Heat shock proteins and Bcl-2 expression and function in relation to the differential hyperthermic sensitivity between leukemic and normal hematopoietic cells

Scientific knowledge about gene expression in ruminants under heat stress - A scientometric review

Heat stress can alter the expression of genes in the individual's molecular response. The identification of these genes makes it possible to better understand the molecular response, identifying biomarker genes and indirect response pathways that can help with genetic improvement studies, animal welfare, separating more thermotolerant varieties and mitigating the effects of heat stress. The aim of this scientometric review was to characterize the state of the art of scientific research into gene expression in ruminants under heat stress, to define the most studied species, biology systems and genes, as well as the related biological pathways and processes. The articles for the dataset were compiled in the Web of Science database, refined individually and analyzed using the CiteSpace, RStudio, Excel and GraphPad Prism programs and the KEGG (Kyoto Encyclopedia of Genes and Genomes) database. The publications formed a data set containing 271 articles and an H-index of 37. The number of publications increased from 2011. The countries with the highest frequency of publications are India, the United States, China and Brazil, the ruminant species are cattle, buffaloes, sheep and goats, all zootechnical interest, and biology systems was reproduction, blood and lactation, due to the economic importance of the quality and quantity of production, to the ease of collecting and possibility of studies in vitro. Cattle have been extensively studied in comparison to other ruminants. The HSP70 gene has been the most studied, followed by the HSP family, HSF, BAX, TLR and BCL-2, these genes can be molecular markers of heat stress. The main pathways and biological processes of genes were in cattle the cancer pathway; in goats the Mixed, incl. myd88-dependent toll-like receptor signaling pathway, and lipopolys; in sheep the oxidoreductase; and in buffalo it was the BCL-2 family. The molecular responses are still recent and have not been established.

In vitro culture of sheep early-antral follicles: Milestones, challenges and future perspectives

Early antral follicles (EAFs) represent the transitional stage between pre-antral and antral follicles, containing oocytes that have completed most of their growth phase. Therefore, they offer an easily exploitable reserve for producing mature oocytes and preserving genetic resources, given their higher abundance compared to antral follicles (AFs) and shorter culture period than other pre-antral follicles (PAFs). Despite these advantages, the culture of EAFs remains challenging, and the success rates of in vitro embryo production (IVEP) from EAF-derived oocytes are still far below the standard achieved with fully grown oocytes in ruminant species. The difficulty is related to developing suitable in vitro culture systems tailored with nutrients, growth factors, and other signaling molecules to support oocyte growth. In this review, we focus on the in vitro development of sheep EAFs to provide an informative reference to current research progress. We also summarize the basic aspect of folliculogenesis in sheep and the main achievements and limitations of the current methods for EAF isolation, in vitro culture systems, and medium supplementation. Finally, we highlight future perspectives and challenges for improving EAF culture outcomes.

Trimethylation profile of histones H3 lysine 4 and 9 in late preantral and early antral caprine follicles grown in vivo versus in vitro in the presence of anethole

This study assessed the histones methylation profile (H3K4me3 and H3K9me3) in late preantral (PA) and early antral (EA) caprine follicles grown in vivo and in vitro, and the anethole effect during in vitro culture of PA follicles. Uncultured in vivo-grown follicles (PA, n = 64; EA, n = 73) were used as controls to assess the methylation profile and genes' expression related to apoptosis cascade (BAX, proapoptotic; BCL2, antiapoptotic), steroidogenesis (CYP17, CYP19A1), and demethylation (KDM1AX1, KDM1AX2, KDM3A). The isolated PA follicles (n = 174) were cultured in vitro for 6 days in α-MEM+ in either absence (control) or presence of anethole. After culture, EA follicles were evaluated for methylation, mRNA abundance, and morphometry. Follicle diameter increased after culture, regardless of treatment. The methylation profile and the mRNA abundance were similar between in vivo-grown PA and EA follicles. Anethole treatment led to higher H3K4me3 fluorescence intensity in EA follicles. The mRNA abundances of BAX, CYP17, and CYP19A1 were higher, and BCL2 and KDM3A were lower in in vitro-grown EA follicles than in vivo-grown follicles. In conclusion, in vitro follicle culture affected H3K4me3 fluorescence intensity, mRNA abundance of apoptotic genes, and steroidogenic and demethylase enzymes compared with in vivo-grown follicles.

Impact of REAC Regenerative Endogenous Bioelectrical Cell Reprogramming on MCF7 Breast Cancer Cells

Human breast adenocarcinoma is a form of cancer which has the tendency to metastasize to other tissues, including bones, lungs, brain, and liver. Several chemotherapeutic drugs are used to treat breast tumors. Their combination is used to simultaneously target different mechanisms involved in cell replication. Radio electric asymmetric conveyer (REAC) technology is an innovative technology, used both in vitro and in vivo, to induce cell reprogramming and counteract senescence processes. Within this context, we treated MCF-7 cells with a regenerative (RGN) REAC treatment for a period ranging between 3 and 7 days. We then analyzed cell viability by trypan blue assays and gene and protein expression by real time-qPCR and confocal microscope, respectively. We also detected the levels of the main proteins involved in tumor progression, DKK1 and SFRP1, by ELISA and cell senescence by β-galactosidase tests. Our results showed the ability of REAC RGN to counteract MCF-7 proliferation, probably inducing autophagy via the upregulation of Beclin-1 and LC3-I, and the modulation of specific tumorigenic biomarkers, such as DKK1 and SPFR1. Our results could suggest the application of the REAC RGN in future in vivo experiments, as an aid for the therapeutic strategies usually applied for breast cancer treatment.

Heat-Induced Proteotoxic Stress Response in Placenta-Derived Stem Cells (PDSCs) Is Mediated through HSPA1A and HSPA1B with a Potential Higher Role for HSPA1B

Placenta-derived stem cells (PDSCs), due to unique traits such as mesenchymal and embryonic characteristics and the absence of ethical constraints, are in a clinically and therapeutically advantageous position. To aid in stemness maintenance, counter pathophysiological stresses, and withstand post-differentiation challenges, stem cells require elevated protein synthesis and consequently augmented proteostasis. Stem cells exhibit source-specific proteostasis traits, making it imperative to study them individually from different sources. These studies have implications for understanding stem cell biology and exploitation in the augmentation of therapeutic applications. Here, we aim to identify the primary determinants of proteotoxic stress response in PDSCs. We generated heat-induced dose-responsive proteotoxic stress models of three stem cell types: placental origin cells, the placenta-derived mesenchymal stem cells (pMSCs), maternal origin cells, the decidua parietalis mesenchymal stem cells (DPMSCs), and the maternal–fetal interface cells, decidua basalis mesenchymal stem cells (DBMSCs), and measured stress induction through biochemical and cell proliferation assays. RT-PCR array analysis of 84 genes involved in protein folding and protein quality control led to the identification of Hsp70 members HSPA1A and HSPA1B as the prominent ones among 17 significantly expressed genes and with further analysis at the protein level through Western blotting. A kinetic analysis of HSPA1A and HSPA1B gene and protein expression allowed a time series evaluation of stress response. As identified by protein expression, an active stress response is in play even at 24 h. More prominent differences in expression between the two homologs are detected at the translational level, alluding to a potential higher requirement for HSPA1B during proteotoxic stress response in PDSCs.

Fine-tuned control of stress priming and thermotolerance

A common signature of cell adaptation to stress is the improved resistance upon priming by prior stress exposure. In the context of hyperthermia, priming or preconditioning with sublethal heat shock can be a useful tool to confer thermotolerance and competitive advantage to cells. In the present study, we develop a data-driven modeling framework that is simple and generic enough to capture a broad set of adaptation behaviors to heat stress at both molecular and cellular levels. The model recovers the main features of thermotolerance and clarifies the tradeoff principles which maximize the thermotolerance effect. It therefore provides an effective predictive tool to design preconditioning and fractionation hyperthermia protocols for therapeutic purpose.

Hybrid Graphene-Gold Nanoparticle-based Nucleic Acid Conjugates for Cancer-Specific Multimodal Imaging and Combined Therapeutics

Nanoparticle-based nucleic acid conjugates (NP-NACs) hold great promise for theragnostic (diagnostic and therapeutic) applications. However, several limitations have hindered the realization of their full potential in the clinical treatment of cancer and other diseases. In diagnosis, NP-NACs, combined with conventional optical sensing systems, have been applied for cancer detection in vitro, but low signal-to-noise ratios limit their broad in vivo applications. Meanwhile, the efficiency of NP-NAC-mediated cancer therapies has been limited through the adaptation of alternative pro-survival pathways in cancer cells. The recent emergence of personalized and precision medicine has outlined the importance of both accurate diagnosis and efficient therapeutics in a single platform. As such, we report the controlled assembly of hybrid graphene oxide/gold nanoparticle-based cancer-specific NACs (Au@GO NP-NACs) for multimodal imaging and combined therapeutics. Our developed Au@GO NP-NACs shows excellent surface-enhanced Raman scattering (SERS)-mediated live-cell cancer detection and multimodal synergistic cancer therapy through the use of photothermal, genetic, and chemotherapeutic strategies. Synergistic and selective killing of cancer cells were then demonstrated by using in vitro microfluidic models and nine different cancer cell lines by further incorporating near-infrared photothermal hyperthermia, a Topoisomerase II anti-cancer drug, and cancer targeting peptides. Moreover, with distinctive advantages of the Au@GO NP-NACs for cancer theragnostics, we further demonstrated precision cancer treatment through the detection of cancer cells in vivo using SERS followed by efficient ablation of the tumor. Therefore, our Au@GO NP-NACs could pave a new road for the advanced theragnostics of cancer as well as many other diseases.

First pregnancy after in vitro culture of early antral follicles in goats: Positive effects of anethole on follicle development and steroidogenesis

This study aimed to evaluate the role of anethole during the in vitro culture of caprine early antral follicles. Early antral follicles were isolated from caprine ovaries and cultured for 18 days without (control) or with anethole (300 µg/ml). After culture, the cumulus-oocyte complexes were subjected to in vitro maturation, followed by parthenogenetic activation or in vitro fertilization (IVF) and embryo culture. Follicular walls were used for the quantification of messenger RNA (mRNA) of CYP19A1, CYP17, MMP-9, TIMP-2, Bax, and Bcl-2 genes, and culture medium was used for evaluation of ferric reducing antioxidant power (FRAP) and estradiol levels. After in vitro follicle culture (IVFC), anethole induced higher total antioxidant capacity, that is, it produced higher FRAP levels, reduced the Bax/Bcl-2 ratio, and increased the levels of mRNA for CYP19A1 and CYP17, which was associated with a greater estradiol production (p < .05). Also, anethole improved the ability of oocytes to resume meiosis and reach metaphase II stage, as well as yielded higher (p < .05) embryo production (e.g., morulas and blastocysts) in both parthenogenetic activation and IVF techniques. One pregnancy (Day 30) was obtained from IVFC with anethole. In conclusion, anethole promoted in vitro growth and maturation of goat early antral follicles and oocytes and enabled embryo production. Furthermore, this study reports, for the first time in goats, a pregnancy after IVF using oocytes originated from early antral follicles grown in vitro.

Examining the Effect of Heat Stress on Montastraea cavernosa (Linnaeus 1767) from a Mesophotic Coral Ecosystem (MCE)

Coral reefs are under increasing pressure from global warming. Little knowledge, however, exists regarding heat induced stress on deeper mesophotic coral ecosystems (MCEs). Here, we examined the effect of acute (72 h) and chronic (480 h) heat stress on the host coral Montastraea cavernosa (Linnaeus 1767) collected from an upper MCE (~30 m) in Florida, USA. We examined six immune/stress-related genes: ribosomal protein L9 (RpL9), ribosomal protein S7 (RpS7), B-cell lymphoma 2 apoptosis regulator (BCL-2), heat shock protein 90 (HSP90), catalase, and cathepsin L1, as a proxy for coral response to heat stress. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to evaluate the gene expression. Overall, both acute and chronic heat stress treatments elicited a response in gene expression relative to control samples. Acute heat exposure resulted in up-regulation of catalase, BCL-2, and HSP90 at all time points from hour 24 to 48, suggesting the activation of an oxidative protective enzyme, molecular chaperone, and anti-apoptotic protein. Fewer genes were up-regulated in the chronic experiment until hour 288 (30 °C) where catalase, RpL9, and RpS7 were significantly up-regulated. Chronic heat exposure elicited a physiological response at 30 °C, which we propose as a heat-stress threshold for Montastraea cavernosa (M. cavernosa) collected from an MCE.

Heat stress modulates differential response in skin fibroblast cells of native cattle (Bos indicus) and riverine buffaloes (Bubalus bubalis)

Heat stress in hot climates is a major cause that negatively affects dairy animals, leading to substantial economic loss. The present study was aimed to analyze the effect of heat stress on cellular and molecular levels in dermal fibroblast of cattle and buffaloes. Primary fibroblast culture was established using ear pinna tissue samples of cattle (Bos indicus) and riverine buffaloes (Bubalus Bubalis). The cells were exposed to thermal stress at 42°C for 1 h and subsequently allowed to recover and harvest at 37°C at different time points (0, 2, 4, 8, 16, and 24 h) along with control samples. Different cellular parameters viz., apoptosis, proliferation, mitochondrial membrane potential (ΔΨm), oxidative stress, along with expression pattern of heat responsive genes and miRNAs were determined. Cell viability and proliferation rate of heat-stressed fibroblasts decreased significantly (P < 0.05) albeit to a different extent in both species. The cell cytotoxicity, apoptosis, production of reactive oxygen species, and ΔΨm increased more significantly (P < 0.01) in heat stressed fibroblasts of buffalo than cattle. The pattern of heat shock proteins, inflammation/immune genes, and heat responsive miRNA showed differences in induction of their expression level in buffalo and native cattle fibroblasts. Conclusively, finding indicates that heat stress induces more profound impact on buffalo fibroblasts than native cattle fibroblasts. The differential response of cellular parameters, HSP genes, and miRNA expression could be due to better adaptive capacity of skin fibroblast of Bos indicus cattle in comparison with riverine buffaloes.

Cavitation Induced by Janus-Like Mesoporous Silicon Nanoparticles Enhances Ultrasound Hyperthermia

The presence of nanoparticles lowers the levels of ultrasound (US) intensity needed to achieve the therapeutic effect and improves the contrast between healthy and pathological tissues. Here, we evaluate the role of two main mechanisms that contribute to the US-induced heating of aqueous suspensions of biodegradable nanoparticles (NPs) of mesoporous silicon prepared by electrochemical etching of heavily boron-doped crystalline silicon wafers in a hydrofluoric acid solution. The first mechanism is associated with an increase of the attenuation of US in the presence of NPs due to additional scattering and viscous dissipation, which was numerically simulated and compared to the experimental data. The second mechanism is caused by acoustic cavitation leading to intense bubble collapse and energy release in the vicinity of NPs. This effect is found to be pronounced for as-called Janus NPs produced via a nano-stopper technique, which allow us to prepare mesoporous NPs with hydrophobic inner pore walls and hydrophilic external surface. Such Janus-like NPs trap air inside the pores when dispersed in water. The precise measurement of the heating dynamics in situ enabled us to detect the excessive heat production by Janus-like NPs over their completely hydrophilic counterparts. The excessive heat is attributed to the high intensity cavitation in the suspension of Janus-like NPs. The present work elicits the potential of specifically designed Janus-like mesoporous silicon NPs in the field of nanotheranostics based on ultrasound radiation.

Characterization of the acute heat stress response in gilts: III. Genome-wide association studies of thermotolerance traits in pigs

Heat stress is one of the limiting factors negatively affecting pig production, health, and fertility. Characterizing genomic regions responsible for variation in HS tolerance would be useful in identifying important genetic factor(s) regulating physiological responses to HS. In the present study, we performed genome-wide association analyses for respiration rate (RR), rectal temperature (TR), and skin temperature (TS) during HS in 214 crossbred gilts genotyped for 68,549 single nucleotide polymorphisms (SNP) using the Porcine SNP 70K BeadChip. Considering the top 0.1% smoothed phenotypic variances explained by SNP windows, we detected 26, 26, 21, and 14 genes that reside within SNPs explaining the largest proportion of variance (top 25 SNP windows) and associated with change in RR (ΔRR) from thermoneutral (TN) conditions to HS environment, as well as the change in prepubertal TR (ΔTR), change in postpubertal ΔTR, and change in TS (ΔTS), respectively. The region between 28.85 Mb and 29.10 Mb on chromosome 16 explained about 0.05% of the observed variation for ΔRR. The growth hormone receptor (GHR) gene resides in this region and is associated with the HS response. The other important candidate genes associated with ΔRR (PAIP1, NNT, and TEAD4), ΔTR (LIMS2, TTR, and TEAD4), and ΔTS (ERBB4, FKBP1B, NFATC2, and ATP9A) have reported roles in the cellular stress response. The SNP explaining the largest proportion of variance and located within and in the vicinity of genes were related to apoptosis or cellular stress and are potential candidates that underlie the physiological response to HS in pigs.

Glioma progression through the prism of heat shock protein mediated extracellular matrix remodeling and epithelial to mesenchymal transition

Glial tumor is one of the intrinsic brain tumors with high migratory and infiltrative potential. This essentially contributes to the overall poor prognosis by circumvention of conventional treatment regimen in glioma. The underlying mechanism in gliomagenesis is bestowed by two processes- Extracellular matrix (ECM) Remodeling and Epithelial to mesenchymal transition (EMT). Heat Shock Family of proteins (HSPs), commonly known as "molecular chaperons" are documented to be upregulated in glioma. A positive correlation also exists between elevated expression of HSPs and invasive capacity of glial tumor. HSPs overexpression leads to mutational changes in glioma, which ultimately drive cells towards EMT, ECM modification, malignancy and invasion. Differential expression of HSPs - a factor providing cytoprotection to glioma cells, also contributes towards its radioresistance /chemoresistance. Various evidences also display upregulation of EMT and ECM markers by various heat shock inducing proteins e.g. HSF-1. The aim of this review is to study in detail the role of HSPs in EMT and ECM leading to radioresistance/chemoresistance of glioma cells. The existing treatment regimen for glioma could be enhanced by targeting HSPs through immunotherapy, miRNA and exosome mediated strategies. This could be envisaged by better understanding of molecular mechanisms underlying glial tumorigenesis in relation to EMT and ECM remodeling under HSPs influence. Our review might showcase fresh potential for the development of next generation therapeutics for effective glioma management.

Selective killing of cancer cells by nanoparticle-assisted ultrasound

BACKGROUND

Intense ultrasound, such as that used for tumor ablation, does not differentiate between cancerous and normal cells. A method combining ultrasound and biocompatible gold or magnetic nanoparticles (NPs) was developed under in vitro conditions using human breast and lung epithelial cells, which causes ultrasound to preferentially destroy cancerous cells.

RESULTS

Co-cultures of BEAS-2B normal lung cells and A549 cancerous lung cells labeled with green and red fluorescent proteins, respectively, were treated with focused ultrasound beams with the addition of gold and magnetic nanoparticles. There were significantly more necrotic A549 cells than BEAS-2 cells when gold nanoparticles were added to the culture medium [(50.6 ± 15.1) vs. (7.4 ± 2.9) %, respectively, P < 0.01]. This selective damage to cancer cells was also observed for MDA-MB231 breast cancer cells relative to MCF-10A normal breast cells after treatment with magnetic nanoparticles.

CONCLUSIONS

The data obtained for different cell lines indicate that nanoparticle-assisted ultrasound therapy (NAUT) could be an effective new tool for cancer-specific treatment and could potentially be combined with conventional methods of cancer diagnosis and therapy to further increase the overall cancer cure rate.

The effect of heat stress on gene expression, synthesis of steroids, and apoptosis in bovine granulosa cells

Summer heat stress (HS) is a major contributing factor in low fertility in lactating dairy cows in hot environments. Heat stress inhibits ovarian follicular development leading to diminished reproductive efficiency of dairy cows during summer. Ovarian follicle development is a complex process. During follicle development, granulosa cells (GCs) replicate, secrete hormones, and support the growth of the oocyte. To obtain an overview of the effects of heat stress on GCs, digital gene expression profiling was employed to screen and identify differentially expressed genes (DEGs; false discovery rate (FDR) ≤ 0.001, fold change ≥2) of cultured GCs during heat stress. A total of 1211 DEGs including 175 upregulated and 1036 downregulated ones were identified, of which DEGs can be classified into Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. The results suggested that heat stress triggers a dramatic and complex program of altered gene expression in GCs. We hypothesized that heat stress could induce the apoptosis and dysfunction of GCs. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was used to evaluate the expression of steroidogenic genes (steroidogenic acute regulatory protein (Star), cytochrome P-450 (CYP11A1), CYP19A1, and steroidogenic factor 1 (SF-1)) and apoptosis-related genes (caspase-3, BCL-2, and BAX). Radio immunoassay (RIA) was used to analyze the level of 17β-estradiol (E2) and progesterone (P4). We also assessed the apoptosis of GCs by flow cytometry. Our data suggested that heat stress induced GC apoptosis through the BAX/BCL-2 pathway and reduced the steroidogenic gene messenger RNA (mRNA) expression and E2 synthesis. These results suggest that the decreased function of GCs may cause ovarian dysfunction and offer an improved understanding of the molecular mechanism responsible for the low fertility in cattle in summer.

The global effect of heat on gene expression in cultured bovine mammary epithelial cells

Heat stress (HS) in hot climates is a major cause that strongly negatively affects milk yield in dairy cattle, leading to immeasurable economic loss. The heat stress response of bovine mammary epithelial cells (BMECs) is one component of the acute systemic response to HS. Gene networks of BMECs respond to environmental heat loads with both intra- and extracellular signals that coordinate cellular and whole-animal metabolism. Our experimental objective was to characterize the direct effects of heat stress on the cultured bovine mammary epithelial cells by microarray analyses. The data identified 2716 differentially expressed genes in 43,000 transcripts which were changed significantly between heat-stressed and normal bovine mammary epithelial cells (fold change ≥2, P ≤ 0.001). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these differentially expressed genes are involved in different pathways that regulate cytoskeleton, cell cycle, and stress response processes. Our study provides an overview of gene expression profile and the interaction between gene expression and heat stress, which will lead to further understanding of the potential effects of heat stress on bovine mammary glands.

Differential sensitivity of telomerase from human hematopoietic stem cells and leukemic cell lines to mild hyperthermia

We have investigated the effects of hyperthermia (HT) on cell proliferation and telomerase activity of human hematopoietic stem cells (HSCs) and compared with human leukemic cell lines (TF-1, K562 and HL-60). The cells were exposed to HT at 42 and 43 °C up to 120 min. The cells were incubated at 37 °C for 96 h. Then the cells were collected and assayed for cell proliferation, viability, telomerase activity, and terminal restriction fragment (TRF) lengths. The enzyme activity from HSCs was decreased up to 68.6 at 42 and 85.1 % at 43 °C for 120 min. This inhibition in leukemic cells was up to 28.9 and 53.6 % in TF-1; 53 and 63.9 % in K562; 45.2 and 61.1 % in HL-60 cells. The treated cells showed TRF lengths about 5.3 kb for control HL-60 cells, 5.0 kb for HL-60 cells treated at 42 and 4.5 kb at 43 °C for 120 min. In HSCs, the TRF length was about 4.5 kb for untreated cells and 4.0-4.5 kb for treated cells at 42 and 43 °C for 120 min. The time response curves indicated that, inhibition of the enzyme activity in leukemic cells was dependent to the time of exposure to HT. But in HSCs, the inhibition was reached to steady state at 15 min exposure to 43 °C heat stress. TRF length was constant at treated two types of cells, which implies that in cells subjected to mild HT no telomere shortening was observed.

Role of heat shock proteins in stem cell behavior

Stress response is well appreciated to induce the expression of heat shock proteins (Hsps) in the cell. Numerous studies have demonstrated that Hsps function as molecular chaperones in the stabilization of intracellular proteins, repairing damaged proteins, and assisting in protein translocation. Various kinds of stem cells (embryonic stem cells, adult stem cells, or induced pluripotent stem cells) have to maintain their stemness and, under certain circumstances, undergo stress. Therefore, Hsps should have an important influence on stem cells. Actually, numerous studies have indicated that some Hsps physically interact with a number of transcription factors as well as intrinsic and extrinsic signaling pathways. Importantly, alterations in Hsp expression have been demonstrated to affect stem cell behavior including self-renewal, differentiation, sensitivity to environmental stress, and aging. This chapter summarizes recent findings related to (1) the roles of Hsps in maintenance of stem cell dormancy, proliferation, and differentiation; (2) the expression signature of Hsps in embryonic/adult stem cells and differentiated stem cells; (3) the protective roles of Hsps in transplanted stem cells; and (4) the possible roles of Hsps in stem cell aging.

Regulation of apoptotic mediators reveals dynamic responses to thermal stress in the reef building coral Acropora millepora

Background

Mass coral bleaching is increasing in scale and frequency across the world's coral reefs and is being driven primarily by increased levels of thermal stress arising from global warming. In order to understand the impacts of projected climate change upon corals reefs, it is important to elucidate the underlying cellular mechanisms that operate during coral bleaching and subsequent mortality. In this respect, increased apoptotic cell death activity is an important cellular process that is associated with the breakdown of the mutualistic symbiosis between the cnidarian host and their dinoflagellate symbionts.

Methodology/Principal Findings

The present study reports the impacts of different stressors (colchicine and heat stress) on three phases of apoptosis: (i) the potential initiation by differential expression of Bcl-2 members, (ii) the execution of apoptotic events by activation of caspase 3-like proteases and (iii) and finally, the cell disposal indicated by DNA fragmentation in the reef building coral Acropora millepora. In corals incubated with colchicine, an increase in caspase 3-like activity and DNA fragmentation was associated with a relative down-regulation of Bcl-2, suggesting that the initiation of apoptosis may be mediated by the suppression of an anti-apoptotic mechanism. In contrast, in the early steps of heat stress, the induction of caspase-dependent apoptosis was related to a relative up-regulation of Bcl-2 consecutively followed by a delayed decrease in apoptosis activity.

Conclusions/Significance

In the light of these results, we propose a model of heat stress in coral hosts whereby increasing temperatures engage activation of caspase 3-dependent apoptosis in cells designated for termination, but also the onset of a delayed protective response involving overexpression of Bcl-2 in surviving cells. This mitigating response to thermal stress could conceivably be an important regulatory mechanism for cell survival in corals exposed to sudden environmental changes.