Stress Damages and Expressions of Hsp60 and Hsf-1 in the Heat Stressed Myocardial Cells of Neonatal Rats in vitro.pdf

1、Heat stress causes harmful changes in the cells, and prolonged duration leads to loss of function in cells, either by necrosis or by apoptosis.Heat shock proteins (Hsps) play an important role to maintain the homeostasis

2、 of the cell and help it to survive even during stressful period.Hsp60 is one the main protein of Heat shock proteins's family and it is mainly called as mitochondrial protein.The main purpose of this study was to invest

3、igate the expression and transcription of Hsp60 and HSF-1 and their corresponding mRNA in primary myocardial cells of neonatal rats in vitro, to correlate the relationship of Hsp60 and HSF-1 at various durations of heat

4、stress, to observe the cytoprotective mechanism of Hsp60 in response to heat stress.For this purpose the primary myocardial cells were cultured and divided into 9 groups including control group which is kept at 37℃ at 5％

5、CO2 and 95％ humidity.Rest of groups was heat stressed for various durations from 10, 20, 40, 60, 120, 240, 360 and 480 min respectively at 42℃ at 5％ CO2 and 95％ humidity.The heat stress model of primary myocardial ceils

6、of neonatal rats was developed through detection of myocardial enzyme elevation including AST, LDH, CK, CK-MB, as these are considered as myocardial markers and by observing the cytopathological lesions in control as wel

7、l as heat stressed myocardial cells.The enzymes showed varying degrees of elevations.Level of AST was found to be significantly high throughout the stress period as compared to control group, whereas LDH displayed the si

8、gnificant elevation at 20 and 60 min of heat stress.CK was found significantly higher at 120 min and CK-MB activity was observed 60 and 120 min of heat stress.The cytopathological lesions were observed at the beginning o

9、f heat stress i.e 10 min with granular and vacuolar degeneration and were found persistent throughout the heat stress period, with obvious pyknotic nucleus after 120 min of heat stress treatment.These findings revealed t

10、hat myocardial cells of neonatal rats are damaged by heat stress.The western blot results showed that Hsp60 expression was decreased significantly after 20 and 40 min and then increased after 120 min of heat stress and w

11、as found stable till 240 min of heat stress.Meanwhile the immunocytochemical results showed the most prominent signals with thick Hsp60 density after 240 min of heat stress at 42 ℃ as compared to that of 60 min.This chan

12、ge in Hsp60 density indicated that due to consumption of Hsp60, the cells started to produce sufficient Hsp60 after 240 min of heat stress.Whereas, the cytopathological lesions showed the vacuolar degeneration after 60mi

13、n of heat stress and pyknosis occurred at 240 min of heat stress.These findings suggest that myocardial cells were protected to certain extent from heat stress until and unless Hsp60 was produced to help myocardial cells

14、The in vitro relationship between Hsf-1 and Hsp60 and their corresponding mRNA was observed to find whether Hsf-1 production influence Hsp60 formation or not.Hsp60expression showed fluctuations during heat stress and obs

15、erved significantly low after 20min of heat stress and then increased at 120 min and remained elevated up to 240 min of heat stress.After that point, Hsp60 expression was reduced as compared to control group.However, hsp

16、60 mRNA transcription levels increased significantly after 20 min and followed the same pattern up to 240 min of heat stress and then decreased significantly after 360 min of heat stress.The levels of Hsf-1 expression we

17、re declined till 120 min of heat stress but increased significantly after that point and remained elevated till 480 min of heat stress, whereas Hsf-1 mRNA levels increased significantly after 10 min and sustained same pa

18、ttern up to the end of heat treatment that is 480 min.These results indicate that Hsf-1 is not the only factor involved in regulating the hsp60 mRNA transcription and is involved in the formation of other Hsps too.It was

19、 also observed that Hsp60 production could not prevent the apoptosis, if the heat stress duration is too long because the levels of Hsp60 expression decreased after 20 min and then increased at 120 min and then decreased

20、 at 360 min.But the expression of Caspase-3 and Cytochrome-c increased significantly after 40 min of heat stress, suggesting that myocardial cells were unable to cope with the persistent heat stress and going to apoptosi

21、s.The changes in levels of Cytochrome-c are similar to that of cleaved Caspase-3,suggesting the two proteins are closely related during heat stress.However, Caspase 8 and 9 found relatively stable during the stress perio