MicroRNA-216b inhibits heat stress-induced cell apoptosis by targeting Fas in bovine mammary epithelial cells

Circ_002033 Regulates Proliferation, Apoptosis, and Oxidative Damage of Bovine Mammary Epithelial Cells via the miR-199a-5p-MAP3K11 Axis in Heat Stress

Heat stress is becoming the major factor regarding dairy cow health and milk quality because of global warming. Circular RNAs (circRNAs) represent a special type of noncoding RNAs, which are related to regulating many biological processes. Nonetheless, little is known concerning their effects on heat-stressed bovine mammary epithelial cells (BMECs). Here, this study found a novel circRNA, circ_002033, using RNA sequencing (RNA-seq) and explored the role and underlying regulatory mechanism in proliferation, apoptosis, and oxidative damage in a heat-stressed bovine mammary epithelial cell line (MAC-T). According to the previous RNA-seq analysis, the abundance of circ_002033 in mammary gland tissue of heat-stressed cows increased relative to nonheat-stressed counterparts. This study found that the knockdown of circ_002033 promoted proliferation and alleviated apoptosis and oxidative damage in heat-stressed MAC-T. Mechanistically, circ_002033 localizes to miR-199a-5p in the cytoplasm of MAC-T to regulate mitogen-activated protein kinase kinase 11 (MAP3K11) expression. Meanwhile, miR-199a-5p and MAP3K11 are also involved in regulating the proliferation and apoptosis of heat-stressed MAC-T. Importantly, circ_002033 knockdown promoted the expression of miR-199a-5p while decreasing that of MAP3K11, thereby enhancing proliferation while alleviating apoptosis and oxidative damage in heat-stressed MAC-T. In summary, we found that circ_002033 regulates the proliferation, apoptosis, and oxidative damage of heat-stressed BMECs through the miR-199a-5p/MAP3K11 axis, providing the theoretical molecular foundation for mitigating heat stress of dairy cows.

Cyclical heat stress during lactation influences the microstructure of the bovine mammary gland

This study aimed to evaluate the impact of heat stress on mammary epithelial cell (MEC) losses into milk, secretory mammary tissue structure, and mammary epithelial cell activity. Sixteen multiparous Holstein cows (632 ± 12 kg BW) approximately 100 d in milk housed in climate-controlled rooms were paired by body weight and randomly allocated to one of 2 treatments, heat stress (HS) or pair feeding thermoneutral (PFTN) using 2 cohorts. Each cohort was subjected to 2 periods of 4 d each. In period 1, both treatments had ad libitum access to a common total mixed ration and were exposed to a controlled daily temperature-humidity index (THI) of 64. In period 2, HS cows were exposed to controlled cyclical heat stress (THI: 74 to 80), while PFTN cows remained at 64 THI and daily dry matter intake was matched to HS. Cows were milked twice daily, and milk yield was recorded at each milking. Individual milk samples on the last day of each period were used to quantify MEC losses by flow cytometry using butyrophilin as a cell surface marker. On the final day of period 2, individual bovine mammary tissue samples were obtained for histomorphology analysis, assessment of protein abundance, and evaluation of gene expression of targets associated with cellular capacity for milk and milk component synthesis, heat response, cellular proliferation, and autophagy. Statistical analysis was performed using the GLIMMIX procedure of SAS. Milk yield was reduced by 4.3 kg by HS (n = 7) compared with PFTN (n = 8). Independent of treatment, MEC in milk averaged 174 cells/mL (2.9% of total cells). There was no difference between HS vs. PFTN cows for MEC shed or concentration in milk. Alveolar area was reduced 25% by HS, and HS had 4.1 more alveoli than PFTN. Total number of nucleated MEC per area were greater in HS (389 ± 1.05) compared with PFTN (321 ± 1.05); however, cell number per alveolus was similar between groups (25 ± 1.5 vs. 26 ± 1.4). There were no differences in relative fold expression for GLUT1, GLUT8, CSN2, CSN3, LALBA, FASN, HSPA5, and HSPA8 in HS compared with PFTN. Immunoblotting analyses showed a decrease abundance for phosphorylated STAT5 and S6K1, and an increase in LC3 II in HS compared with PFTN. These results suggest that even if milk yield differences and histological changes occur in the bovine mammary gland after 4 d of heat exposure, MEC loss into milk, nucleated MEC number per alveolus, and gene expression of nutrient transport, milk component synthesis, and heat stress related targets are unaffected. In contrast, the abundance of proteins related to protein synthesis and cell survival decreased significantly, while an upregulation of proteins associated with autophagy in HS compared with PFTN.

The Effects of Zinc Oxide Nanoparticles on Antioxidation, Inflammation, Tight Junction Integrity, and Apoptosis in Heat-Stressed Bovine Intestinal Epithelial Cells In Vitro

Zinc oxide nanoparticles (nano-ZnO) have diverse applications in numerous biomedical processes. The present study explored the effects of these nanoparticles on antioxidation, inflammation, tight junction integrity, and apoptosis in heat-stressed bovine intestinal epithelial cells (BIECs). Primary BIECs that were isolated and cultured from calves either were subjected to heat stress alone (42°C for 6 h) or were simultaneously heat-stressed and treated with nano-ZnO (0.8 μg/mL). Cell viability, apoptosis, and expression of genes involved in antioxidation (Nrf2, HO-1, SOD1, and GCLM), inflammation-related genes (TLR4, NF-κB, TNF-α, IL-6, IL-8, and IL-10), intestinal barrier genes (Claudin, Occludin, and ZO-1), and apoptosis-related genes (Cyt-c, Caspase-3, and Caspase-9) were assessed to evaluate the effect of nano-ZnO on heat-stressed BIECs. The nanoparticles significantly increased cell viability and decreased the rate of apoptosis of BIECs induced by heat stress. In addition, nano-ZnO promoted the expression of antioxidant-related genes HO-1 and GCLM and anti-inflammatory cytokine gene IL-10, and inhibited the pro-inflammatory cytokine-related genes IL-6 and IL-8. The nanoparticles also enhanced expression of the Claudin and ZO-1 genes, and decreased expression of the apoptosis-related genes Cyt-c and Caspase-3. These results reveal that nano-ZnO improve the antioxidant and immune capacity of BIECs and mitigate apoptosis of intestinal epithelial cells induced by heat stress. Thus, nano-ZnO have potential for detrimental the adverse effects of heat stress in dairy cows.

L-arginine reduces injury from heat stress to bovine intestinal epithelial cells by improving antioxidant and inflammatory response

Heat stress (HS) has a negative impact on the health and performance of dairy cows, resulting in economic losses. Damage to the intestinal epithelium is the main cause of the adverse effects of heat stress on bovine health. This study investigated the repair capability of L-arginine (L-Arg) in reducing the adverse effects of HS on bovine intestinal epithelial cells (BIECs). BIECs were treated as follows: (1) control cells were cultured at 37 °C continuously and received no L-Arg; (2) cells in HS group were grown at 42 °C for 6 h followed by 12 h at 37 °C; and (3) the L-Arg group was cultured at 42 °C for 6 h, then treated with L-Arg at 37 °C for 12 h. HS disrupted redox homeostasis and reduced viability in BIECs, while treatment with L-Arg (6 mmol/L) for 12 h markedly reduced the negative effects of HS. L-Arg protected cells by preventing HS-induced changes in mitochondrial membrane-potential, inflammation, apoptosis-related gene expression and regulation of antioxidant enzymes. The above results indicated that L-Arg reduced the level of damage from HS in BIECs by lowering oxidant stress and inflammation, suggesting that L-Arg could be an effective dietary addition to protect cows from adverse intestinal effects caused by HS.

Progress in epigenetic regulation of milk synthesis, with particular emphasis on mRNA regulation and DNA methylation

Inadequate milk secretion and a lack of nutrients in humans and mammals are serious problems. It is of great significance to clarify the mechanisms of milk synthesis and treatment methods. Epigenetic modification, represented by RNA methylation, is an important way of gene expression regulation that profoundly affects human gene expression and participates in various physiological and pathological mechanisms. Epigenetic disorders also have an important impact on the production and secretion of milk. This review systematically summarized the research results of epigenetics in the process of lactation in PubMed, Web of Science, NSTL, and other databases and reviewed the effects of epigenetics on human and mammalian lactation, including miRNAs, circRNAs, lncRNAs, DNA methylations, and RNA methylations. The abnormal expression of miRNAs was closely related to the synthesis and secretion of milk fat, milk protein, and other nutrients in the milk of cattle, sheep, and other mammals. MiRNAs are also involved in the synthesis of human milk and the secretion of nutrients. CircRNAs and lncRNAs mainly target miRNAs and regulate the synthesis of nutrients in milk by ceRNA mechanisms. The abnormal expression of DNA and RNA methylation also has an important impact on milk synthesis. Epigenetic modification has the potential to regulate the milk synthesis of breast epithelial cells. Analyzing the mechanisms of human and mammalian milk secretion deficiency and nutrient deficiency from the perspective of epigenetics will provide a new perspective for the treatment of postpartum milk deficiency in pregnant women and mammalian milk secretion deficiency.

Integrated analysis of expression profiles with meat quality traits in cattle

MicroRNAs (miRNAs) play a vital role in improving meat quality by binding to messenger RNAs (mRNAs). We performed an integrated analysis of miRNA and mRNA expression profiling between bulls and steers based on the differences in meat quality traits. Fat and fatty acids are the major phenotypic indices of meat quality traits to estimate between-group variance. In the present study, 90 differentially expressed mRNAs (DEGs) and 18 differentially expressed miRNAs (DEMs) were identified. Eighty-three potential DEG targets and 18 DEMs were used to structure a negative interaction network, and 75 matching target genes were shown in this network. Twenty-six target genes were designated as intersection genes, screened from 18 DEMs, and overlapped with the DEGs. Seventeen of these genes enriched to 19 terms involved in lipid metabolism. Subsequently, 13 DEGs and nine DEMs were validated using quantitative real-time PCR, and seven critical genes were selected to explore the influence of fat and fatty acids through hub genes and predict functional association. A dual-luciferase reporter and Western blot assays confirmed a predicted miRNA target (bta-miR-409a and PLIN5). These findings provide substantial evidence for molecular genetic controls and interaction among genes in cattle.

Heat treatment reduced the expression of miR-7-5p to facilitate insulin-stimulated lactate secretion by targeting IRS2 in boar Sertoli cells

Insulin dysfunction of diabetes mellitus (DM) disorders the glucose metabolism in Sertoli cells (SCs), resulting in the impairment of spermatogenesis.Insulin signaling system in Sertoli cells (SCs) plays an important role in regulating lactate secretion. Heat treatment could increase the lactate secretion of boar SCs, but whether heat treatment participates in lactate secretion by improving the sensitivity of insulin is unknown. In the current study, the primary SCs from 21-day-old boar were employed to treat with 100 nM insulin for 24 h or heat treatment (43 °C, 30 min). Heat treatment strengthened the effect of insulin on the effect of lactate secretion. In addition, heat treatment increased the expression of insulin-induced insulin receptor substrate 2 (IRS2), but reduced the expression of miR-7-5p. Using dual luciferase reporter assay and Western blot, the study found that IRS2 is a potential target gene of miR-7-5p. Heat treatment also enhanced the Phosphorylation of insulin-stimulated PI3K/Akt, and increased lactate secretion by promoting the expression of Glucose Transporter 3 (GLUT3), Lactate Dehydrogenase-A (LDHA) and monocarboxylate transporter 1 (MCT1). Furthermore, miR-7-5p inhibitor could partly mimic the effects of heat treatment on lactate production of SCs, indicating that heat treatment improves insulin sensitivity by regulating the expression of miR-7-5p/IRS2/PI3K/Akt. These results reveal a novel miRNA-mediated mechanism of heat treatment on the regulation of lactate metabolism production, and suggest that targeting miR-7-5p is a probably therapeutic method to insulin dysfunction-induced metabolic diseases.

The Role of microRNAs in the Mammary Gland Development, Health, and Function of Cattle, Goats, and Sheep

Milk is an integral and therefore complex structural element of mammalian nutrition. Therefore, it is simple to conclude that lactation, the process of producing milk, is as complex as the mammary gland, the organ responsible for this biochemical activity. Nutrition, genetics, epigenetics, disease pathogens, climatic conditions, and other environmental variables all impact breast productivity. In the last decade, the number of studies devoted to epigenetics has increased dramatically. Reports are increasingly describing the direct participation of microRNAs (miRNAs), small noncoding RNAs that regulate gene expression post-transcriptionally, in the regulation of mammary gland development and function. This paper presents a summary of the current state of knowledge about the roles of miRNAs in mammary gland development, health, and functions, particularly during lactation. The significance of miRNAs in signaling pathways, cellular proliferation, and the lipid metabolism in agricultural ruminants, which are crucial in light of their role in the nutrition of humans as consumers of dairy products, is discussed.

Effect of hyperthermia on cell viability, amino acid transfer, and milk protein synthesis in bovine mammary epithelial cells

The reduction of milk yield caused by heat stress in summer is the main condition restricting the economic benefits of dairy farms. To examine the impact of hyperthermia on bovine mammary epithelial (MAC-T) cells, we incubated the MAC-T cells at thermal-neutral (37°C, CON group) and hyperthermic (42°C, HS group) temperatures for 6 h. Subsequently, the cell viability and apoptotic rate of MAC-T cells, apoptosis-related genes expression, casein and amino acid transporter genes, and the expression of the apoptosis-related proteins were examined. Compared with the CON group, hyperthermia significantly decreased the cell viability (p < 0.05) and elevated the apoptotic rate (p < 0.05) of MAC-T cells. Moreover, the expression of heat shock protein (HSP)70, HSP90B1, Bcl-2-associated X protein (BAX), Caspase-9, and Caspase-3 genes was upregulated (p < 0.05). The expression of HSP70 and BAX (pro-apoptotic) proteins was upregulated (p < 0.05) while that of B-cell lymphoma (BCL)2 (antiapoptotic) protein was downregulated (p < 0.05) by hyperthermia. Decreased mRNA expression of mechanistic target of rapamycin (mTOR) signaling pathway-related genes, amino acid transporter genes (SLC7A5, SLC38A3, SLC38A2, and SLC38A9), and casein genes (CSNS1, CSN2, and CSN3) was found in the heat stress (HS) group (p < 0.05) in contrast with the CON group. These findings illustrated that hyperthermia promoted cell apoptosis and reduced the transport of amino acids into cells, which inhibited the milk proteins synthesis in MAC-T cells.

Identification and bioinformatics analysis of differentially expressed milk exosomal microRNAs in milk exosomes of heat-stressed Holstein cows

In summer, heat stress is one of the primary reasons for the compromised health and low milk productivity of dairy cows. Hyperthermia affects milk synthesis and secretion in the mammary glands of dairy cows. As molecules for intercellular communication, milk-derived exosomes carry genetic material, proteins, and lipids, playing a crucial role in mammary tissue growth and milk synthesis in dairy cows. The aim of this study was to explore the milk exosomal miRNA profile of heat-stressed and normal Holstein cows. We isolated and identified milk exosomes to screening for differentially expressed miRNAs using small RNA sequencing. Then, TargetScan and miRanda algorithms were used to predict the putative targets of the differentially expressed miRNAs, whereas GO and KEGG pathway enrichment analyses were performed for the differentially expressed miRNA-target genes. Our results showed that 215 miRNAs were significantly differentially expressed in heat-stressed milk exosomes, of which one was upregulated and 214 were significantly downregulated. GO and KEGG enrichment analyses indicated that differentially expressed miRNAs might play a role in apoptosis, autophagy, and the p38 MAPK pathway. qRT-PCR assay verified that the expression of miRNAs was consistent with the sequencing results, warranting further verification of their specific targets of action. In conclusion, changes in the miRNA expression profile of milk exosomes indicated the role of exosomal miRNAs in regulating heat stress resistance and apoptosis in dairy cows. Our results suggested that milk-derived exosomal miRNAs could increase mammary gland resistance to heat stress, thereby enhancing milk synthesis in dairy cows.

Enhanced supply of methionine regulates protein synthesis in bovine mammary epithelial cells under hyperthermia condition

Recent evidence has shown that methionine (Met) supplementation can improve milk protein synthesis under hyperthermia (which reduces milk production). To explore the mechanism by which milk protein synthesis is affected by Met supplementation under hyperthermia, mammary alveolar (MAC-T) cells were incubated at a hyperthermic temperature of 42°C for 6 h in media with different concentrations of Met. While the control group (CON) contained a normal amino acid concentration profile (60 μg/mL of Met), the three treatment groups were supplemented with Met at concentrations of 10 μg/mL (MET70, 70 μg/mL of Met), 20 μg/mL (MET80, 80 μg/mL of Met), and 30 μg/mL (MET90,90 μg/mL of Met). Our results show that additional Met supplementation increases the mRNA and protein levels of BCL2 (B-cell lymphoma-2, an anti-apoptosis agent), and decreases the mRNA and protein levels of BAX (Bcl-2-associated X protein, a pro-apoptosis agent), especially at an additional supplementary concentration of 20 μg/mL (group Met80). Supplementation with higher concentrations of Met decreased the mRNA levels of Caspase-3 and Caspase-9, and increased protein levels of heat shock protein (HSP70). The total protein levels of the mechanistic target of rapamycin (mTOR) and the mTOR signalling pathway-related proteins, AKT, ribosomal protein S6 kinase B1 (RPS6KB1), and ribosomal protein S6 (RPS6), increased with increasing Met supplementation, and peaked at 80 μg/mL Met (group Met80). In addition, we also found that additional Met supplementation upregulated the gene expression of αS1-casein (CSN1S1), β-casein (CSN2), and the amino acid transporter genes SLC38A2, SLC38A3 which are known to be mTOR targets. Additional Met supplementation, however, had no effect on the gene expression of κ-casein (CSN3) and solute carrier family 34 member 2 (SLC34A2). Our results suggest that additional Met supplementation with 20 μg/mL may promote the synthesis of milk proteins in bovine mammary epithelial cells under hyperthermia by inhibiting apoptosis, activating the AKT-mTOR-RPS6KB1 signalling pathway, and regulating the entry of amino acids into these cells.

Multifaceted roles of HSF1 in cell death: A state-of-the-art review

Cell death is a common and active process that is involved in various biological processes, including organ development, morphogenesis, maintaining tissue homeostasis and eliminating potentially harmful cells. Abnormal regulation of cell death significantly contributes to tumor development, progression and chemoresistance. The mechanisms of cell death are complex and involve not only apoptosis and necrosis but also their cross-talk with other types of cell death, such as autophagy and the newly identified ferroptosis. Cancer cells are chronically exposed to various stresses, such as lack of oxygen and nutrients, immune responses, dysregulated metabolism and genomic instability, all of which lead to activation of heat shock factor 1 (HSF1). In response to heat shock, oxidative stress and proteotoxic stresses, HSF1 upregulates transcription of heat shock proteins (HSPs), which act as molecular chaperones to protect normal cells from stresses and various diseases. Accumulating evidence suggests that HSF1 regulates multiple types of cell death through different signaling pathways as well as expression of distinct target genes in cancer cells. Here, we review the current understanding of the potential roles and molecular mechanism of HSF1 in regulating apoptosis, autophagy and ferroptosis. Deciphering HSF1-regulated signaling pathways and target genes may help in the development of new targeted anti-cancer therapeutic strategies.

Characterization of Short-Term Heat Stress in Holstein Dairy Cows Using Altered Indicators of Metabolomics, Blood Parameters, Milk MicroRNA-216 and Characteristics

Simple Summary

In this study, we characterize the influence of short-term (4 days) heat stress on Holstein cows during early lactation. The use of indicators, such as production performance, physiological variables, blood parameters, micro-RNA expression, and metabolomes, in heat-stressed cows during early lactation—which is a high-stress phase—may provide insights into how to deal with the level of damage to dairy cows, through appropriate nutritional and management strategies. We identify that short-term heat stress has a negative effect, to some extent, on feed and water intake, rectal temperature, heart rate, blood hematology and metabolites, milk characteristics, miRNA expression in milk, and metabolomics in blood.

Abstract

This study aims to characterize the influence of short-term heat stress (HS; 4 day) in early lactating Holstein dairy cows, in terms of triggering blood metabolomics and parameters, milk yield and composition, and milk microRNA expression. Eight cows (milk yield = 30 ± 1.5 kg/day, parity = 1.09 ± 0.05) were homogeneously housed in environmentally controlled chambers, assigned into two groups with respect to the temperature humidity index (THI) at two distinct levels: approximately ~71 (low-temperature, low-humidity; LTLH) and ~86 (high-temperature, high-humidity; HTHH). Average feed intake (FI) dropped about 10 kg in the HTHH group, compared with the LTLH group (p = 0.001), whereas water intake was only numerically higher (p = 0.183) in the HTHH group than in the LTLH group. Physiological parameters, including rectal temperature (p = 0.001) and heart rate (p = 0.038), were significantly higher in the HTHH group than in the LTLH group. Plasma cortisol and haptoglobin were higher (p < 0.05) in the HTHH group, compared to the LTLH group. Milk yield, milk fat yield, 3.5% fat-corrected milk (FCM), and energy-corrected milk (ECM) were lower (p < 0.05) in the HTHH group than in the LTLH group. Higher relative expression of milk miRNA-216 was observed in the HTHH group (p < 0.05). Valine, isoleucine, methionine, phenylalanine, tyrosine, tryptophan, lactic acid, 3-phenylpropionic acid, 1,5-anhydro-D-sorbitol, myo-inositol, and urea were decreased (p < 0.05). These results suggest that early lactating cows are more vulnerable to short-term (4 day) high THI levels—that is, HTHH conditions—compared with LTLH, considering the enormous negative effects observed in measured blood metabolomics and parameters, milk yield and compositions, and milk miRNA-216 expression.

CDK5RAP3, a Novel Nucleoplasmic Shuttle, Deeply Regulates HSF1-Mediated Heat Stress Response and Protects Mammary Epithelial Cells from Heat Injury

CDK5RAP3 was regarded as the most significant regulator of cellular responses against heat stress, which is associated with dysfunctions of the immune system and animal susceptibility to disease. Despite this, little known about how CDK5RAP3 regulates heat stress response. In this study, CDK5RAP3 conditional Knockout (CKO) mice, CDK5RAP3-/- mouse embryo fibroblasts (MEFs) and bovine mammary epithelial cells (BMECs) were used as an in vitro and in vivo model, respectively to reveal the role of CDK5RAP3 in regulating the heat stress response. The deletion of CDK5RAP3 unexpectedly caused animal lethality after 1.5-h heat stimulations. Furthermore, BMECs were re-cultured for eight hours after heat stress and was found that the expression of CDK5RAP3 and HSPs showed a similar fluctuating pattern of increase (0-2, 4-6 h) and decrease (2-4, 6-8 h). In addition to the remarkably enhanced expression of heat shock protein, apoptosis rate and endoplasmic reticulum stress, the deletion of CDK5RAP3 also affected nucleoplasmic translocation and trimer formation of heat shock factor 1 (HSF1). These programs were further confirmed in the mammary gland of CDK5RAP3 CKO mice and CDK5RAP3-/- MEFs as well. Interestingly, genetic silencing of HSF1 downregulated CDK5RAP3 expression in BMECs. Immunostaining and immunoprecipitation studies suggested a physical interaction between CDK5RAP3 and HSF1 being co-localized in the cytoplasm and nucleus. Besides, CDK5RAP3 also interacted with HSP90, suggesting an operative machinery at both transcriptional level and protein functionality of HSP90 per se. Together, our findings suggested that CDK5RAP3 works like a novel nucleoplasmic shuttle or molecular chaperone, deeply participating in HSF1-mediated heat stress response and protecting cells from heat injury.

Significance of molecular chaperones and micro RNAs in acquisition of thermo-tolerance in dairy cattle

Ambient temperature is considered as the major abiotic factor which regulates body physiological mechanisms of all living creatures across the globe. Variation in ambient temperature which emulates thermoneutral zone culminates in heat stress. Heat stress has been emerged as major ultimatum to livestock's growth, development, production and reproduction across the world. Livestock's responds to the heat stress via different mechanisms such as behavioral, physiological, biochemical, endocrine and molecular mechanisms. Amongst the aforementioned mechanisms, molecular mechanism plays crucial role to achieve thermo-tolerance via expression of highly conserved family of proteins known as heat shock proteins (HSPs) across livestock species. HSPs serve as molecular chaperones to ameliorate the menace of heat stress in domestic species. In addition, microRNAs are small non-coding RNA which down regulates post-transcriptional gene expression by targeting various HSPs to regulate the thermoregulatory responses in livestock species. Despite of thermal adaptation mechanisms, heat stress breaches animal body homeostasis thereby depresses their production and productivity. Therefore, veterinary researches have been targeting to explore different repertoire of HSPs and microRNAs expression to counteract the rigors of heat stress thereby confer thermo-tolerance in livestock species. The present review highlights the significance of molecular chaperones and microRNAs in the acquisition of thermo-tolerance in dairy cattle.

Effect of heat stress on udder health of dairy cows

This Research Reflection short review presents an overview of the effects of heat stress on dairy cattle udder health and discusses existing heat stress mitigation strategies for a better understanding and identification of appropriate abatement plans for future stress management. Due to high ambient temperatures with high relative humidity in summer, dairy cows respond by changes of physical, biochemical and biological pathways to neutralize heat stress resulting in decreased production performance and poorer immunity resulting in an increased incidence of intramammary infections (IMI) and a higher somatic cell count (SCC). In vitro studies on bovine polymorphonuclear cells (PMN) suggested that heat stress reduces the phagocytosis capacity and oxidative burst of PMN and alters the expression of apoptotic genes and miRNA which, together with having a negative effect on the immune system, may explain the increased susceptibility to IMI. Although there are limited data regarding the incidence rate of clinical mastitis in many countries or regions, knowledge of SCC at the cow or bulk tank level helps encourage farmers to improve herd health and to develop strategies for infection prevention and cure. Therefore, more research into bulk tank SCC and clinical mastitis rates is needed to explain the effect of heat stress on dairy cow udder health and functions that could be influenced by abatement plans.

Hyperthermia and protein homeostasis: Cytoprotection and cell death

Protein homeostasis or proteostasis, the correct balance between production and degradation of proteins, is an essential pillar for proper cellular function. Among the several cellular mechanisms that disrupt homeostatic conditions in cancer cells, hyperthermia (HT) has shown promising anti-tumor effects. However, cancer cells are also capable of thermoresistance. Indeed, HT-induced protein denaturation and aggregation results in the up regulation of heat shock proteins, a group of molecular chaperones with cytoprotective and anti-apoptotic properties via stress-inducible transcription factor, heat shock factor 1(HSF1). Heat shock proteins assist in the refolding of misfolded proteins and aids in their elimination if they become irreversibly damaged by various stressors. Furthermore, HSF1 also initiates the unfolded protein response in the endoplasmic reticulum (ER) to assist in the protein folding capacity of ER and also promotes the translation of pro-survival proteins' mRNA such as activating transcription factor 4 (ATF 4). Moreover, HT associated induction of microRNAs is also involved in thermal resistance of cancer cells via up-regulation of anti-apoptotic Bcl-2 proteins and down regulation of pro-apoptotic Bax and caspase 3 activities. Another cellular protection in response to stressors is Autophagy, which is regulated by the Mammalian target of rapamycin (mTOR) protein. Kinase activity in mTOR phosphorylates HSF1 and promotes its nuclear translocation for heat shock protein synthesis. Over-expression of heat shock proteins are reported to up-regulate Beclin-1, an autophagy initiator. Moreover, HT-induced reactive oxygen species (ROS) generation is sensitized by transcription factor NF-E2 related factor 2 (Nrf2) and activates the cellular expression of antioxidants and autophagy gene. Furthermore, ROS also potentiates autophagy via activation of Beclin-1. Inhibition of thermotolerance can potentiate HT-induced apoptosis. Here, we outlined that heat stress alters cellular proteins which activates cellular homeostatic processes to promote cell survival and make cancer cells thermotolerant.

Integrating miRNA and mRNA expression profiles in plasma of laying hens associated with heat stress

High temperature is one of the most common environmental stressors plaguing animal husbandry worldwide. Little is known about the regulatory roles of miRNAs in response to heat stress in laying hens. To systematically identify heat stress-responsive miRNAs and their targets in laying hens, the differential expression of miRNAs and mRNAs was compared under heat stress and normal temperature. We identified 16 miRNAs and 502 genes that were significantly changed in heat-stressed laying hens. By comparing the differentially expressed genes (DEGs) and the putative targets of the altered miRNAs based on bioinformatics prediction, 82 coordinated genes were identified. Gene ontology classification analyses of the 82 putative target genes showed that the biological category 'cellular response to stress' was prominently annotated. Notably, the response-related gene autophagy-related protein 9A was most likely controlled by the upregulated miRNAs gga-miR-92-5p, gga-miR-1618-5p, gga-miR-1737, and gga-miR-6557 in response to heat stress. Analysis of DEGs also revealed an increase in lipid metabolism in heat-stressed laying hens. Some of these genes were negatively correlated with the altered miRNAs, suggesting that they are potential targets of the miRNAs. Taken together, our results advance our understanding of the regulatory mechanism of heat-stress-induced injury in laying hens, specifically with regard to miRNAs.

Understanding microRNAs regulation in heat shock response in the sea cucumber Apostichopus japonicus

The sea cucumber Apostichopus japonicus is a valuable species in China. The extreme high temperature in the summer often results in high mortality. MicroRNAs (miRNAs) play important post-transcriptional regulatory roles in gene expression and can influence heat shock response (HSR) greatly. In this study, we determined the expression profiles of miRNAs under heat stress (HS) in A. japonicus by using high-throughput sequencing technique. Among the differential expression miRNAs, we highlighted 41 differentially expressed miRNAs, many of which were involved in immunity process and disease regulation. Gene ontology and pathway analyses of putative target genes were also carried out. Cell-substrate adherens junction and cell-substrate junction were significantly enriched in GO analysis. Moreover, we made a correlation analysis between remarkable miRNAs and the differentially expressed genes (DEGs) in sea cucumbers under HS. We identified 17 key miRNA-target pairs potentially regulated HSR of sea cucumbers. These results will provide new insights about miRNAs regulation and molecular adaptive mechanisms in sea cucumbers under HS.