Protective Effects of α-Lipoic Acid and Chlorogenic Acid on Cadmium-Induced Liver Injury in Three-Yellow Chickens

Abstract

Cadmium (Cd) is a type of noxious heavy metal that is distributed widely. It can severely injure the hepatocytes and cause liver dysfunction by inducing oxidative stress and mitochondrial damage. We evaluated the protective effects of α-lipoic acid (α-LA) or chlorogenic acid (CGA) and their combination on counteracting cadmium toxicity in vivo in three-yellow chickens. For three months, CdCl₂ (50 mg/L) was administrated through their drinking water, α-LA (400 mg/kg) was added to feed and CGA (45 mg/kg) was employed by gavage. The administration of Cd led to variations in growth performance, biochemical markers (of the liver, kidney and heart), hematological parameters, liver histopathology (which suggested hepatic injury) and ultrastructure of hepatocytes. Some antioxidant enzymes and oxidative stress parameters showed significant differences in the Cd-exposure group when compared with the control group. The groups treated with Cd and administrated α-LA or CGA showed significant amelioration with inhibited mitochondrial pathway-induced apoptosis. Combining both drugs was the most effective in reducing Cd toxicity in the liver. In summary, the results demonstrated that α-LA and CGA may be beneficial in alleviating oxidative stress induced by oxygen free radicals and tissue injury resulting from Cd-triggered hepatotoxicity.

Keywords: cadmium; chicken liver damage; chlorogenic acid; oxidative stress; α-lipoic acid.

Figure 1

Effects of α- lipoic acid and chlorogenic acid on the coefficients of four different organs of cadmium poisoned chickens (n = 3, x ± s). Electronic balance was used to weigh heart, liver, kidney and brain. Organ coefficient % = (organ mass/body mass) × 100%. * p < 0.05 vs. control.

Figure 2

Effects of α-lipoic acid and chlorogenic acid on serum biochemical markers of cadmium-poisoned chickens. (A) The content of TP, ALB and GLB and the ratio of ALB/GLB was measured by the automatic blood biochemical analyzer. (B) The activities of ALP and AST are specific hepatic-enzymes. The method was same as above. (C) The activities of CREA and UA were detected to indicate renal injury. (D) The variation of CK represents the cardiac function. (E) RBC and HGB are indexes about hematological changes. (F) ICP-MS was used in measurement of concentration of Cd in serum. * p < 0.05, ** p < 0.01 vs. control, ^# p < 0.05, ^## p < 0.01 compared to the Cd-treatment group and ^Δ p < 0.05 compared to the α-LA + CGA + Cd group.

Figure 3

The effect of α-lipoic acid and chlorogenic acid on histopathology of cadmium-exposed chicken liver (50 μm). (A): Control group, (B): Cd group, (C): α-LA group, (D): CGA group, (E): α-LA + CGA group, (F): Cd + α-LA group, (G): Cd + CGA group and (H): Cd + α-LA + CGA group.

Figure 4

The effect of α-lipoic acid and chlorogenic acid on the nuclei of hepatocytes in cadmium-exposed chickens (6000×). (A): Control group, (B): Cd group, (C): α-LA group, (D): CGA group, (E): α-LA + CGA group, (F): Cd + α-LA group, (G): Cd + CGA group and (H): Cd + α-LA + CGA group.

Figure 5

The effect of α-lipoic acid and chlorogenic acid on mitochondria of cadmium-exposed chicken liver (12,000×). (A): Control group, (B): Cd group, (C): α-LA group, (D): CGA group, (E): α-LA + CGA group, (F): Cd + α-LA group, (G): Cd + CGA group and (H): Cd + α-LA + CGA group.

Figure 6

Effects of α-lipoic acid and chlorogenic acid on antioxidative properties and Cd concentration of cadmium-exposed chicken liver. (A) Thiobarbituric acid (TBA) method was used to measure the content of MDA. The T-SOD assay kit was used to detect the activity of T-SOD. (B) The activities of CAT and H₂O₂ was measured by spectrophotometry according to CAT and H₂O₂ assay kits. (C) Antioxidant parameters—GST, GSH and GSH-Px activities were detected by the GST, GSH and GSH-Px assay kits. (D) The activity of T-AOC represents total antioxidant capacity of body. (E) Concentration of Cd in liver was detected by ICP-MS. * p < 0.05, ** p < 0.01 vs. control, ^# p < 0.05, ^## p < 0.01 compared to Cd-treatment group and ^Δ p < 0.05 compared to α-LA + CGA + Cd group.

Figure 7

Effects of α-lipoic acid and chlorogenic acid on apoptosis protein Bax in cadmium-exposed chicken liver detected by immunohistochemical (200×). The photographs of immunohistochemistry—(A) control group; (B) Cd group; (C) α-LA group; (D) CGA group; (E) α-LA + CGA group; (F) Cd + α-LA group; (G) Cd + CGA group; (H) Cd + α-LA + CGA group. (I) The positive ratio of Bax in all groups. ** p < 0.01 vs. control, ^# p < 0.05, ^## p < 0.01 compared to the Cd-treatment group.

Figure 8

Effects of α-lipoic acid and chlorogenic acid on mitochondrial apoptosis gene in cadmium poisoned chicken liver. The mRNA levels of (A) Bax; (B) Bcl-2; (C) ratio of Bcl-2/Bax; (D) Cyt C; (E) Caspase 3; (F) Caspase 9 were measured by q-RT PCR. * p < 0.05, ** p < 0.01 vs. control, ^# p < 0.05, ^## p < 0.01 compared to the Cd-treatment group, ^Δ p < 0.05 and ^ΔΔ p < 0.01 compared to the α-LA + CGA + Cd group.