Eleostearic acid induces RIP1-mediated atypical apoptosis in a kinase-independent manner via ERK phosphorylation, ROS generation and mitochondrial dysfunction

The Active Fraction of Polyrhachis vicina Roger (AFPR) activates ERK to cause necroptosis in colorectal cancer

ETHNOPHARMACOLOGICAL RELEVANCE

Polyrhachis vicina Roger (P. vicina), a traditional Chinese medicinal animal, has been used to treat rheumatoid arthritis, hepatitis, cancer, and other conditions. Due to its anti-inflammatory properties, our previous pharmacological investigations have demonstrated that it is effective against cancer, depression, and hyperuricemia. Nevertheless, the key active components and targets of P. vicina in cancers are still unexplored.

AIM OF THE STUDY

The study aimed to evaluate the pharmacological treatment mechanism of the active fraction of P. vicina (AFPR) in treating colorectal cancer (CRC) and to further reveal its active ingredients and key targets.

METHODS

To examine the inhibitory impact of AFPR on CRC growth, tumorigenesis assays, cck-8 assays, colony formation assays, and MMP detection were utilized. The primary components of AFPR were identified by GC-MS analysis. The network pharmacology, molecular docking, qRT-PCR, western blotting, CCK-8 assays, colony formation assay, Hoechst staining, Annexin V-FITC/PI double staining, and MMP detection were performed to pick out the active ingredients and potential key targets of AFPR. The function of Elaidic acid on necroptosis was investigated through siRNA interference and the utilization of inhibitors. Elaidic acid's effectiveness to suppress CRC growth in vivo was assessed using a tumorigenesis experiment.

RESULTS

Studies confirmed that AFPR prevented CRC from growing and evoked cell death. Elaidic acid was the main bioactive ingredient in AFPR that targeted ERK. Elaidic acid greatly affected the ability of SW116 cells to form colonies, produce MMP, and undergo necroptosis. Additionally, Elaidic acid promoted necroptosis predominantly by activating ERK/RIPK1/RIPK3/MLKL.

CONCLUSION

According to our findings, Elaidic acid is the main active component of AFPR, which induced necroptosis in CRC through the activation of ERK. It represents a promising alternative therapeutic option for CRC. This work provided experimental support for the therapeutic application of P. vicina Roger in the treatment of CRC.

MiR-204-3p overexpression inhibits gastric carcinoma cell proliferation by inhibiting the MAPK pathway and RIP1/MLK1 necroptosis pathway to promote apoptosis

BACKGROUND

Gastric carcinoma (GC) is the third most frequent cause of cancer-related death, highlighting the pressing need for novel clinical treatment options. In this regard, microRNAs (miRNAs) have emerged as a promising therapeutic strategy. Studies have shown that miRNAs can regulate related signaling pathways, acting as tumor suppressors or tumor promoters.

AIM

To explore the effect of miR-204-3p on GC cells.

METHODS

We measured the expression levels of miR-204-3p in GC cells using quantitative real-time polymerase chain reaction, followed by the delivery of miR-204-3p overexpression and miR-204-3p knockdown vectors into GC cells. CCK-8 was used to detect the effect of miR-204-3p on the proliferation of GC cells, and the colony formation ability of GC cells was detected by the clonal formation assay. The effects of miR-204-3p on GC cell cycle and apoptosis were detected by flow cytometry. The BABL/c nude mouse subcutaneous tumor model using MKN-45 cells was constructed to verify the effect of miR-204-3p on the tumorigenicity of GC cells. Furthermore, the study investigated the effects of miR-204-3p on various proteins related to the MAPK signaling pathway, necroptosis signaling pathway and apoptosis signaling pathway on GC cells using Western blot techniques.

RESULTS

Firstly, we found that the expression of miR-204-3p in GC was low. When treated with the lentivirus overexpression vector, miR-204-3p expression significantly increased, but the lentivirus knockout vector had no significant effect on miR-204-3p. In vitro experiments confirmed that miR-204-3p overexpression inhibited GC cell viability, promoted cell apoptosis, blocked the cell cycle, and inhibited colony formation ability. In vivo animal experiments confirmed that miR-204-3p overexpression inhibited subcutaneous tumorigenesis ability in BABL/c nude mice. Simultaneously, our results verified that miR-204-3p overexpression can inhibit GC cell proliferation by inhibiting protein expression levels of KRAS and p-ERK1/2 in the MAPK pathway, as well as inhibiting protein expression levels of p-RIP1 and p-MLK1 in the necroptosis pathway to promote the BCL-2/BAX/Caspase-3 apoptosis pathway.

CONCLUSION

MiR-204-3p overexpression inhibited GC cell proliferation by inhibiting the MAPK pathway and necroptosis pathway to promote apoptosis of GC cells. Thus, miR-204-3p may represent a new potential therapeutic target for GC.

PTPMT1 protects cardiomyocytes from necroptosis induced by γ-ray irradiation through alleviating mitochondria injury

Radiation-induced heart disease (RIHD) progresses over time and may manifest decades after the initial radiation exposure, which is associated with significant morbidity and mortality. The clinical benefit of radiotherapy is always counterbalanced by an increased risk of cardiovascular events in survivors. There is an urgent need to explore the effect and the underlying mechanism of radiation-induced heart injury. Mitochondrial damage widely occurs in irradiation-induced injury, and mitochondrial dysfunction contributes to necroptosis development. Experiments were performed using induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) and rat H9C2 cells to investigate the effect of mitochondrial injury on necroptosis in irradiated cardiomyocytes and to further elucidate the mechanism underlying radiation-induced heart disease and discover possible preventive targets. After γ-ray irradiation, the expression levels of necroptosis markers were increased, along with higher oxidative stress and mitochondrial injury. These effects could be abated by overexpression of protein tyrosine phosphatase, mitochondrial 1 (PTPMT1). Inhibiting oxidative stress or increasing the expression of PTPMT1 could protect against radiation-induced mitochondrial injury and then decrease the necroptosis of cardiomyocytes. These results suggest that PTPMT1 may be a new target for the treatment of radiation-induced heart disease.NEW & NOTEWORTHY Effective strategies are still lacking for treating RIHD, with unclear pathological mechanisms. In cardiomyocytes model of radiation-induced injuries, we found γ-ray irradiation decreased the expression of PTPMT1, increased oxidative stress, and induced mitochondrial dysfunction and necroptosis in iPSC-CMs. ROS inhibition attenuated radiation-induced mitochondrial damage and necroptosis. PTPMT1 protected cardiomyocytes from necroptosis induced by γ-ray irradiation by alleviating mitochondrial injury. Therefore, PTPMT1 might be a potential strategy for treating RIHD.

Necrostatin-1 prevents skeletal muscle ischemia reperfusion injury by regulating Bok-mediated apoptosis

BACKGROUND

Receptor interacting serine/threonine kinase 1 (RIPK1) mediates apoptosis by regulating the classic proapoptotic effectors Bcl-2-associated X protein (Bax) and Bcl-2 homologous antagonist/killer (Bak). Although Bcl-2-related ovarian killer (Bok) is structurally similar to Bak and Bax, it is unclear whether it mediates apoptosis in skeletal muscle ischemia reperfusion (IR) injury. We hypothesized that by regulating Bok-mediated apoptosis, inhibiting RIPK1 with necrostatin-1 would reduce skeletal muscle IR injury.

METHODS

Rats were randomized into four groups: sham (SM), IR, IR treated with necrostatin-1 (NI), or vehicle dimethyl sulfoxide (DI). For the IR group, the right femoral artery was clamped for 4 hours and then reperfused for 4 hours, and for the NI and DI groups, necrostatin-1 (1.65 mg/kg) and the equal volume of dimethyl sulfoxide were intraperitoneally administered prior to IR induction. The structural damage of muscle tissue and protein expression of Bok, Bcl-2, and cleaved caspase-3 were investigated, and apoptotic cells were identified with terminal dUTP nick-end labeling (TUNEL) staining. In vitro, human skeletal muscle cells (HSMCs) were exposed to 6 hours of oxygen-glucose deprivation followed by normoxia for 6 hours to establish an oxygen-glucose deprivation/reoxygenation (OGD/R) model. To determine the role of Bok, cell viability, lactate dehydrogenase (LDH) release, and flow cytometry were examined to demonstrate the effects of necrostatin-1 and Bok knockdown on the OGD/R insult of HSMCs.

RESULTS

Necrostatin-1 pretreatment markedly reduced IR-induced muscle damage and RIPK1, Bok, and cleaved caspase-3 expression, whereas upregualted Bcl-2 expression (p < 0.05). Furthermore, necrostatin-1 prevented mitochondrial damage and decreased TUNEL-positive muscle cells (p < 0.05). In vitro, HSMCs treated with necrostatin-1 showed reduced Bok expression, increased cell viability, and reduced LDH release in response to OGD/R (p < 0.05), and Bok knockdown significantly blunted the OGD/R insult in HSMCs.

CONCLUSION

Necrostatin-1 prevents skeletal muscle from IR injury by regulating Bok-mediated apoptosis.

Apoptosis detection: a purpose-dependent approach selection

Apoptosis is closely associated with many diseases. Detection of apoptosis can be achieved by morphology, biochemistry, molecular biology, immunology, and other techniques. However, as technologies are increasingly used for the detection of apoptosis, many researchers are confused about how to choose a suitable method to detect apoptosis. Selection of a suitable detection method for apoptosis will help clinical diagnosis and prevention of diseases. This article reviews the selection of optimal apoptosis-detection methods based on research purposes and technique principles.

Ferroptotic cell death triggered by conjugated linolenic acids is mediated by ACSL1

Ferroptosis is associated with lipid hydroperoxides generated by the oxidation of polyunsaturated acyl chains. Lipid hydroperoxides are reduced by glutathione peroxidase 4 (GPX4) and GPX4 inhibitors induce ferroptosis. However, the therapeutic potential of triggering ferroptosis in cancer cells with polyunsaturated fatty acids is unknown. Here, we identify conjugated linoleates including α-eleostearic acid (αESA) as ferroptosis inducers. αESA does not alter GPX4 activity but is incorporated into cellular lipids and promotes lipid peroxidation and cell death in diverse cancer cell types. αESA-triggered death is mediated by acyl-CoA synthetase long-chain isoform 1, which promotes αESA incorporation into neutral lipids including triacylglycerols. Interfering with triacylglycerol biosynthesis suppresses ferroptosis triggered by αESA but not by GPX4 inhibition. Oral administration of tung oil, naturally rich in αESA, to mice limits tumor growth and metastasis with transcriptional changes consistent with ferroptosis. Overall, these findings illuminate a potential approach to ferroptosis, complementary to GPX4 inhibition.

RIPK1 contributes to cisplatin-induced apoptosis of esophageal squamous cell carcinoma cells via activation of JNK pathway

AIMS

Previous studies have uncovered the function of receptor-interacting protein kinase 1 (RIPK1) to mediate both cell survival and death. Moreover, RIPK1 modulates apoptosis and necroptosis depending on its activity, phosphorylation or ubiquitylation status. Many studies have explained the role or mechanism of RIPK1 in necroptosis. However, the role of RIPK1 has not been elucidated fully in human esophageal squamous cell carcinoma (ESCC) cells.

MATERIALS AND METHODS

The protein and mRNA expression levels of RIPK1 in a panel of ESCC cell lines by Western blot and real-time quantitative reverse transcription PCR (qRT-PCR) were analyzed. MTS assay was used to examine cellular proliferation, flow cytometric analysis to detect apoptosis, mitochondrial membrane potential and reactive oxygen species production. ESCC cells with either inhibitor or overexpressed RIPK1were analyzed to determine cell proliferation, colony formation and apoptosis. Flow cytometry and western blotting assays were used to explore the underlying mechanism.

KEY FINDINGS

In our study, RIPK1 expression was found to contribute significantly to cisplatin-induced apoptosis in the human ESCC cells. The reduced RIPK1 expression promoted cells proliferation and overexpressed RIPK1 facilitated cell apoptosis. Mechanistic investigations have revealed that the inhibition of proliferation for RIPK1 in ESCC cells was regulated via activation of c-Jun NH2-terminal kinase signaling. Additionally, damages were observed in the mitochondrial membrane, depletion of ATP and increased generation in reactive oxygen species.

SIGNIFICANCE

Our findings verified the evidence that RIPK1 can promote cell death in ESCC cells, with potential implications for activating c-Jun NH2-terminal kinase pathway as a novel approach to the disease.

Critical contribution of RIPK1 mediated mitochondrial dysfunction and oxidative stress to compression-induced rat nucleus pulposus cells necroptosis and apoptosis

The aim of this study was to investigate whether RIPK1 mediated mitochondrial dysfunction and oxidative stress contributed to compression-induced nucleus pulposus (NP) cells necroptosis and apoptosis, together with the interplay relationship between necroptosis and apoptosis in vitro. Rat NP cells underwent various periods of 1.0 MPa compression. To determine whether compression affected mitochondrial function, we evaluated the mitochondrial membrane potential, mitochondrial permeability transition pore (mPTP), mitochondrial ultrastructure and ATP content. Oxidative stress-related indicators reactive oxygen species, superoxide dismutase and malondialdehyde were also assessed. To verify the relevance between oxidative stress and necroptosis together with apoptosis, RIPK1 inhibitor necrostatin-1(Nec-1), mPTP inhibitor cyclosporine A (CsA), antioxidants and small interfering RNA technology were utilized. The results established that compression elicited a time-dependent mitochondrial dysfunction and elevated oxidative stress. Nec-1 and CsA restored mitochondrial function and reduced oxidative stress, which corresponded to decreased necroptosis and apoptosis. CsA down-regulated mitochondrial cyclophilin D expression, but had little effects on RIPK1 expression and pRIPK1 activation. Additionally, we found that Nec-1 largely blocked apoptosis; whereas, the apoptosis inhibitor Z-VAD-FMK increased RIPK1 expression and pRIPK1 activation, and coordinated regulation of necroptosis and apoptosis enabled NP cells survival more efficiently. In contrast to Nec-1, SiRIPK1 exacerbated mitochondrial dysfunction and oxidative stress. In summary, RIPK1-mediated mitochondrial dysfunction and oxidative stress play a crucial role in NP cells necroptosis and apoptosis during compression injury. The synergistic regulation of necroptosis and apoptosis may exert more beneficial effects on NP cells survival, and ultimately delaying or even retarding intervertebral disc degeneration.

A novel nanoformulation of α-eleostearic acid restores molecular pathogenesis of hypersensitivity

AIM

The present work provides first-time empirical and molecular interaction evidence to establish the higher biofunctionality of a therapeutic lipid, α-eleostearic acid (ESA), encapsulated in a novel and thoroughly characterized biocompatible nanoemulsion (NE) system (particle size <200 nm).

MATERIALS & METHODS

A novel methodology was employed to fabricate novel formulations of ESA. Molecular biological tools and assays were used to arrive at definite conclusions.

RESULTS

The proinflammatory profile was found to be significantly mitigated in the hypersensitized rats administered with the ESA-NE formulation more emphatically as compared with ESA-conventional emulsion in both in vivo and ex vivo models.

CONCLUSION

The novel ESA-NE formulation shows a lot of palpable promise for clinical applications.

Necrostatin-1 protects C2C12 myotubes from CoCl2-induced hypoxia

Necrostatin-1 (Nec-1) is a selective and potent allosteric inhibitor of necroptosis by specifically inhibiting the activity of receptor-interacting protein (RIP) 1 kinase. The aim of the present study was to determine the effect of Nec-1 on an anoxia model comprising mouse skeletal C2C12 myotubes. In the present study, a hypoxic mimetic reagent, cobalt chloride (CoCl₂), was used to induce hypoxia in C2C12 myotubes. The cytotoxic effects of CoCl₂-induced hypoxia were determined by a Cell Counting kit-8 assay and flow cytometry. Transmission electron microscopy (TEM) was used to characterize the morphological characteristics of dead cells at the ultrastructural level. To clarify the signaling pathways in CoCl₂-mediated cell death, the expression levels of RIP1, RIP3, extracellular signal-regulated kinase (ERK)1/2, hypoxia-inducible factor (HIF)-1α and B cell lymphoma-2 adenovirus E1B 19-kDa interacting protein 3 (BNIP3) were investigated by western blotting. Oxidative stress was determined using 2′,7′-dichlorofluorescin diacetate to measure intracellular reactive oxygen species (ROS) and the fluorescent dye JC-1 was used to measure mitochondrial membrane potential (Δψm). The results showed that the ratios of apoptotic and necrotic C2C12 cells were increased following CoCl₂ treatment, typical necroptotic morphological characteristics were able to observe by TEM, whereas Nec-1 exhibited a protective effect against CoCl₂-induced oxidative stress. Treatment with Nec-1 significantly decreased the levels of RIP1, p-ERK1/2, HIF-1α, BNIP3 and ROS induced by CoCl₂, and promoted C2C12 differentiation. Nec-1 reversed the CoCl₂-induced decrease in mitochondrial membrane potential. Together, these findings suggested that Nec-1 protected C2C12 myotubes under conditions of CoCl₂-induced hypoxia.

Necrostatin-1 enhances the resolution of inflammation by specifically inducing neutrophil apoptosis

Neutrophils play a central role in innate immunity and are rapidly recruited to sites of infection and injury. Neutrophil apoptosis is essential for the successful resolution of inflammation. Necrostatin-1 (Nec-1,methyl-thiohydantoin-tryptophan (MTH-Trp)), is a potent and specific inhibitor of necroptosis[1] (a newly identified type of cell death representing a form of programmed necrosis or regulated non apoptotic cell death) by inhibiting the receptor interacting protein 1(RIP1) kinase. Here we report that Nec-1 specifically induces caspase-dependent neutrophils apoptosis and overrides powerful anti-apoptosis signaling from survival factors such as GM-CSF and LPS. We showed that Nec-1 markedly enhanced the resolution of established neutrophil-dependent inflammation in LPS-induced acute lung injury in mice. We also provided evidence that Nec-1 promoted apoptosis by reducing the expression of the anti-apoptotic protein Mcl-1 and increasing the expression of pro-apoptotic protein Bax. Thus, Nec-1 is not only an inhibitor of necroptosis, but also a promoter of apoptosis, of neutrophils, enhancing the resolution of established inflammation by inducing apoptosis of inflammatory cells. Our results suggest that Nec-1 may have potential roles for the treatment of diseases with increased or persistent inflammatory responses.

Mitochondrial Dynamics as a Therapeutic Target for Treating Cardiac Diseases

Mitochondria are dynamic in nature and are able to shift their morphology between elongated interconnected mitochondrial networks and a fragmented disconnected arrangement by the processes of mitochondrial fusion and fission, respectively. Changes in mitochondrial morphology are regulated by the mitochondrial fusion proteins - mitofusins 1 and 2 (Mfn1 and 2), and optic atrophy 1 (Opa1) as well as the mitochondrial fission proteins - dynamin-related peptide 1 (Drp1) and fission protein 1 (Fis1). Despite having a unique spatial arrangement, cardiac mitochondria have been implicated in a variety of disorders including ischemia-reperfusion injury (IRI), heart failure, diabetes, and pulmonary hypertension. In this chapter, we review the influence of mitochondrial dynamics in these cardiac disorders as well as their potential as therapeutic targets in tackling cardiovascular disease.

Mitochondrial fusion and fission proteins as novel therapeutic targets for treating cardiovascular disease

The past decade has witnessed a number of exciting developments in the field of mitochondrial dynamics - a phenomenon in which changes in mitochondrial shape and movement impact on cellular physiology and pathology. By undergoing fusion and fission, mitochondria are able to change their morphology between elongated interconnected networks and discrete fragmented structures, respectively. The cardiac mitochondria, in particular, have garnered much interest due to their unique spatial arrangement in the adult cardiomyocyte, and the multiple roles they play in cell death and survival. In this article, we review the role of the mitochondrial fusion and fission proteins as novel therapeutic targets for treating cardiovascular disease.

Necrosis-dependent and independent signaling of the RIP kinases in inflammation

It is now widely accepted that some forms of necrosis are controlled by a dedicated signaling pathway triggered by various cell surface and intracellular receptors. This regulated form of necrosis is mediated by the kinase activity of receptor-interacting protein kinase 1 (RIP1/RIPK1) and/or RIP3/RIPK3. A number of studies using the RIP1 kinase inhibitor Necrostatin-1 (Nec-1) and its derivatives, or RIP3-deficient mice demonstrated that RIP1 and RIP3 are involved in various infectious and sterile inflammatory diseases. As a consequence, these specific phenotypes were construed to depend on necrosis. However, emerging evidence indicates that the RIP1 kinase activity and RIP3 can also control apoptosis and inflammatory cytokine production independent of necrosis. Therefore, we may need to re-interpret conclusions drawn based on loss of RIP1 or RIP3 functions in in vivo models. We propose that studies of RIP1 and RIP3 in different inflammatory responses need to consider cell death-dependent and independent mechanisms of the RIP kinases.

Necrostatin-1 attenuates ischemia injury induced cell death in rat tubular cell line NRK-52E through decreased Drp1 expression

Necrostatin-1 (Nec-1) inhibits necroptosis and is usually regarded as having no effect on other cell deaths. Here, this study explored whether the addition of Nec-1 has an effect on cell death induced by simulated ischemia injury in rat tubular cell line NRK-52E. In addition, we also investigated the mechanism of Nec-1 attenuates cell death in this renal ischemia model. The NRK-52E cells were incubated with TNF-α + antimycinA (TA) for 24 h with or without Nec-1. Cell death was observed under fluorescent microscope and quantified by flow cytometry. Cell viabilities were detected by MTT assay. The protein expression of dynamin-related protein 1 (Drp1) was detected by Western blotting and immunofluorescence assay. Increased cell death in simulated ischemia injury of NRK-52E cells were markedly attenuated in the Nec-1 pretreated ischemia injury group. Meanwhile, cell viability was significantly improved after using Nec-1. In addition, we also observed that the protein expression of Drp1, a mediator of mitochondrial fission, was significantly increased in simulated ischemia injury group. Increased Drp1 expression in the ischemia injury group can be abolished by Nec-1 or Drp1-knock down, accompanied with decreased cell death and improved cell viabilities. These results suggest that Nec-1 may inhibit cell death induced by simulated ischemia injury in the rat tubular cell line NRK-52E through decreased Drp1 expression.

ERK plays the baddie (again)

It has been known for many years that elevated signaling by the ERK1/2 pathway is frequently associated with the growth and survival of many tumor cell types under a variety of normal and stressful conditions, including the response of cells to other cancer interventional therapeutic strategies e.g., references 1–4. There is, however, a modest significant literature showing that enhanced ERK1/2 signaling can also cause tumor cell death e.g., references 5–8. The role of ERK1/2 signaling is clearly complex, for example as shown by the Koumenis group where inhibition of radiation-induced ERK1/2 signaling caused radiosensitization, whereas inhibition of curcumin-hyper-stimulated ERK1/2 signaling reduced radiosensitivity. 7 Presumably this Janus-faced behavior of the ERK1/2 pathway in terms of cell survival regulation will depend upon the tumor cell type, the intensity of ERK1/2 stimulation, and the molecular intervention/drug being used.