During exosome biogenesis, which involves formation of endosomes from the cell membrane through endocytosis, CIRP also gets packaged within the endosomes along with DNA, and RNA and other proteins. Subsequently, intraluminal vesicles (ILVs) are formed following the inward budding of the endosomal membrane, turning the endosomes into multi-vesicle bodies (MVBs). Finally, the MVBs fuse with the cell membrane to form exosomes. As a result, CIRP can also be secreted out of cells through the lysosomal pathway as Extracellular CIRP (eCIRP). Extracellular CIRP (eCIRP) is implicated in various conditions, including sepsis, ischemia-reperfusion damage, lung injury, and neuroinflammation, through the release of exosomes. In addition, CIRP interacts with TLR4, TREM-1, and IL-6R, and therefore are involved in triggering immune and inflammatory responses. Accordingly, eCIRP has been studied as potential novel targets for disease therapy. C23 and M3, polypeptides that oppose eCIRP binding to its receptors, are beneficial in numerous inflammatory illnesses. Some natural molecules such as Luteolin and Emodin can also antagonize CIRP, which play roles similar to C23 in inflammatory responses and inhibit macrophage-mediated inflammation. This review aims to provide a better understanding on CIRP translocation and secretion from the nucleus to the extracellular space and the mechanisms and inhibitory roles of eCIRP in diverse inflammatory illnesses.

Extracellular CIRP dysregulates macrophage bacterial phagocytosis in sepsis

In sepsis, macrophage bacterial phagocytosis is impaired, but the mechanism is not well elucidated. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern that causes inflammation. However, whether eCIRP regulates macrophage bacterial phagocytosis is unknown. Here, we reported that the bacterial loads in the blood and peritoneal fluid were decreased in CIRP^-/- mice and anti-eCIRP Ab-treated mice after sepsis. Increased eCIRP levels were correlated with decreased bacterial clearance in septic mice. CIRP^-/- mice showed a marked increase in survival after sepsis. Recombinant murine CIRP (rmCIRP) significantly decreased the phagocytosis of bacteria by macrophages in vivo and in vitro. rmCIRP decreased the protein expression of actin-binding proteins, ARP2, and p-cofilin in macrophages. rmCIRP significantly downregulated the protein expression of βPIX, a Rac1 activator. We further demonstrated that STAT3 and βPIX formed a complex following rmCIRP treatment, preventing βPIX from activating Rac1. We also found that eCIRP-induced STAT3 phosphorylation was required for eCIRP's action in actin remodeling. Inhibition of STAT3 phosphorylation prevented the formation of the STAT3-βPIX complex, restoring ARP2 and p-cofilin expression and membrane protrusion in rmCIRP-treated macrophages. The STAT3 inhibitor stattic rescued the macrophage phagocytic dysfunction induced by rmCIRP. Thus, we identified a novel mechanism of macrophage phagocytic dysfunction caused by eCIRP, which provides a new therapeutic target to ameliorate sepsis.

Chronic Kidney Disease Induces Proarrhythmic Remodeling

BACKGROUND

Patients with chronic kidney disease (CKD) are at increased risk of developing cardiac arrhythmogenesis and sudden cardiac death; however, the basis for this association is incompletely known.

METHODS

Here, using murine models of CKD, we examined interactions between kidney disease progression and structural, electrophysiological, and molecular cardiac remodeling.

RESULTS

C57BL/6 mice with adenine supplemented in their diet developed progressive CKD. Electrocardiographically, CKD mice developed significant QT prolongation and episodes of bradycardia. Optical mapping of isolated-perfused hearts using voltage-sensitive dyes revealed significant prolongation of action potential duration with no change in epicardial conduction velocity. Patch-clamp studies of isolated ventricular cardiomyocytes revealed changes in sodium and potassium currents consistent with action potential duration prolongation. Global transcriptional profiling identified dysregulated expression of cellular stress response proteins RBM3 (RNA-binding motif protein 3) and CIRP (cold-inducible RNA-binding protein) that may underlay the ion channel remodeling. Unexpectedly, we found that female sex is a protective factor in the progression of CKD and its cardiac sequelae.

CONCLUSIONS

Our data provide novel insights into the association between CKD and pathologic proarrhythmic cardiac remodeling. Cardiac cellular stress response pathways represent potential targets for pharmacologic intervention for CKD-induced heart rhythm disorders.

The CDR3 region as the major driver of TREM-1 interaction with its ligands, an in silico characterization

The triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor heavily investigated in infectious and non-infectious diseases. Because of its role in amplifying inflammation, TREM-1 has been explored as a diagnostic/prognostic biomarker. Further, as the receptor has been implicated in the pathophysiology of several diseases, therapies aiming at modulating its activity represent a promising strategy to constrain uncontrolled inflammatory or infectious diseases. Despite this, several aspects concerning its interaction with ligands and activation process, remain unclear. Although many molecules have been suggested as TREM-1 ligands, only five have been confirmed to interact with the receptor: actin, eCIRP, HMGB1, Hsp70 and PGLYRP1. However, the domains involved in the interaction between the receptor and these proteins are not clarified yet. Therefore, here we used in silico approaches to investigate the putative binding domains in the receptor, using hot spots analysis, molecular docking and molecular dynamics simulations between TREM-1 and its five known ligands. Our results indicated the complementarity-determining regions (CDRs) of the receptor as the main mediators of antigen recognition, especially the CDR3 loop. We believe that our study could be used as structural basis for the elucidation of TREM-1's recognition process, and may be useful for prospective in silico and biological investigations exploring the receptor in different contexts.

NEUTROPHIL EXTRACELLULAR TRAPS AS A THERAPEUTIC TARGET IN SYSTEMIC COMPLICATIONS OF ACUTE PANCREATITIS

The review focuses on the role of neutrophilic extracellular traps (NETs) in systemic complications of acute pancreatitis. NETs can activate trypsin, cause inflammation and pancreatic tissue damage, and clog the excretory ducts. The main fatal complications of acute pancreatitis, such as acute lung injury, kidney, myocardial and CNS damage, intestinal dysfunction, hemocoagulation disorders are associated with NETs. Focusing on the formation and degradation of NETs may be a way to develop strategies for treating organ damage in severe acute pancreatitis. Current data on the use of NET-targeted therapy in experimental severe acute pancreatitis, which is aimed at blocking the NETs formation and disassembly of the DNA scaffold, inhibition of proteins toxicity in NETs, are considered.

Immunopathology of chronic critical illness in sepsis survivors: Role of abnormal myelopoiesis

Sepsis remains the single most common cause of mortality and morbidity in hospitalized patients requiring intensive care. Although earlier detection and improved treatment bundles have reduced in-hospital mortality, long-term recovery remains dismal. Sepsis survivors who experience chronic critical illness often demonstrate persistent inflammation, immune suppression, lean tissue wasting, and physical and functional cognitive declines, which often last in excess of 1 year. Older patients and those with preexisting comorbidities may never fully recover and have increased mortality compared with individuals who restore their immunologic homeostasis. Many of these responses are shared with individuals with advanced cancer, active autoimmune diseases, chronic obstructive pulmonary disease, and chronic renal disease. Here, we propose that this resulting immunologic endotype is secondary to a persistent maladaptive reprioritization of myelopoiesis and pathologic activation of myeloid cells. Driven in part by the continuing release of endogenous alarmins from chronic organ injury and muscle wasting, as well as by secondary opportunistic infections, ongoing myelopoiesis at the expense of lymphopoiesis and erythropoiesis leads to anemia, recurring infections, and lean tissue wasting. Early recognition and intervention are required to interrupt this pathologic activation of myeloid populations.

The role of triggering receptor expressed on myeloid cells-1 (TREM-1) in central nervous system diseases

Triggering receptor expressed on myeloid cells-1 (TREM-1) is a member of the immunoglobulin superfamily and is mainly expressed on the surface of myeloid cells such as monocytes, macrophages, and neutrophils. It plays an important role in the triggering and amplification of inflammatory responses, and it is involved in the development of various infectious and non-infectious diseases, autoimmune diseases, and cancers. In recent years, TREM-1 has also been found to participate in the pathological processes of several central nervous system (CNS) diseases. Targeting TREM-1 may be a promising strategy for treating these diseases. This paper aims to characterize TREM-1 in terms of its structure, signaling pathway, expression, regulation, ligands and pathophysiological role in CNS diseases.

MCPIP-1-Mediated Immunosuppression of Neutrophils Exacerbates Acute Bacterial Peritonitis and Liver Injury

Monocyte chemotactic protein-1-induced protein-1 (MCPIP-1) is highly expressed in activated immune cells and negatively regulates immune responses, while the mechanisms underlying the immunoregulation of neutrophils in acute bacterial infection and liver injury remain elusive. Here, we examined the role of MCPIP-1 in regulating neutrophil functions during acute bacterial peritonitis and liver injury. Mice with myeloid cell-specific overexpression (McpipMye-tg) or knockout (McpipΔMye) of MCPIP-1 were generated. We found that reactive oxygen species and myeloperoxidase production, formation of neutrophil extracellular traps, and migratory capacity were deficient in McpipMye-tg neutrophils but enhanced in McpipΔMye neutrophils. The recruitment of neutrophils and pathogen clearance were markedly suppressed in McpipMye-tg mice following intraperitoneal infection with Salmonella typhimurium while intensified in McpipΔMye mice. Severe acute S. typhimurium-infected peritonitis and liver injury occurred in McpipMye-tg mice but were alleviated in McpipΔMye mice. RNA sequencing, RNA-binding protein immunoprecipitation and qPCR analysis revealed that MCPIP-1 downregulated the protective functions of neutrophils via degrading the mRNA of cold inducible RNA-binding protein. Consistently, MCPIP-1 was highly expressed in neutrophils of patients with acute infectious diseases, especially in those with liver injury. Collectively, we uncover that MCPIP-1 negatively regulates the antibacterial capacities of neutrophils, leading to exacerbating severe acute bacterial peritonitis and liver injury. It may serve as a candidate target for maintaining neutrophil homeostasis to control acute infectious diseases.

Primary Resistance to Immunotherapy-Based Regimens in First Line Hepatocellular Carcinoma: Perspectives on Jumping the Hurdle

Simple Summary

Immune checkpoint inhibitors (ICIs) had been explored extensively in patients affected by unresectable hepatocellular carcinoma. These agents were expected to be the keystones of the disease’s first-line treatment because they were theoretically able to revert the immune suppressive tumor microenvironment of the cancerous liver, and because of their manageable safety profile. However, when used as monotherapies, they showed important activity and efficacy limitations. In this mini-review, we summarize the characteristics of the different ICIs-based regimens which constitute the present gold standard of first-line treatment, then, moving from their shortcomings, we discuss the rationale supporting the strategies currently under investigation: systemic triplets and new paradigms of immune-therapeutic agents such as CAR-T and vaccines.

Abstract

Immune checkpoint inhibitors (ICIs) are a key component of different stages of hepatocellular carcinoma (HCC) treatment, particularly in the first line of treatment. A lesson on the primary resistance which hampers their efficacy and activity was learned from the failure of the trials which tested them as first-line mono-therapies. Despite the combination of anti-PD(L)1 agents with anti-VEGF, anti CTLA4, or TKIs demonstrating relevant improvements in efficacy, the “doublets strategy” still shows room for improvement, due to a limited overall survival benefit and a high rate of progressive disease as best response. In this review, we discuss the results from the currently tested doublet strategies (i.e., atezolizumab+bevacizumab, durvalumab+tremelimumab with a mention to the newly presented ICIs/TKIs combinations), which highlight the need for therapeutic improvement. Furthermore, we examine the rationale and provide an overview of the ongoing trials testing the treatment intensification strategy with triplet drugs: anti-PD1+anti-CTLA4+anti-VEGF/TKIs and anti-PD1+anti-VEGF+alternative immunity targets. Lastly, we report on the alternative strategy to integrate ICIs into the new paradigm of immune therapeutics constituted by CAR-T and anti-cancer vaccines. This review provides up-to-date knowledge of ongoing clinical trials of the aforementioned strategies and critical insight into their mechanistic premises.

Extracellular CIRP induces acute kidney injury via endothelial TREM-1

Introduction: Acute kidney injury is associated with elevated serum levels of extracellular cold-inducible RNA-binding protein (eCIRP), a damage-associated molecular pattern released during ischemia/reperfusion injury, hemorrhagic shock, and sepsis. It is unknown if circulating eCIRP and eCIRP-induced activation of receptor triggering receptor expressed on myeloid cells-1 (TREM-1), expressed on endothelial cells, play an important role in the pathogenesis of AKI.

Methods: Male B6 wild-type (WT) and TREM-1^−/− mice were subjected to intravenous injection of recombinant murine (rm) CIRP. Serum, urine, and renal tissue were collected 6 h later for analysis. Additionally, primary human renal glomerular endothelial cells (HRGEC) were stimulated in vitro with rmCIRP after pretreatment with M3, a novel inhibitory peptide of TREM-1, or vehicle. Supernatants and cells were collected 20 h after stimulation.

Results: After injection with rmCIRP, WT mice had a significant increase in serum levels of BUN, creatinine, and NGAL compared to control. Additionally, NGAL was significantly increased in the urine of rmCIRP-injected mice, suggesting that circulating eCIRP can directly induce AKI. The levels of TREM-1 mRNA in the kidneys, as well as soluble (s) TREM-1 released into the serum and urine, were significantly increased in rmCIRP-injected mice. TREM-1^−/− mice injected with rmCIRP had attenuated AKI, indicated by significantly decreased serum BUN, creatinine, and NGAL, and renal mRNA expression of NGAL and KIM-1 compared to WT mice. TREM-1^−/− mice also had attenuated endothelial activation, with decreased mRNA and protein expression of ICAM-1 in renal tissue. HRGEC stimulated with rmCIRP in vitro had significant increases in cytokine production and sTREM-1 release, which was attenuated in cells treated with M3.

Conclusion: Activation of renal TREM-1 with circulating eCIRP is sufficient to cause AKI. Elevated levels of eCIRP may be critical for the development of AKI under conditions such as ischemia/reperfusion injury, hemorrhagic shock, and sepsis. Mice deficient in the TREM-1 receptor have attenuated AKI and reduced endothelial cell activation after injection of rmCIRP. TREM-1 inhibition with M3 attenuates HRGEC activation after eCIRP stimulation. Targeting eCIRP activation of TREM-1 may provide a novel and effective treatment for AKI.

Hepatic ER stress suppresses adipose browning through ATF4-CIRP-ANGPTL3 cascade

Hepatic endoplasmic reticulum (ER) stress is a hallmark of obesity-induced liver steatosis and contributes to the progress of steatosis and insulin resistance in liver. However, its influence on adipose function is still unclear. Here, we identify a hepatic ER stress-induced activating transcription factor 4 (ATF4)-cold-inducible RNA-binding protein (CIRP)-angiopoietin-related protein3 (ANGPTL3) cascade critical for the regulation of adipose browning. We find that obesity increases CIRP expression in liver through ER stress-induced ATF4. CIRP in turn binds to the 3' UTR and increases mRNA stability of ANGPTL3. ANGPTL3 secreted from liver suppresses uncoupling protein 1 expression through integrin α_vβ₃ and c-Jun N-terminal kinase in adipose tissue. While hepatic expression of either ATF4, CIRP, or ANGPTL3 suppresses adipose browning, knockdown of CIRP and ANGPTL3 in liver or administration of integrin α_vβ₃ inhibitor cilengitide increases adipose browning process. Taken together, we identify a communication mechanism to link hepatic ER stress and adipose browning that may imply a reciprocal regulation of obesity and liver steatosis.

Role of alarmins in poststroke inflammation and neuronal repair

Severe loss of cerebral blood flow causes hypoxia and glucose deprivation in the brain tissue, resulting in necrotic cell death in the ischemic brain. Several endogenous molecules, called alarmins or damage-associated molecular patterns (DAMPs), are extracellularly released from the dead cells to activate pattern recognition receptors (PRRs) in immune cells that infiltrate into ischemic brain tissue following the disruption of the blood-brain barrier (BBB) after stroke onset. The activated immune cells produce various inflammatory cytokines and chemokines, triggering sterile cerebral inflammation in the ischemic brain that causes further neuronal cell death. Poststroke inflammation is resolved within several days after stroke onset, and neurological functions are restored to some extent as neural repair occurs around peri-infarct neurons. Clearance of DAMPs from the injured brain is necessary for the resolution of poststroke inflammation. Neurons and glial cells also express PRRs and receive DAMP signaling. Although the role of PRRs in neural cells in the ischemic brain has not yet been clarified, the signaling pathway is likely to be contribute to stroke pathology and neural repair after ischemic stroke. This review describes the molecular dynamics, signaling pathways, and functions of DAMPs in poststroke inflammation and its resolution.

Regulation of CIRP by genetic factors of SP1 related to cold sensitivity

Cold-inducible RNA-binding-protein (CIRP) is a cold shock protein that plays a protective role in genotoxic stress response. CIRP modulates inflammation in human diseases, inhibits cell proliferation, and protects cells from genotoxic damage during cellular stress. The mild cold responsive element and specificity protein 1 (SP1) play a role in Cirp expression at low temperatures. Although previous studies have provided insights into the immune functions of SP1 or CIRP, the mechanisms by which CIRP and SP1 me diate inflammatory responses remain largely unknown. Therefore, in the current study, we examined whether Cirp expression is affected by genetic factors related to temperature sensitivity as well as under low temperature. We performed a genome-wide association study on cold sensitivity in 2,000 participants. Fifty-six genome-wide significant trait-locus pairs were identified (p&lt;1×10-5, false discovery rate &lt; 0.05). Among these variants, rs1117050 and rs11170510 had a strong linkage disequilibrium (r2 &gt; 0.8) relationship and expression quantitative trait locus-associated signals with the nearest Sp1 gene. We confirmed that the minor alleles of rs11170510 and rs58123204 were associated with increased Sp1 expression. Additionally, Sp1 overexpression led to CIRP translocation from the nucleus to the cytoplasm. CIRP protein levels increased in serum samples that had minor alleles of rs11170510 and rs58123204. Levels of various pro-inflammatory cytokines were also significantly increased in human peripheral blood mononuclear cells with minor alleles of rs11170510 and rs58123204. These results suggest that genetic factors related to cold sensitivity regulate CIRP expression and function and provide valuable insights into prediction of potential diseases through analysis of inherent genetic factors in humans.

Extracellular CIRP Upregulates Proinflammatory Cytokine Expression via the NF-kappaB and ERK1/2 Signaling Pathways in Psoriatic Keratinocytes

Psoriasis is a chronic inflammatory skin disease, and elevation of proinflammatory cytokine levels is a critical driver of the pathogenesis of psoriasis. Extracellular cold-inducible RNA-binding protein (eCIRP) has been shown to play a role in various acute and chronic inflammatory diseases. C23, a short peptide derived from CIRP, competitively binds CIRP receptors and reduces damage in inflammatory diseases. However, the effect of eCIRP in psoriasis has not been studied. In the present study, we investigated the role of eCIRP in the expression of proinflammatory cytokines in keratinocytes. Our data show that eCIRP expression was increased in the sera of psoriasis patients and imiquimod- (IMQ-) induced psoriatic mice and cells stimulated with proinflammatory cytokines (IL-1α, IL-17A, IL-22, oncostatin M, and TNF-α; mix M5). Recombinant human CIRP (rhCIRP) promoted the expression of the proinflammatory cytokines TNF-α, IL-6, and IL-8 and the activation of NF-kappaB (NF-κB) and ERK1/2 in cultured keratinocytes. We then found that the above effects of eCIRP could be blocked by C23 in both normal keratinocytes and M5-stimulated psoriatic keratinocytes. In addition, in vivo experiments revealed that C23 could effectively ameliorate IMQ-induced psoriatic dermatitis. TNF-α and IL-6 mRNA expressions were reduced in the skin lesions of mice with C23-treated IMQ-induced psoriasis, and this effect was accompanied by inhibition of the NF-κB and ERK1/2 signaling pathways. In summary, eCIRP plays an important role in the pathogenesis of psoriasis and may become a new target for psoriasis treatment.

Innate immunity and immunotherapy for hemorrhagic shock

Hemorrhagic shock (HS) is a shock result of hypovolemic injury, in which the innate immune response plays a central role in the pathophysiology ofthe severe complications and organ injury in surviving patients. During the development of HS, innate immunity acts as the first line of defense, mediating a rapid response to pathogens or danger signals through pattern recognition receptors. The early and exaggerated activation of innate immunity, which is widespread in patients with HS, results in systemic inflammation, cytokine storm, and excessive activation of complement factors and innate immune cells, comprised of type II innate lymphoid cells, CD4⁺ T cells, natural killer cells, eosinophils, basophils, macrophages, neutrophils, and dendritic cells. Recently, compelling evidence focusing on the innate immune regulation in preclinical and clinical studies promises new treatment avenues to reverse or minimize HS-induced tissue injury, organ dysfunction, and ultimately mortality. In this review, we first discuss the innate immune response involved in HS injury, and then systematically detail the cutting-edge therapeutic strategies in the past decade regarding the innate immune regulation in this field; these strategies include the use of mesenchymal stem cells, exosomes, genetic approaches, antibody therapy, small molecule inhibitors, natural medicine, mesenteric lymph drainage, vagus nerve stimulation, hormones, glycoproteins, and others. We also reviewed the available clinical studies on immune regulation for treating HS and assessed the potential of immune regulation concerning a translation from basic research to clinical practice. Combining therapeutic strategies with an improved understanding of how the innate immune system responds to HS could help to identify and develop targeted therapeutic modalities that mitigate severe organ dysfunction, improve patient outcomes, and reduce mortality due to HS injury.

Damage associated molecular patterns and neutrophil extracellular traps in acute pancreatitis

Previous researches have emphasized a trypsin-centered theory of acute pancreatitis (AP) for more than a century. With additional studies into the pathogenesis of AP, new mechanisms have been explored. Among them, the role of immune response bears great importance. Pro-inflammatory substances, especially damage-associated molecular patterns (DAMPs), play an essential role in activating, signaling, and steering inflammation. Meanwhile, activated neutrophils attach great importance to the immune defense by forming neutrophil extracellular traps (NETs), which cause ductal obstruction, premature trypsinogen activation, and modulate inflammation. In this review, we discuss the latest advances in understanding the pathological role of DAMPs and NETs in AP and shed light on the flexible crosstalk between these vital inflammatory mediators. We, then highlight the potentially promising treatment for AP targeting DAMPs and NETs, with a focus on novel insights into the mechanism, diagnosis, and management of AP.

The mRNA expression of the three major described cold-inducible proteins, including CIRBP, differs in the bovine endometrium and ampulla during the estrous cycle

The cold-inducible proteins (CIPs) are essential for post-transcriptional gene regulation playing diverse tissue-specific roles in maintaining normal cellular function and morphogenesis. The potential implications of CIPs in reproductive events raise questions about their role in the physiology of the bovine reproductive tract. However, the expression changes of CIPs during the bovine estrous cycle have not been studied so far. Here, we hypothesized that the bovine estrous cycle could affect the mRNA expression of the CIPs and other candidate transcripts in the reproductive tract. This study aimed to examine estrous cycle-dependent mRNA expression patterns in the bovine endometrium and ampulla of three of the major described CIPs (CIRBP, RBM3, SRSF5), a set of inflammatory cytokines (IL-10, IL-18, IL-1β), and other candidate genes (IL-10RA, IL-10RB, BCL2, NLRP3, STAT1, STAT3, STAT5A, STAT6). Endometrial and ampullar tissues were assessed by RT-qPCR. Additionally, the mRNA expression levels were correlated among them and with follicular progesterone and estradiol concentrations. The transcript levels of CIPs increased in the endometrium during stage III (Days 11-17) compared to stage I (Days 1-4) and IV (Days 18-20). In the ampulla, the mRNA expression of CIRBP increased during the late luteal phase (stage III), but no differences in the expression of other CIPs were observed. This study expands the current knowledge regarding mRNA expression in the endometrium and oviductal ampulla of cycling heifers, focusing mainly on the CIPs. A better understanding of the mechanisms within the uterus and oviduct during the estrous cycle is crucial to improving the fertility rate.

Chromatin-Associated Molecular Patterns (CAMPs) in sepsis

Several molecular patterns have been identified that recognize pattern recognition receptors. Pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) are commonly used terminologies to classify molecules originating from pathogen and endogenous molecules, respectively, to heighten the immune response in sepsis. Herein, we focus on a subgroup of endogenous molecules that may be detected as foreign and similarly trigger immune signaling pathways. These chromatin-associated molecules, i.e., chromatin containing nuclear DNA and histones, extracellular RNA, mitochondrial DNA, telomeric repeat-containing RNA, DNA- or RNA-binding proteins, and extracellular traps, may be newly classified as chromatin-associated molecular patterns (CAMPs). Herein, we review the release of CAMPs from cells, their mechanism of action and downstream immune signaling pathways, and targeted therapeutic approaches to mitigate inflammation and tissue injury in inflammation and sepsis.

Neuronal MD2 induces long-term mental impairments in septic mice by facilitating necroptosis and apoptosis

Sepsis-associated encephalopathy (SAE) is a complication of sepsis with high morbidity rates. Long-lasting mental health issues in patients with SAE result in a substantial decrease in quality of life. However, its underlying mechanism is unclear, and effective treatments are not available. In the current study, we explored the role of apoptosis and necroptosis related to mental dysfunction in sepsis. In a mouse model of sepsis constructed by cecal ligation and puncture (CLP), altered behavior was detected by the open field, elevated-plus maze and forced swimming tests on the fourteenth day. Moreover, apoptosis- and necroptosis-associated proteins and morphological changes were examined in the hippocampus of septic mice. Long-lasting depression-like behaviors were detected in the CLP mice, as well as significant increases in neuronal apoptosis and necroptosis. Importantly, we found that apoptosis and necroptosis were related according to Ramsay’s rule in the brains of the septic mice. Inhibiting myeloid differentiation factor 2 (MD2), the crosstalk mediator of apoptosis and necroptosis, in neurons effectively reduced neuronal loss and alleviated depression-like behaviors in the septic mice. These results suggest that neuronal death in the hippocampus contributes to the mental impairments in SAE and that inhibiting neuronal MD2 is a new strategy for treating mental health issues in sepsis by inhibiting necroptosis and apoptosis.

Neutrophil trogocytosis during their trans-endothelial migration: role of extracellular CIRP

Background

Neutrophils are the most abundant innate immune cells in the circulating blood, and they act as the first responder against bacterial and fungal infection. However, accumulation of activated neutrophils can cause severe inflammation and tissue damage. Recently, neutrophil trogocytosis or membrane transfer with neighboring cells was reported to modulate immune responses. Extracellular cold-inducible RNA binding protein (eCIRP) is a newly identified damage-associated molecular pattern (DAMP). eCIRP can activate neutrophils to be more pro-inflammatory. This study aimed to identify the role of eCIRP in neutrophil trogocytosis during their trans-endothelial migration.

Methods

A trans-endothelial migration (TEM) assay using bone marrow neutrophils and mouse primary lung vascular endothelial cells was conducted using transwell chambers and neutrophil trogocytosis was assessed in vitro. In an in vivo mouse model of acute lung injury, neutrophil trogocytosis was assessed from bronchoalveolar lavage fluid.

Results

In TEM assay, the trogocytosis of neutrophils occurred during trans-endothelial migration and eCIRP significantly increased the percentage of these neutrophils. The trogocytosed neutrophils acquired the endothelial membrane containing junctional adhesion molecule-C (JAM-C) and VE-cadherin, and these membrane patches were polarized by Mac-1 binding. Furthermore, eCIRP-induced JAM-C positive trogocytosed neutrophils are more pro-inflammatory than the JAM-C negative counterpart. JAM-C positive trogocytosed neutrophils were also observed in the bronchoalveolar lavage fluid of a mouse model of acute lung injury.

Conclusion

These data suggest that during the paracellular trans-endothelial migration of neutrophils in response to inflammation, eCIRP induces trogocytosis of neutrophils, and the trogocytosed neutrophils exhibit an exaggerated pro-inflammatory phenotype promoting acute lung injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00515-3.

Serum concentration of extracellular cold-inducible RNA-binding protein is associated with respiratory failure in COVID-19

Uncontrolled release of damage-associated molecular patterns (DAMPs) is suggested to be a major trigger for the dysregulated host immune response that leads to severe COVID-19. Cold-inducible RNA-binding protein (CIRP), is a newly identified DAMP that aggravates inflammation and tissue injury, and induces respiratory failure in sepsis. Whether CIRP contributes to the pathogenesis of respiratory failure in COVID-19 has not yet been explored.

Aim

To investigate if the concentration of extracellular CIRP (eCIRP) in serum associates with respiratory failure and lung involvement by chest computed tomography (CT) in COVID-19.

Methods

Herein we report a prospective observational study of patients with COVID-19 included at two University Hospitals in Sweden between April 2020 and May 2021. Serum from hospitalized patients in Örebro (N=97) were used to assess the association between eCIRP and the level of respiratory support and its correlation with pulmonary involvement on chest CT and inflammatory biomarkers. A cohort of hospitalized and non-hospitalized patients from Umeå (N=78) was used as an external validation cohort. The severity of disease was defined according to the highest degree of respiratory support; mild disease (no oxygen), non-severe hypoxemia (conventional oxygen or high-flow nasal oxygen, HFNO &lt;50% FiO2), and severe hypoxemia (HFNO ≥50% FiO2, mechanical ventilation). Unadjusted and adjusted linear regression was used to evaluate peak eCIRP day 0-4 in respect to severity, age, sex, Charlson comorbidity score, symptom duration, and BMI.

Results

Peak eCIRP concentrations were higher in patients with severe hypoxemia and were independently associated with the degree of respiratory support in both cohorts (Örebro; p=0.01, Umeå; p&lt;0.01). The degree of pulmonary involvement measured by CT correlated with eCIRP, rs=0.30, p&lt;0.01 (n=97).

Conclusion

High serum levels of eCIRP are associated with acute respiratory failure in COVID-19. Experimental studies are needed to determine if treatments targeting eCIRP reduces the risk of acute respiratory failure in COVID-19.

Necroptosis-Mediated eCIRP Release in Sepsis

Introduction

Extracellular cold-inducible RNA-binding protein (eCIRP) is an endogenous pro-inflammatory mediator that exacerbates injury in inflammation and sepsis. The mechanisms in which eCIRP is released have yet to be fully explored. Necroptosis is a programmed cell death that is dependent on the activation of mixed lineage kinase domain-like pseudo kinase (MLKL) which causes the release of damage-associated molecular patterns. We hypothesize that eCIRP is released through necroptosis and intensifies inflammation in sepsis.

Methods

RAW264.7 cells were treated with pan-caspase inhibitor z-VAD (15 μM) 1 h before stimulation with LPS (1 μg/mL). Necroptosis inhibitor, Necrostatin-1 (Nec-1) (10 μM) was added to the cells with LPS simultaneously. After 24 h of LPS stimulation, cytotoxicity was determined by LDH assay. eCIRP levels in the culture supernatants and phospho-MLKL (p-MLKL) from cell lysates were assessed by Western blot. p-MLKL interaction with the cell membrane was visualized by immunofluorescence. Sepsis was induced in C57BL/6 mice by cecal ligation and puncture (CLP). Mice were treated with Nec-1 (1 mg/kg) or DMSO. 20 h post-surgery, serum and peritoneal fluid levels of eCIRP, TNF-α and IL-6 were determined by ELISA. H&E staining of lung tissue sections was performed.

Results

We found that in RAW264.7 cells, LPS+z-VAD induces necroptosis as evidenced by an increase in p-MLKL levels and causes eCIRP release. Nec-1 reduces both p-MLKL activation and eCIRP release in LPS+z-VAD-treated RAW264.7 cells. Nec-1 also inhibits the release of eCIRP, TNF-α and IL-6 in the serum and peritoneal fluid in CLP-induced septic mice. We predicted a transient interaction between eCIRP and MLKL using a computational model, suggesting that eCIRP may exit the cell via the pores formed by p-MLKL.

Conclusion

Necroptosis is a novel mechanism of eCIRP release in sepsis. Targeting necroptosis may ameliorate inflammation and injury in sepsis by inhibiting eCIRP release.

Extracellular CIRP Promotes GPX4-Mediated Ferroptosis in Sepsis

Sepsis is characterized by life-threatening organ dysfunction caused by a dysregulated host response to infection. Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern (DAMP) that promotes inflammation and induces cell death via apoptosis, NETosis, and/or pyroptosis. Ferroptosis is a form of regulated cell death characterized by the accumulation of lipid peroxide on cellular membranes. We hypothesize that eCIRP induces ferroptosis in macrophages and lung tissue during sepsis. RAW 264.7 cells stimulated with recombinant murine (rm) CIRP significantly decreased the expression of glutathione peroxidase 4 (GPX4), a negative regulator of ferroptosis, and increased lipid reactive oxygen species (ROS) in a TLR4 dependent manner. In TLR4^-/- peritoneal macrophages, depression of GPX4 expression and increase in lipid ROS levels were attenuated after rmCIRP-treatment compared to WT macrophages. rmCIRP also induced cell death in RAW 264.7 cells which was corrected by the ferroptosis inhibitor, ferrostatin-1 (Fer-1). Intraperitoneal injection of rmCIRP decreased GPX4 expression and increased lipid ROS in lung tissue, whereas the increase of lipid ROS was reduced by Fer-1 treatment. GPX4 expression was significantly decreased, while malondialdehyde (MDA), iron levels, and injury scores were significantly increased in lungs of WT mice after cecal ligation and puncture (CLP)-induced sepsis compared to CIRP^-/- mice. Treatment with C23, a specific eCIRP inhibitor, in CLP mice alleviated the decrease in GPX4 and increase in MDA levels of lung tissue. These findings suggest that eCIRP induces ferroptosis in septic lungs by decreasing GPX4 and increasing lipid ROS. Therefore, regulation of ferroptosis by targeting eCIRP may provide a new therapeutic approach in sepsis and other inflammatory diseases.

Change in Oxidative Stress and Mitochondrial Dynamics in Response to Elevated Cold-Inducible RNA-Binding Protein in Cardiac Surgery-Associated Acute Kidney Injury

Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common yet serious complication that is closely related to cardiopulmonary bypass (CPB). Extracellular cold-inducible RNA-binding protein (eCIRP) can mediate aseptic inflammation and trigger intracellular oxidative stress. In the present study, expression of serum CIRP was significantly elevated post-CPB ( $785.0\pm 640.5$  pg/mL vs. $149.5\pm 289.1$  pg/mL, $P<0.001$ ) and was positively correlated with CPB duration ( $r=0.502$ , $P<0.001$ ). Patients with high expression of CIRP had higher risks of postoperative AKI than patients with low CIRP expression (OR: 1.67, 95% CI 1.04-2.68). In a rat CPB model, the serum CIRP concentration increased significantly after CPB. Similarly, the levels of Scr and BUN significantly increased 4 hours after CPB. KIM-1 and NGAL mRNA levels in the CPB group were 8.2 and 4.3 times higher than the sham group, respectively. In addition, the levels of inflammatory cell infiltration, oxidative stress, and apoptosis in the renal tissue of the CPB group were significantly higher compared to the sham group. The expression levels of serum inflammatory factors at 4 hours post-CPB were also increased. Administration of recombinant human CIRP protein promoted the expression of NADPH oxidase via the TLR-4/MyD88 pathway, aggravated intracellular oxidative stress, mediated mitochondrial dynamics disorder, and eventually increased apoptosis in HK-2 cells. However, the CIRP inhibitor C23 improved the CIRP-mediated oxidative stress and mitochondrial dysfunction in both rat and cell models. In summary, elevated CIRP could mediate oxidative stress and mitochondrial dynamics in the kidney to promote CSA-AKI.

TREM-1 Modulation Strategies for Sepsis

The triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor, which can be upregulated in inflammatory diseases as an amplifier of immune responses. Once activated, TREM-1 induces the production and release of pro-inflammatory cytokines and chemokines, in addition to increasing its own expression and circulating levels of the cleaved soluble extracellular portion of TREM-1 (sTREM-1). This amplification of the inflammatory response by TREM-1 has now been considered as a critical contributor to the dysregulated immune responses in sepsis. Studies have shown that in septic patients there is an elevated expression of TREM-1 on immune cells and increased circulating levels of sTREM-1, associated with increased mortality. As a result, a considerable effort has been made towards identifying endogenous ligands of TREM-1 and developing TREM-1 inhibitory peptides to attenuate the exacerbated inflammatory response in sepsis. TREM-1 modulation has proven a promising strategy for the development of therapeutic agents to treat sepsis. Therefore, this review encompasses the ligands investigated as activators of TREM-1 thus far and highlights the development and efficacy of novel inhibitors for the treatment of sepsis and septic shock.

The Fatal Circle of NETs and NET-Associated DAMPs Contributing to Organ Dysfunction

The innate immune system is the first line of defense against invading pathogens or sterile injuries. Pattern recognition receptors (PRR) sense molecules released from inflamed or damaged cells, or foreign molecules resulting from invading pathogens. PRRs can in turn induce inflammatory responses, comprising the generation of cytokines or chemokines, which further induce immune cell recruitment. Neutrophils represent an essential factor in the early immune response and fulfill numerous tasks to fight infection or heal injuries. The release of neutrophil extracellular traps (NETs) is part of it and was originally attributed to the capture and elimination of pathogens. In the last decade studies revealed a detrimental role of NETs during several diseases, often correlated with an exaggerated immune response. Overwhelming inflammation in single organs can induce remote organ damage, thereby further perpetuating release of inflammatory molecules. Here, we review recent findings regarding damage-associated molecular patterns (DAMPs) which are able to induce NET formation, as well as NET components known to act as DAMPs, generating a putative fatal circle of inflammation contributing to organ damage and sequentially occurring remote organ injury.

Decreased Expression of CIRP Induced by Therapeutic Hypothermia Correlates with Reduced Early Brain Injury after Subarachnoid Hemorrhage

Early brain injury is considered to be a primary reason for the poor prognosis of patients suffering from subarachnoid hemorrhage (SAH). Due to its pro-inflammatory activity, cold-inducible RNA-binding protein (CIRP) has been implicated in the ischemic brain insult, but its possible interplay with hypothermia in SAH treatment remains to be evaluated. One-hundred and thirty-eight Sprague-Dawley rats (300–350 g males) were randomly allocated into the following groups: sham-operated (Sham); SAH; and SAH + hypothermia (SAH + H), each comprised of 46 animals. After treatments, the brain tissues of the three groups were randomly collected after 12 h, 1 d, 3 d, and 7 d, and the expression levels of the CIRP and mitochondrial apoptosis pathway-related proteins Bax, Bcl-2, caspase-9, caspase-3, and cytochrome c measured using Western blotting and real-time PCR. Brain damage was assessed by TUNEL and Nissl staining, the electron microscopy of brain tissue slices as well as functional rotarod tests. Expression of CIRP, Bax, caspase-9, caspase-3, and cytochrome c as well as reduced motor function incidence were higher in the SAH group, particularly during the first 3 d after SAH induction. Hypothermia blunted these SAH responses and apoptosis, thereby indicating reduced inflammatory signaling and less brain cell injury in the early period after SAH. Hypothermia treatment was found to effectively protect the brain tissue from early SAH injury in a rat model and its further evaluation as a therapeutic modality in SAH patients requires further study.

Neutrophil phenotypes and functions in cancer: A consensus statement

Neutrophils are the first responders to infection and inflammation and are thus a critical component of innate immune defense. Understanding the behavior of neutrophils as they act within various inflammatory contexts has provided insights into their role in sterile and infectious diseases; however, the field of neutrophils in cancer is comparatively young. Here, we summarize key concepts and current knowledge gaps related to the diverse roles of neutrophils throughout cancer progression. We discuss sources of neutrophil heterogeneity in cancer and provide recommendations on nomenclature for neutrophil states that are distinct in maturation and activation. We address discrepancies in the literature that highlight a need for technical standards that ought to be considered between laboratories. Finally, we review emerging questions in neutrophil biology and innate immunity in cancer. Overall, we emphasize that neutrophils are a more diverse population than previously appreciated and that their role in cancer may present novel unexplored opportunities to treat cancer.