Differential expression of small heat shock proteins in the brain of broiler embryo; the effects of embryonic thermal manipulation

https://doi.org/10.1016/j.jtherbio.2020.102719Get rights and content

Highlights

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    HSPB1, HSPB5, HSPB8, and HSPB9 are all expressed in both normal and thermal manipulated cerebrums.

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    The expression of investigated SHSPs in the cerebral tissue is responsive to TM at the late-term embryogenesis of chicken.

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    HSPB1 is the most responsive gene to the thermal manipulation at the late-term embryogenesis of chicken.

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    Thermal manipulation had no major deleterious effects on the cerebral tissue except for mild degeneration.

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    The brain may be protected against TM through SHSPs pathways.

Abstract

Broilers are more vulnerable to high temperatures than mammals due to the feather cover, lack of sweat glands, fast growth and intensive breeding in commercial systems. Thermal stresses affect the function of various organs and change the expression profiles of hundreds of genes in the different tissues of broilers. Thermal manipulation (TM) during embryogenesis can increase heat tolerance in growing broilers. Small heat shock proteins (SHSPs) are a group of HSPs which participate in many cellular functions like response to different stressors. However, their role in the thermotolerance has not been fully elucidated. Ninety fertilized eggs were randomly divided into three groups (30 eggs/group; 10 eggs/replicate). Normal control (NC) eggs were incubated at 37.5 °C throughout the incubation period whereas heat stress (HS) and cold stress (CS) groups were kept at 41 °C and 33 °C from 15 to 17th day of incubation for 3 h each day, respectively. On day 20, samples from the cerebrums were harvested for histopathology and mRNA expression analyses of HSPB1, HSPB5, HSPB8, and HSPB9. There were no significant differences in survivability, defected embryos, hatchability, and body weight among treatments. TM had no major deleterious effects on the cerebral tissue except for mild degeneration in the HS group. HSPB1, HSPB5, HSPB8, and HSPB9 were expressed in the presence and absence of TM. All SHSP genes tested were downregulated in response to TM except for HSPB9 which was upregulated in the HS group. The highest change in gene expression due to TM observed for HSPB1. This study presents a broader understanding of mechanisms underlying response to TM in broilers. The results suggest that HSPB1, HSPB5, HSPB8, and HSPB9 are involved in thermotolerance in broilers and SHSPs could be involved in the gene expression profiling of TM. It may propose the use of nutritional supplements in the poultry industry to modulate SHSPs.

Section snippets

Author contribution

Mehdi BasakiNazila SahraiyKamran KeykavusiGhasem AkbariAmir Ali ShahbazfarDavoud Kianifard

Experimental design and sample preparation

Ninety fertilized eggs (Ross 308; 55 ± 2 g) were obtained from Behparvar, Orumieh, Iran. After candling, fertilized eggs randomly divided into three groups (30 eggs/group; 10 eggs/repeat); as heat stress (HS), cold stress (CS) and normal control (NC). In NC group eggs were incubated at 37.5 °C throughout the incubation period while in HS and CS groups eggs were kept at 41 °C and 33 °C from 15th to 17th day of incubation for 3 h each day, respectively (Loyau et al., 2015). The relative humidity

Results

Table 1 shows the frequency of survivability and defected embryos on day 20; the frequency of hatchability and the BW at birth. No significant difference was found among treatments for survivability, defected embryos, hatchability, and BW (Table 1).

There were no deleterious effects on the cerebral tissue in group CS. In HS group degenerative alterations including mild diffused gliosis, satellitosis, and neuronophagia in the cerebral tissue were observed (Fig. 1; Table 1).

HSPB1, HSPB5, HSPB8,

Discussion

Ambient temperatures affect animal production and welfare (Loyau et al., 2015). The results of the present study showed that TM during embryogenesis can alter the SHSPs expression and induce mild degeneration in the cerebral tissue.

There are reports that TM can affect organ functions and make some tissue injuries in chickens. Exposure of chicken myocardial cells to high temperatures caused vacuolar and granular degeneration and karyopyknosis (Wu et al., 2016). HS induced inflammatory

Conclusion

The expression of HSPB1, HSPB5, HSPB8, and HSPB9 is responsive to TM at the late-term embryogenesis of broilers. This can propose a protective mechanism of the brain against TM through SHSPs pathways. SHSPs could be involved in the gene expression profiling in TM studies. Furthermore, the use of nutritional supplements in the poultry industry to modulate the SHSPs may support the production and welfare of broilers under thermal stress. However, the exact mechanisms of SHSPs regulation in

Declaration of competing interest

The authors disclose that there is no conflict of interest.

Acknowledgments

This work was funded by the University of Tabriz [grant number 4305968892].

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