Grand challenges in cell death and survival: apoptosis vs. necroptosis

Necroptosis Blockade Potentiates the Neuroprotective Effect of Hypothermia in Neonatal Hypoxic-Ischemic Encephalopathy

Neonatal encephalopathy (NE) caused by hypoxia-ischemia (HI) affects around 1 per 1000 term newborns and is the leading cause of acquired brain injury and neurodisability. Despite the use of hypothermia (HT) as a standard of care, the incidence of NE and its devastating outcomes remains a major issue. Ongoing research surrounding add-on neuroprotective strategies against NE is important as HT effects are limited, leaving 50% of treated patients with neurological sequelae. Little is known about the interaction between necroptotic blockade and HT in neonatal HI. Using a preclinical Lewis rat model of term human NE induced by HI, we showed a neuroprotective effect of Necrostatin-1 (Nec-1: a compound blocking necroptosis) in combination with HT. The beneficial effect of Nec-1 added to HT against NE injuries was observed at the mechanistic level on both pMLKL and TNF-α, and at the anatomical level on brain volume loss visualized by magnetic resonance imaging (MRI). HT alone showed no effect on activated necroptotic effectors and did not preserve the brain MRI volume. This study opens new avenues of research to understand better the specific cell death mechanisms of brain injuries as well as the potential use of new therapeutics targeting the necroptosis pathway.

Necroptosis: A Pathogenic Negotiator in Human Diseases

Over the past few decades, mechanisms of programmed cell death have attracted the scientific community because they are involved in diverse human diseases. Initially, apoptosis was considered as a crucial mechanistic pathway for programmed cell death; recently, an alternative regulated mode of cell death was identified, mimicking the features of both apoptosis and necrosis. Several lines of evidence have revealed that dysregulation of necroptosis leads to pathological diseases such as cancer, cardiovascular, lung, renal, hepatic, neurodegenerative, and inflammatory diseases. Regulated forms of necrosis are executed by death receptor ligands through the activation of receptor-interacting protein kinase (RIPK)-1/3 and mixed-lineage kinase domain-like (MLKL), resulting in the formation of a necrosome complex. Many papers based on genetic and pharmacological studies have shown that RIPKs and MLKL are the key regulatory effectors during the progression of multiple pathological diseases. This review focused on illuminating the mechanisms underlying necroptosis, the functions of necroptosis-associated proteins, and their influences on disease progression. We also discuss numerous natural and chemical compounds and novel targeted therapies that elicit beneficial roles of necroptotic cell death in malignant cells to bypass apoptosis and drug resistance and to provide suggestions for further research in this field.

Molecular Events Involved in Influenza A Virus-Induced Cell Death

Viral infection usually leads to cell death. Moderate cell death is a protective innate immune response. By contrast, excessive, uncontrolled cell death causes tissue destruction, cytokine storm, or even host death. Thus, the struggle between the host and virus determines whether the host survives. Influenza A virus (IAV) infection in humans can lead to unbridled hyper-inflammatory reactions and cause serious illnesses and even death. A full understanding of the molecular mechanisms and regulatory networks through which IAVs induce cell death could facilitate the development of more effective antiviral treatments. In this review, we discuss current progress in research on cell death induced by IAV infection and evaluate the role of cell death in IAV replication and disease prognosis.

Natural Products as Inducers of Non-Canonical Cell Death: A Weapon against Cancer

Simple Summary

Anticancer therapeutic approaches based solely on apoptosis induction are often unsuccessful due to the activation of resistance mechanisms. The identification and characterization of compounds capable of triggering non-apoptotic, also called non-canonical cell death pathways, could represent an important strategy that may integrate or offer alternative approaches to the current anticancer therapies. In this review, we critically discuss the promotion of ferroptosis, necroptosis, and pyroptosis by natural compounds as a new anticancer strategy.

Abstract

Apoptosis has been considered the main mechanism induced by cancer chemotherapeutic drugs for a long time. This paradigm is currently evolving and changing, as increasing evidence pointed out that antitumor agents could trigger various non-canonical or non-apoptotic cell death types. A considerable number of antitumor drugs derive from natural sources, both in their naturally occurring form or as synthetic derivatives. Therefore, it is not surprising that several natural compounds have been explored for their ability to induce non-canonical cell death. The aim of this review is to highlight the potential antitumor effects of natural products as ferroptosis, necroptosis, or pyroptosis inducers. Natural products have proven to be promising non-canonical cell death inducers, capable of overcoming cancer cells resistance to apoptosis. However, as discussed in this review, they often lack a full characterization of their antitumor activity together with an in-depth investigation of their toxicological profile.

TRIP13 predicts poor prognosis in clear cell renal cell carcinoma

What is the leading molecular mechanism that causes broad resistance to systemic therapies remains a key question in renal cancer related research. We explored associations of TRIP13 expression with the clinical course using the tissue microarray (TMA). The TMA contained specimens from 87 patients diagnosed with clear cell renal cell carcinoma (ccRCC). We performed immunohistochemistry to investigate TRIP13 protein expression levels. The overall survival (OS) was analyzed using the Kaplan-Meier method and log-rank statistics. Univariate and multivariate analyses were conducted using Cox proportional hazard models. Median follow up for the TMA cohort was 7.0 years. Tissues from 28.74% of patients demonstrated high TRIP13 expression. Mean TRIP13 expression in TRIP13-rich tumors was significantly higher comparing to adjacent normal tissues (P < 0.05). TRIP13 expression did not significantly correlate with stage nor tumor grade (P > 0.05). Elevated expression of TRIP13 served as an independent unfavorable prognostic indicator of survival in ccRCC (P < 0.05). TRIP13 overexpression predicts poor prognosis in ccRCC. Together with the emerging reports, this observation raises a suspicion that TRIP13 is a substantial driver of resistance to systemic therapies against kidney cancer.

Application of the buccal micronucleus cytome assay on child population exposed to sinus X-ray

PURPOSE

Diagnostic X-ray examinations of paranasal sinuses use a low-dose ionizing radiation to achieve medically indicated purposes. The effects of low-dose radiation are still controversial, making it a highly prioritized field of research. As there is a need to evaluate the effects of low-dose ionizing radiation and that children might be a more vulnerable population, we performed simultaneous physical dosimetry and buccal cell micronucleus cytome assay on pediatric patients before and after an X-ray examination of the sinuses.

METHODS

The study comprised 20 subjects aged 11.9 ± 3.6 years, and BMI < 25 kg/m². Physical dosimetry was performed using radiophotoluminiscent (RPL) glass dosimeters placed on four positions on the head. The buccal cell micronucleus cytome assay was performed before and 14 ± 1 days after the X-ray exam, to monitor DNA damaging, replicative, cytostatic, and cell death effects.

RESULTS

The doses in the primary beam ranged 371-1106 μGy and were several fold higher than at the other positions on the head. As for biological changes, we did not observe any DNA damaging effects. However, a significant increase in cells with condensed chromatin was observed, indicating more cells undergoing early stages of apoptosis. We also observed inter-individual differences between the subjects. A correlation between the doses detected and biological effects was not observed.

CONCLUSION

Although we did not observe significant increase in DNA damage, further studies are needed to increase the statistical power of the results and ensure patients' safety and optimal health care.

A multifunctional magnetic nanosystem based on "two strikes" effect for synergistic anticancer therapy in triple-negative breast cancer

Multifunctional magnetic nanoparticles (MNPs) were widely used for ablation of cancer cells because of their potential on physical treatment. Herein, we developed the "cell targeting destructive" multifunctional polymeric nanoparticles (named as HA-Olb-PPMNPs) based on PEI-PLGA co-loaded with the anticancer drug Olaparib (Olb) and superparamagnetic iron oxide nanoparticles (Fe₃O₄ NPs), and further coated with a low molecular weight hyaluronic acid (HA) on its surface. Due to the high affinity between HA and CD44-receptor on cell surface of triple negative breast cancer (TNBC), an active targeting can be achieved. Under a rotating magnetic field (RMF), HA-Olb-PPMNPs produced a physical transfer of mechanical force by incomplete rotation. This mechanical force could cause the "two strikes" effect on the cells, in which "First-strike" was to damage the cell membrane structure (magneto-cell-lysis), another "Second-strike" could activate the lysosome-mitochondrial pathway by injuring lysosomes to induce cell apoptosis (magneto-cell-apoptosis). Therefore, the mechanical force and Olb exert dual anti-tumor effect to achieve synergistic therapeutic in the presence of RMF. This study proposes a novel multi-therapeutic concept for TNBC, as well as provided evidences of new anti-tumor therapeutic effects induced by the magnetic nanoparticles drug system.

Role of cholinergic agents in proliferation and caspase activity of hemin-induced erythroid differentiated K562 cells

Background: Muscarinic receptors have many functions in the cells and tissues. Acetylcholine (ACh) plays an important role in cellular physiology. ACh also acts at the different parts of the central nervous system and nonneuronal cells. Cholinergic receptors also have different functions in many cell types and tissues. Caspases (cysteine aspartic proteases and cysteine aspartases) are cysteine dependent aspartate-specific proteases. They are an important role in necrosis and cell death and inflammation signaling pathways. They are also the primary mediators of apoptosis. During apoptosis, different caspase types participate in different functions. We have previously shown that carbachol (CCh) inhibits K562 cell proliferation. This study was performed to investigate the anti-tumor efficacy of cholinergic drugs in hemin-induced erythroid differentiated K562 cells. The aim of this study was to address the mechanism of cholinergic drugs on hemin-induced erythroid differentiated K562 cell proliferation and caspase activities. We detected M₃ muscarinic receptor expression in erythroid differentiated K562 cell line.Methods: K562 cells were differentiated with hemin (50 μM). The expression of the M₃ muscarinic receptor was detected by the western blotting technique. Erythroid differentiated K562 cells treated with CCh (100 μM). After 24 and 48 h, cells were counted by BrdU cell proliferation kit. Caspase 3,8, and 9 activities were measured by enzyme-linked immunosorbent assay (ELISA) kits according to the manufacturer's instructions.Results: Erythroid differentiated K562 cell proliferation was not significantly increased after CCh treatment. In the meantime, caspases 8 and 9 activities in erythroid differentiated K562 cell line was significantly higher than undifferentiated K562 cells (p < .05).

RIP1/RIP3-regulated necroptosis as a target for multifaceted disease therapy (Review)

Necroptosis is a type of programmed cell death with necrotic morphology, occurring in a variety of biological processes, including inflammation, immune response, embryonic development and metabolic abnormalities. The current nomenclature defines necroptosis as cell death mediated by signal transduction from receptor‑interacting serine/threonine kinase (RIP) 1 to RIP3 (hereafter called RIP1/RIP3). However, RIP3‑dependent cell death would be a more precise definition of necroptosis. RIP3 is indispensable for necroptosis, while RIP1 is not consistently involved in the signal transduction. Notably, deletion of RIP1 even promotes RIP3‑mediated necroptosis under certain conditions. Necroptosis was previously thought as an alternate process of cell death in case of apoptosis inhibition. Currently, necroptosis is recognized to serve a pivotal role in regulating various physiological processes. Of note, it mediates a variety of human diseases, such as ischemic brain injury, immune system disorders and cancer. Targeting and inhibiting necroptosis, therefore, has the potential to be used for therapeutic purposes. To date, research has elucidated the suppression of RIP1/RIP3 via effective inhibitors and highlighted their potential application in disease therapy. The present review focused on the molecular mechanisms of RIP1/RIP3‑mediated necroptosis, explored the functions of RIP1/RIP3 in necroptosis, discussed their potential as a novel therapeutic target for disease therapy, and provided valuable suggestions for further study in this field.

Necroptotic Cell Death Promotes Adaptive Immunity Against Colonizing Pneumococci

Pore-forming toxin (PFT) induced necroptosis exacerbates pulmonary injury during bacterial pneumonia. However, its role during asymptomatic nasopharyngeal colonization and toward the development of protective immunity was unknown. Using a mouse model of Streptococcus pneumoniae (Spn) asymptomatic colonization, we determined that nasopharyngeal epithelial cells (nEC) died of pneumolysin (Ply)-dependent necroptosis. Mice deficient in MLKL, the necroptosis effector, or challenged with Ply-deficient Spn showed less nEC sloughing, increased neutrophil infiltration, and altered IL-1α, IL-33, CXCL2, IL-17, and IL-6 levels in nasal lavage fluid (NALF). Activated MLKL correlated with increased presence of CD11c⁺ antigen presenting cells in Spn-associated submucosa. Colonized MLKL KO mice and wildtype mice colonized with Ply-deficient Spn produced less antibody against the bacterial surface protein PspA, were delayed in bacterial clearance, and were more susceptible to a lethal secondary Spn challenge. We conclude that PFT-induced necroptosis is instrumental in the natural development of protective immunity against opportunistic PFT-producing bacterial pathogens.

Cytokinesis-block micronucleus cytome assay parameters in peripheral blood lymphocytes of the general population: Contribution of age, sex, seasonal variations and lifestyle factors

The cytokinesis-block micronucleus cytome (CBMN Cyt) assay was used to evaluate the baseline frequency of cytogenetic damage in peripheral blood lymphocytes of the general population (average age, 38.28 ± 12.83 years) in relation to age, sex, body mass index, seasonal variations (season of sampling, period of sampling and different meteorological parameters) and lifestyle factors (smoking habit, alcohol consumption, exposure to medications and diagnostic radiation, physical activity, and family history of cancer). The background frequency of micronuclei (MNi) for the 200 subjects assayed was 5.06 ± 3.11 per 1000 binucleated cells, while the mean frequency of nucleoplasmic bridges (NPBs) was 1.21 ± 1.46 and of nuclear buds (NBUDs) 3.48 ± 2.14. The background frequency of apoptosis and necrosis was 1.58 ± 1.50 and 1.39 ± 1.56, respectively, while the mean nuclear division index (NDI) was 1.99 ± 0.14. The cut-off value, which corresponds to the 95th percentile of the distribution of 200 individual values, was 11 MNi, 4 NPBs and 7 NBUDs. The study also confirmed an association of the above mentioned parameters with age, sex and several lifestyle factors. Moreover, significant confounders based on our results are also sampling season, sampling period and different meteorological parameters that were dependent on the CBMN Cyt assay parameters. In line with the above mentioned, several factors should be taken into account when it comes to the monitoring of exposed populations using cytogenetic biomarkers. Moreover, the normal and cut-off values obtained in this study present background data for the general population, and can later serve as baseline values for further biomonitoring studies.

Targeting activator protein 1 signaling pathway by bioactive natural agents: Possible therapeutic strategy for cancer prevention and intervention

Activator protein 1 (AP-1) is a key transcription factor in the control of several cellular processes responsible for cell survival proliferation and differentiation. Dysfunctional AP-1 expression and activity are involved in several severe diseases, especially inflammatory disorders and cancer. Therefore, targeting AP-1 has recently emerged as an attractive therapeutic strategy for cancer prevention and therapy. This review summarizes our current understanding of AP-1 biology and function as well as explores and discusses several natural bioactive compounds modulating AP-1-associated signaling pathways for cancer prevention and intervention. Current limitations, challenges, and future directions of research are also critically discussed.

North African Medicinal Plants Traditionally Used in Cancer Therapy

Background: Cancer is a major cause of mortality worldwide with increasing numbers by the years. In North Africa, the number of cancer patients is alarming. Also shocking is that a huge number of cancer patients only have access to traditional medicines due to several factors, e.g., economic difficulties. In fact, medicinal plants are widely used for the treatment of several pathologies, including cancer. Truthfully, herbalists and botanists in North African countries prescribe several plants for cancer treatment. Despite the popularity and the potential of medicinal plants for the treatment of cancer, scientific evidence on their anticancer effects are still scarce for most of the described plants.

Objective: Bearing in mind the lack of comprehensive and systematic studies, the aim of this review is to give an overview of studies, namely ethnobotanical surveys and experimental evidence of anticancer effects regarding medicinal plants used in North Africa for cancer therapy.

Method: The research was conducted on several popular search engines including PubMed, Science Direct, Scopus and Web of Science. The research focused primarily on English written papers published between the years 2000 and 2016.

Results: This review on plants traditionally used by herbalists in North Africa highlights that Morocco and Algeria are the countries with most surveys on the use of medicinal plants in folk medicine. Among the plethora of plants used, Nigella sativa and Trigonella foenum-graecum are the most referred ones by herbalists for the treatment of cancer. Moreover, a plethora of scientific evidence qualifies them as candidates for further drug development. Furthermore, we report on the underlying cellular and molecular mechanisms.

Conclusion: Overall, this review highlights the therapeutic potential of some medicinal plants as anticancer agents. The North African flora offers a rich source of medicinal plants for a wide array of diseases, including cancer. The elucidation of their modes of action represents an indispensable condition for the rational development of new drugs for cancer treatment. Furthermore, testing the anticancer activity in vivo and in clinical trials are warranted to explore the full therapeutic potential of North African plants for cancer therapy.

Prevention of Cyclophilin D-Mediated mPTP Opening Using Cyclosporine-A Alleviates the Elevation of Necroptosis, Autophagy and Apoptosis-Related Markers Following Global Cerebral Ischemia-Reperfusion

The mitochondrial permeability transition pore (mPTP) is a complex channel of the inner membrane, the opening of which leads to mitochondrial swelling and dissipation of mitochondrial membrane potential (MMP). Here, we aimed to evaluate the role of the cyclophilin D (CypD) as a prominent mediator of mPTP, on necroptosis and autophagy as well as apoptosis, beyond the global cerebral ischemia-reperfusion (I/R) injury. We showed that while cerebral I/R injury is accompanied by loss of MMP, mitochondrial swelling and programmed cell death, pretreatment with cyclosporine-A (CsA) as a potent inhibitor of CypD, led to partial but significant reduction in necroptosis markers, RIP1 and RIP3 as well as activity of glutamate-ammonia ligase (GLUL) and glutamate dehydrogenase 1 (GLUD1), downstream enzymes of RIP3. Administration of CsA also partially decreased autophagy associated proteins. Furthermore, we demonstrated that Bax/Bcl-2 ratio as well as caspase-3 activation, as the executioner of apoptosis, noticeably decreased by CsA pretreatment. Taken together, our results suggest that the CypD alongside the apoptosis regulation plays a partial role in inducing necroptosis and autophagy.

Discovery of piperlongumine as a potential novel lead for the development of senolytic agents

Accumulating evidence indicates that senescent cells play an important role in many age-associated diseases. The pharmacological depletion of senescent cells (SCs) with a "senolytic agent", a small molecule that selectively kills SCs, is a potential novel therapeutic approach for these diseases. Recently, we discovered ABT-263, a potent and highly selective senolytic agent, by screening a library of rationally-selected compounds. With this screening approach, we also identified a second senolytic agent called piperlongumine (PL). PL is a natural product that is reported to have many pharmacological effects, including anti-tumor activity. We show here that PL preferentially killed senescent human WI-38 fibroblasts when senescence was induced by ionizing radiation, replicative exhaustion, or ectopic expression of the oncogene Ras. PL killed SCs by inducing apoptosis, and this process did not require the induction of reactive oxygen species. In addition, we found that PL synergistically killed SCs in combination with ABT-263, and initial structural modifications to PL identified analogs with improved potency and/or selectivity in inducing SC death. Overall, our studies demonstrate that PL is a novel lead for developing senolytic agents.

HMGB1 Enhances Drug Resistance and Promotes In Vivo Tumor Growth of Lung Cancer Cells

Drug resistance is an obstacle in the chemotherapeutic treatment of lung cancers. In the present study, the effects of high-mobility group box 1 (HMGB1) protein in chemotherapeutic resistance and the relationships between HMGB1 and chemotherapy drug-induced cell apoptosis or necrosis were clarified. We used cisplatin-sensitive A549 cells and cisplatin-resistant A549/DDP cells as cell models with IC50 of 11.58 and 46.95 μM, respectively. A549/DDP had higher level of HMGB1 compared with A549 cells. Interestingly, with the increasing concentration of DDP, HMGB1 was gradually located into cytoplasm in cisplatin-sensitive A549 cells. Moreover, interference with endogenous HMGB1 sensitized the effects of chemotherapeutic drugs, including 5-Fu, DDP, and OXA. Furthermore, results from an in vivo tumorigenesis experiment demonstrated that serum concentration of HMGB1 was much lower in the group inoculated with HMGB1 shRNA-transfected A549 cells than in the N.C. shRNA-transfected A549 inoculated group, as well as the tumor volume, suggesting that serum HMGB1 contributed to tumor growth in a mouse model. In conclusion, higher levels of HMGB1 probably contributed to chemotherapy drug resistance, and higher serum concentration of HMGB1 promoted in vivo tumor growth. The study would provide new clues to overcome drug resistance in chemotherapy of human lung cancers.

The Natural Polyphenol Epigallocatechin Gallate Protects Intervertebral Disc Cells from Oxidative Stress

Oxidative stress-related phenotypic changes and a decline in the number of viable cells are crucial contributors to intervertebral disc degeneration. The polyphenol epigallocatechin 3-gallate (EGCG) can interfere with painful disc degeneration by reducing inflammation, catabolism, and pain. In this study, we hypothesized that EGCG furthermore protects against senescence and/or cell death, induced by oxidative stress. Sublethal and lethal oxidative stress were induced in primary human intervertebral disc cells with H₂O₂ (total n = 36). Under sublethal conditions, the effects of EGCG on p53-p21 activation, proliferative capacity, and accumulation of senescence-associated β-galactosidase were tested. Further, the effects of EGCG on mitochondria depolarization and cell viability were analyzed in lethal oxidative stress. The inhibitor LY249002 was applied to investigate the PI3K/Akt pathway. EGCG inhibited accumulation of senescence-associated β-galactosidase but did not affect the loss of proliferative capacity, suggesting that EGCG did not fully neutralize exogenous radicals. Furthermore, EGCG increased the survival of IVD cells in lethal oxidative stress via activation of prosurvival PI3K/Akt and protection of mitochondria. We demonstrated that EGCG not only inhibits inflammation but also can enhance the survival of disc cells in oxidative stress, which makes it a suitable candidate for the development of novel therapies targeting disc degeneration.

5-Aminolevulinic Acid-Mediated Sonodynamic Therapy Inhibits RIPK1/RIPK3-Dependent Necroptosis in THP-1-Derived Foam Cells

Necroptosis, or programmed necrosis, contributes to the formation of necrotic cores in atherosclerotic plaque in animal models. However, whether inhibition of necroptosis ameliorates atherosclerosis is largely unknown. In this study, we demonstrated that necroptosis occurred in clinical atherosclerotic samples, suggesting that it may also play an important role in human atherosclerosis. We established an in vitro necroptotic model in which necroptosis was induced in THP-1-derived foam cells by serum deprivation. With this model, we demonstrated that 5-aminolevulinic acid-mediated sonodynamic therapy (ALA-SDT) inhibited necroptosis while promoting apoptosis. ALA-SDT activated the caspase-3 and caspase-8 pathways in foam cells, which is responsible for the switch from necroptosis to apoptosis. The inhibition of either caspase-8 or caspase-3 abolished the anti-necroptotic effect of ALA-SDT. In addition, we found that caspase-3 activation peaked 4 hours after ALA-SDT treatment, 2 hours earlier than maximal caspase-8activation. Taken together, our data indicate that ALA-SDT mediates the switch from necroptosis to apoptosis by activating the caspase-3 and caspase-8 pathways and may improve the prognosis of atherosclerosis.

Potential of apoptotic pathway-targeted cancer therapeutic research: Where do we stand?

Underneath the intricacy of every cancer lies mysterious events that impel the tumour cell and its posterity into abnormal growth and tissue invasion. Oncogenic mutations disturb the regulatory circuits responsible for the governance of versatile cellular functions, permitting tumour cells to endure deregulated proliferation, resist to proapoptotic insults, invade and erode normal tissues and above all escape apoptosis. This disruption of apoptosis has been highly implicated in various malignancies and has been exploited as an anticancer strategy. Owing to the fact that apoptosis causes minimal inflammation and damage to the tissue, apoptotic cell death-based therapy has been the centre of attraction for the development of anticancer drugs. Increased understanding of the molecular pathways underlying apoptosis has enabled scientists to establish unique approaches targeting apoptosis pathways in cancer therapeutics. In this review, we reconnoitre the two major pathways (intrinsic and extrinsic) targeted cancer therapeutics, steering toward chief modulators of these pathways, such as B-cell lymphoma 2 protein family members (pro- and antiapoptotic), inhibitor of apoptosis proteins, and the foremost thespian of extrinsic pathway regulator, tumour necrosis factor-related apoptosis-inducing agent. Together, we also will have a look from clinical perspective to address the agents (drugs) and therapeutic strategies adopted to target these specific proteins/pathways that have entered clinical trials.

Inhibition of mTOR Pathway by Rapamycin Reduces Brain Damage in Rats Subjected to Transient Forebrain Ischemia

The aims of this study are to clarify the role of mTOR in mediating cerebral ischemic brain damage and the effects of rapamycin on ischemic outcomes. Ten minutes of forebrain ischemia was induced in rats, and their brains were sampled after 3 h, 16 h, and 7 days reperfusion for histology, immunohistochemistry and biochemical analysis. Our data demonstrated that cerebral ischemia resulted in both apoptotic and necrotic neuronal death; cerebral ischemia and reperfusion led to significant increases of mRNA and protein levels of p-mTOR and its downstream p-P70S6K and p-S6; elevation of LC3-II, and release of cytochrome c into the cytoplasm in both the cortex and hippocampus. Inhibition of mTOR by rapamycin markedly reduced ischemia-induced damage; suppressed p-Akt, p-mTOR, p-P70S6K and p-S6 protein levels; decreased LC3-II and Beclin-1; and prevented cytochrome c release in the two structures. All together, these data provide evidence that cerebral ischemia activates mTOR and autophagy pathways. Inhibition of mTOR deactivates the mTOR pathway, suppresses autophagy, prevents cytochrome c release and reduces ischemic brain damage.

Aptamer-Dendrimer Bioconjugates for Targeted Delivery of miR-34a Expressing Plasmid and Antitumor Effects in Non-Small Cell Lung Cancer Cells

Metastasis and drug resistance are major barriers for the treatment of non-small cell lung cancer (NSCLC). To explore new therapeutic options, we successfully encapsulated MicroRNA-34a (miR-34a), a potent endogenous tumor suppressor in NSCLC into S6 aptamer-conjugated dendrimer to form lung cancer-targeted gene delivery nanoparticles (PAM-Ap/pMiR-34a NPs). PAM-Ap/pMiR-34a NPs had a diameter of 100-200 nm and Zeta potential of ~30 mV at applied N/P ratio. The aptamer conjugation significantly improved cellular uptake as well as gene transfection efficiency of PAM-Ap/pMiR-34a NPs in cultured NSCLC cells. We showed that PAM-Ap/pMiR-34a NPs enhanced the regulation of targeted genes, BCL-2 and p53 in vitro. In addition, we revealed PAM-Ap/pMiR-34a NPs significantly inhibited cell growth, migration, invasion and induced apoptosis of lung cancer cells compared with non-targeted NPs. The method provided a novel therapeutic strategy for the experimental treatment of NSCLC.

A novel function of RIP1 in postnatal development and immune homeostasis by protecting against RIP3-dependent necroptosis and FADD-mediated apoptosis

RIP1 is an adaptor kinase originally identified as being able to associate with TNFR1 and Fas, and is later shown to be involved in signaling induced by TLRs. Major signaling pathways regulated by RIP1 include necroptosis, apoptosis, and pro-survival/inflammation NF-κB activation. Previous studies show that RIP1 deficiency has no effect on mouse embryogenesis, but blocks postnatal development. This phenotype could not readily be explained, since mice lacking TNFR1, Fas, or TLRs show no apparent developmental defect. Certain types of RIP1-deficient cells are hypersensitive to TNF-induced apoptosis. However, in our previous study, deletion of the apoptotic adaptor protein, FADD, provides marginal improvement of postnatal development of rip1^−/− mice. Remarkably, the current data shows that haploid insufficiency of RIP3, a known mediator of necroptosis, allowed survival of rip1^−/−fadd^−/− mice beyond weaning age, although the resulting rip1^−/−fadd^−/− rip3^+/− mice were significant smaller in size and weight. Moreover, complete absence of RIP3 further improved postnatal development of the resulting rip1^−/−fadd^−/−rip3^−/− mice, which display normal size and weight. In such triple knockout (TKO) mice, lymphocytes underwent normal development, but progressively accumulated as mice age. This lymphoproliferative (lpr) disease in TKO mice is, however, less severe than that of fadd^−/−rip3^−/− double knockout mice. In total, the data show that the postnatal developmental defect in rip1^−/− mice is due in part to FADD-mediated apoptosis as well as RIP3-dependent necroptosis. Moreover, the function of RIP1 contributes to development of lpr diseases.