DNase II mediates a parthanatos-like developmental cell death pathway in Drosophila primordial germ cells

METTL3-dependent m6A modification of SNAP29 induces "autophagy-mitochondrial crisis" in the ischemic microenvironment after soft tissue transplantation

Necrosis at the ischemic distal end of flap transplants increases patients' pain and economic burden. Reactive oxygen species (ROS) and mitochondrial damage are crucial in regulating parthanatos, but the mechanisms linking disrupted macroautophagic/autophagic flux to parthanatos in ischemic flaps remain unclear. The results of western blotting, immunofluorescence staining, and a proteomic analysis revealed that the autophagic protein SNAP29 was deficient in ischemic flaps, resulting in disrupted autophagic flux, increased ROS-induced parthanatos, and aggravated ischemic flap necrosis. The use of AAV vector to restore SNAP29 in vivo mitigated the disruption of autophagic flux and parthanatos. Additionally, quantification of the total m6A level and RIP-qPCR, MeRIP-qPCR, and RNA stability assessments were performed to determine differential Snap29 mRNA m6A methylation levels and mRNA stability in ischemic flaps. Various in vitro and in vivo tests were conducted to verify the ability of METTL3-mediated m6A methylation to promote SNAP29 depletion and disrupt autophagic flux. Finally, we concluded that restoring SNAP29 by inhibiting METTL3 and YTHDF2 reversed the "autophagy-mitochondrial crisis", defined for the first time as disrupted autophagic flux, mitochondrial damage, mitochondrial protein leakage, and the occurrence of parthanatos. The reversal of this crisis ultimately promoted the survival of ischemic flaps.Abbreviations: AAV = adeno-associated virus; ACTA2/α-SMA = actin alpha 2, smooth muscle, aorta; AIFM/AIF = apoptosis-inducing factor, mitochondrion-associated; ALKBH5 = alkB homolog, RNA demythelase; Baf A1 = bafilomycin A1; CQ = chloroquine; DHE = dihydroethidium; ECs = endothelial cells; F-CHP = 5-FAM-conjugated collagen-hybridizing peptide; GO = gene ontology; HUVECs = human umbilical vein endothelial cells; KEGG = Kyoto Encyclopedia of Genes and Genomes; LC-MS/MS = liquid chromatography-tandem mass spectrometry; LDBF = laser doppler blood flow; m6A = N6-methyladenosine; MAP1LC3/LC3 = microtubule-associated protein 1 light chain 3; MeRIP = methylated RNA immunoprecipitation; METTL3 = methyltransferase 3, N6-adenosine-methyltransferase complex catalytic subunit; NAC = N-acetylcysteine; OGD = oxygen glucose deprivation; PAR = poly (ADP-ribose); PARP1 = poly (ADP-ribose) polymerase family, member 1; PECAM1/CD31 = platelet/endothelial cell adhesion molecule 1; ROS = reactive oxygen species; RT-qPCR = reverse transcription quantitative polymerase chain reaction; RIP = RNA immunoprecipitation; SNAP29 = synaptosomal-associated protein 29; SNARE = soluble N-ethylmaleimide-sensitive factor attachment protein receptor; SQSTM1 = sequestosome 1; SRAMP = sequence-based RNA adenosine methylation site predicting; STX17 = syntaxin 17; TMT = tandem mass tag; TUNEL = terminal deoxynucleotidyl transferase dUTP nick end labeling; VAMP8 = vesicle-associated membrane protein 8; WTAP = WT1 associating protein; YTHDF2 = YTH N6-methyladenosine RNA binding protein 2; 3' UTR = 3'-untranslated region.

Origin and establishment of the germline in Drosophila melanogaster

The continuity of a species depends on germ cells. Germ cells are different from all the other cell types of the body (somatic cells) as they are solely destined to develop into gametes (sperm or egg) to create the next generation. In this review, we will touch on 4 areas of embryonic germ cell development in Drosophila melanogaster: the assembly and function of germplasm, which houses the determinants for germ cell specification and fate and the mitochondria of the next generation; the process of pole cell formation, which will give rise to primordial germ cells (PGCs); the specification of pole cells toward the PGC fate; and finally, the migration of PGCs to the somatic gonadal precursors, where they, together with somatic gonadal precursors, form the embryonic testis and ovary.

Micro-interfacial behavior of antibiotic-resistant bacteria and antibiotic resistance genes in the soil environment: A review

Overutilization and misuse of antibiotics in recent decades markedly intensified the rapid proliferation and diffusion of antibiotic resistance genes (ARGs) within the environment, thereby elevating ARGs to the status of a global public health crisis. Recognizing that soil acts as a critical reservoir for ARGs, environmental researchers have made great progress in exploring the sources, distribution, and spread of ARGs in soil. However, the microscopic state and micro-interfacial behavior of ARGs in soil remains inadequately understood. In this study, we reviewed the micro-interfacial behaviors of antibiotic-resistant bacteria (ARB) in soil and porous media, predominantly including migration-deposition, adsorption, and biofilm formation. Meanwhile, adsorption, proliferation, and degradation were identified as the primary micro-interfacial behaviors of ARGs in the soil, with component of soil serving as significant determinant. Our work contributes to the further comprehension of the microstates and processes of ARB and ARGs in the soil environments and offers a theoretical foundation for managing and mitigating the risks associated with ARG contamination.

Transient caspase-mediated activation of caspase-activated DNase causes DNA damage required for phagocytic macrophage differentiation

Phagocytic macrophages are crucial for innate immunity and tissue homeostasis. Most tissue-resident macrophages develop from embryonic precursors that populate every organ before birth to lifelong self-renew. However, the mechanisms for versatile macrophage differentiation remain unknown. Here, we use in vivo genetic and cell biological analysis of the Drosophila larval hematopoietic organ, the lymph gland that produces macrophages. We show that the developmentally regulated transient activation of caspase-activated DNase (CAD)-mediated DNA strand breaks in intermediate progenitors is essential for macrophage differentiation. Insulin receptor-mediated PI3K/Akt signaling regulates the apoptosis signal-regulating kinase 1 (Ask1)/c-Jun kinase (JNK) axis to control sublethal levels of caspase activation, causing DNA strand breaks during macrophage development. Furthermore, caspase activity is also required for embryonic-origin macrophage development and efficient phagocytosis. Our study provides insights into developmental signaling and CAD-mediated DNA strand breaks associated with multifunctional and heterogeneous macrophage differentiation.

Understanding Developmental Cell Death Using Drosophila as a Model System

Cell death plays an essential function in organismal development, wellbeing, and ageing. Many types of cell deaths have been described in the past 30 years. Among these, apoptosis remains the most conserved type of cell death in metazoans and the most common mechanism for deleting unwanted cells. Other types of cell deaths that often play roles in specific contexts or upon pathological insults can be classed under variant forms of cell death and programmed necrosis. Studies in Drosophila have contributed significantly to the understanding and regulation of apoptosis pathways. In addition to this, Drosophila has also served as an essential model to study the genetic basis of autophagy-dependent cell death (ADCD) and other relatively rare types of context-dependent cell deaths. Here, we summarise what is known about apoptosis, ADCD, and other context-specific variant cell death pathways in Drosophila, with a focus on developmental cell death.

Acne Transcriptomics: Fundamentals of Acne Pathogenesis and Isotretinoin Treatment

This review on acne transcriptomics allows for deeper insights into the pathogenesis of acne and isotretinoin's mode of action. Puberty-induced insulin-like growth factor 1 (IGF-1), insulin and androgen signaling activate the kinase AKT and mechanistic target of rapamycin complex 1 (mTORC1). A Western diet (hyperglycemic carbohydrates and milk/dairy products) also co-stimulates AKT/mTORC1 signaling. The AKT-mediated phosphorylation of nuclear FoxO1 and FoxO3 results in their extrusion into the cytoplasm, a critical switch which enhances the transactivation of lipogenic and proinflammatory transcription factors, including androgen receptor (AR), sterol regulatory element-binding transcription factor 1 (SREBF1), peroxisome proliferator-activated receptor γ (PPARγ) and signal transducer and activator of transcription 3 (STAT3), but reduces the FoxO1-dependent expression of GATA binding protein 6 (GATA6), the key transcription factor for infundibular keratinocyte homeostasis. The AKT-mediated phosphorylation of the p53-binding protein MDM2 promotes the degradation of p53. In contrast, isotretinoin enhances the expression of p53, FoxO1 and FoxO3 in the sebaceous glands of acne patients. The overexpression of these proapoptotic transcription factors explains isotretinoin's desirable sebum-suppressive effect via the induction of sebocyte apoptosis and the depletion of BLIMP1(+) sebocyte progenitor cells; it also explains its adverse effects, including teratogenicity (neural crest cell apoptosis), a reduced ovarian reserve (granulosa cell apoptosis), the risk of depression (the apoptosis of hypothalamic neurons), VLDL hyperlipidemia, intracranial hypertension and dry skin.

Cuproptosis: p53-regulated metabolic cell death?

Cuproptosis is a novel type of copper-induced cell death that primarily occurs in cells that utilize oxidative phosphorylation as the main metabolic pathway to produce energy. Copper directly associates with the lipoylated proteins of the tricarboxylic acid cycle, leading to the disulfide-bond-dependent aggregation of these lipoylated proteins, destabilization of the iron-sulfur cluster proteins, and consequent proteotoxic stress. Cancer cells prefer glycolysis (Warburg effect) to oxidative phosphorylation for producing intermediate metabolites and energy, thereby achieving resistance to cuproptosis. Interestingly, the tumor suppressor p53 is a crucial metabolic regulator that inhibits glycolysis and drives a metabolic switch towards oxidative phosphorylation in cancer cells. Additionally, p53 regulates the biogenesis of iron-sulfur clusters and the copper chelator glutathione, which are two critical components of the cuproptotic pathway, suggesting that this tumor suppressor might play a role in cuproptosis. Furthermore, the possible roles of mutant p53 in regulating cuproptosis are discussed. In this essay, we review the recent progress in the understanding of the mechanism underlying cuproptosis, revisit the roles of p53 in metabolic regulation and iron-sulfur cluster and glutathione biosynthesis, and propose several potential mechanisms for wild-type and mutant p53-mediated cuproptosis regulation.

Oxidative DNA Damage-induced PARP-1-mediated Autophagic Flux Disruption Contributes to Bupivacaine-induced Neurotoxicity During Pregnancy

OBJECTIVE

Severe neurologic complications after spinal anesthesia are rare but highly distressing, especially in pregnant women. Bupivacaine is widely used in spinal anesthesia, but its neurotoxic effects have gained attention.

METHODS

Furthermore, the etiology of bupivacaine-mediated neurotoxicity in obstetric patients remains unclear. Female C57BL/6 mice were intrathecally injected with 0.75% bupivacaine on the 18th day of pregnancy. We used immunohistochemistry to examine DNA damage after bupivacaine treatment in pregnant mice and measured γ-H2AX (Ser139) and 8-OHdG in the spinal cord. A PARP-1 inhibitor (PJ34) and autophagy inhibitor (3-MA) were administered with bupivacaine in pregnant mice. Parp-1flox/flox mice were crossed with Nes-Cre transgenic mice to obtain neuronal conditional knockdown mice. Then, LC3B and P62 staining were performed to evaluate autophagic flux in the spinal cords of pregnant wild-type (WT) and Parp-1-/- mice. We performed transmission electron microscopy (TEM) to evaluate autophagosomes.

RESULTS

The present study showed that oxidative stress-mediated DNA damage and neuronal injury were increased after bupivacaine treatment in the spinal cords of pregnant mice. Moreover, PARP-1 was significantly activated, and autophagic flux was disrupted. Further studies revealed that PARP-1 knockdown and autophagy inhibitors could alleviate bupivacaine-mediated neurotoxicity in pregnant mice.

CONCLUSION

Bupivacaine may cause neuronal DNA damage and PARP-1 activation in pregnant mice. PARP-1 further obstructed autophagic flux and ultimately led to neurotoxicity.

Distinct p53 isoforms code for opposing transcriptional outcomes

p53 genes are conserved transcriptional activators that respond to stress. These proteins can also downregulate genes, but the mechanisms are not understood and are generally assumed to be indirect. Here, we investigate synthetic and native cis-regulatory elements in Drosophila to examine opposing features of p53-mediated transcriptional control in vivo. We show that transcriptional repression by p53 operates continuously through canonical DNA binding sites that confer p53-dependent transactivation at earlier developmental stages. p53 transrepression is correlated with local H3K9me3 chromatin marks and occurs without the need for stress or Chk2. In sufficiency tests, two p53 isoforms qualify as transrepressors and a third qualifies as a transcriptional activator. Targeted isoform-specific knockouts dissociate these opposing transcriptional activities, highlighting features that are dispensable for transactivation but critical for repression and for proper germ cell formation. Together, these results demonstrate that certain p53 isoforms function as constitutive tissue-specific repressors, raising important implications for tumor suppression by the human counterpart.

Sensitive-stage embryo irradiation affects embryonic neuroblasts and adult motor function

Background

Cranial radiation therapy for treating childhood malignancies in the central nervous system or accidental radiation exposure may result in neurological side effects in surviving adults. As tissue homeostasis is maintained by stem cells, understanding the effect of radiation on neural stem cells will provide clues for managing the neurological effects. Drosophila embryos were used as a model system whose sensitivity to irradiation-induced cell death changes from the sensitive to resistant stage during development.

Objective

Drosophila embryos at the radiation-sensitive stage were irradiated at various doses and the radiation sensitivity was tested regarding the appearance of apoptotic cells in the embryos and the embryonic lethality. Cell fates of the neural stem cells called neuroblasts (NBs) and adult motor function after irradiation were also investigated.

Result

Irradiation of Drosophila embryos at the radiation-sensitive stage resulted in a dose-dependent increase in the number of embryos containing apoptotic cells 75 min after treatment starting at 3 Gy. Embryonic lethality assayed by hatch rate was induced by 1 Gy irradiation, which did not induce cell death. Notably, no apoptosis was detected in NBs up to 2 h after irradiation at doses as high as 40 Gy. At 3 h after irradiation, as low as 3 Gy, the number of NBs marked by Dpn and Klu was decreased by an unidentified mechanism regardless of the cell death status of the embryo. Furthermore, embryonic irradiation at 3 Gy, but not 1 Gy, resulted in locomotor defects in surviving adults.

Conclusion

Embryonic NBs survived irradiation at doses as high as 40 Gy, while cells in other parts of the embryos underwent apoptosis at doses higher than 3 Gy within 2 h after treatment. Three hours after exposure to a minimum dose of 3 Gy, the number of NBs marked by Dpn and Klu decreased, and the surviving adults exhibited defects in locomotor ability.

Nod-like Receptors: Critical Intracellular Sensors for Host Protection and Cell Death in Microbial and Parasitic Infections

Cell death is an essential immunological apparatus of host defense, but dysregulation of mutually inclusive cell deaths poses severe threats during microbial and parasitic infections leading to deleterious consequences in the pathological progression of infectious diseases. Nucleotide-binding oligomerization domain (NOD)-Leucine-rich repeats (LRR)-containing receptors (NLRs), also called nucleotide-binding oligomerization (NOD)-like receptors (NLRs), are major cytosolic pattern recognition receptors (PRRs), their involvement in the orchestration of innate immunity and host defense against bacteria, viruses, fungi and parasites, often results in the cleavage of gasdermin and the release of IL-1β and IL-18, should be tightly regulated. NLRs are functionally diverse and tissue-specific PRRs expressed by both immune and non-immune cells. Beyond the inflammasome activation, NLRs are also involved in NF-κB and MAPK activation signaling, the regulation of type I IFN (IFN-I) production and the inflammatory cell death during microbial infections. Recent advancements of NLRs biology revealed its possible interplay with pyroptotic cell death and inflammatory mediators, such as caspase 1, caspase 11, IFN-I and GSDMD. This review provides the most updated information that caspase 8 skews the NLRP3 inflammasome activation in PANoptosis during pathogen infection. We also update multidimensional roles of NLRP12 in regulating innate immunity in a content-dependent manner: novel interference of NLRP12 on TLRs and NOD derived-signaling cascade, and the recently unveiled regulatory property of NLRP12 in production of type I IFN. Future prospects of exploring NLRs in controlling cell death during parasitic and microbial infection were highlighted.

Impact of Parthanatos on the Increased Risk of Onset and Mortality in Male Patients With Pulmonary Hypertension

There have been no studies as to whether parthanatos, a poly (adenosine diphosphate-ribose) polymerase-1 (PARP-1)-dependent and apoptosis-inducing factor (AIF)-mediated caspase-independent programmed cell death, is present in pulmonary hypertension (PH). Basic studies have, however, been conducted on several of the key molecules in parthanatos, such as PARP-1, AIF, and macrophage migration inhibitory factor (MIF). For this study, we collected blood samples from 88 incident male patients with PH and 50 healthy controls at the Shanghai Pulmonary Hospital. We measured the key factors of parthanatos (PARP-1, PAR, AIF, and MIF) by enzyme-linked immunosorbent assay and performed a logistic regression, Cox proportional hazards analysis, and Kaplan-Meier test to assess the prognostic value of the key molecules in diagnosing and predicting survival. The patients who ultimately died had a significantly poorer clinical status during the study than those who survived. The PARP-1, PAR, AIF, and MIF levels were significantly higher in the patients than in the controls (all p < .0001), and the PARP-1, PAR, and AIF levels were higher in the nonsurvivors than in the survivors (all p < .0001). PARP-1 and AIF levels served as independent predictors of disease onset and mortality in these patients (all p < .005). Patients with PARP-1 levels <11.24 ng/mL or AIF levels <1.459 pg/mL had significantly better survival than those with higher PARP-1 or AIF levels (p < .0001). Circulating levels of PARP-1 and AIF were independent predictors for PH onset and mortality, which indicated that parthanatos might be associated with the pathogenesis of PH.