Apoptosis-inducing factor (Aif1) mediates anacardic acid-induced apoptosis in Saccharomyces cerevisiae

Lipopeptides from Bacillus velezensis induced apoptosis-like cell death in the pathogenic fungus Fusarium concentricum

AIMS

Stem rot caused by Fusarium concentricum is a new disease of Paris polyphylla reported by our research group. The present study investigates the growth inhibitory and apoptotic effects of Bacillus velezensis FJAT-54560 lipopeptide against F. concentricum.

METHODS AND RESULTS

HPLC preparation and LC-MS analysis results show that the crude lipopeptides secreted by Bacillus velezensis FJAT-54560 isolated from Jasminum sambac consist of C14-17 iturin A, C14 fengycin B, C16 fengycin A/A2, C18 fengycin A, C20 fengycin B2, C21 fengycin A2, C22-23 fengycin A, C12-16 surfactin A, and C15 surfactin A derivatives. The mass ratios (g/g) of iturin, fengycin, and surfactin in lipopeptides are 2.40, 67.51, and 30.08%, respectively. Through inhibition zone and inhibition rate experiments, we found that crude lipopeptides and purified fengycin exhibit strong antifungal activity against F. concentricum, including accumulation of reactive oxygen species, loss of mitochondrial membrane potential, DNA fragmentation, Ca2+ accumulation, chromatin condensation, and phosphatidylserine externalization. Transcriptomic analysis indicates that crude lipopeptide-induced apoptosis in F. concentricum cells may be mediated by apoptosis-inducing factors and apoptosis mediators and can serve as a metacaspase-independent model.

CONCLUSION

Lipopeptides from Bacillus velezensis FJAT-54560 can control the pathogenic fungus F. concentricum by inducing apoptosis.

Isobavachalcone exhibits antifungal and antibiofilm effects against C. albicans by disrupting cell wall/membrane integrity and inducing apoptosis and autophagy

Isobavachalcone (IBC) is a natural flavonoid with multiple pharmacological properties. This study aimed to evaluate the efficacy of IBC against planktonic growth and biofilms of Candida albicans (C. albicans) and the mechanisms underlying its antifungal action. The cell membrane integrity, cell metabolic viability, and cell morphology of C. albicans treated with IBC were evaluated using CLSM and FESEM analyses. Crystal violet staining, CLSM, and FESEM were used to assess the inhibition of biofilm formation, as well as dispersal and killing effects of IBC on mature biofilms. RNA-seq combined with apoptosis and autophagy assays was used to examine the mechanisms underlying the antifungal action of IBC. IBC exhibited excellent antifungal activity with 8 μg/mL of MIC for C. albicans. IBC disrupted the cell membrane integrity, and inhibited biofilm formation. IBC dispersed mature biofilms and damaged biofilm cells of C. albicans at 32 μg/mL. Moreover, IBC induced apoptosis and autophagy-associated cell death of C. albicans. The RNA-seq analysis revealed upregulation or downregulation of key genes involved in cell wall synthesis (Wsc1 and Fks1), ergosterol biosynthesis (Erg3, and Erg11), apoptisis (Hsp90 and Aif1), as well as autophagy pathways (Atg8, Atg13, and Atg17), and so forth, in response to IBC, as evidenced by the experiment-based phenotypic analysis. These results suggest that IBC inhibits C. albicans growth by disrupting the cell wall/membrane, caused by the altered expression of genes associated with β-1,3-glucan and ergosterol biosynthesis. IBC induces apoptosis and autophagy-associated cell death by upregulating the expression of Hsp90, and altering autophagy-related genes involved in the formation of the Atg1 complex and the pre-autophagosomal structure. Together, our findings provide important insights into the potential multifunctional mechanism of action of IBC.

Human OVCA2 and its homolog FSH3-induced apoptosis in Saccharomyces cerevisiae

Mammalian ovarian tumor suppressor candidate 2 (OVCA2) gene belongs to the family of serine hydrolase (FSH). This study aimed to elucidate the functional similarities of OVCA2 with its yeast homolog genes (FSH1, FSH2, and FSH3) regarding apoptosis. We found that the expression of OVCA2 in Saccharomyces cerevisiae increased production of reactive oxygen species (ROS), decreased cell growth, disturbed mitochondrial morphology, reduced membrane potential, increased chromatin condensation, and externalization of phosphatidylserine (PS) (annexin V/propidium iodide staining) indicating induced apoptotic cell death in yeast. We also showed that complementation of OVCA2 in fsh3Δ cells reduced cell growth and increased the apoptotic phenotypes. Collectively, our results suggest that complementation of human OVCA2 in fsh3Δ cells induced apoptosis in S. cerevisiae.

Analysis of Apoptosis-Related Genes Reveals that Apoptosis Functions in Conidiation and Pathogenesis of Fusarium pseudograminearum

Apoptosis, a type of programmed cell death, plays crucial roles in various physiological processes, from development to adaptive responses. Key features of apoptosis have been verified in various fungal microbes but not yet in Fusarium species. Here, we identified 19 apoptosis-related genes in Fusarium pseudograminearum using a genome-wide survey. Expression profile analysis revealed that several apoptosis-related genes were significantly increased during conidiation and infection stages. Among these is FpBIR1, with two BIR (baculovirus inhibitor-of-apoptosis protein repeat) domains at the N-terminal end of the protein, a homolog of Saccharomyces cerevisiae BIR1, which is a unique apoptosis inhibitor. FpNUC1 is the ortholog of S. cerevisiae NUC1, which triggers AIF1- or YCA1-independent apoptosis. The functions of these two proteins were assessed by creating Δfpbir1 and Δfpnuc1 mutants via targeted gene deletion. The Δfpbir1 mutant had more cells with nuclear fragmentation and exhibited reduced conidiation, conidial formation, and infectivity. Correspondingly, the Δfpnuc1 mutant contained multiple nuclei, produced thicker and more branched hyphae, was reduced in conidiation, and exhibited faster conidial formation and higher infection rates. Taken together, our results indicate that the apoptosis-related genes FpBIR1 and FpNUC1 function in conidiation, conidial germination, and infection by F. pseudograminearumIMPORTANCE The plant-pathogenic fungus F. pseudograminearum is the causal agent of Fusarium crown rot (FCR) in wheat and barley, resulting in substantial yield losses worldwide. Particularly, in the Huanghuai wheat-growing region of China, F. pseudograminearum was reported as the dominant Fusarium species in FCR infections. Apoptosis is an evolutionarily conserved mechanism in eukaryotes, playing crucial roles in development and cell responses to biotic and abiotic stresses. However, few reports on apoptosis in plant fungal pathogens have been published. In this study, we identified 19 conserved apoptosis-related genes in F. pseudograminearum, several of which were significantly increased during conidiation and infection stages. Potential apoptosis functions were assessed by deletion of the putative apoptosis inhibitor gene FpBIR1 and apoptosis trigger gene FpNUC1 in F. pseudograminearum The FpBIR1 deletion mutant exhibited defects in conidial germination and pathogenicity, whereas the FpNUC1 deletion mutant experienced faster conidial formation and higher infection rates. Apoptosis appears to negatively regulate the conidial germination and pathogenicity of F. pseudograminearum To our knowledge, this study is the first report of apoptosis contributing to infection-related morphogenesis and pathogenesis in F. pseudograminearum.

Apoptosis inducing factor and mitochondrial NADH dehydrogenases: redox-controlled gear boxes to switch between mitochondrial biogenesis and cell death

The mitochondrial complex I serves as entry point for NADH into the electron transport chain. In animals, fungi and plants, additional NADH dehydrogenases carry out the same electron transfer reaction, however they do not pump protons. The apoptosis inducing factor (AIF, AIFM1 in humans) is a famous member of this group as it was the first pro-apoptotic protein identified that can induce caspase-independent cell death. Recent studies on AIFM1 and the NADH dehydrogenase Nde1 of baker's yeast revealed two independent and experimentally separable activities of this class of enzymes: On the one hand, these proteins promote the functionality of mitochondrial respiration in different ways: They channel electrons into the respiratory chain and, at least in animals, promote the import of Mia40 (named MIA40 or CHCHD4 in humans) and the assembly of complex I. On the other hand, they can give rise to pro-apoptotic fragments that are released from the mitochondria to trigger cell death. Here we propose that AIFM1 and Nde1 serve as conserved redox switches which measure metabolic conditions on the mitochondrial surface and translate it into a binary life/death decision. This function is conserved among eukaryotic cells and apparently used to purge metabolically compromised cells from populations.

MicroRNA-138 attenuates myocardial ischemia reperfusion injury through inhibiting mitochondria-mediated apoptosis by targeting HIF1-α

Myocardial ischemia-reperfusion (I/R) injury is considered to have a detrimental role in coronary heart disease, which is considered to be the leading cause of death worldwide. However, the molecular mechanism involved in the progression of myocardial I/R injury is still unclear. The current study aimed to investigate the expression and function of microRNA (miR)-138 in the process of myocardial I/R injury. First, miR-138 expression levels were analyzed both in myocardium with I/R injury and control myocardium using reverse transcription-quantitative polymerase chain reaction analysis. Then, the relationship between the levels of miR-138 and hypoxia-inducible factor (HIF)1-α was also investigated using a luciferase reporter assay. Assessment of myocardial infarct size, measurements of serum myocardial enzymes and electron microscopy analysis were all utilized to analyse the effect of miR-138 on myocardial I/R injury. The authors of current study also used western blotting to examine the expression levels of the mitochondrial fission-related proteins dynamin-1-like protein and mitochondrial fission 1 protein. It was found that miR-138 is downregulated and HIF1-α is upregulated after myocardial ischemia reperfusion injury. Overexpression of miR-138 reduced myocardial I/R injury-induced infarct sizes and myocardial enzyme levels, and it also inhibited the expression of proteins related to mitochondrial morphology and myocardial I/R-induced mitochondrial apoptosis by targeting HIF1-α. Taken together, these findings provide a novel insight into the molecular mechanism of miR-138 and HIF1-α in the progression of myocardial I/R injury. miR-138 has the potential to become a promising therapeutic target for treating myocardial I/R injury.

FSH3 mediated cell death is dependent on NUC1 in Saccharomyces cerevisiae

Family of Serine Hydrolases (FSH) members FSH1, FSH2 and FSH3 in Saccharomyces cerevisiae share conserved sequences with the human candidate tumor suppressor OVCA2. In this study, hydrogen peroxide (H2O2) exposure increased the expression of both mRNA and protein levels of FSH3 in wild-type (WT) yeast cells. The deletion of FSH3 improved the yeast growth rate under H2O2-induction as compared to WT control cells. The overexpression of FSH3 in WT yeast cells caused an apoptotic phenotype, including accumulation of reaction oxygen species, decreased cell viability and cell death. The double deletions fsh1Δ fsh2Δ, fsh1Δ fsh3Δ and fsh2Δ fsh3Δ displayed increased growth compared to WT cells. However, the overexpression of FSH3 effectively inhibited cell growth in all double deletions. Moreover, the overexpression of FSH3 in cells lacking NUC1 did not cause any growth defect in the presence or absence of H2O2. Our results suggest that FSH3 induced apoptosis of yeast in a NUC1 dependent manner.

Tubeimoside I induces accumulation of impaired autophagolysosome against cervical cancer cells by both initiating autophagy and inhibiting lysosomal function

Cervical cancer is one of the most aggressive human cancers with poor prognosis due to constant chemoresistance and repeated relapse. Tubeimoside I (TBM) has been identified as a potent antitumor agent that inhibits cancer cell proliferation by triggering apoptosis and inducing cell cycle arrest. Nevertheless, the detailed mechanism remains unclear and needs to be further elucidated, especially in cervical cancer. In this study, we found that TBM could induce proliferation inhibition and cell death in cervical cancer cells both in vitro and in vivo. Further results demonstrated that treatment with TBM could induce autophagosome accumulation, which was important to TBM against cervical cancer cells. Mechanism studies showed that TBM increased autophagosome by two pathways: First, TBM could initiate autophagy by activating AMPK that would lead to stabilization of the Beclin1-Vps34 complex via dissociating Bcl-2 from Beclin1; Second, TBM could impair lysosomal cathepsin activity and block autophagic flux, leading to accumulation of impaired autophagolysosomes. In line with this, inhibition of autophagy initiation attenuated TBM-induced cell death, whereas autophagic flux inhibition could exacerbated the cytotoxic activity of TBM in cervical cancer cells. Strikingly, as a novel lethal impaired autophagolysosome inducer, TBM might enhance the therapeutic effects of chemotherapeutic drugs towards cervical cancer, such as cisplatin and paclitaxel. Together, our study provides new insights into the molecular mechanisms of TBM in the antitumor therapy, and establishes potential applications of TBM for cervical cancer treatment in clinic.

Anacardic acid suppresses fibroblast-like synoviocyte proliferation and invasion and ameliorates collagen-induced arthritis in a mouse model

Anacardic acid, which is abundant in nutshell of Anacardium occidentale, has multiple pharmacological activities. In this study, we examined the therapeutic potential of anacardic acid in treating rheumatoid arthritis (RA). We explored the effects of anacardic acid on collagen-induced arthritis (CIA) in mice and on the proliferation and invasion of RA fibroblast-like synoviocytes (RA-FLSs). The underlying molecular mechanism was investigated. Anacardic acid treatment markedly suppressed paw swelling, joint destruction, and arthritis scores in CIA mice. The serum levels of tumor necrosis factor alpha (TNF- α) and interleutkin-1beta (IL- 1β) were significantly lowered by anacardic acid. In vitro assays demonstrated that anacardic acid impaired the proliferation and invasion abilities of RA-FLSs in the presence of TNF- α or IL- 1β. Western blot analysis revealed the reduction of Akt protein expression and phoshporylation in RA-FLSs by anacardic acid. However, the mRNA level of Akt remained unchanged. Anacardic acid treatment significantly increased the expression of miR-633 in RA-FLSs. Akt was identified as a novel target of miR-633. Overexpression of miR-633 significantly inhibited the proliferation and invasion of RA-FLSs, which was rescued by enforced expression of Akt. Depletion of miR-633 prevented anacardic acid-mediated suppression of proliferation and invasion of RA-FLSs, which was accompanied by increased expression of Akt protein. In conclusion, anacardic acid may serve as a promising agent in the treatment of RA.