International Journal of Preventive Medicine

: 2020  |  Volume : 11  |  Issue : 1  |  Page : 111-

Chlorella sp. protective effect on acetaminophen-induced liver toxicity in ICR mice

Jia-Ping Wu 
 Research Center for Healthcare Industry Innovation, National Taipei University of Nursing and Health Sciences, Taipei City, Taiwan, Republic of China

Correspondence Address:
Jia-Ping Wu
Research Center for Healthcare Industry Innovation, National Taipei University of Nursing and Health Sciences, No. 365, Mingde Road, Beitou District, Taipei City 11219, Taiwan
Republic of China


Background: A Chlorella sp. (CLC) has a health supplement in health effects including an ability to treat cancer. The Chlorella sp. Ability to reduce acetaminophen-induced liver injury is still unknown. The hepatoprotective function of CLC was determined in an APAP-induced liver injury mouse model. Methods: Male ICR mice were randomly divided into normal control, APAP, APAP + Sm (silymarin) and APAP + CLC (0.2%, 0.5% and 1%) groups. The glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), Albumin, and BUN plasma activities were detected using blood biochemistry assay. The hepatic tissue GOT, GPT, superoxide dismutase (SOD) and catalase (CAT) activity were also detected. Lipid peroxidation, MDA, protein expression levels were examined. Results: The results showed that the 1% CLC supplementation group and Silymarin (Sm) could significantly alleviate increased serum GOT, GPT and BUN, and the decreased serum Albumin. At the same time, the increased hepatic tissue GOT and GPT activities were alleviated as well as MDA. Enhanced SOD and CAT protein expression levels were increased in APAP-induced liver injury. Lipofuscin and hepatic veins cups disappeared in the Sm and 1% CLC supplementation groups shown with H&E staining. Conclusions: Therefore, CLC probably could develop hepatoprotective products against chemical-induced liver damage.

How to cite this article:
Wu JP. Chlorella sp. protective effect on acetaminophen-induced liver toxicity in ICR mice.Int J Prev Med 2020;11:111-111

How to cite this URL:
Wu JP. Chlorella sp. protective effect on acetaminophen-induced liver toxicity in ICR mice. Int J Prev Med [serial online] 2020 [cited 2020 Aug 4 ];11:111-111
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Microalgae are usually used as additives in food to enhance the nutritional value and improve the health of humans and animals because of their chemical composition and bioactive molecules.[1],[2] The high-protein content of microalgae is the major reason for the non-traditional source of protein. The microalgae amino acids synthesize essential amino acids in humans and animals and compare favorably with that of other food proteins. In addition, many valuable antioxidants are present in microalgae, e.g., chlorophyll, carotenoids, astaxanthin, lutein, and phycobiliproteins. A Chlorella sp. is a type of unicellular green algae, which is a popular food supplement or health food worldwide.[3],[4],[5] Taiwan is one of the major producers of Chlorella-related products. Chlorella sp. has been reported to have certain beneficial physiological effects, such as antihypertensive, antioxidative, hypocholesterolemic, and antitumor activities in animal and human studies.[6],[7],[8],[9] However, the hepatoprotective activity of the extract derived from Chlorella sp. has not been extensively studied. Some reports indicated that Chlorella sp. is a good prophylactic-therapeutic agent against obesity-related complications.[10] Acetaminophen, or N-acetyl-para-amino-phenol (APAP), is widely used analgesic-antipyretic drugs. Although they are considered safe drugs,[11] they cause hepatic necrosis and renal failure when given in high doses. Increasing acute liver failure cases attributed to APAP use during the last two decades have been reported. Oxidative stress is reported to play a fundamental role in APAP-induced liver damage pathogenesis.[12] The search for new bioactive products with antioxidant activities is necessary to overcome APAP-induced hepatic oxidative damage.[13] Therefore, the present study was undertaken to evaluate the protective effect of the protein and antioxidant-enriched crude lysate from Chlorella sp. against APAP-induced liver injury in mice.

 Materials and Methods

Microalgal strain, Chlorella sp., cultivation

Freshwater microalgae Chlorella sp. was originally obtained from the Taiwan Fisheries Research Institute collection (Pingtung, Taiwan).


Male ICR mice (4 weeks old; 20 ± 2 g) were obtained from the National Laboratory Animal Center (NLAC, Taipei, Taiwan). Mice were quarantined and acclimated for 1 week prior to experimentation. The animals were handled under standard laboratory conditions including a 12-h light/dark cycle in a temperature and humidity controlled room (at 22 ± 2°C and 60 ± 5% relatively humidity). Food (normal chow diet) and water were available adlibitum. Our Institutional Animal Care and Use Committee approved the protocols for this animal study. The animals were cared for in accordance with the institutional ethical guideline.


The animals were randomly divided into 6 groups with each consisting of 6 mice. Mice groups and treatments are listed in [Table 1]. The group control served as the normal control and was given PBS buffer as a placebo by intraperitoneal injection (IP). The group control, APAP (Sigma-Aldrich), 0.1% silymarin (SM) (Sigma-Aldrich), 0.2%, 0.5%, and 1% CLC (Chlorella sp.), and animals were administered 200 mg/kg body weight of APAP dissolved in PBS buffer by IP twice a week for a period of 4 weeks. After APAP intoxication, group APAP served as the APAP negative control.{Table 1}

Blood biochemistry assay

The glutamic oxaloacetic transaminase (GOT), glutamic pyruvic transaminase (GPT), blood urea nitrogen (BUN), and albumin activities in serum were measured to evaluate hepatoxicity and renal toxicity. An autoanalyzer (DRI-CHEM 3500s; FUJIFILM, Kanagawa, Japan) was used in these experiments.

Hepatic tissue GOT, GPT, SOD, and CAT activity determination

GOT and GPT activities were measured according to the ELISA protocol of a commercially available kit (Cayman Chemical Company). The SOD activity was evaluated by using a tetrazolium salt for detection of superoxide radicals generated by xanthine oxidase and hypoxanthine. One unit of SOD is defined as the amount of enzyme needed to exhibit 50% dismutation of the superoxide radical. The SOD activity is standardized using the cytochrome c and xanthine oxidase coupled assay. The CAT activity was measured using H2O2 decomposition according to the Aebi. The final reaction mixture comprised 10 mM H2O2 in 50 mM phosphate buffer at pH 7.0. The decomposition of H2O2 was followed by spectrophotometry at 240 nm.

Hepatic tissue malondialdehyde, lipid peroxidation, and intermediate determination

The malondialdehyde (MDA) content (Ann Arbor, MI, USA), a measure of polyunsaturated fatty acids peroxidation, was assayed in the form of thiobarbituric acid-reactive substances. Briefly, a volume of 0.5 ml of liver homogenate was mixed with 3 ml of 1% H3 PO4(v/v) and 1 ml of 0.6% thiobarbituric acid (TBA, w/v), and then, heated to and maintained at 100°C for 40 min. The samples were allowed to reach room temperature, and 2 ml of butanol was added. After shaking vigorously with the vortex, the butanolic phase was obtained by centrifugation at 3,000 ×g for 10 min to determinate the absorbance at 535 nm.

Histopathology hematoxylin and eosin staining examination

Liver samples were dissected out and excised from experimental animals from each group, then washed with normal saline, fixed in 10% formalin, and processed for paraffin embedding following the microtome technique. The sections were taken at 6 μ thickness, processed in alcohol-xylene series, and stained with hematoxylin and eosin (H and E stain). The sections were examined microscopically for the evaluation of histopathological changes.


Data were compared with one-way analysis of variance test to evaluate differences among multiple groups. All results are expressed as the mean ± standard deviation (SD).*P < 0.05 or#P < 0.05 differences were considered statistically significant. A statistical analysis was performed using statistical software (SPSS, Chicago, IL, USA).


Preparation of the crude lysate of a Chlorella sp.(CLC).

Chlorella sp. biomass chemical composition is shown and compared in [Table 2]. The main feature is the abundant protein content (50–55%). The crude protein, soluble carbohydrates, total fiber, fat, ashes, and nucleic acids obtained in the CLC biomass were 63.7 ± 2.1, 17.3 ± 1.1, 4.5 ± 0.6, 3.4 ± 0.6, 5.6 ± 0.7, and 1.4 ± 0.2 (g/100 g), respectively individually after ultrasonic extraction [Table 2]. The ultrasonic-extracted CLC biomass crude protein was 1.2 times higher than that of non-extracted biomass (P < 0.05). The CLC also contains a number of biologically active compounds such as chlorophylls (2093.7 ± 166.3 mg/100 g) and carotenoids (211.3 ± 19.7 mg/100 g) (P < 0.05) compared with non-extracted biomass. These compounds have free radical scavenging potential, i.e., antioxidative activity. The chlorophylls and carotenoids of CLC biomass both were increased 1.5 to 2.0-fold compared with that of non-extracted biomass (P < 0.05).{Table 2}

Chlorella sp. (CLC) supplementation effect on liver marker enzymes in serum after APAP-induced hepatotoxicity

The ICR mice were fed with a chow diet containing 0.2%, 0.5%, and 1% (w/w) of CLC and 0.1% SM to test feeding APAP toxicity. After 28 days, the ICR mice were sacrificed to determine the serum GOT, GPT, albumin, and BUN activities for evaluating the liver function [Figure 1]. As shown in [Figure 1]a, the average serum GOT level results in group 1% (w/w) of CLC and SM had significant differences compared between the group APAP-induced the hepatotoxicity (P < 0.05). At the same time, both of SM administration and 1% CLC supplementation could reduce the increases in serum GTP-induced by APAP treatment [Figure 1]b. The mice challenged with APAP for 4 weeks showed significant increases in serum GOT and GPT activities compared with those in the control indicating that APAP-induced the hepatotoxicity (P < 0.01) [Figure 1]a and [Figure 1]b. However, APAP-induced the hepatotoxicity led serum albumin decreased compared with control (P < 0.01) [Figure 1]c, once SM and 1% CLC supplementation had increased serum albumin (P < 0.01) compared with APAP-induced injury. The serum BUN levels after APAP-induced increased hepatotoxicity when compared with control (P < 0.01) [Figure 1]c. SM and 1% CLC among these groups were significantly reduced BUN activity compared with APAP-induced [Figure 1]d. Hence, 1% CLC in feed was selected to evaluate the Chlorella sp. supplementation effect against APAP-induced liver injury in the study.{Figure 1}

Chlorella sp. (CLC) supplementation effect on hepatic tissue function markers, GOT, GPT, SOD, and CAT activity after APAP-induced hepatotoxicity

Overdosed APAP administration would induce oxidative stress in the liver because of hepatic function markers, GOT, and GPT, increased (P < 0.05) [Figure 2]a and [Figure 2]b, but decreased hepatic tissue, SOD, and CAT activities (P < 0.05) compared with control [Figure 2]c and [Figure 2]d. In APAP-treated and SM administration, hepatic GOT and GPT activities were significantly reduced (P < 0.05) compared with APAP-treated. We also observed 1% CLC administration for APAP-induced hepatotoxicity was significantly reduced (P < 0.05). By contrast, hepatic tissue antioxidative enzymes and CAT activities were increased in SM and 1% CLC (P < 0.05), when compared with APAP-induced hepatotoxicity group [Figure 2]d. However, hepatic tissue antioxidative enzymes and SOD activities displayed no significant differences after CLC supplementation in APAP-induced oxidative stress [Figure 2]c. It is indicated that the low degree of CLC concentration not reflected on serum and tissue. On the contrast, the high degree levels defense for the APAP-induced oxidative stress by CLC were close with that by SM administration.{Figure 2}

Chlorella sp. (CLC) supplementation effect on hepatic lipid peroxidation, malondialdehyde, after APAP-induced hepatotoxicity

Furthermore, we wanted to know the CLC supplementation effect on lipid peroxidation against APAP-induced oxidative stress in ICR mice [Figure 2]e. Experimental animals treated with APAP caused a significant increase in the primary lipid peroxidation and MDA product levels in comparison to the normal control (P < 0.05). ICR mice supplemented with SM and 1% CLC showed significantly inhibited hepatic APAP-induced hepatotoxicity elevation (P < 0.05). These eliminated MDA levels by 1% CLC supplementation were statistically similar to the level in the SM treatment group.

Histopathological changes in Chlorella sp. (CLC) supplementation on liver tissue after APAP-induced hepatotoxicity

Histopathological examinations showed that the APAP administration section observed collagen released (black arrows); the liver tissue cross-sections revealed severe hepatocyte necrosis with inflammatory cell infiltrate (brown arrows) [Figure 2]f. Mice livers simultaneously administered with APAP after supplementation with 1% CLC revealed improved liver condition not showed the inflammatory cell infiltration. The minimal hepatocyte necrosis damage shown in 0.5% CLC and the situation was comparable to that of mice administrated with SM and 1% CLC. According to histopathological examinations, severe hepatic lesions induced by APAP were remarkably reduced by 1% CLC supplementation, which was in good consistency with the results found in liver marker enzymes in serum and hepatic oxidative stress and lipid peroxidation.


The Chlorella sp. (CLC) is a protein-enriched powder containing around 65% of microalgae proteins. Marine macro- and microalgae-derived bioactive peptides have been widely applied for human nutrition and health. Marine-derived bioactive peptides have been identified as having antioxidant, antihypertensive, anticoagulant, or antimicrobial activities.[14],[15],[16] In the present study, the crude lysate of Chlorella sp. was prepared and used as a diet supplement to investigate the bioactivity functions on hepatoprotection. Significantly, different liver injury in the mice administrated with APAP was found. However, the liver injury could be recovered by CLC supplementation added in the diet for mice. According to our knowledge, the Chlorella sp. crude extracts against the drug APAP-induced hepatotoxicity. The similar result in a rat model test has also been reported from the hot-water-extraction from C. vulgaris supplementation.[17] There is a lack of study reports on the effects of Chlorella sp. supplementation on APAP-induced liver injury. Our current results showed that CLC supplementation is responsible for the increased resistance to oxidative stress induced by APAP. CLC supplementation could significantly alleviate the increased SOD and CAT activities in the APAP-treated mice. Oxidative stress was reported to play a fundamental role in the pathogenesis of APAP-induced liver damage.[18],[19],[20] Lipid peroxidation, MDA, is one of the major outcomes of free radical-mediated injury that directly damages membranes and generates a number of secondary products.[21] Antioxidant function and protection against lipid peroxidation are probably the most invoked mechanisms of protection by Chlorella sp. extracts.[22] The antioxidant enzymes such as SOD and CAT are related to direct elimination of ROS to prevent and neutralize the free radical-induced damage.[23],[24],[25] In APAP-induced hepatotoxicity, the balance between ROS production and these antioxidant defenses may be lost; oxidative stress results through a series of events deregulates the cellular functions leading to hepatic necrosis. According to the results, we proposed such oxidative liver injury induced by APAP could be reduced by CLC supplementation.

The potential antioxidant capacity of Chlorella sp. has been attributed to the effect of specific ingredients in Chlorella sp., such as chlorophylls and carotenoids compounds. The chlorophylls and carotene effect on ROS scavenging ability has been reported, with the theory that a few water-soluble or lipid-soluble ingredients of Chlorella sp. can decrease oxidative stress in vivo and ex vivo.[26] Chlorophyll is not only a benefit in treating liver recovery and ulcers but is also predicted to stimulate tissue growth because the chemical structure of chlorophyll is similar to that of hemoglobin.[27],[28],[29],[30] The present study demonstrated the Chlorella sp. may have protective functions such as ROS scavenger, meaning that Chlorella sp. could be used as a therapeutic treatment for oxidative stress-induced liver diseases such as APAP hepatotoxicity. Therefore, Chlorella sp. lysate may be considered as a potential source of natural antioxidant with hepatoprotective activity. Further, detailed investigations on this microalgae strain are needed to identify and isolate the hepatoprotective components in the extract and to justify its use in the treatment of liver disorders.


This work was supported by a grant from the National Science Council, Republic of China.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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