Necrostatin-1 protects against oleic acid-induced acute respiratory distress syndrome in rats

Acute lung injury: a view from the perspective of necroptosis

BACKGROUND

ALI/ARDS is a syndrome of acute onset characterized by progressive hypoxemia and noncardiogenic pulmonary edema as the primary clinical manifestations. Necroptosis is a form of programmed cell necrosis that is precisely regulated by molecular signals. This process is characterized by organelle swelling and membrane rupture, is highly immunogenic, involves extensive crosstalk with various cellular stress mechanisms, and is significantly implicated in the onset and progression of ALI/ARDS.

METHODS

The current body of literature on necroptosis and ALI/ARDS was thoroughly reviewed. Initially, an overview of the molecular mechanism of necroptosis was provided, followed by an examination of its interactions with apoptosis, pyroptosis, autophagy, ferroptosis, PANOptosis, and NETosis. Subsequently, the involvement of necroptosis in various stages of ALI/ARDS progression was delineated. Lastly, drugs targeting necroptosis, biomarkers, and current obstacles were presented.

CONCLUSION

Necroptosis plays an important role in the progression of ALI/ARDS. However, since ALI/ARDS is a clinical syndrome caused by a variety of mechanisms, we emphasize that while focusing on necroptosis, it may be more beneficial to treat ALI/ARDS by collaborating with other mechanisms.

RIP1 kinase inactivation protects against LPS-induced acute respiratory distress syndrome in mice

Acute respiratory distress syndrome (ARDS) is characterized by lung tissue oedema and inflammatory cell infiltration, with limited therapeutic interventions available. Receptor-interacting protein kinase 1 (RIPK1), a critical regulator of cell death and inflammation implicated in many diseases, is not fully understood in the context of ARDS. In this study, we employed RIP1 kinase-inactivated (Rip1K45A/K45A) mice and two distinct RIPK1 inhibitors to investigate the contributions of RIP1 kinase activity in lipopolysaccharide (LPS)-induced ARDS pathology. Our results indicated that RIPK1 kinase inactivation, achieved through both genetic and chemical approaches, significantly attenuated LPS-induced ARDS pathology, as demonstrated by reduced polymorphonuclear neutrophil percentage (PMN%) in alveolar lavage fluid, expression of inflammatory and fibrosis-related factors in lung tissues, as well as histological examination. Results by tunnel staining and qRT-PCR analysis indicated that RIPK1 kinase activity played a role in regulating cell apoptosis and inflammation induced by LPS administration in lung tissue. In summary, employing both pharmacological and genetic approaches, this study demonstrated that targeted RIPK1 kinase inactivation attenuates the pathological phenotype induced by LPS inhalation in an ARDS mouse model. This study enhances our understanding of the therapeutic potential of RIPK1 kinase modulation in ARDS, providing insights for the pathogenesis of ARDS.

The role of RIPK1 in chronic obstructive pulmonary disease

Necroptosis has emerged as one of the crucial pathological processes involved in the regulation of cell death and inflammation in chronic obstructive pulmonary disease (COPD). Airway epithelial necroptosis is closely linked to COPD pathogenesis. Necroptotic lung cells can release damage-associated molecular patterns (DAMPs) that can initiate a robust inflammatory response. However, the underlying mechanism of necroptosis in COPD is still not clearly understood. Therefore, we aimed to explore the roles and mechanisms of receptor-interacting serine/threonine-protein kinase 1 (RIPK1)-mediated necroptosis in the regulation of inflammatory responses in COPD to provide insights into RIPK1-inhibitor drug discovery efforts and their therapeutic benefits in COPD.

Necroptosis in Pneumonia: Therapeutic Strategies and Future Perspectives

Pneumonia remains a major global health challenge, necessitating the development of effective therapeutic approaches. Recently, necroptosis, a regulated form of cell death, has garnered attention in the fields of pharmacology and immunology for its role in the pathogenesis of pneumonia. Characterized by cell death and inflammatory responses, necroptosis is a key mechanism contributing to tissue damage and immune dysregulation in various diseases, including pneumonia. This review comprehensively analyzes the role of necroptosis in pneumonia and explores potential pharmacological interventions targeting this cell death pathway. Moreover, we highlight the intricate interplay between necroptosis and immune responses in pneumonia, revealing a bidirectional relationship between necrotic cell death and inflammatory signaling. Importantly, we assess current therapeutic strategies modulating necroptosis, encompassing synthetic inhibitors, natural products, and other drugs targeting key components of the programmed necrosis pathway. The article also discusses challenges and future directions in targeting programmed necrosis for pneumonia treatment, proposing novel therapeutic strategies that combine antibiotics with necroptosis inhibitors. This review underscores the importance of understanding necroptosis in pneumonia and highlights the potential of pharmacological interventions to mitigate tissue damage and restore immune homeostasis in this devastating respiratory infection.

Therapeutic effects of minocycline on oleic acid-induced acute respiratory distress syndrome (ARDS) in rats

Acute respiratory distress syndrome (ARDS) is a serious intensive care condition. Despite advances in treatment over the previous few decades, ARDS patients still have high fatality rates. Thus, more research is needed to improve the outcomes for people with ARDS. Minocycline is an antibiotic with antioxidant, anti-inflammatory, and anti-apoptotic effects. In the current investigation, the therapeutic effects of minocycline on oleic acid-induced ARDS were evaluated. Male rats were classified into 6 groups, 1. control (normal saline), 2. oleic acid (100 µL, i.v.), 3-5. oleic acid + minocycline (50, 100, 200 mg/kg, i.p.), and 6. minocycline (200 mg/kg, i.p.) alone. Twenty-four hours after the oleic acid injection, the lung tissue is isolated, weighed, and the middle part of the right lung is immediately placed in the freezer, while the middle part of the left lung is placed in formalin and sent to the laboratory for pathology testing. Then, the amounts of malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), cytokines (interleukin-1 beta (IL-1β), tumor necrosis factor-α (TNF-α)), B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X (Bax), and cleaved caspase-3 were determined in lung tissue. Administration of oleic acid increased emphysema, inflammation, vascular congestion, hemorrhage, MDA amount, Bax/Bcl-2 ratio, cleaved caspase-3, IL-1β, TNF-α levels, and decreased GSH, SOD, and CAT levels in comparison with the control group. The administration of minocycline could significantly reduce pathological and biochemical alterations induced by oleic acid. Minocycline has a therapeutic effect on oleic acid-induced ARDS through antioxidant, anti-inflammatory, and anti-apoptotic properties.

Non-apoptotic programmed cell deaths in diabetic pulmonary dysfunction: the new side of advanced glycation end products

Diabetes mellitus (DM) is a chronic metabolic disorder that affects multiple organs and systems, including the pulmonary system. Pulmonary dysfunction in DM patients has been observed and studied for years, but the underlying mechanisms have not been fully understood. In addition to traditional mechanisms such as the production and accumulation of advanced glycation end products (AGEs), angiopathy, tissue glycation, oxidative stress, and systemic inflammation, recent studies have focused on programmed cell deaths (PCDs), especially the non-apoptotic ones, in diabetic pulmonary dysfunction. Non-apoptotic PCDs (NAPCDs) including autophagic cell death, necroptosis, pyroptosis, ferroptosis, and copper-induced cell death have been found to have certain correlations with diabetes and relevant complications. The AGE-AGE receptor (RAGE) axis not only plays an important role in the traditional pathogenesis of diabetes lung disease but also plays an important role in non-apoptotic cell death. In this review, we summarize novel studies about the roles of non-apoptotic PCDs in diabetic pulmonary dysfunction and focus on their interactions with the AGE-RAGE axis.

The therapeutic potential of targeting regulated non-apoptotic cell death

Cell death is critical for the development and homeostasis of almost all multicellular organisms. Moreover, its dysregulation leads to diverse disease states. Historically, apoptosis was thought to be the major regulated cell death pathway, whereas necrosis was considered to be an unregulated form of cell death. However, research in recent decades has uncovered several forms of regulated necrosis that are implicated in degenerative diseases, inflammatory conditions and cancer. The growing insight into these regulated, non-apoptotic cell death pathways has opened new avenues for therapeutic targeting. Here, we describe the regulatory pathways of necroptosis, pyroptosis, parthanatos, ferroptosis, cuproptosis, lysozincrosis and disulfidptosis. We discuss small-molecule inhibitors of the pathways and prospects for future drug discovery. Together, the complex mechanisms governing these pathways offer strategies to develop therapeutics that control non-apoptotic cell death.

Recent Advances (2015-2020) in Drug Discovery for Attenuation of Pulmonary Fibrosis and COPD

A condition of scarring of lung tissue due to a wide range of causes (such as environmental pollution, cigarette smoking (CS), lung diseases, some medications, etc.) has been reported as pulmonary fibrosis (PF). This has become a serious problem all over the world due to the lack of efficient drugs for treatment or cure. To date, no drug has been designed that could inhibit fibrosis. However, few medications have been reported to reduce the rate of fibrosis. Meanwhile, ongoing research indicates pulmonary fibrosis can be treated in its initial stages when symptoms are mild. Here, an attempt is made to summarize the recent studies on the effects of various chemical drugs that attenuate PF and increase patients' quality of life. The review is classified based on the nature of the drug molecules, e.g., natural/biomolecule-based, synthetic-molecule-based PF inhibitors, etc. Here, the mechanisms through which the drug molecules attenuate PF are discussed. It is shown that inhibitory molecules can significantly decrease the TGF-β1, profibrotic factors, proteins responsible for inflammation, pro-fibrogenic cytokines, etc., thereby ameliorating the progress of PF. This review may be useful in designing better drugs that could reduce the fibrosis process drastically or even cure the disease to some extent.

RIPK1 in the inflammatory response and sepsis: Recent advances, drug discovery and beyond

Cytokine storms are an important mechanism of sepsis. TNF-α is an important cytokine. As a regulator of TNF superfamily receptors, RIPK1 not only serves as the basis of the scaffold structure in complex I to promote the activation of the NF-κB and MAPK pathways but also represents an important protein in complex II to promote programmed cell death. Ubiquitination of RIPK1 is an important regulatory function that determines the activation of cellular inflammatory pathways or the activation of death pathways. In this paper, we introduce the regulation of RIPK1, RIPK1 PANoptosome's role in Inflammatory and sepsis, and perspectives.

An in vitro evaluation of the antioxidant activities of necroptosis and apoptosis inhibitors: the potential of necrostatin-1 and necrostatin-1i to have radical scavenging activities

BACKGROUND

Necroptosis inhibitors, including necrostatin-1 (Nec-1), are attracting attention as potential therapeutic agents against various diseases, such as acute lung injury, chronic obstructive pulmonary disease, acute kidney injury, nonalcoholic fatty liver, and neurodegenerative disease, where necroptosis is thought to act as a contributing factor. Nec-1 suppresses necroptosis by inhibiting receptor-interacting protein (RIP) 1 kinase and can also reduce reactive oxygen species (ROS) production; however, the underlying molecular mechanisms mediating ROS reduction remain unclear.

METHODS

The antioxidant effects of necroptosis inhibitors, including Nec-1 and apoptosis inhibitors, were quantified by performing a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Nec-1-related compounds were subsequently assayed for cupric ion-reducing capacity and superoxide dismutase (SOD)-like activity.

RESULTS

Considering all examined apoptosis and necroptosis inhibitors, Nec-1and Nec-1i exhibited antioxidant activity in DPPH radical scavenging assay. In the cupric ion-reducing capacity assay, Nec-1i showed stronger antioxidant capacity than Nec-1. In the SOD-like activity assay, both Nec-1 and Nec-1i were found to have stronger antioxidant capacity than ascorbic acid (IC₅₀ = 4.6 ± 0.040 and 61 ± 0.54 µM, respectively).

CONCLUSION

These results suggest that Nec-1 and Nec-1i may exhibit direct radical scavenging ability against superoxide anions, independent of RIP1 inhibition.

Potential therapeutic value of necroptosis inhibitor for the treatment of COVID-19

The coronavirus disease 2019 (COVID-19), caused by a novel virus of the beta-coronavirus genus (SARS-CoV-2), has spread rapidly, posing a significant threat to global health. There are currently no drugs available for effective treatment. Severe cases of COVID-19 are associated with hyperinflammation, also known as cytokine storm syndrome. The reduce inflammation are considered promising treatments for COVID-19. Necroptosis is a type of programmed necrosis involved in immune response to viral infection, and severe inflammatory injury. Inhibition of necroptosis is pivotal in preventing associated inflammatory responses. The expression of key regulators of the necroptosis pathway is generally up-regulated in COVID-19, indicating that the necroptosis pathway is activated. Thus, necroptosis inhibitors are expected to be novel therapeutic candidates for the treatment of COVID-19.Better knowledge of the necroptosis pathway mechanism is urgently required to solve the remaining mysteries surrounding the role of necroptosis in COVID-19. In this review, we briefly introduce the pathogenesis of necroptosis, the relationship between necroptosis, cytokine storm, and COVID-19 also summarizes the progress of inhibitors of necroptosis. This research provides a timely and necessary suggest of the development of necroptosis inhibitors to treat COVID-19 and clinical transformation of inhibitors of necroptosis.

Advanced development and mechanism of sepsis-related acute respiratory distress syndrome

The introduction of the Sepsis 3.0 guidelines in 2016 improved our understanding of sepsis diagnosis and therapy. Personalized treatment strategies and nursing methods for sepsis patients are recommended in the "Save Sepsis Campaign" in 2021. However, mortality in sepsis patients remains high. Patients with sepsis-related acute respiratory distress syndrome account for around 30% of them, with fatality rates ranging from 30 to 40%. Pathological specimens from individuals with sepsis-related ARDS frequently demonstrate widespread alveolar damage, and investigations have revealed that pulmonary epithelial and pulmonary endothelial injury is the underlying cause. As a result, the purpose of this work is to evaluate the mechanism and research progress of pulmonary epithelial and pulmonary endothelial damage in sepsis-related ARDS, which may provide new directions for future research, diagnosis, and therapy.

Examination of the role of necroptotic damage-associated molecular patterns in tissue fibrosis

Fibrosis is defined as the abnormal and excessive deposition of extracellular matrix (ECM) components, which leads to tissue or organ dysfunction and failure. However, the pathological mechanisms underlying fibrosis remain unclear. The inflammatory response induced by tissue injury is closely associated with tissue fibrosis. Recently, an increasing number of studies have linked necroptosis to inflammation and fibrosis. Necroptosis is a type of preprogrammed death caused by death receptors, interferons, Toll-like receptors, intracellular RNA and DNA sensors, and other mediators. These activate receptor-interacting protein kinase (RIPK) 1, which recruits and phosphorylates RIPK3. RIPK3 then phosphorylates a mixed lineage kinase domain-like protein and causes its oligomerization, leading to rapid plasma membrane permeabilization, the release of cellular contents, and exposure of damage-associated molecular patterns (DAMPs). DAMPs, as inflammatory mediators, are involved in the loss of balance between extensive inflammation and tissue regeneration, leading to remodeling, the hallmark of fibrosis. In this review, we discuss the role of necroptotic DAMPs in tissue fibrosis and highlight the inflammatory responses induced by DAMPs in tissue ECM remodeling. By summarizing the existing literature on this topic, we underscore the gaps in the current research, providing a framework for future investigations into the relationship among necroptosis, DAMPs, and fibrosis, as well as a reference for later transformation into clinical treatment.

Uridine alleviates LPS-induced ARDS and improves insulin sensitivity by decreasing oxidative stress and inflammatory processes

Acute respiratory distress syndrome (ARDS) refers to the injury of alveolar epithelial cells and capillary endothelial cells due to various injury factors. Research on the pathogenesis of ARDS has made great progress, but the exact pathogenesis of ARDS has not been fully elucidated. Up to now, the prevention and treatment of ARDS is still an important scientific problem that needs to be solved urgently. In this work, we analyzed the effect of uridine on ARDS. An ARDS model was successfully constructed by lipopolysaccharide (LPS) stimulation. Western-blotting, IFA, ELISA, RT-PCT and CLSM were conducted to investigate the effect of uridine on ARDS and insulin resistance, and the results showed that lung histopathological alterations were significantly attenuated by uridine treatment. Further work showed that the levels of proinflammatory cytokines were significantly down-regulated in the lung tissue after treatment with uridine. Additionally, the numbers of total cells and neutrophils in the bronchoalveolar lavage fluid (BALF) were also decreased in the uridine-treated ARDS mice. We further explored the potential mechanism by which uridine could treat ARDS, and the results indicated that NF-κB signaling was down-regulated by uridine treatment. Next, we studied insulin sensitivity in the ARDS mice, and found that insulin signaling was significantly down-regulated, and uridine could enhance insulin sensitivity in the ARDS mice model. Furthermore, we found that the levels of inflammation and oxidative stress were decreased by uridine treatment, which may be the potential mechanism by which uridine could improve insulin sensitivity. Taken together, the current work provides evidence that uridine can serve as a potential drug to treat ARDS and insulin resistance.

The role of necroptosis in common respiratory diseases in children

Studies have shown that necroptosis (NEC) relies on a unique gene-regulated molecular pathway to cause cell death. With the development of knockout mouse models and specific molecular inhibitors of necrotic proteins, this cell death pathway has been considered one of the important causes of the pathogenesis of human diseases. In this review, we explored the possible roles and mechanisms of NEC in common respiratory diseases in children, such as acute lung injury, acute respiratory distress syndrome, pulmonary infection, childhood asthma, pulmonary hypertension, etc., in order to provide new ideas for the prevention and treatment of such diseases.

The role of necroptosis in disease and treatment

Necroptosis, a distinctive type of programmed cell death different from apoptosis or necrosis, triggered by a series of death receptors such as tumor necrosis factor receptor 1 (TNFR1), TNFR2, and Fas. In case that apoptosis process is blocked, necroptosis pathway is initiated with the activation of three key downstream mediators which are receptor-interacting serine/threonine protein kinase 1 (RIPK1), RIPK3, and mixed lineage kinase domain-like protein (MLKL). The whole process eventually leads to destruction of the cell membrane integrity, swelling of organelles, and severe inflammation. Over the past decade, necroptosis has been found widely involved in life process of human beings and animals. In this review, we attempt to explore the therapeutic prospects of necroptosis regulators by describing its molecular mechanism and the role it played in pathological condition and tissue homeostasis, and to summarize the research and clinical applications of corresponding regulators including small molecule inhibitors, chemicals, Chinese herbal extracts, and biological agents in the treatment of various diseases.

Necroptosis in Pulmonary Diseases: A New Therapeutic Target

In the past decades, apoptosis has been the most well-studied regulated cell death (RCD) that has essential functions in tissue homeostasis throughout life. However, a novel form of RCD called necroptosis, which requires receptor-interacting protein kinase-3 (RIPK3) and mixed-lineage kinase domain-like pseudokinase (MLKL), has recently been receiving increasing scientific attention. The phosphorylation of RIPK3 enables the recruitment and phosphorylation of MLKL, which oligomerizes and translocates to the plasma membranes, ultimately leading to plasma membrane rupture and cell death. Although apoptosis elicits no inflammatory responses, necroptosis triggers inflammation or causes an innate immune response to protect the body through the release of damage-associated molecular patterns (DAMPs). Increasing evidence now suggests that necroptosis is implicated in the pathogenesis of several human diseases such as systemic inflammation, respiratory diseases, cardiovascular diseases, neurodegenerative diseases, neurological diseases, and cancer. This review summarizes the emerging insights of necroptosis and its contribution toward the pathogenesis of lung diseases.

Necrosis Rather Than Apoptosis is the Dominant form of Alveolar Epithelial Cell Death in Lipopolysaccharide-Induced Experimental Acute Respiratory Distress Syndrome Model

Alveolar epithelial cell (AEC) death, which is classified as apoptosis or necrosis, plays a critical role in the pathogenesis of acute respiratory distress syndrome (ARDS). In addition to apoptosis, some types of necrosis are known to be molecularly regulated, and both apoptosis and necrosis can be therapeutic targets for diseases. However, the relative contribution of apoptosis and necrosis to AEC death during ARDS has not been elucidated. Here, we evaluated which type of AEC death is dominant and whether regulated necrosis is involved in lipopolysaccharide (LPS)-induced lung injury, an experimental ARDS model. In the bronchoalveolar lavage fluid from the LPS-induced lung injury mice, both the levels of cytokeratin 18-M65 antigen (a marker of total epithelial cell death) and cytokeratin 18-M30 antigen (an epithelial apoptosis marker) were increased. The M30/M65 ratio, which is an indicator of the proportion of apoptosis to total epithelial cell death, was significantly lower than that in healthy controls. In addition, the number of propidium iodide-positive, membrane-disrupted cells was significantly higher than the number of TUNEL-positive apoptotic cells in the lung sections of lung injury mice. Activated neutrophils seemed to mediate AEC death. Finally, we demonstrated that necroptosis, a regulated necrosis pathway, is involved in AEC death during LPS-induced lung injury. These results indicate that necrosis including necroptosis, rather than apoptosis, is the dominant type of AEC death in LPS-induced lung injury. Although further studies investigating human ARDS subjects are necessary, targeting necrosis including its regulated forms might represent a more efficient approach to protecting the alveolar epithelial barrier during ARDS.

Tanshinone IIA Combined With Cyclosporine A Alleviates Lung Apoptosis Induced by Renal Ischemia-Reperfusion in Obese Rats

Acute lung injury (ALI), which is induced by renal ischemia-reperfusion (IR), is one of the leading causes of acute renal IR-related death. Obesity raises the frequency and severity of acute kidney injury (AKI) and ALI. Tanshinone IIA (TIIA) combined with cyclosporine A (CsA) was employed to lessen the lung apoptosis led by renal IR and to evaluate whether TIIA combined with CsA could alleviate lung apoptosis by regulating mitochondrial function through the PI3K/Akt/Bad pathway in obese rats. Hematoxylin-eosin (HE) staining was used to assess the histology of the lung injury. Terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) was used to assess apoptosis of the lung. Electron microscopy was used to assess mitochondrial morphology in lung cells. Arterial blood gas and pulmonary function were used to assess the external respiratory function. Mitochondrial function was used to assess the internal respiratory function and mitochondrial dynamics and biogenesis. Western blot (WB) was used to examine the PI3K/Akt/Bad pathway-related proteins. TIIA combined with CsA can alleviate lung apoptosis by regulating mitochondrial function through the PI3K/Akt/Bad pathway in obese rats.

Necrostatin-1 and necroptosis inhibition: Pathophysiology and therapeutic implications

Necrostatin-1 (Nec-1) is a RIP1-targeted inhibitor of necroptosis, a form of programmed cell death discovered and investigated in recent years. There are already many studies demonstrating the essential role of necroptosis in various diseases, including inflammatory diseases, cardiovascular diseases and neurological diseases. However, the potential of Nec-1 in diseases has not received much attention. Nec-1 is able to inhibit necroptosis signaling pathway and thus ameliorate necroptotic cell death in disease development. Recent research findings indicate that Nec-1 could be applied in several types of diseases to alleviate disease development or improve prognosis. Moreover, we predict that Nec-1 has the potential to protect against the complications of coronavirus disease 2019 (COVID-19). This review summarized the effect of Nec-1 in disease models and the underlying molecular mechanism, providing research evidence for its future application.

Necrostatin-1 Synergizes the Pan Caspase Inhibitor to Attenuate Lung Injury Induced by Ischemia Reperfusion in Rats

BACKGROUND

Both apoptosis and necroptosis have been recognized to be involved in ischemia reperfusion-induced lung injury. We aimed to compare the efficacies of therapies targeting necroptosis and apoptosis and to determine if there is a synergistic effect between the two therapies in reducing lung ischemia reperfusion injury.

METHODS

Forty Sprague-Dawley rats were randomized into 5 groups: sham (SM) group, ischemia reperfusion (IR) group, necrostatin-1+ischemia reperfusion (NI) group, carbobenzoxy-Val-Ala-Asp-fluoromethylketone+ischemia reperfusion (ZI) group, and necrostatin-1+carbobenzoxy-Val-Ala-Asp-fluoromethylketone+ischemia reperfusion (NZ) group. The left lung hilum was exposed without being clamped in rats from the SM group, whereas the rats were subjected to lung ischemia reperfusion by clamping the left lung hilum for 1 hour, followed by reperfusion for 3 hours in the IR group. 1 mg/kg necrostatin-1 (Nec-1: a specific necroptosis inhibitor) and 3 mg/kg carbobenzoxy-Val-Ala-Asp-fluoromethylketone (z-VAD-fmk: a pan caspase inhibitor) were intraperitoneally administrated prior to ischemia in NI and ZI groups, respectively, and the rats received combined administration of Nec-1 and z-VAD-fmk in the NZ group. Upon reperfusion, expressions of receptor-interacting protein 1 (RIP1), receptor-interacting protein 3 (RIP3), and caspase-8 were measured, and the flow cytometry analysis was used to assess the cell death patterns in the lung tissue. Moreover, inflammatory marker levels in the bronchoalveolar lavage fluid and pulmonary edema were evaluated.

RESULTS

Both Nec-1 and z-VAD-fmk, either alone or in combination, significantly reduced morphological damage, inflammatory markers, and edema in lung tissues following reperfusion, and cotreatment of z-VAD-fmk with Nec-1 produced the optimal effect. The rats treated with Nec-1 had lower levels of inflammatory markers in the bronchoalveolar lavage fluid than those receiving z-VAD-fmk alone (P < 0.05). Interestingly, the z-VAD-fmk administration upregulated RIP1 and RIP3 expressions in the lung tissue from the ZI group compared to those in the IR group (P < 0.05). Reperfusion significantly increased the percentages of necrotic and apoptotic cells in lung tissue single-cell suspension, which could be decreased by Nec-1 and z-VAD-fmk, respectively (P < 0.05).

CONCLUSIONS

Nec-1 synergizes the pan caspase inhibitor to attenuate lung ischemia reperfusion injury in rats. Our data support the potential use of Nec-1 in lung transplantation-related disorders.

A Natural Dietary Flavone Myricetin as an α-Hemolysin Inhibitor for Controlling Staphylococcus aureus Infection

Staphylococcus aureus, an important agent for lethal bacterial infections, can cause a broad spectrum of diseases in various host species. The emergence of multidrug-resistant and highly virulent strains has raised increasing concerns about the novel therapeutic strategies or agents available for treating S. aureus infection. The critical role of Hla, an essential virulence determinant, in the pathogenicity of S. aureus renders this toxin an attractive target for effective therapeutic applications. Here, we have identified myricetin as an effective inhibitor of Hla that simultaneously inhibits Hla production and neutralizes Hla activity without affecting bacterial growth. Myricetin treatment reduced the oligomerization of Hla and Hla-mediated biofilm formation. The addition of myricetin to the coinfection system of host cells and S. aureus significantly decreased cell injury and downregulated the inflammatory response in cells. Furthermore, S. aureus-infected mice that received myricetin showed alleviated tissue damage in the lung. Our results indicated that myricetin inhibits S. aureus virulence by targeting Hla and downregulates the inflammatory response in host cells. Overall, in addition to traditional antibiotics with antibacterial activity, myricetin may represent a potential candidate, and strategy for S. aureus infection.

Ammonia regulates chicken tracheal cell necroptosis via the LncRNA-107053293/MiR-148a-3p/FAF1 axis

Ammonia (NH₃) is a known harmful gas that causes injury to the respiratory system. Ammonia also exists in haze, forming secondary organic aerosols. However, the specific damage caused by NH₃ in chicken trachea has not been determined. The regulatory mechanism of ceRNA and its multiple roles have been proposed in many pathomechanisms; therefore, we investigated the functional role of ceRNA in chicken trachea after NH₃ inhalation. Broiler chicken trachea exposed to NH₃ was selected as the research object. The pathological ultrastructure was observed by transmission electron microscopy. Transcriptome analyses were applied and referenced, and lncRNA-107053293 and miR-148a-3p and FAF1 were selected. A dual-luciferase reporter assay verified the target relationship. Real-time quantitative PCR (RT-PCR) and western blotting were performed to examine the expression levels of necroptosis genes, such as RIPK1, RIPK3, MLKL, caspase 8, and FADD. Our results indicated that lncRNA-107053293 regulated necroptosis by acting as a competing endogenous RNA of miR-148a-3p. FAF1, as a gene target of miR-148a-3p, also affects necroptosis.

Necrostatin-1 Alleviates Bleomycin-Induced Pulmonary Fibrosis and Extracellular Matrix Expression in Interstitial Pulmonary Fibrosis

Background

Interstitial pulmonary fibrosis (IPF) is harmful for patients’ life and health. The effective treatment of IPF is lacking because of unclear pathogenesis. Necrostatin-1 has protective effects on lung injury and can suppress the fibrosis development. I this study we investigated whether necrostatin-1 could decrease the proliferation of pulmonary fibroblasts, pulmonary fibrosis and expression of extracellular matrix (ECM) in IPF.

Material/Methods

The IPF mice model was conducted by intra-tracheal injection of bleomycin (BLM) (2 mg/kg) for C57BL/6N mice. Necrostatin-1 treatment was performed with 1 mg/kg necrostatin-1 by an intravenous injection for C57BL/6N mice. Lung tissue structures and collagen deposition were observed by hematoxylin and eosin staining and Masson staining. IPF in vitro model was constructed by MRC-5 cells induced by transforming growth factor beta 1 (TGF-β1). And, 20 μM necrostatin-1 was used to treat the TGF-β1 induced MRC-5 cells. Cell Counting Kit-8 (CCK-8) assay detected the viability of MRC-5 cells. The expression of receptor-interacting protein kinase-1 and -3 (RIPK1 and RIPK3), α smooth muscle actin (α-SMA), collagen IV, collagen I, fibronectin (FN), and transforming growth factor-β (TGF-β) in lung tissues and MRC-5 cells was measured by western blot analysis. The α-SMA expression in lung tissues was also analyzed by immunohistochemistry.

Results

The expression of RIPK1 and RIPK3 in lung tissues of BLM induced mice was increased. The degree of pulmonary fibrosis and expression of α-SMA, collagen IV, collagen I, FN, and TGF-β in lung tissues of BLM induced mice was enhanced. The proliferation of MRC-5 cells was increased when MRC-5 cells were induced by TGF-β. The expression of RIPK1, RIPK3, α-SMA, collagen IV, collagen I, and FN was increased in TGF-β induced MRC-5 cells. And, necrostatin-1 could effectively reverse the changes of pulmonary fibrosis, RIPK1, RIPK3, and ECM in vivo and in vitro experiments.

Conclusions

Necrostatin-1 attenuated pulmonary fibrosis in lung tissues of BLM induced mice and inhibited the fibroblast proliferation. And, necrostatin-1 also decreased the expression of RIPK1, RIPK3, and ECM in lung tissues of BLM induced mice and TGF-β induced fibroblasts. Necrostatin-1 could be a new effective drug for the treatment of IPF.

Necroptosis in the Pathophysiology of Disease

Over the past 15 years, elegant studies have demonstrated that in certain conditions, programed cell death resembles necrosis and depends on a unique molecular pathway with no overlap with apoptosis. This form of regulated necrosis is represented by necroptosis, in which the receptor-interacting protein kinase-3 and its substrate mixed-lineage kinase domain-like protein play a crucial role. With the development of knockout mouse models and molecular inhibitors unique to necroptotic proteins, this cell death has been found to occur in virtually all tissues and diseases evaluated. There are different immunologic consequences depending on whether cells die through apoptosis or necroptosis. Therefore, distinguishing between these two forms of cell death may be crucial during pathologic evaluations. In this review, we provide an understanding of necroptotic cell-death and highlight diseases in which necroptosis has been found to play a role. We also discuss the inhibitors of necroptosis and the ways these inhibitors have been used in preclinical models of diseases. These two discussions offer an understanding of the role of necroptosis in diseases and will foster efforts to pharmacologically target this unique yet pervasive form of programed cell death in the clinic.

TREM-1 Attenuates RIPK3-mediated Necroptosis in Hyperoxia-induced Lung Injury in Neonatal Mice

Hyperoxia-induced injury to the developing lung, impaired alveolarization, and dysregulated vascularization are critical factors in the pathogenesis of bronchopulmonary dysplasia (BPD); however, mechanisms for hyperoxia-induced development of BPD are not fully known. In this study, we show that TREM-1 (triggering receptor expressed on myeloid cells 1) is upregulated in hyperoxia-exposed neonatal murine lungs as well as in tracheal aspirates and lungs of human neonates with respiratory distress syndrome and BPD as an adaptive response to survival in hyperoxia. Inhibition of TREM-1 function using an siRNA approach or deletion of the Trem1 gene in mice showed enhanced lung inflammation, alveolar damage, and mortality of hyperoxia-exposed neonatal mice. The treatment of hyperoxia-exposed neonatal mice with agonistic TREM-1 antibody decreased lung inflammation, improved alveolarization, and was associated with diminished necroptosis-regulating protein RIPK3 (receptor-interacting protein kinase 3). Mechanistically, we show that TREM-1 activation alleviates lung inflammation and improves alveolarization through downregulating RIPK3-mediated necroptosis and NLRP3 (nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3) inflammasome activation in hyperoxia-exposed neonatal mice. These data show that activating TREM-1, enhancing angiopoietin 1 signaling, or blocking the RIPK3-mediated necroptosis pathway may be used in new therapeutic interventions to control adverse effects of hyperoxia in the development of BPD.

Rip 1-dependent endothelial necroptosis participates in ischemia-reperfusion injury of mouse flap

BACKGROUND

Ischemia reperfusion injury plays an important role in free flap necrosis. However, the detailed mechanism is not clear, and effective methods for improving the survival rate of skin flap are still lacking.

OBJECTIVE

To investigate the regulation and functional link between necroptosis and ischemia-reperfusion injury of mouse flap.

METHODS

We established a mouse ischemia-reperfusion injury flap model and a cell Oxygen Glucose Deprivation (OGD) model intervened with Necrostatin-1. The mouse flap tissues were harvested in vivo for histological immunofluorescence analysis and western blotting analyses. The HUVECs cells with various treatments in vitro were assessed by using Transwell assay, tube formation assay, cell counting kit-8 analysis and flow cytometry. A Rip3-knockout cell line and a TNFR1-knockout cell line were generated from HUVEC cells using the CRISPR-Cas9 technology and were subsequently used to explore the related mechanisms.

RESULTS

The expression of p-Rip3 is positive in both mouse and cell culture models. When necroptosis is completely or partially inhibited in vivo, damaged tissues are repaired with better efficiency. The cells treated with Necrostatin-1 in vitro exhibit faster migration, proliferation and better tube formation. Deficiency of TNFR1 can block the necroptosis pathway by blocking the phosphorylation of Rip3 in HUVEC OGD/ROG model. Meanwhile, the levels of APJ, HIF-1α, and VEGF are reduced when necroptosis is inhibited by Necrostatin-1.

CONCLUSION

TNFR1 mediates Rip1/Rip3 in ischemia-reperfusion injury. Inhibition of necroptosis attenuates the ischemia-reperfusion injury of flap and may enhance hypoxic tolerance of HUVECs and vascular homeostasis through regulation of the HIF-1α signaling pathways.

Collateral damage: necroptosis in the development of lung injury

Cell death is increasingly recognized as a driving factor in the development of acute lung injury. Necroptosis, an immunogenic regulated cell death program important in innate immunity, has been implicated in the development of lung injury in a diverse range of conditions. Characterized by lytic cell death and consequent extracellular release of endogenous inflammatory mediators, necroptosis can be both beneficial and deleterious to the host, depending on the context. Here, we review recent investigations linking necroptosis and the development of experimental lung injury. We assess the consequences of necroptosis during bacterial pneumonia, viral infection, sepsis, and sterile injury, highlighting increasing evidence from in vitro studies, animal models, and clinical studies that implicates necroptosis in the pathogenesis of ARDS. Lastly, we highlight current challenges in translating laboratory findings to the bedside.

Involvement of Alveolar Epithelial Cell Necroptosis in Idiopathic Pulmonary Fibrosis Pathogenesis

Alveolar epithelial cell (AEC) injury leading to cell death is involved in the process of fibrosis development during idiopathic pulmonary fibrosis (IPF). Among regulated/programmed cell death, the excessive apoptosis of AECs has been widely implicated in IPF pathogenesis. Necroptosis is a type of regulated/programmed necrosis. A multiprotein complex composed of receptor-interacting protein kinase (RIPK)-1 and -3 plays a key regulatory role in initiating necroptosis. Although necroptosis participates in disease pathogeneses through the release of damage-associated molecular patterns, its association with IPF progression remains elusive. In this study, we attempted to illuminate the involvement of RIPK3-regulated necroptosis in IPF pathogenesis. IPF lung tissues were used to detect necroptosis, and the role of RIPK3 was determined using cell culturing models of AECs. Lung fibrosis models of bleomycin (BLM) treatment were also used. RIPK3 expression levels were increased in IPF lungs, and both apoptosis and necroptosis were detected mainly in AECs. Necrostatin-1 and RIPK3 knockout experiments in AECs revealed the participation of necroptosis in BLM and hydrogen peroxide-induced cell death. BLM treatment induced RIPK3 expression in AECs and increased high-mobility group box 1 and IL-1β levels in mouse lungs. The efficient attenuation of BLM-induced lung inflammation and fibrosis was determined in RIPK3 knockout mice and by necrostatin-1 with a concomitant reduction in high-mobility group box 1 and IL-1β. RIPK3-regulated necroptosis in AECs is involved in the mechanism of lung fibrosis development through the release of damage-associated molecular patterns as part of the pathogenic sequence of IPF.

Close Relationship between cIAP2 and Human ARDS Induced by Severe H7N9 Infection

Background

cIAP2 is involved in necroptosis as a key upstream regulation factor. We aimed to investigate the role of cIAP2 in ARDS/ALI induced by H7N9 virus through regulating the RIPK1/3 necroptosis pathway.

Methods

Lung tissues of 11 patients who died from ARDS-complicated H7N9 infection between 2013 and 2016 were obtained as the H7N9-ARDS group. Lung tissues near benign lung nodules were acquired as the control group. Histological changes were evaluated by H&E staining. Protein levels of cIAP2, RIPK1, RIPK3, p-RIPK3, MLKL, and p-MLKL in the lung tissues were detected by Western Blot. The mRNA levels of cIAP2, RIPK1, and RIPK3 were detected by real-time PCR.

Results

H7N9 virus infection had a high mortality, with ARDS being the leading cause of death. The protein level of cIAP2 in the experimental group was lower than that in the control group (P<0.05). However, the experimental group showed higher RIPK1, RIPK3, and p-RIPK3 protein levels than the control group (P<0.05), as well as the expression level of MLKL and p-MLKL protein, which is a key downstream protein in necroptosis (P<0.05).

Conclusion

In tissues from patients with fatal H7N9, downregulation of cIAP2 and induction of necroptosis was observed. We could speculate that necroptosis of the pulmonary epithelium is associated with severe H7N9 infection leading to ARDS. Thus, necroptosis inhibition may be a novel therapy for H7N9 influenza virus.

Cell Death in the Lung: The Apoptosis-Necroptosis Axis

Regulated cell death is a major mechanism to eliminate damaged, infected, or superfluous cells. Previously, apoptosis was thought to be the only regulated cell death mechanism; however, new modalities of caspase-independent regulated cell death have been identified, including necroptosis, pyroptosis, and autophagic cell death. As an understanding of the cellular mechanisms that mediate regulated cell death continues to grow, there is increasing evidence that these pathways are implicated in the pathogenesis of many pulmonary disorders. This review summarizes our understanding of regulated cell death as it pertains to the pathogenesis of chronic obstructive pulmonary disease, asthma, idiopathic pulmonary fibrosis, acute respiratory distress syndrome, and pulmonary arterial hypertension.

The clinical relevance of necroinflammation-highlighting the importance of acute kidney injury and the adrenal glands

Necroinflammation is defined as the inflammatory response to necrotic cell death. Different necrotic cell death pathways exhibit different immune reponses, despite a comparable level of intracellular content release (referred to as damage associated molecular patterns or DAMPs). In addition to DAMP release, which is inevitably associated with necrotic cell death, the active production of pro/anti-inflammatory cytokines characterizes certain necrotic pathways. Necroptosis, ferroptosis and pyroptosis, therefore, are immunogenic to a different extent. In this review, we discuss the clinical relevance of necroinflammation highlighting potential human serum markers. We focus on the role of the adrenal glands and the lungs as central organs affected by systemic and/or local DAMP release and underline their role in intensive care medicine. In addition, data from models of acute kidney injury (AKI) and kidney transplantation have significantly shaped the field of necroinflammation and may be helpful for the understanding of the potential role of dialysis and plasma exchange to treat ongoing necroinflammation upon intensive care unit (ICU) conditions. In conclusion, we are only beginning to understand the importance of necroinflammation in diseases and transplantation, including xenotransplantation. However, given the existing efforts to develop inhibitors of necrotic cell death (ferrostatins, necrostatins, etc), we consider it likely that interference with necroinflammation reaches clinical routine in the near future.

Pretreatment of ferulic acid attenuates inflammation and oxidative stress in a rat model of lipopolysaccharide-induced acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is a fatal clinical condition that can be caused by pulmonary and non-pulmonary diseases. Oxidative stress and inflammation play key roles in the development of ARDS. In this study, we investigated whether ferulic acid (FA), an anti-oxidant, was beneficial for prophylaxis of ARDS. We established an ARDS rat model using lipopolysaccharide (LPS) administration. Lung injury was assessed by lung wet/dry ratio and broncho-alveolar lavage fluid (BALF) analysis. Hematoxylin and eosin staining was performed to evaluate the histological changes of the lungs. Enzyme-linked immunosorbent assay (ELISA) and immunoblotting were performed to detect proteins in BALF and lung tissue, respectively. Pulmonary function was determined by testing the oxygen level in BALF. FA pretreatment significantly alleviated LPS-induced pulmonary histological changes. FA reversed LPS-induced changes of lung wet/dry ratio, total protein in BALF, P(A-a)O₂, and PaO₂/FiO₂. In addition, LPS dramatically up-regulated the secretion of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α, and IL-10 in BALF (P < 0.01). However, pretreatment of FA significantly improved LPS-induced inflammation. We found that FA indeed reduced oxidative stress in the lungs by testing malondialdehyde level, myeloperoxidase level, and total anti-oxidant capacity. We also proved that FA inactivated multiple mitogen-activated protein kinase signaling pathways in the lungs. In conclusion, FA alleviated LPS-induced ARDS through its anti-inflammatory and anti-oxidant activities.

Inhibition of necroptosis attenuates lung injury and improves survival in neonatal sepsis

BACKGROUND

Neonatal sepsis represents a unique therapeutic challenge owing to an immature immune system. Necroptosis is a form of programmed cell death that has been identified as an important mechanism of inflammation-induced cell death. Receptor-interacting protein kinase 1 plays a key role in mediating this process. We hypothesized that pharmacologic blockade of receptor-interacting protein kinase 1 activity would be protective in neonatal sepsis.

METHODS

Sepsis was induced in C57BL/6 mouse pups (5-7 days old) by intraperitoneal injection of adult cecal slurry. At 1 hour after cecal slurry injection, the receptor-interacting protein kinase 1 inhibitor necrostatin-1 (10 µg/g body weight) or vehicle (5% dimethyl sulfoxide in phosphate buffered saline) was administered via retro-orbital injection. At 20 hours after cecal slurry injection, blood and lung tissues were collected for various analyses.

RESULTS

At 20 hours after sepsis induction, vehicle-treated pups showed a marked increase in serum levels of interleukin 6, interleukin 1-beta, and interleukin 18 compared to sham. With necrostatin-1 treatment, serum levels of interleukin 6, interleukin 1-beta, and interleukin 18 were decreased by 77%, 81%, and 63%, respectively, compared to vehicle. In the lungs, sepsis induction resulted in a 232-, 10-, and 2.8-fold increase in interleukin 6, interleukin 1-beta, and interleukin 18 mRNA levels compared to sham, while necrostatin-1 treatment decreased these levels to 40-, 4-, and 0.8-fold, respectively. Expressions of the neutrophil chemokines keratinocyte chemoattractant and macrophage-inflammatory-protein-2 were also increased in the lungs in sepsis, while necrostatin-1 treatment decreased these levels by 81% and 61%, respectively, compared to vehicle. In addition, necrostatin-1 treatment significantly improved the lung histologic injury score and decreased lung apoptosis in septic pups. Finally, treatment with necrostatin-1 increased the 7-day survival rate from 0% in the vehicle-treated septic pups to 29% (P = .11).

CONCLUSION

Inhibition of receptor-interacting protein kinase 1 by necrostatin-1 decreases systemic and pulmonary inflammation, decreases lung injury, and increases survival in neonatal mice with sepsis. Targeting the necroptosis pathway might represent a new therapeutic strategy for neonatal sepsis.

Inhibition of regulated necrosis attenuates receptor-interacting protein kinase 1-mediated ischemia-reperfusion injury after lung transplantation

BACKGROUND

Increasing evidence indicates that regulated necrosis plays a critical role during cell death caused by ischemia-reperfusion (IR) injury. Necroptosis is one form of regulated necrosis. Necrostatin-1 (Nec-1), an inhibitor of receptor-interacting protein kinase 1 (RIPK1), is known to reduce necroptosis. We investigated the effect of Nec-1 treatment on IR-induced lung injury in a rat lung transplant model.

METHODS

Lewis rats were divided into 4 groups (n = 6 each): (1) Control (no treatment), (2) Donor treatment (D), (3) Recipient treatment (R), and (4) Donor plus Recipient treatment (D+R) groups. Donor lungs were flushed and preserved for 18 hours at 4ºC before transplantation. Recipient animals underwent a left single lung transplant. After 2 hours of reperfusion, we assessed the physiologic function, cytokine expression, pathway activation, and the extent of necrosis.

RESULTS

Pulmonary gas exchange in D+R group was significantly better than in the other 3 groups (p = 0.003). Lung edema was significantly lower in the D+R group compared with the Control group (p = 0.006). The expression of interleukin-6 in lung tissue and plasma was significantly reduced in the D+R group compared with the Control group (p = 0.036). The percentage of necrotic cells in D+R group was significantly lower than in the Control and D groups (p = 0.01), indicating Nec-1inhibited regulated necrosis.

CONCLUSIONS

The administration of Nec-1 to both donor and recipient improved graft function after lung transplantation through the reduction of necroptosis. The inhibition of regulated necrosis appears to be a promising strategy to attenuate IR lung injury after lung transplantation.

New Insights into the Immune Molecular Regulation of the Pathogenesis of Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome is an inflammatory disease characterized by dysfunction of pulmonary epithelial and capillary endothelial cells, infiltration of alveolar macrophages and neutrophils, cell apoptosis, necroptosis, NETosis, and fibrosis. Inflammatory responses have key effects on every phase of acute respiratory distress syndrome. The severe inflammatory cascades impaired the regulation of vascular endothelial barrier and vascular permeability. Therefore, understanding the relationship between the molecular regulation of immune cells and the pulmonary microenvironment is critical for disease management. This article reviews the current clinical and basic research on the pathogenesis of acute respiratory distress syndrome, including information on the microenvironment, vascular endothelial barrier and immune mechanisms, to offer a strong foundation for developing therapeutic interventions.

Simvastatin attenuated rat thoracic aorta remodeling by decreasing ROCK2‑mediated CyPA secretion and CD147‑ERK1/2‑cyclin pathway

Reactive oxygen species-induced cyclophilin A (CyPA) release from vascular smooth muscle cells (VSMCs) may be inhibited by simvastatin in vitro. The present study aimed to further examine the effect of simvastatin on serum CyPA levels and the basigin (CD147)-extracellular signal-regulated kinase (ERK) 1/2-cyclin pathway during thoracic aorta remodeling. The mechanisms through which simvastatin may inhibit CyPA secretion from VSMCs were further investigated. Serum CyPA levels and the expression kinetics of CyPA-associated signaling pathways were examined following simvastatin treatment in rat thoracic aortas during hypertension. Cell lysates were prepared from middle layer of thoracic aortas at 1, 4, 8 and 12 weeks subsequent to surgery. ELISA analysis revealed that serum CyPA levels were gradually increased with the progression of thoracic aorta remodeling. Western blotting demonstrated that the expression of CD147, phosphorylated-ERK1/2, cyclin D1, cyclin A, and cyclin E were increased with the progression of thoracic aorta remodeling. Simvastatin administration for 4, 8 and 12 weeks diminished all these changes, as observed in the hypertensive group. VSMCs from simvastatin-treated rats secreted a decreased amount of CyPA compared with VSMCs from hypertensive rats. In addition, pretreatment with geranylgeraniol partly reversed the inhibitory effect of simvastatin on LY83583-induced CyPA secretion in cultured VSMCs, whereas GGTI-298 and KD025 [a selective Rho-associated protein kinase 2 (ROCK2) inhibitor] mimicked the inhibitory effect of simvastatin. The present study demonstrated that simvastatin alleviated thoracic aorta remodeling by reducing CyPA secretion and expression of the CD147-ERK1/2-cyclin signaling pathway. In addition, the results of the present study demonstrated that the Rho-ROCK2 pathway mediated CyPA secretion from VSMCs.