Curcumin prevents renal cell apoptosis in acute kidney injury in a rat model of dry-heat environment heatstroke via inhibition of the mitochondrial apoptotic pathway

Abstract

Heatstroke is a life-threatening illness that is characterised by a core body temperature >40^°C and central nervous system dysfunction. Acute kidney injury (AKI) is a common complication of heatstroke, and the mitochondrial apoptotic pathway has been demonstrated to be one of the leading causes of tissue damage and cell death in AKI. Curcumin is a phenol that is extracted from turmeric and demonstrates anti-apoptotic properties. To test if curcumin can protect the kidney from injury caused by heat stress, the effect of curcumin administration on renal injury and apoptosis of renal tissue was examined in a rat model of dry-heat environment. A total of 50 Sprague-Dawley rats were randomly divided into five groups (n=10): Standard temperature control, dry-heat control and curcumin treatment groups (50, 100 and 200 mg/kg groups). After exposure to a dry-heat environment for 150 min, the rats were anesthetized and euthanized. Blood, urine and renal tissue were collected to quantify the expression of specific mitochondrial apoptosis-related molecules. Curcumin pre-treatment decreased blood urea nitrogen and serum creatinine, urinary kidney injury molecule-1, and neutrophil gelatinase-associated lipocalin levels compared with the dry-heat control group. Curcumin was also revealed to downregulate c-Jun N-terminal kinases (JNK), cytochrome c, caspase-3 and caspase-9 expression upon treatment with 100 and 200 mg/kg curcumin, which may result in inhibition of the mitochondrial apoptotic pathway in renal cells. The current study revealed that Curcumin may to have potential for preventing heatstroke-induced AKI.

Keywords: acute kidney injury; curcumin; heatstroke; mitochondrial apoptotic pathway; rat model.

Figure 1

Blood serum analysis. Concentration of (A) creatinine and (B) BUN in blood serum samples in the control, dry heat or curcumin treatment groups. Compared with the NT control group, the concentration of creatinine and BUN in serum samples was significantly increased in the DH and all curcumin treatment groups. Pre-treatment with increasing concentrations of curcumin resulted in a significant decrease in BUN and creatinine levels compared with the DH control. Values are expressed as means ± SE (n=10) and analysed using one-way ANOVA. ^*P<0.05 vs. NT. ^#P<0.05 vs. DH. BUN, blood urea nitrogen.

Figure 2

Expression of Acute kidney injury markers. Levels of (A) KIM-1 and (B) NGAL in urine samples in the control, dry heat or curcumin treatment groups. KIM-1 and NGAL increased significantly in the DH and all curcumin treatment groups compared with the NT control group. At all different curcumin concentrations, the expression of KIM-1 and NGAL were significantly decreased compared with the DH control group. Values are expressed as means ± SE (n=10) and analysed using one-way ANOVA. ^*P<0.05 vs. NT. ^#P<0.05 vs. DH. KIM-1, kidney injury molecule-1; NGAL, neutrophil gelatinase-associated lipocalin.

Figure 3

Expression of apoptotic-related markers. Changes in the expression of (A) Cyto-C and JNK and (B) caspase-9 and caspase-3 in the control, dry heat or curcumin treatment groups. The expression of (C) Cyto-C, (D) JNK, (E) caspase-3 and (F) caspase-9 was revealed to be increased in the DH and all curcumin treatment groups compared with the NT control group. However, 100 and 200 mg/kg curcumin pe-treatment group caused the expression of these apoptosis-related proteins to significantly decrease. Values are expressed as means ± SE (n=10) and analysed using one-way ANOVA. ^*P<0.05 vs. NT. ^#P<0.05 vs. DH. Cyto C, cytochrome c.

Figure 4

TUNEL staining and apoptosis index of renal tissue sections (magnification, x400). ^*P<0.05 vs. NT. ^#P<0.05 vs. DH.

Figure 5

Electron microscopy (magnification, x4,000). Changes in cellular morphology observed under an electron microscope in the dry heat or curcumin treatment groups.