Peripheral blood mononuclear cells: a potential cellular system to understand differential heat shock response across native cattle (Bos indicus), exotic cattle (Bos taurus), and riverine buffaloes (Bubalus bubalis) of India

Comparative physiological and biochemical assessment of the heat tolerance of dwarf Vechur, Kasaragod, and standard-size crossbred cattle under humid, hot conditions

Reduced body size is an ecological response to climate change. Differential responses to heat stress in phenotypically diverse bovine lineages may imply a body size-dependent stress response. Heat-tolerant dwarf Vechur, Kasaragod (Bos taurus indicus), and heat-sensitive crossbred (CB, B. t. indicus x B. t. taurus) cattle were tested physiologically, biochemically, and in terms of cellular protein expression. Thirty adult lactating cows (ten Vechur, Kasaragod, and CBs each) were allowed to graze during the summer. The environmental parameters measured included Ta (ambient temperature), RH (humidity), WS (wind speed), and SR (solar radiation intensity). In addition, the temperature humidity index (THI), heat load index (HLI), and accumulated heat load (AHL) were computed. The panting score (PS) was determined using breath characteristics. Numerous physiological (rectal temperature-RT, respiratory rate-RR and pulse rate-PR), haematological, and biochemical (serum cortisol) heat stress markers were identified and validated. RT, RR and PR were evaluated to determine the linear correlation coefficients and predictors. The correlation coefficients in CB were significantly higher than in Vechur and Kasaragod (p < 0.01). Stepwise regressions showed that in CB, Ta alone was the environmental measure that best described the indicator variables PS, the difference between RT recorded at half-hour intervals (RTdiff, R2 = 0.925), and white blood cell count (R2 = 0.984). Differences in cellular protein expression were also evident. Under heat stress conditions, linear discriminants based on RT, RR, and PR separated dwarf (Vechur and Kasaragod) and crossbred cattle into various clusters, and significant breed-wise grouping was identified based on haematological parameters in pre-stress and heat stress. The study established the variable heat stress response of phenotypically divergent Bos lineages and relevant heat stress markers and thermal indices for measuring heat stress.

A systematic review on the trend of transcriptomic study in livestock: An effort to unwind the complexity of adaptation in a climate change environment

Heat stress has been proven to cause negative effects on livestock leading to lower productivity and economic value. Understanding how heat stress manifests within an animal's body is the first step in devising a heat stress mitigation strategy; transcriptomic studies are one of the methods used. Here, using a systematic literature review methodology, we examine the recent decade of transcriptomics' application to the study of livestock adaptation. We identified 152 studies that met our criteria for using transcriptome methods to heat stress adaptation and were published within the last ten years. Our analysis demonstrates the growing popularity and application of transcriptome approaches in the investigation of the response of ruminants, pigs, and poultry livestock to heat stress. Majority of the works was done in chicken and cattle using multiple organs as the sample, with qRT-PCR as the most employed technique. It has been established that a variety of biomarkers can be used to assess animals under heat stress, such as the HSPs, ILs, and TLRs. Although transcriptomics has lately been employed extensively to uncover the mechanism of heat adaptation, this adaptive feature's complex mechanism remains unclear, leaving many knowledge gaps for investigation. A more complex studies involving more various cell types, organs, or even model organisms using multi-omics approach could be the future research direction in understanding the heat stress effects on livestock better.

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.

Hypoxia related genes modulate in similar fashion in skin fibroblast cells of yak (Bos grunniens) adapted to high altitude and native cows (Bos indicus) adapted to tropical climate during hypoxia stress

The present study was conducted to understand transcriptional response of skin fibroblast of yak (Bos grunniens) and cows of Bos indicus origin to hypoxia stress. Six primary fibroblast cell lines derived from three individuals each of Ladakhi yak (Bos grunniens) and Sahiwal cows (Bos indicus) were exposed to low oxygen concentration for a period of 24 h, 48 h and 72 h. The expression of 10 important genes known to regulate hypoxia response such as HIF1A, VEGFA, EPAS1, ATP1A1, GLUT1, HMOX1, ECE1, TNF-A, GPx and SOD were evaluated in fibroblast cells of Ladakhi yak (LAY-Fb) and Sahiwal cows (SAC-Fb) during pre- and post-hypoxia stress. A panel of 10 reference genes (GAPDH, RPL4, EEF1A1, RPS9, HPRT1, UXT, RPS23, B2M, RPS15, ACTB) were also evaluated for their expression stability to perform accurate normalization. The expression of HIF1A was significantly (p < 0.05) induced in both LAY-Fb (2.29-fold) and SAC-Fb (2.07-fold) after 24 h of hypoxia stress. The angiogenic (VEGFA), metabolic (GLUT1) and antioxidant genes (SOD and GPx) were also induced after 24 h of hypoxia stress. However, EPAS1 and ATP1A1 induced significantly (p < 0.05) after 48 h whereas, ECE1 expression induced significantly (p < 0.05) at 72 h after exposure to hypoxia. The TNF-alpha which is a pro-inflammatory gene induced significantly (p < 0.05) at 24 h in SAC-Fb and at 72 h in LAY-Fb. The induction of hypoxia associated genes indicated the utility of skin derived fibroblast as cellular model to evaluate transcriptome signatures post hypoxia stress in populations adapted to diverse altitudes.

Functional transcriptome analysis revealed major changes in pathways affecting systems biology of Tharparkar cattle under seasonal heat stress

Heat stress significantly disturbs the production, reproduction, and systems biology of dairy cattle. A complex interaction among biological systems helps to combat and overcome heat stress. Indicine cattle breed Tharparkar has been well known for its thermal adaptability. Therefore, present investigation considered RNA-seq technology to explore the functional transcriptomics of Tharparkar cattle with the help of samples collected in spring and summer season. Among differentially expressed genes, about 3280 genes were highly dysregulated, in which 1207 gene were upregulated and 2073 genes were downregulated (|log2fold change|≥ 1 and p ≤ 0.05). Upregulated genes were related to insulin activation, interferons, and potassium ion transport. In contrast, downregulated genes were related to RNA processing, translation, and ubiquitination. Functional annotation revealed that the pathways associated with nervous system (NPFFR1, ROBO3) and metal ion transport (KCNG2, ATP1A2) were highly activated while mRNA processing and translation (EIF4A, EIF4B) and protein processing pathway (VPS4B, PEX13) were highly downregulated. Protein-protein interactions identified hub genes such as ATP13A3, IFNGR2, UBXN7, EIF4A2, SLC12A8 found to play an important role in immune, ubiquitination, translation and transport function. Co-expression network includes LYZ, PNRC1, SQSTM1, EIF4AB and DDX17 genes which are involved in lysosomal activity, tumor inhibition, ubiquitination, and translation initiation. Chemokine signaling pathway associated with immune response was highly upregulated in cluster analysis. The findings of this study provide insights into transcriptome expression and regulation which may better explain complex thermal resilience mechanism of Tharparkar cattle in heat stress under natural conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-024-04018-2.

Effect of seven days heat stress on feed and water intake, milk characteristics, blood parameters, physiological indicators, and gene expression in Holstein dairy cows

This study examined the effects of 7 days of heat stress on eight early lactating Holstein cows in climate-controlled chambers. The early lactating Holstein cows (42 ± 2 days in milk, 29.27 ± 0.38 kg/day milk yield, 1.21 ± 0.05 parity) were subjected to two 14-day periods, each consisting of 7 days of adaptation and 7 days of heat stress. Conditions were set to 22 °C and 50% humidity during adaptation, followed by heat stress periods with low-temperature, low-humidity (LTLH, 71 THI) and high-temperature, high-humidity (HTHH, 86 THI) treatments. Data from the last 7 days were analyzed using a mixed procedure in SAS. In the study, the HTHH group displayed marked physiological and biochemical changes on 14 days of heat stress exposure compared to the LTLH group. Firstly, the HTHH group's dry matter intake decreased by approximately 12% while their water intake increased by about 23%. Secondly, both milk yield and milk protein production in the HTHH group decreased by 10% and 20%, respectively. Thirdly, there was a reduction in white blood cells, hemoglobin, mean corpuscular hemoglobin, and platelets in the HTHH group, with concurrent increases in glucose, non-esterified fatty acids, and albumin concentrations. Additionally, the HTHH group exhibited elevated plasma concentrations of cortisol and haptoglobin. Moreover, the gene expression of heat shock protein 70 and heat shock protein 90 was significantly upregulated in the HTHH group's peripheral blood mononuclear cells. Lastly, key physiological indicators such as rectal temperature, heart rate, and skin temperature showed substantial elevations in the HTHH group. Considering the enormous negative effects observed in the analyzed blood metabolites, milk yield and compositions, and heat shock protein gene expression, early lactating Holstein cows were found to be more vulnerable to HTHH than LTLH over a 7 days exposure to heat stress.

The HSP90AA1 gene is involved in heat stress responses and its functional genetic polymorphisms are associated with heat tolerance in Holstein cows

As the stress-inducible isoform of the heat-shock protein 90 (HSP90), the HSP90AA1 gene encodes HSP90α and plays an important role in heat stress (HS) response. Therefore, this study aimed to investigate the role of the HSP90AA1 gene in cellular responses during HS and to identify functional SNPs associated with thermotolerance in Holstein cattle. For the in vitro validation experiment of acute HS, cells from the Madin-Darby bovine kidney cell line were exposed to 42°C for 1 h, and various parameters were assessed, including cell apoptosis, cell autophagy, and the cellular functions of HSP90α by using its inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG). Furthermore, the polymorphisms identified in the HSP90AA1 gene and their functions related to HS were validated in vitro. Acute HS exposure induced cell apoptosis, cell autophagy, and upregulated expression of the HSP90AA1 gene. Inhibition of HSP90α by 17-AAG treatment had a significant effect on the expression of the HSP90α protein and increased cell apoptosis. However, autophagy decreased in comparison to the control treatment when cells were exposed to 42°C for 1 h. Five SNPs identified in the HSP90AA1 gene were significantly associated with rectal temperature and respiration score in Holstein cows, in which the rs109256957 SNP is located in the 3' untranslated region (3' UTR). Furthermore, we demonstrated that the 3' UTR of HSP90AA1 is a direct target of bta-miR-1224 by cell transfection with exogenous microRNA (miRNA) mimic and inhibitor. The luciferase assays revealed that the SNP rs109256957 affects the regulation of bta-miR-1224 binding activity and alters the expression of the HSP90AA1 gene. Heat stress-induced HSP90AA1 expression maintains cell survival by inhibiting cell apoptosis and increasing cell autophagy. The rs109256957 located in the 3' UTR region is a functional variation and it affects the HSP90AA1 expression by altering its binding activity with bta-miR-1224, thereby associating with the physiological parameters of Holstein cows.

Modulation of heat shock protein 70 (HSP70) gene expression ex vivo in response to heat stress in chicken

The present study was conducted to assess the effect of exposure to heat stress on the HSP70 gene expression pattern ex vivo in chickens. The adult healthy birds (n = 15) grouped into three replicates of n = 5 each were used to isolate peripheral blood mononuclear cells (PBMCs). The PBMCs were subjected to heat stress at 42 °C for 1 h, and cells without heat stress (NHS) were taken as control. The cells were seeded in 24 well plates and incubated in a humidified incubator at 37 °C under 5% CO2 for recovery. HSP70 expression kinetics were evaluated at 0, 2, 4, 6, and 8 h of the recovery period. Compared with NHS, the expression pattern of HSP70 was upregulated gradually from 0 to 4 h with peak (p < 0.05) expression recorded at 4 h of recovery time. mRNA expression of HSP70 escalated in a time-dependent manner from 0 to 4 h of heat exposure and thereafter exhibited a gradually decreasing pattern till 8 h of the recovery period. The findings from this study highlight the protective role of HSP70 against the deleterious effects of heat stress in chicken PBMCs. Further, the study demonstrates the possible use of PBMCs as a cellular system in assessing the heat stress effect in chickens ex vivo.

Editing of HSF-1 and Na/K-ATPase α1 subunit by CRISPR/Cas9 reduces thermal tolerance of bovine skin fibroblasts to heat shock in vitro

A follow-up to our previous findings, the present study was planned to evaluate the role of Na/K-ATPase alpha1-subunit (ATP1A1) gene in heat shock tolerance. The primary fibroblast culture was established using ear pinna tissue samples of Sahiwal cattle (Bos indicus). The knockout cell lines of Na/K-ATP1A1 and HSF-1 (heat shock factor-1, as a positive control) genes were developed by CRISPR/Cas9 method and the gene-editing was confirmed by the genomic cleavage detection assay. The two knockout cell lines (ATP1A1 and HSF-1) and wild-type fibroblasts were exposed to heat shock at 42 °C in vitro and different cellular parameters viz., apoptosis, proliferation, mitochondrial membrane potential (ΔΨm), oxidative stress, along with expression pattern of heat-responsive genes were studied. The results showed that in vitro heat shock given to knockout fibroblast cells of both ATP1A1 and HSF-1 genes resulted in decreased cell viability, while increasing the apoptosis rate, membrane depolarization, and ROS levels. However, the overall impact was more in HSF-1 knockout cells as compared to ATP1A1 knockout cells. Taken together, these results indicated that the ATP1A1 gene plays a critical role as HSF-1 under heat stress and helps cells to cope with heat shock.

Heat stress adaptation in cows - Physiological responses and underlying molecular mechanisms

Heat stress is a key abiotic stressor for dairy production in the tropics which is further compounded by the ongoing climate change. Heat stress not only adversely impacts the production and welfare of dairy cows but severely impacts the economics of dairying due to production losses and increased cost of rearing. Over the years, selection has ensured development of high producing breeds, however, the thermotolerance ability of animals has been largely overlooked. In the past decade, the ill effects of climate change have made it pertinent to rethink the selection strategies to opt for climate resilient breeds, to ensure optimum production and reproduction. This has led to renewed interest in evaluation of the impacts of heat stress on cows and the underlying mechanisms that results in their acclimatization and adaptation to varied thermal ambience. The understanding of heat stress and associated responses at various level of animal is crucial to device amelioration strategies to secure optimum production and welfare of cows. With this review, an effort has been made to provide an overview on temperature humidity index as an important indicator of heat stress, general effect of heat stress in dairy cows, and impact of heat stress and subsequent response at physiological, haematological, molecular and genetic level of dairy cows.

A comparative study on effect of heat stress on physiological and cellular responses of crossbred cattle and riverine buffalo in subtropical region of India

The study was carried out to compare the in vitro and in vivo heat shock responses of cattle and buffaloes. The expression of heat responsive genes (HSP70 and HSF family) were studied in vitro in peripheral blood mononuclear cells (PBMCs) of cattle and buffalo. In vivo observations on animals were carried out to investigate the physiological responses of cattle and buffalo at different THI over a period of 14 months. The study indicated that onset and severity of heat stress at different THI varied significantly between cattle and buffalo. Rectal temperature (RT) showed a significant (p < 0.05) increase at THI 67 in buffaloes and at THI 68 in cattle. Significant (p < 0.01) differences in RT between the species were observed at THI 71, 72, and 73. Respiration rate (RR) significantly (p < 0.05) increased at THI 70 in both the species and significant (p < 0.05) differences in RR were observed between the species at THI 65, 68, 69, and 74. THI had significant (p < 0.05) effect on blood glucose and blood electrolytes of the species with increased levels at higher THI. Serum AST and ALT levels showed less pronounced changes over increasing THI. Heat stress-associated expressions of HSP 70 genes followed temporal changes with incremental THI. The expression of HSPA8 was consistent at lower THI whereas upregulation of HSPA1A and HSPA1L was evident at higher THI. The study concludes that changes in physiological parameters such as RT and RR occur in a phasic pattern in both species and onset of heat stress was early in buffalo as compared to cattle.

Transcriptomic regulations of heat stress response in the liver of lactating dairy cows

BACKGROUND

The global dairy industry is currently facing the challenge of heat stress (HS). Despite the implementation of various measures to mitigate the negative impact of HS on milk production, the cellular response of dairy cows to HS is still not well understood. Our study aims to analyze transcriptomic dynamics and functional changes in the liver of cows subjected to heat stress (HS). To achieve this, a total of 9 Holstein dairy cows were randomly selected from three environmental conditions - heat stress (HS), pair-fed (PF), and thermoneutral (TN) groups - and liver biopsies were obtained for transcriptome analysis.

RESULTS

Both the dry matter intake (DMI) and milk yield of cows in the HS group exhibited significant reduction compared to the TN group. Through liver transcriptomic analysis, 483 differentially expressed genes (DEGs) were identified among three experimental groups. Especially, we found all the protein coding genes in mitochondria were significantly downregulated under HS and 6 heat shock proteins were significant upregulated after HS exposure, indicating HS may affect mitochondria integrity and jeopardize the metabolic homeostasis in liver. Furthermore, Gene ontology (GO) enrichment of DEGs revealed that the protein folding pathway was upregulated while oxidative phosphorylation was downregulated in the HS group, corresponding to impaired energy production caused by mitochondria dysfunction.

CONCLUSIONS

The liver transcriptome analysis generated a comprehensive gene expression regulation network upon HS in lactating dairy cows. Overall, this study provides novel insights into molecular and metabolic changes of cows conditioned under HS. The key genes and pathways identified in this study provided further understanding of transcriptome regulation of HS response and could serve as vital references to mitigate the HS effects on dairy cow health and productivity.

Heat stress effects on milk yield traits and metabolites and mitigation strategies for dairy cattle breeds reared in tropical and sub-tropical countries

Heat stress is an important problem for dairy industry in many parts of the world owing to its adverse effects on productivity and profitability. Heat stress in dairy cattle is caused by an increase in core body temperature, which affects the fat production in the mammary gland. It reduces milk yield, dry matter intake, and alters the milk composition, such as fat, protein, lactose, and solids-not-fats percentages among others. Understanding the biological mechanisms of climatic adaptation, identifying and exploring signatures of selection, genomic diversity and identification of candidate genes for heat tolerance within indicine and taurine dairy breeds is an important progression toward breeding better dairy cattle adapted to changing climatic conditions of the tropics. Identifying breeds that are heat tolerant and their use in genetic improvement programs is crucial for improving dairy cattle productivity and profitability in the tropics. Genetic improvement for heat tolerance requires availability of genetic parameters, but these genetic parameters are currently missing in many tropical countries. In this article, we reviewed the HS effects on dairy cattle with regard to (1) physiological parameters; (2) milk yield and composition traits; and (3) milk and blood metabolites for dairy cattle reared in tropical countries. In addition, mitigation strategies such as physical modification of environment, nutritional, and genetic development of heat tolerant dairy cattle to prevent the adverse effects of HS on dairy cattle are discussed. In tropical climates, a more and cost-effective strategy to overcome HS effects is to genetically select more adaptable and heat tolerant breeds, use of crossbred animals for milk production, i.e., crosses between indicine breeds such as Gir, white fulani, N'Dama, Sahiwal or Boran to taurine breeds such as Holstein-Friesian, Jersey or Brown Swiss. The results of this review will contribute to policy formulations with regard to strategies for mitigating the effects of HS on dairy cattle in tropical countries.

Inflammatory responses of bovine endometrial epithelial cells are increased under in vitro heat stress conditions

Cattle exposed to heat stress have reduced fertility, reduced milk production and increased incidence of postpartum uterine infection. Heat stress is suggested to alter immune function of cattle; however, the mechanisms underlying heat stress mediated uterine infection are unknown. We hypothesized that exposure of endometrial cells to heat stress would further increase expression of inflammatory mediators in response to bacterial components due to altered heat-shock protein expression. Bovine endometrial epithelial cells (BEND) were exposed to Escherichia coli lipopolysaccharide (LPS) or a synthetic triacylated lipopeptide (Pam3CSK4) under heat stress (41.0 °C) or thermoneutral (38.5 °C) conditions for 24 h. Exposure of BEND cells to LPS or Pam3CSK4 increased the expression of the proinflammatory mediators IL1B, IL6, and CXCL8 compared to control medium. However, exposure of BEND cells to heat stress increased LPS and Pam3CSK4 induced expression of IL1B compared to cells exposed to thermoneutral conditions, and expression of LPS induced IL6 was also increased when BEND cells were exposed to heat stress. To determine if heat shock proteins increased BEND cell expression of inflammatory mediators, HSP1A1 and HSF1 were targeted by siRNA knock down. Expression of HSP1A1 and HSF1 were reduced following siRNA knockdown; however, knockdown of HSP1A1 or HSF1 further increased heat stress mediated increased expression of inflammatory mediators. These data suggest that heat stress increased BEND cell inflammatory responses to bacterial components, while heat shock proteins HSP1A1 and HSF1 help to restrain inflammatory responses. These mechanisms may contribute to the increased incidence of uterine infection observed in cows under heat stress conditions.

Expression profiling of heat shock protein genes in whole blood of Romosinuano cattle breed

Background and Aim: Heat shock proteins are highly conserved proteins that work as molecular chaperones expressed in response to thermal stress. This study aimed to determine the expression profile of genes related to the heat stress response in whole blood obtained from the Romosinuano creole breed. Materials and Methods: Real-time polymerase chain reaction was performed to analyze the transcript of hsp90, hsp70, hsp60, and hsf1 in the whole blood of Romosinuano under different temperature-humidity indices (THIs). Results: The expression levels of the hsp70 and hsf1 genes at the high-THI level were higher (p = 0.0011 and p = 0.0003, respectively) than those at the low-THI level. In addition, no differences in the expression levels of the hsp60 and hsP90 genes were detected between the two THIs. Conclusion: The overexpression of hsf1 and hsp70 genes play an important role in protecting cells from damage induced by heat stress. Keywords: climate change, external environment, heat shock proteins, heat stress, mRNA, temperature-humidity index.

Expression profiling of heat shock protein genes in whole blood of Romosinuano cattle breed

Background and Aim

Heat shock proteins are highly conserved proteins that work as molecular chaperones expressed in response to thermal stress. This study aimed to determine the expression profile of genes related to the heat stress response in whole blood obtained from the Romosinuano creole breed.

Materials and Methods

Real-time polymerase chain reaction was performed to analyze the transcript of hsp90, hsp70, hsp60, and hsf1 in the whole blood of Romosinuano under different temperature-humidity indices (THIs).

Results

The expression levels of the hsp70 and hsf1 genes at the high-THI level were higher (p = 0.0011 and p = 0.0003, respectively) than those at the low-THI level. In addition, no differences in the expression levels of the hsp60 and hsP90 genes were detected between the two THIs.

Conclusion

The overexpression of hsf1 and hsp70 genes play an important role in protecting cells from damage induced by heat stress.

Hypoxia-inducible factor-1α is involved in the response to heat stress in lactating dairy cows

Hypoxia-inducible factor-1α (HIF-1α) is important in maintaining cellular oxygen homeostasis and cellular heat tolerance. To explore the role of HIF-1α in the response to heat stress (HS) in dairy cows, 16 Chinese Holstein cows (milk yield: 32 ± 4 kg/d, days in milk: 272 ± 7 d, parity: 2-3) were used to collect coccygeal vein blood and milk samples when cows were under mild (temperature-humidity index = 77) and moderate HS (temperature-humidity index = 84), respectively. Compared to cows under mild HS, the respiratory rate (P < 0.01), rectal temperature (P < 0.01), and blood concentrations of heat shock protein (HSP)70 (P < 0.01) and HSP27 (P < 0.01) were higher, but oxygen saturation (P = 0.02) and hemoglobin (P < 0.01) were lower in cows under moderate HS. Blood HIF-1α concentration was greater (P < 0.01) during moderate HS, indicating that HIF-1α is involved in lactating cows' response to HS. To confirm these findings, we collected coccygeal vein blood and milk samples from 59 dairy cows under moderate HS. The HIF-1α levels were correlated with the levels of heat shock transcription factor (HSF) (r = 0.7857, P < 0.01), HSP70 (r = 0.4543, P < 0.01) and HSP27 (r = 0.8782, P < 0.01). A comparison of 15 cows with higher HIF-1α (>482 ng/L) and 15 cows with lower HIF-1α levels (<439 ng/L) showed that reactive oxidative species were higher (P = 0.02), but superoxide dismutase (P < 0.01), total antioxidation capacity (P = 0.02) and glutathione peroxidase (P < 0.01) were lower in higher HIF-1α cows. These results suggested that HIF-1α may be indicative of the risk of oxidative stress in heat-stressed cows and may participate in the response of cows to HS by synergistically activating the expression of the HSP family with HSF.

The profile of HSPA1A gene expression and its association with heat tolerance in crossbred cattle and the tropically adapted dwarf Vechur and Kasaragod

Certain livestock breeds are adapted to hot and humid environments, and these breeds have genetics that could be useful in a changing climate. The expression of several genes has been identified as a useful biomarker for heat stress. In this study, the responses to heat exposure of heat-tolerant Vechur and Kasaragod cattle found in Kerala state in India (also known as dwarf Bos taurus indicus) were compared to crossbred cattle (crosses of Bos t. taurus with Bos t. indicus). At various time points during heat exposure, rectal temperature and the expression of HSPA1A were determined, and the relationship between them was characterized. We characterized HSPA1A mRNA in Vechur cattle and performed molecular clock analysis. The expression of HSPA1A between the lineages and at different temperature humidity index (THI) was significant. There were significant differences between the expression profiles of HSPA1A in Kasaragod and crossbred (p < 0.01) and Vechur and crossbred (p < 0.01) cattle, but no significant difference in expression was observed between Vechur and Kasaragod cattle. The genetic distance between Vechur, B. grunniens, B. t. taurus, and B. t. indicus was 0.0233, 0.0059, and 0.007, respectively. The genetic distance between Vechur and the Indian dwarf breed Malnad Gidda was 0.0081. A molecular clock analysis revealed divergent adaptive evolution of Vechur cattle to B. t. taurus, with adaptations to the high temperatures and humidity that are prevalent in their breeding tract in Kerala, India. These results could also prove useful in selecting heat-tolerant animals using HSPA1A as a marker.

Hyper-transcription of heat shock factors and heat shock proteins safeguard caprine cardiac cells against heat stress

The present study was undertaken to document the transcriptional abundance of heat shock factors and heat shock proteins and their role in survivability of caprine cardiac cells during heat stress. Cardiac tissues were collected from different goats (n = 6) and primary cardiac cell culture was done in an atmosphere of 5% CO₂ and 95% air at 38.5 °C. Cardiac cells accomplished 70-75% confluence after 72 h of incubation. Confluent cardiac cells were exposed to heat stress at 42 °C for 0 (control), 20, 60, 100 and 200 min. Quantitative RT-PCR for β2m (internal control), heat shock factors (HSF1, HSF2, HSF4, HSF5), heat shock proteins (HSP10, HSP40), and Caspase-3 was done and their transcriptional abundance was assessed by Pfaffl method. Transcriptional abundance of HSF1, HSF2, and HSF4 did not change at 20 min, increased (P < 0.05) from 60 to 200 min and reached zenith at 200 min of heat exposure. However, transcriptional abundance of HSF5 was gradually escalated (P < 0.05) from 20 to 200 min and registered highest at 200 min of heat exposure. Transcriptional abundance of HSP10 and HSP40 followed an similar pattern like that of HSF5. Transcriptional abundance of Caspase-3 was significantly down-regulated at 200 min of heat exposure. It could be speculated that over-expression of HSFs and HSPs might have reduced Caspase-3 expression at 200 min of heat exposure suggesting their involvement in cardiac cells survival under heat stress. Moreover, hyper-expression of HSFs and HSPs could maintain the integrity and endurance of cardiac tissues of goats under heat stress.

Selection of species specific panel of reference genes in peripheral blood mononuclear cells of native livestock species adapted to trans-Himalayan region of Leh-Ladakh

The identification of appropriate references genes is an integral component of any gene expression-based study for getting accuracy and reliability in data interpretation. In this study, we evaluated the expression stability of 10 candidate reference genes (GAPDH, RPL4, EEF1A1, RPS9, HPRT1, UXT, RPS23, B2M, RPS15, ACTB) in peripheral blood mononuclear cells of livestock species that are adapted to high altitude hypoxia conditions of Leh-Ladakh. A total of 37 PBMCs samples from six native livestock species of Leh-Ladakh region such as Ladakhi cattle, Ladakhi yak, Ladakhi donkey, Chanthangi goat, Double hump cattle and Zanskar ponies were included in this study. The commonly used statistical algorithms such as geNorm, Normfinder, BestKeeper and RefFinder were employed to assess the stability of these RGs in all the livestock species. Our study has identified different panel of reference genes in each species; for example, EEF1A1, RPL4 in Ladakhi cattle; GAPDH, RPS9, ACTB in Ladakhi yak; HPRT1, B2M, ACTB in Ladakhi donkey; HPRT1, B2M, ACTB in Double hump camel, RPS9, HPRT1 in Changthangi goat, HPRT1 and ACTB in Zanskar ponies. To the best of our knowledge, this is the first systematic attempt to identify panel of RGs across different livestock species types adapted to high altitude hypoxia conditions. In future, the findings of the present study would be quite helpful in conducting any transcriptional studies to understand the molecular basis of high altitude adaptation of native livestock population of Leh-Ladakh.

Characterization of thermo-physiological, hematological, and molecular changes in response to seasonal variations in two tropically adapted native cattle breeds of Bos indicus lineage in hot arid ambience of Thar Desert

The selection of climate resilient animal is necessary to secure the future of sustainable animal production. The present investigation therefore was an effort to unravel answers to the adaptation at physiological, hematological, and molecular levels in cows of hot arid region that helps them to survive harsh environment, to continue production and reproduction. This investigation was carried out in indicine cows over a period of one year, encompassing four seasons, wherein physiological data of 50 animals, hematological data of 15 animals, and gene expression profile of 5 animals from each of Sahiwal and Kankrej breeds per season was generated. In total, 5600 physiological observations, 1344 hematological observations, and 480 molecular samples were processed. The meteorological data revealed a high diurnal variation of temperature across seasons, with THI exceeding 80 during the months of summer and hot-humid seasons, indicating significant heat stress (HS). The physiological parameters showed an increasing trend with the incremental THI, with significantly (p < 0.05) higher values of rectal temperature (RT), respiration rate (RR), pulse rate (PR), and body surface temperature (BST) at ventral (VT), lateral (LT), dorsal (DT), and frontal (FT), in both breeds recorded during HS. The hematological pictures also revealed significant (p < 0.05) seasonal perturbations in erythrocytic and leucocytic parameters. Moreover, the molecular response was driven by a significant (p < 0.05) upregulation of all the key HSPs, HSP70, HSP90, HSP60, and HSP40, except HSP27 during the hotter months of summer and hot-humid seasons. The expression of HSF1, an important transcriptional regulator of  HSP70 was also significantly (p < 0.05) upregulated during summer season in both breeds. All the molecular chaperones revealed a significant upregulation during the summer season, followed by a decreasing trend by hot-humid season. The study indicated a well-developed thermotolerance mechanism in animals of both breeds, with Kankrej cows exhibiting better thermotolerance compared to Sahiwal cows.

Identification of Internal Reference Genes in Peripheral Blood Mononuclear Cells of Cattle Populations Adapted to Hot Arid Normoxia and Cold Arid Hypoxia Environments

To estimate gene expression in a reliable manner, quantitative real-time polymerase chain reaction data require normalisation using a panel of stably expressed reference genes (RGs). To date, information on an appropriate panel of RGs in cattle populations reared at cold arid high-altitude hypoxia and hot arid tropical normoxia environments is not available. Therefore, the present study was carried out to identify a panel of stably expressed RGs from 10 candidate genes (GAPDH, RPL4, EEF1A1, RPS9, HPRT1, UXT, HMBS, B2M, RPS15, and ACTB) in peripheral blood mononuclear cells (PBMCs) of cattle populations reared at cold arid high-altitude hypoxia and hot arid normoxia environments. Four different statistical algorithms: geNorm, NormFinder, BestKeeper, and RefFinder were used to assess the stability of these genes. A total of 30 blood samples were collected: six adult heifers each of Ladakhi (LAC) and Holstein Frisian crosses (HFX) and 4 Jersey (JYC) cows from cold arid high-altitude hypoxia environments (group I) and five adult heifers each of Sahiwal (SAC), Karan Fries (KFC), and Holstein Friesian (HFC) cows from hot arid normoxia environments (group II). Combined analysis of group I and group II resulted in identification of a panel of RGs like RPS9, RPS15, and GAPDH that could act as a useful resource to unravel the accurate transcriptional profile of PBMCs from diverse cattle populations adapted to distinct altitudes.

Whole-Genome comparative analysis reveals genetic mechanisms of disease resistance and heat tolerance of tropical Bos indicus cattle breeds

The Bos indicus cattle breeds have been naturally selected over thousands of years for disease resistance and thermo-tolerance. However, a genetic mechanism of these specific inherited characteristics needs to be discovered. Hence, in this study, the whole-genome comparative analysis of Bos indicus cattle breeds of Kangayam, Tharparkar, Sahiwal, Red Sindhi, and Hariana of the Indian subcontinent was conducted. The genetic variants identification analysis revealed a total of 15,58,51,012 SNPs and 1,00,62,805 InDels in the mapped reads across all Bos indicus cattle breeds. The functional annotation of 17,252 genes that comprised both, SNPs and InDels, of high functional impact on proteins, has been carried out. The functional annotation results revealed the pathways that were involved in the innate immune response including toll-like receptors, a retinoic acid-inducible gene I like receptors, NOD-like receptors, Jak-STAT signaling pathways, and the non-synonymous variants in the candidate immune genes. Further, we also identified several pathways involved in heat shock response, hair and skin properties, oxidative stress response, osmotic stress response, thermal sweating, feed intake, metabolism, and the non-synonymous variants in the candidate thermo-tolerant genes. These pathways and genes were directly or indirectly contributing to the disease resistance and thermo-tolerance adaptations of Bos indicus cattle breeds.

Long-term heat stress at final gestation: physiological and heat shock responses of Saanen goats

The long exposure to heat negatively changes performance and productivity of animals, particularly when heat stress is associated with gestation. Indeed, little is known about the negative effects of long-term heat stress on the final gestation of dairy goats. In this context, the physiological and cellular responses of Saanen goats submitted to heat stress (37°C from 10:00 to 16:00 h) were investigated from day 60th pre-partum to day 60th post-partum. At final gestation, 46 pregnant Saanen goats were randomly assigned to the treatments: control (CT; thermal neutral conditions) and heat stress (HS; climatic chamber). After partum, all experimental goats were maintained in thermal neutral conditions. The rectal, dorsal, mammary temperatures and respiratory frequency, cortisol release, milk yield, milk quality, and the genes HSP60, HSP70, HSP90, Glucocorticoid receptor and ACTHR. Goats subjected to HS showed significantly (P < 0.05) higher rectal, dorsal, and mammary temperatures and significantly mobilized the increase of respiratory frequency to lose heat as compared to CT goats. The HS challenge significantly increased cortisol release from day 15th pre-partum to day 15th post-partum. CT goats produced more milk than HS from weeks 4 to 10 of lactation (P <0.001), with no difference in milk quality. However, on day 15th post-partum, there was a significant effect of HS treatment on the expression of HSP70 and ACTHR genes as compared to CT treatment, confirming the long-term effect of HS on Saanen goats. In conclusion, the physiological parameters studied increased pre-partum in the hottest hour, and cortisol peaked on day 15 pre-partum for heat-stressed goats. Although on the 15th day post-partum, all goats were in thermal comfort, and the physiological parameters were within the normal range, the concentration of cortisol continued to be significantly higher for goats submitted to thermal stress. Indeed, milk yield was greater for goats subjected to pre-partum thermal comfort. Furthermore, the expression of HSP70 and ACTHR genes on peripheral blood mononuclear cells are interesting biomarkers for studying the long-term effect of heat stress on Saanen goats.

Behavioural, physiological, neuro-endocrine and molecular responses of cattle against heat stress: an updated review

The negative impact of heat stress on cattle growth, development, reproduction and production has been quite alarming across the world. Climate change elevates earth surface temperature which exacerbates the wrath of heat stress on cattle. Moreover, cattle in tropical and sub-tropical countries are most commonly affected by the menace of heat stress which severely wane their production and productivity. In general, cattle exhibit various thermoregulatory responses such as behavioural, physiological, neuro-endocrine and molecular responses to counteract the terrible effects of heat stress. Amongst the aforementioned thermoregulatory responses, behavioural, physiological and neuro-endocrine responses are regarded as most conventional and expeditious responses shown by cattle against heat stress. Furthermore, molecular responses serve as the major adaptive response to attenuate the harmful effects of heat stress. Therefore, present review highlights the significance of behavioural, physiological, neuro-endocrine and molecular responses which act synergistically to combat the deleterious effects of heat stress thereby confer thermo-tolerance in cattle.

Delineation of temperature-humidity index (THI) as indicator of heat stress in riverine buffaloes (Bubalus bubalis) of a sub-tropical Indian region

The erstwhile developed temperature-humidity index (THI) has been popularly used to indicate heat stress in dairy cattle and often in buffaloes. However, scientific literature suggests differences in thermotolerance and physiological responses to heat stress between cattle and buffalo. Therefore, THI range used to indicate degree of heat stress (mild, moderate, and severe) in cattle should be recalibrated for indicating heat stress in buffaloes. The present study was carried out to delineate THI range to indicate onset and severity of heat stress in buffaloes based on physiological, biochemical, and expression profiling of heat shock response (HSR) genes in animals at different THI. The result indicated early onset of heat stress in buffaloes as compared to cattle. Physiological and biochemical parameters indicated onset of mild signs of heat stress in buffaloes at THI 68-69. Significant deviation in these parameters was again observed at THI range 73-76. At THI 77-80, the physiological and biochemical responses of animals were further intensified indicating extreme alteration in homeostasis. The in vivo expression profiling of HSR genes indicated that members of Hsp70 gene family are expressed in a temporal pattern over different THIs, whereas expressions of Hsf genes were evident during intense heat stress. Overall, the study established that amplitude of heat shock response and THI range for indicating severity of thermal stress for buffaloes are not in unison to cattle. The study also suggests skin temperature of the poll region could be used as non-invasive tool for monitoring heat stress in dairy buffaloes.

Identification of key Genes and Pathways Associated With Thermal Stress in Peripheral Blood Mononuclear Cells of Holstein Dairy Cattle

The objectives of the present study were to identify key genes and biological pathways associated with thermal stress in Chinese Holstein dairy cattle. Hence, we constructed a cell-model, applied various molecular biology experimental techniques and bioinformatics analysis. A total of 55 candidate genes were screened from published literature and the IPA database to examine its regulation under cold (25°C) or heat (42°C) stress in PBMCs. We identified 29 (3 up-regulated and 26 down-regulated) and 41 (15 up-regulated and 26 down-regulated) significantly differentially expressed genes (DEGs) (fold change ≥ 1.2-fold and P < 0.05) after cold and heat stress treatments, respectively. Furthermore, bioinformatics analyses confirmed that major biological processes and pathways associated with thermal stress include protein folding and refolding, protein phosphorylation, transcription factor binding, immune effector process, negative regulation of cell proliferation, autophagy, apoptosis, protein processing in endoplasmic reticulum, estrogen signaling pathway, pathways related to cancer, PI3K- Akt signaling pathway, and MAPK signaling pathway. Based on validation at the cellular and individual levels, the mRNA expression of the HIF1A gene showed upregulation during cold stress and the EIF2A, HSPA1A, HSP90AA1, and HSF1 genes showed downregulation after heat exposure. The RT-qPCR and western blot results revealed that the HIF1A after cold stress and the EIF2A, HSPA1A, HSP90AA1, and HSF1 after heat stress had consistent trend changes at the cellular transcription and translation levels, suggesting as key genes associated with thermal stress response in Holstein dairy cattle. The cellular model established in this study with PBMCs provides a suitable platform to improve our understanding of thermal stress in dairy cattle. Moreover, this study provides an opportunity to develop simultaneously both high-yielding and thermotolerant Chinese Holstein cattle through marker-assisted selection.

Heat stress and immune response phenotype affect DNA methylation in blood mononuclear cells from Holstein dairy cows

Heat stress negatively affects health and production in cows. Examining the cellular response to heat stress could reveal underlying protective molecular mechanisms associated with superior resilience and ultimately enable selection for more resilient cattle. This type of investigation is increasingly important as future predictions for the patterns of heat waves point to increases in frequency, severity, and duration. Cows identified as high immune responders based on High Immune Response technology (HIR) have lower disease occurrence compared to their average and low immune responder herd-mates. In this study, our goal was to identify epigenetic differences between high and low immune responder cows in response to heat stress. We examined genome-wide DNA methylation of blood mononuclear cells (BMCs) isolated from high and low cows, before and after in vitro heat stress. We identified differential methylation of promoter regions associated with a variety of biological processes including immune function, stress response, apoptosis, and cell signalling. The specific differentially methylated promoter regions differed between samples from high and low cows, and results revealed pathways associated with cellular protection during heat stress.

Heat shock protein and gene regulation in goats during heat stress

Heat shock proteins (HSPs), also known as molecular chaperons are prominent stress markers. Heat shock proteins consist of highly conserved protein expressed at the time of stress, and play an important role in adaptation to the environmental stress. Although, the expression pattern of HSP70 gene is species and breed specific, variations in adaptation and thermal tolerance is due to the nature of environment and adaptive capacity of a species. The present study was conducted to evaluate the adaptive capability of different goat (Capra hircus) breeds, i.e. Jamunapari, Barbari, Jakhrana and Sirohi under peak dry summer. The targeted gene HSP70 (HSPA6) was evaluated for this purpose using specific primers. The expression of HSP70 gene and protein was estimated by RT PCR and ELISA kits respectively. The expression of HSP70 gene was found lowest in sirohi breeds implying that this breed was more adapted followed by Jakhrana, Barbari and Jamunapari during peak summer season. Whereas, the level of HSP70 protein in blood was significantly higher in Jamunapari, followed by Barbari, Jakhrana and lowest in Sirohi. These results indicated that, during adverse climatic stress the quantum of expression (HSP70 gene and protein) was more in Jamunapari. It is concluded that Sirohi breed is better adapted to heat stress than Jamunapari, Jakhrana and Barbari and HSP70 may be a potential molecular biomarker in the future for selection of climate resilient animals.

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.

Appropriate THI model and its threshold for goats in semi-arid regions of India

The present study was attempted to identify an appropriate THI model and threshold THI for goats of semi-arid regions of India. Sixty non-pregnant goats each from Jamunapari and Barbari breeds were selected for the study. The study was conducted from last week of February to first week of June, during which average THI ranged between 53 and 92. Pulse rate (PR), respiration rate (RR) and rectal temperature (RT) were recorded at 1430 h on alternate days from six goats of each breed randomly during the experiment. Nine THI models were used to calculate THI. An appropriate THI model was predicted on the basis of correlation between THIs calculated from each model and physiological responses. The data of physiological parameters were linked to the THI calculated from identified THI model and threshold THI for each parameter was determined using segmented regression analysis (SegReg Software). The THI models; THI₁{(1.8 × Tdb+32)-[(0.55-0.0055 × RH) × (1.8 × Tdb-26.8)]} and THI₈{(0.8 × Tdb)+[(RH/100) × (Tdb-14.4)]+46.4)} were found to be equally appropriate for assessing environmental heat stress. Threshold THIs with respect to PR, RR and RT in Jamunapari goat were 71.78, 75.14 and 85.94, respectively and in Barbari goats, threshold THIs for PR and RR were 79.48 and 84.40, respectively. A threshold THI could not be identified for RT in Barbari goats. It can be concluded that THI₁ and THI₈ were the appropriate THI models for measuring environmental heat stress in goats. Results suggested that PR is the first physiological parameter which alters after the onset of heat stress and is followed by changes in RR and RT. On the basis of differential threshold THIs, it can be concluded that Barbari is better adapted than Jamunapari goats in semi-arid regions of India.

Thermoregulatory responses in riverine buffaloes against heat stress: An updated review

High heat and humidity stress have been a perpetual perilous for the buffalo's production and productivity in tropics and subtropics including India. Productive potential of livestock's species including buffaloes is maximum with in thermo-neutral zone (TNZ) and if ambient temperature exceeds TNZ and upper critical temperature expose livestock's to heat stress conditions. For decades, heat stress has been the prime factor to plummet buffalo's growth, development, reproduction and production in tropics and subtropics including India. In general, buffaloes are homeotherms and known as temperature regulators as they resist the variations in ambient temperatures. Generally, buffaloes like other livestock's display amalgamation of thermoregulatory responses to withstand the changes occurred in their micro and macro environment. These thermoregulatory responses are behavioural, physiological, neuro-endocrine and molecular responses acting synergistically to counteract the deleterious effects of heat stress. Amidst all responses, molecular responses play major role to confer thermo-tolerance through expression of highly conserved family of proteins known as heat shock proteins (HSPs). Despite of these thermoregulatory responses, heat stress prodigiously muddles buffalo's production and productivity. The present review highlights the thermoregulatory responses manifested by riverine buffaloes against heat stress.

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.

Prospects for gene introgression or gene editing as a strategy for reduction of the impact of heat stress on production and reproduction in cattle

In cattle, genetic variation exists in regulation of body temperature and stabilization of cellular function during heat stress. There are opportunities to reduce the impact of heat stress on cattle production by identifying the causative mutations responsible for genetic variation in thermotolerance and transferring specific alleles that confer thermotolerance to breeds not adapted to hot climates. An example of a mutation conferring superior ability to regulate body temperature is the group of frame-sift mutations in the prolactin receptor gene (PRLR) that lead to a truncated receptor and development of cattle with a short, sleek hair coat. Slick mutations in PRLR have been found in several extant breeds derived from criollo cattle. The slick mutation in Senepol cattle has been introgressed into dairy cattle in Puerto Rico, Florida and New Zealand. An example of a mutation that confers cellular protection against elevated body temperature is a deletion mutation in the promoter region of a heat shock protein 70 gene called HSPA1L. Inheritance of the mutation results in amplification of the transcriptional response of HSPA1L to heat shock and increased cell survival. The case of PRLR provides a promising example of the efficacy of the genetic approach outlined in this paper. Identification of other mutations conferring thermotolerance at the whole-animal or cellular level will lead to additional opportunities for using genetic solutions to reduce the impact of heat stress.

Heat-Shock Proteins Gene Expression in Peripheral Blood Mononuclear Cells as an Indicator of Heat Stress in Beef Calves

Simple Summary

This study explores the effects of heat stress on the expression of various heat-shock protein (HSP) genes in bovine peripheral blood mononuclear cells (PBMCs) and cell viability as an indicator of stress in beef calves. We found that heat stress inhibits cell proliferation and increases the expression of HSPs in an in vitro model. In addition, HSPs were found to regulate the physiological mechanisms of adaptation to heat stress in an in vivo model. The results showed that HSPs expression in PBMCs can be used as an indicator of heat stress (HS) in beef calves.

Abstract

This study was conducted to investigate the effect of HS on HSPs gene expression in bovine PBMCs of beef calves in in vitro and in vivo models. In the in vitro experiment, blood samples were collected from the jugular vein of five beef calves (age: 174.2 ± 5.20 days, BW: 145.2 ± 5.21 kg). In the in vivo experiment, sixteen Korean native male beef calves (age: 169.6 ± 4.60 days, BW: 136.9 ± 6.23 kg) were exposed to ambient temperature for seven days (22 to 24 °C, relative humidity 60%; temperature–humidity index (THI) = 68 to 70) and subsequently to the temperature and humidity corresponding to the target THI level for 21 days (HS). For PBMC isolation, blood samples were collected every three days. In the in vitro model, the cell viability was significantly decreased in HS groups compared with the control group (p = 0.015). The expression of HSP70 (p = 0.022), HSP90 (p = 0.003) and HSPB1 (p = 0.026) genes was increased in the HS group in in vitro model. In the in vivo experiment, the HSP70 gene expression was increased after sudden exposure to HS conditions (severe THI levels; THI = 88 to 90), whereas HSP90 and HSPB1 showed no differences among the THI groups (p > 0.05). However, in the severe THI group, the HSP70 gene expression returned to normal range after six days of continuous HS. In conclusion, the HSP70 gene plays a pivotal role in protecting cells from damage and is sensitive to HS in immune cells compared with other HSP genes in in vitro and in vivo models. In addition, the in vivo models suggest that calves exhibit active physiological mechanisms of adaptation to HS after six days of continuous exposure by regulating the HSP70 gene expression.

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.

Aspirin Enhances the Protection of Hsp90 from Heat-Stressed Injury in Cardiac Microvascular Endothelial Cells Through PI3K-Akt and PKM2 Pathways

Heat stress (HS) often causes sudden death of humans and animals due to heart failure, mainly resulting from the contraction of cardiac microvasculature followed by myocardial ischemia. Cardiac microvascular endothelial cells (CMVECs) play an important role in maintaining vasodilatation. Aspirin (ASA) is well known for its protective abilities of febrile animals. However, there is little knowledge about molecular resistance mechanisms of CMVECs and which role ASA may play in this context. Therefore, we used a heat stress model of rat cardiac microvascular endothelial cell cultures in vitro and investigated the cell injuries and molecular resistance mechanism of CMVECs caused by heat stress, and the effect of aspirin (ASA) on it. HS induced severe pathological damage of CMVECs and cellular oxidative stress and dysfunction of NO release. Hsp90 was proven to be indispensable for resisting HS-injury of CMVECs through PI3K-Akt and PKM2 signaling pathways. Meanwhile, PKM2 functioned in reducing Akt phosphorylation. ASA treatment of CMVECs induced a significant expression of Hsp90, which promoted both Akt and PKM2 signals, which are beneficial for relieving HS damage and maintaining the function of CMVECs. Akt activation also promoted HSF-1 that regulates the expression of Hsp70, which is known to assist Hsp90′s molecular chaperone function and when released to the extracellular liquid to protect myocardial cells from HS damage. To the best of our knowledge, this is the first study to show that HS damages CMVECs and the protection mechanism of Hsp90 on it, and that ASA provides a new potential strategy for regulating cardiac microcirculation preventing HS-induced heart failure.

Prospects of HSP70 as a genetic marker for thermo-tolerance and immuno-modulation in animals under climate change scenario

Heat stress induced by long periods of high ambient temperature decreases animal productivity, leading to heavy economic losses. This devastating situation for livestock production is even becoming worse under the present climate change scenario. Strategies focused to breed animals with better thermo-tolerance and climatic resilience are keenly sought these days to mitigate impacts of heat stress especially in high input livestock production systems. The 70-kDa heat shock proteins (HSP70) are a protein family known for its potential role in thermo-tolerance and widely considered as cellular thermometers. HSP70 function as molecular chaperons and have major roles in cellular thermotolerance, apoptosis, immune-modulation and heat stress. Expression of HSP70 is controlled by various factors such as, intracellular pH, cyclic adenosine monophosphate (cyclic AMP), protein kinase C and intracellular free calcium, etc. Over expression of HSP70 has been observed under oxidative stress leading to scavenging of mitochondrial reactive oxygen species and protection of pulmonary endothelial barrier against bacterial toxins. Polymorphisms in flanking and promoter regions in HSP70 gene have shown association with heat tolerance, weaning weight, milk production, fertility and disease susceptibility in livestock. This review provides insight into pivotal roles of HSP70 which make it an ideal candidate genetic marker for selection of animals with better climate resilience, immune response and superior performance.

Heat loss efficiency and HSPs gene expression of Nellore cows in tropical climate conditions

Adaptation is a relevant characteristic to be understood in livestock animals in order to maintain and raise productivity. In Brazil, the Nellore beef cattle are widely disseminated and well-adapted breed that present good thermoregulatory characteristics for tropical environment conditions. Conversely, the physiological and cellular mechanisms required for thermoregulation and thermotolerance in this breed are still limited. The aim of this study was to comprehend the heat loss efficiency at the whole animal level and heat shock response at the cellular level of Nellore cows in tropical climate conditions. Healthy purebred Nellore cows were classified according to their capacity to lose body heat as Efficient or Inefficient based on vaginal temperature which was continuously monitored by data-loggers. Rectal, tail, and ocular temperatures, sweating rate, and respiratory frequency were collected to assess other thermoregulatory responses. Peripheral mononuclear cells were used for gene expression of heat shock proteins 60, 70, and 90 induced by in vitro heat treatments at 38, 40, and 42 °C. In our findings, the Efficient cows presented higher sweating rates compared to Inefficient cows that presented higher rectal temperature with greater amplitude of vaginal temperature profile. Transcription of the HSP genes was stable at 38 and 40 °C and decreased for all HSP genes at 42 °C. In conclusion, the Nellore efficiency to lose heat was mainly associated with their sweating capacity and cellular thermotolerance confirmed by the maintenance of heat shock proteins transcripts under heat stress. Taken together, this knowledge contributes as a future key for genetic selection of adapted animals.

Characterizing binding sites of heat responsive microRNAs and their expression pattern in heat stressed PBMCs of native cattle, exotic cattle and riverine buffaloes

It is generally believed that due to evolutionary differences and adaptation to tropical conditions, Indian native cattle has superior heat tolerant ability than Bos taurus cattle. In the present study, 3'-UTR of two most important heat responsive genes i.e., heat shock protein 70.1 (HSP70.1) and heat shock factor- 1 (HSF-1) were sequence characterized in different breeds of Indian native cattle to identify the variations and miRNA binding sites. In addition, the impact of heat stress was assessed in a total of 57 PBMCs samples of native Sahiwal cows (Bos indicus), exotic Holstein cows (Bos taurus) and Murrah buffaloes (Bubalus bubalis) using various cellular parameters like cell viability, cytotoxicity and apoptosis. Further, expression profile of 12 heat responsive miRNAs were also evaluated in unstressed and stressed PBMCs to understand post transcriptional changes in native cows, exotic cows and Murrah buffaloes. The sequence data showed 3'-UTR of HSP70.1 gene of Indian cattle to be exactly similar to Bos taurus with no miRNA binding site. Whereas, sequencing of 3'-UTR of HSF-1 gene revealed 3 SNPs at positions G1762T; C1811T and C1983T with 7 well conserved miRNA binding sites. The impact of heat stress on various cellular parameters in terms of cell viability, cytotoxicity and apoptosis was highest in PBMCs of Holstein cows followed by Murrah buffaloes and Sahiwal cows. Further, in contrast to Holstein Frisian cows and Murrah buffaloes, the expression pattern of 12 heat responsive miRNAs, in heat stressed PBMCs of Sahiwal cows were quite distinct. There was a significant (p < 0.05) induction in expression of most of the miRNAs after heat stress in PBMCs of Sahiwal cows followed by a rapid decline. The distinct cellular response and pattern of miRNA expression across cattle types and buffaloes might be influencing their PBMCs tolerance level to heat stress.

Alpha lipoic acid supplementation ameliorates the wrath of simulated tropical heat and humidity stress in male Murrah buffaloes

A supplement which ameliorates temperature-humidity menace in food producing livestock is a prerequisite to develop climate smart agricultural packages. A study was conducted to investigate the heat stress ameliorative efficacy of alpha lipoic acid (ALA) in male Murrah water buffaloes (Bubalus bubalis). Eighteen animals (293.61 ± 4.66Kg Bwt) were randomly allocated into three groups (n = 6); NHSC (non-heat-stressed control), HS (heat-stressed) and HSLA (heat-stressed-supplemented with ALA@32 mg/kg Bwt orally) based on the temperature humidity index (THI) and ALA supplementation. HS and HSLA were exposed to simulated heat challenge in a climatically controlled chamber (40 °C) for 21 consecutive days, 6 h daily. Physiological responses viz. Respiration rate (RR), Pulse rate (PR) and Rectal temperature (RT) were recorded daily before and after heat exposure. Blood samples were collected at the end of heat exposure on days 1, 6, 11, 16, and 21 and on day 28 (7th day post exposure which is considered as recovery) for peripheral blood mononuclear cells (PBMCs) separation, followed by RNA and Protein extraction for Real time quantitative PCR and Western blot analysis respectively, of heat shock proteins (HSPs). Two-way repeated measure ANOVA was performed between groups at different experimental periods. RR (post exposure) in HS and HSLA was significantly higher (P < 0.05) than NHSC from day 1 onwards but HSLA varied significantly from the HS 8th day onwards. Post exposure RT and PR in both HS and HSLA varied (P < 0.05) from NHSC throughout the study; but between HS and HSLA, RT significantly varied on initial 2 days and last 6 days (from days 16 to 21). HSP70 mRNA expression significantly up regulated in high THI groups with respect to the low THI group throughout the experimental period. During chronic stress (days 16 and 21) HSP70 significantly (P < 0.05) increased in HS but not in HSLA (P > 0.05) with respect to NHSC. ALA supplementation up-regulates and sustains (P < 0.05) the expression of HSP90 in HSLA in comparison to the HS and NHSC. HSP105 expression was significantly up-regulated (P < 0.05) in HS on days 16 and 21 (during long-term exposure) but only on day 21 (P < 0.05) in HSLA. HSP70, HSP90, and HSP105 protein expression dynamics were akin to the mRNA transcript data between the study groups. In conclusion, supplementing ALA ameliorates the deleterious effect of heat stress as reflected by improved physiological and cellular responses. ALA supplementation improved cellular antioxidant status and sustained otherwise easily decaying heat shock responses which concertedly hasten the baton change from a limited window of thermo tolerance to long run acclimatization.

Vitamin C mitigates heat damage by reducing oxidative stress, inducing HSP expression in TM4 Sertoli cells

Heat stress is a major stressor that can lead to male reproductive dysfunction. Sertoli cells play a crucial role in spermatogenesis by providing germ cells with structural and nutritional support, and contributing to blood-testis barrier formation. Vitamin C (Vc) is an antioxidant capable of neutralizing reactive oxygen species and preventing lipid peroxidation widely used because it is inexpensive and highly accessible. In the present study, we investigated the protective effect of Vc on TM4 cells following heat stress. Pretreatment with Vc could effectively inhibit apoptosis (p < 0.01), lipid peroxidation, and lactate dehydrogenase (LDH) activity. However, a significant increase in the malondialdehyde (MDA) level and LDH activity (p < 0.01) was observed in TM4 cells without Vc-pretreatment, in conjunction with vacuole degeneration and karyopyknosis. In addition, both the messenger RNA and protein levels of CryAB, Hsp27, Hsp70, and Hsp110 substantially increased in the 3 and 12 hr recovery groups (p < 0.01). Vc also prevented microtubule aggregation following heat stress. These results suggest that pretreatment with Vc-protected TM4 cells against heat stress by reducing the level of oxidative stress and inducing heat shock protein expression.

Differential expression of cytokines in PBMC of Bos indicus and Bos taurus × Bos indicus cattle due to Brucella abortus S19 antigen

Brucellosis is the most dreadful disease among bovines, although breed differences have been observed in prevalence of disease, worldwide. In present study, antibody response and relative expression of proinflammatory cytokines was compared in Bos indicus (zebu) and Bos taurus × Bos indicus (crossbred) cattle vaccinated by live attenuated Brucella abortus S19 antigen. Six female calves (4-6 months age) of both groups were vaccinated with B.abortus S19 strain. Blood samples were collected before vaccination (0d) and 7^th (7d), 14^th (14d) and 28^th (28d) days after vaccination. Indirect ELISA showed high (p < .05) anti-Brucella antibody level after vaccination; with no significant difference between the groups. During Real-time expression, IFNγ, TNFα, IL6 and IL10 genes initially showed down regulation followed by upregulation in both the groups; however, the trend was much prominent in crossbreds. The expressions of IFNγ, TNFα and IL6, proinflammatory molecules important for initial containment of the Brucella were significantly (p < .01) higher in crossbred. The study showed that the Sahiwal cattle were less responsive to B.abortus S19 antigen than crossbreds, indicating its lower sensitivity to the Brucella, comparatively. In contrary, higher expression of the proinflammatory molecules in crossbreds could be important for containment of the organism during initial stage of infection.

Metabolomics Reveals that Crossbred Dairy Buffaloes Are More Thermotolerant than Holstein Cows under Chronic Heat Stress

Heat stress (HS) threatens the worldwide dairy industry by decreasing animal production performance and health. Holstein cows and dairy buffaloes are the most important dairy animals, but their differences in the metabolic mechanism of thermotolerance remain elusive. In this study, we used serum metabolomics to evaluate the differences in thermotolerance between Holstein cows and crossbred dairy buffaloes under chronic heat stress (HS) and thermal-neutral conditions. In response to HS, the body temperatures and respiratory rates were increased more for Holstein cows than for dairy buffaloes (38.78 vs 38.24 °C, p < 0.001; 43.6 vs 32.5 breaths/min, p < 0.001). HS greatly affected serum metabolites associated with amino acids, fatty acids, and bile acids. The enriched metabolic pathways of these serum metabolites are closely related to HS. We demonstrated that buffaloes adapt to HS by adopting a metabolism of branched-chain amino acids and ketogenic amino acids and gluconeogenesis, but Holstein cows decrease the effect of HS with citrulline and proline metabolism. Both physiological parameters and serum metabolic profiles indicate that dairy buffaloes are more thermotolerant than Holstein cows, providing the feasibility to vigorously develop the buffalo dairy industry in tropical and subtropical regions.

Genetic mechanisms underlying spermatic and testicular traits within and among cattle breeds: systematic review and prioritization of GWAS results

Reduced bull fertility imposes economic losses in bovine herds. Specifically, testicular and spermatic traits are important indicators of reproductive efficiency. Several genome-wide association studies (GWAS) have identified genomic regions associated with these fertility traits. The aims of this study were as follows: 1) to perform a systematic review of GWAS results for spermatic and testicular traits in cattle and 2) to identify key functional candidate genes for these traits. The identification of functional candidate genes was performed using a systems biology approach, where genes shared between traits and studies were evaluated by a guilt by association gene prioritization (GUILDify and ToppGene software) in order to identify the best functional candidates. These candidate genes were integrated and analyzed in order to identify overlapping patterns among traits and breeds. Results showed that GWAS for testicular-related traits have been developed for beef breeds only, whereas the majority of GWAS for spermatic-related traits were conducted using dairy breeds. When comparing traits measured within the same study, the highest number of genes shared between different traits was observed, indicating a high impact of the population genetic structure and environmental effects. Several chromosomal regions were enriched for functional candidate genes associated with fertility traits. Moreover, multiple functional candidate genes were enriched for markers in a species-specific basis, taurine (Bos taurus) or indicine (Bos indicus). For the different candidate regions identified in the GWAS in the literature, functional candidate genes were detected as follows: B. Taurus chromosome X (BTX) (TEX11, IRAK, CDK16, ATP7A, ATRX, HDAC6, FMR1, L1CAM, MECP2, etc.), BTA17 (TRPV4 and DYNLL1), and BTA14 (MOS, FABP5, ZFPM2). These genes are responsible for regulating important metabolic pathways or biological processes associated with fertility, such as progression of spermatogenesis, control of ciliary activity, development of Sertoli cells, DNA integrity in spermatozoa, and homeostasis of testicular cells. This study represents the first systematic review on male fertility traits in cattle using a system biology approach to identify key candidate genes for these traits.

Acute heat stress induces changes in physiological and cellular responses in Saanen goats

The relationships between rectal temperatures and physiological and cellular responses to heat stress can improve the productivity of Saanen goats in tropical environments. In this context, this study evaluated the physiological responses and gene expression of heat shock proteins (HSP60, 70, and 90) and genes related to apoptosis (Bax, Bcl-2, and p53) of Saanen goats subjected to acute heat stress. Ten health Saanen goats were exposed to solar radiation during 3 consecutive days. The expression of HSP60, HSP70, HSP90, Bax, Bcl-2, and p53 genes in blood leukocytes, rectal and superficial temperatures, respiratory frequency, cortisol, triiodothyronine, and thyroxine was measured at 06:00, 13:00, and 18:00 h. In vitro, blood leukocytes were subjected to 38 °C and 40 °C for 3 h to measure the expression of the same target genes. The temperature humidity index, measured from 12:00 to 15:00, was greater than 80 and black globe temperatures were greater at 40 °C, indicating the intensity of the solar radiation. Although the solar radiation caused acute heat stress, increased cortisol release, and the expression of HSP60 and 70 in dry Saanen goats, the increased respiratory frequency and decreased T4 and T3 restored the homeothermy of the experimental goats. In vitro, the 40 °C increased the expression of p53 (pro-apoptotic protein), Bcl-2 (anti-apoptotic protein), HSP60, HSP70, and HSP90, suggesting that these genes have protective functions. However, further studies are necessary to understand the physiological and cellular responses to heat stress.