Hyperthermia protects mice against chronic unpredictable stress-induced anxiety-like behaviour and hippocampal CA3 cell apoptosis

Figures & data

Table 1.  Behaviour of HSF^−/− and HSF1^+/+ in the elevated plus maze.

	HSF1^−/−		HSF1^+/+
	PTOA	ROVCA	PTOA	ROVCA
NS	36.58 ± 1.59	58.95 ± 4.62	29.67 ± 0.85	42.41 ± 1.74
HS	46.23 ± 2.55	88.35 ± 9.98	30.33 ± 2.73	44.61 ± 5.47
CUS	12.75 ± 3.16*	15.66 ± 4.16*	12.17 ± 1.68*	14.37 ± 2.49*
HS + CUS	8.50 ± 3.96^#,*	11.67 ± 6.16*	20.63 ± 3.99^Δ	29.20 ± 7.14^Δ

HSF1^−/−, hsf1-null mice; HSF1^+/+, wild-type mice; PTOA, percentage time that mice spent in open arms; ROVCA, ratio of time in open versus closed arms; mean ± SE. *p < 0.01 versus. NS or HS; ^#p = 0.06 versus CUS; ^Δp < 0.05 versus CUS.

Figure 1. Behavioural analysis in open field test. Mean number of squares crossed in 5 min. Significant anxiolytic action of hyperthermia was seen in hsf1^+/+ mice, but not in hsf1^−/− mice. NS group: non-experimental stress group; HS group: hyperthermia group; CUS group: chronic unpredictable stress group; HS + CUS group: hyperthermia + chronic unpredictable stress group. *p < 0.05, ^#p < 0.05 versus NS and HS groups; **p < 0.05, ^##p < 0.05 versus CUS group; OF: open field, N = 14.

Figure 2. Western blot analysis of Hsp72 expression in mice hippocampus. Upper panel: semi-quantitative analysis of Hsp72 expression. In hsf1^+/+ mice, mice in HS, and HS + CUS groups were treated with hyperthermia (39° ± 2°C) for 15 min. The Hsp72 expression was significantly higher in HS and HS + CUS groups than NS and CUS groups after 8 weeks (*p < 0.05). In hsf1^−/− mice, Hsp72 expression was abolished in all groups. Lower panel: representative Western blot of HSP and β-actin expression. Animals were grouped as described in Figure 1.

Figure 3. Apoptosis in hippocampal CA3 area in the hsf1^+/+ mice. (A) TUNEL staining of hippocampal CA3 area, original magnification ×400. The apoptotic cells exhibited condensed chromatin and smaller, dark brown nucleus. (B) The amount of apoptotic cells in WT mice. In hsf1^+/+ mice, chronic unpredictable stress increase apoptosis in the CA3, but hyperthermia decrease chronic unpredictable stress induced apoptosis (n = 8–12). *p < 0.05 versus NS. Animals were grouped as described in Figure 1.

Figure 4. Apoptosis in hippocampal CA3 area in the hsf1^−/− mice. (A) TUNEL staining of hippocampal CA3 area, original magnification ×400. The apoptotic cells exhibited condensed chromatin and smaller, dark brown nucleus. (B) The amount of apoptotic cell in hsf1^−/− mice. Chronic unpredictable stress increased apoptosis in the CA3 cells, but hyperthermia further increase CUS-induced apoptosis (n = 8–12). *p < 0.01 versus NS. Animals were grouped as described in Figure 1.

Figure 5. Correlation between apoptotic hippocampal CA3 cells and anxiety-like behaviours. (A) Correlation between the number of apoptotic hippocampal CA3 cells and the percentage of time spent in the open arm in EPM test (r = −0.33, p < 0.05). (B) Correlation between the number of apoptotic hippocampal CA3 cells and the ratio of time in open versus closed arms in EPM test (r = −0.28, p < 0.05). (C) Correlation between the number of apoptotic hippocampal CA3 cells and the mean number of square crossed in 5 min in the open field test (r = −0.54, p < 0.05).