Lycopene Supplement Restores the Oxidation/Antioxidation Balance Through Efficient Antioxidant Activities in Wistar Rats with Cadmium-induced Oxidative Stress

Lycopene (C40H56) is a bioactive phytochemical classified as a non-provitamin A carotenoid (Yin et al., 2019). It is produced as an intermediate metabolite during the synthesis of carotenoids in plants (Mozos et al., 2018). Lycopene is a lipid-soluble organic pigment found primarily in tomatoes, red and orange-colored vegetables, fruits such as watermelon, pink grapefruit and apricots (Arballo et al., 2021). The highest concentrations of lycopene are encountered in tomatoes (Hedayati et al., 2019). Around 90% of dietary lycopene being sourced from tomato and tomato-based products (Przybylska, 2020).
       
Research has demonstrated that lycopene has various health benefits, serving as a preventative measure against a wide range of diseases (Joshi et al., 2020). The clinically beneficial effects of lycopene include anticancer properties, cardioprotection, antiobesity effects, renoprotection, osteoprotective, neuroprotection, antidiabetic effects, treatment for skin diseases, anti-inflammatory properties, hepatoprotection and addressing reproductive disorders (Doyle, 2020).
       
Oxidative stress occurs when there is an imbalance between the production of reactive oxygen species (ROS) and the body’s ability to neutralize them with its antioxidant systems. Excess generation of ROS is a major contributor to oxidative stress and the associated damage (Meléndez-Martínez, 2019; Hasan et al., 2024).
       
The endogenous antioxidant system is specifically designed to accurately detect free radicals (an example of type oxidative metabolite), block their reaction sequences and mitigate their potentially damaging effects (Ellis et al., 2019; Rebai et al., 2023).
       
Cadmium (Cd) is a well-known toxic heavy metal and its presence is associated with oxidative damage in tissues, particularly in the liver and kidneys. This metal significantly contributes to the initiation and progression of oxidative stress (Naviglio et al., 2019).
       
There is growing interest in natural antioxidants as dietary supplements (Basheer et al., 2023; Hidayatik et al., 2024), which can serve as preventive and therapeutic agents for various significant health conditions, including cancer, cardiovascular diseases, neurodegenerative disorders, arthritis and age-related changes (Joshi et al., 2020; Moatasem et al., 2023).
       
This study aims to evaluate the antioxidant properties of lycopene in male Wistar rats subjected to heavy metal toxicity. Specifically, it investigates how lycopene can alleviate the harmful effects of oxidative stress induced by cadmium toxicity.

Ethical considerations
 
Laboratory rats were cared for and utilized according to the guidelines established by the Research Ethics Committee of Imam Mohammad Ibn Saud Islamic University (IMSIU), which comply with both institutional and national regulations (LAB-rats-2023-0223).
 
Experimental rats
 
Eighty adult male Wistar rats, aged three months weighing between 130-210 g, were used in this investigation. The rats were obtained from the inbred colonies at the animal house of the College of Pharmacy, King Saud University, Riyadh, Saudi Arabia. The standard laboratory conditions, ambient temperature of 24±1°C, a 12-hour dark-light cycle and relative humidity ranging from 35-70%, were maintained.
 
Lycopene
 
Lycopene (Carotene,2,6,10,14,19,23,27,31-Octamethyl-dotriaconta-2,6,8,10,12,14,16,18,20,22,24,26,30-tridecaene) (C40H56) ³98% (HPLC) from tomato (Molecular Weight: 536.87), was purchased from Sigma-Aldrich (Darmstadt, Germany) (CAS Number: 502-65-8). Lycopene was dissolved in chloroform to achieve a final concentration of 5 mg/mL.
 
Cadmium
 
Cadmium (Cd) was used in the form of cadmium chloride (CdCl2) of analytical grade (Merck, Darmstadt, Germany) (Product No. 655198). Cadmium was dissolved in purified water to prepare the required aqueous solution.
 
Experimental design
 
The experimental work was carried out at Biology Department, College of Science, Imam Mohammad Ibn Saud Islamic University over a period extending from September to December, 2023. The rats were acclimatized for one week and then randomly allotted into four groups; of 20 rats each, designated as Groups 1, 2, 3 and 4. Group 1 served as the untreated control (not exposed to cadmium and did not received lycopene). Group 2 rats were administered daily with lycopene via oral route at a dose rate of 80 mg/kg b.wt. (Baz et al., 2022) at a rate of 1 mL/kg b.wt. Rats in Group 3 received CdCl2 as an aqueous solution through oral gavage at a final concentration of 5 mg/kg b.wt. (Adeleke et al., 2023)/day at a rate of 1 mL/kg b.wt. The control rats received an equivalent volume of saline. Rats in Group 4 were administered with CdCl2 and lycopene orally at the same aforementioned doses. A 10-hour gap was maintained between the daily administration of CdCl2 and lycopene. The experimental duration was eight weeks. The rats were fed ad libitum with pellet feed and water.
 
Hematological and biochemical assays
 
The rats were anesthetized with 3% isoflurane at the termination of the experiment and blood samples were collected via cardiac puncture from all experimental rats. Various haematological indices were assessed using blood samples collected with an anticoagulant (EDTA). Serum harvested from coagulated blood samples was stored at -20°C until biochemical assays were performed. Rats were then sacrificed after silencing with diazepam and with suitable anesthetic then liver and kidney tissues were removed and homogenized in 150 mM NaCl. The homogenates were centrifuged at 3000 ´ g at 4°C for 10 minutes and various biochemical parameters were measured using the collected supernatants.
 
Blood cadmium level
 
To assess cadmium levels in the blood, 1 mL blood samples were digested using a mixture of HClO₄ and HNO₃ and blood cadmium levels were determined using an atomic absorption spectrophotometer (CBC 906 AA).
 
Statistical analysis
 
Data in this study are expressed as means ± standard deviation (S.D.). To compare means between different groups, one-way ANOVA and SPSS software (SPSS Inc., Chicago, IL, USA) was used for statistical analysis. The normality and homogeneity of variances were checked and the independence of observations was ensured. The normality of the data was verified using the Shapiro-Wilk test. Results with a P-value less than 0.05 (P<0.05) were considered statistically significant.
 

Rats that were given lycopene, both alone and in combination with exposure to cadmium, showed normal behavioral activity and food intake when compared to the untreated control rats. In contrast, rats that were exposed to cadmium without lycopene treatment displayed a decrease in activity and food intake starting from third week of the experiment compared to the control rats. No deaths were reported in any of the experimental groups.
       
The blood cadmium level in control rats was measured at 0.0024±0.0001 ppm, which significantly increased (P<0.05) in rats exposed to cadmium (0.573±0.018 ppm). Blood cadmium levels were comparatively lower in rats exposed to cadmium and received lycopene (0.217±0.016 ppm) than in cadmium-exposed rats.
       
Table (1) shows the estimated hematological parameters in rats that received lycopene, rats exposed to cadmium and rats exposed to cadmium and administered with lycopene compared to the control rats.


       
Tables (2) (a, b, c) shows the biochemical parameters (serum levels) in rats that received lycopene, rats exposed to cadmium and rats exposed to cadmium and lycopene compared to the control rats.






       
Table (3) shows the levels of total thiols, glutathione, catalase, glutathione peroxidase, superoxide dismutase, TAC, H₂O₂, MDA in the liver and kidney homogenates of rats that received lycopene, rats exposed to cadmium and rats exposed to cadmium and lycopene compared to the control rats.


       
The toxic effects of cadmium include the oxidation of cell membrane lipids, which significantly reduces the production of ATP and glutathione in the mitochondria. Additionally, cadmium toxicity impairs the function of antioxidant enzymes, thereby exacerbating existing oxidative stress. Ultimately, cadmium-induced toxicity leads to apoptosis due to the activation of the caspase cascade (Kawata et al., 2018).
       
Indicators of antioxidative status, such as total thiols, glutathione, superoxide dismutase, glutathione peroxidase, catalase and total antioxidant capacity, were remarkably decreased in rats exposed to cadmium. It is postulated that the generated ROS in the course of cadmium toxicity caused oxidation of these endogenous antioxidants and consequently dramatically suppressed their capacity to overcome the resultant oxidative damage.
       
Glutathione and catalase are among the endogenous antioxidants that work directly to eradicate free radicals (Liu et al., 2018). Oxidation of these antioxidants leads to the accumulation of free radicals and exacerbation of oxidative stress. Catalase decomposes hydrogen peroxide (H₂O₂), which accounts for lipid peroxidation. Inhibited   catalase activity allows hydrogen peroxide to induce severe oxidizing effects in rats. H₂O₂ action is the base of the Fenton reaction, which generates the highly oxidizing hydroxyl radical (OH) (Shi et al., 2024).
       
The present significant increase in the levels of malondialdehyde (MDA) in cadmium-intoxicated rats is ascribed to lipid peroxidation of the cell membranes. MDA, being a marker of lipid peroxidation, is one of the consequences of oxidative damage (Wang et al., 2018; Shamsi et al., 2020).The antioxidant activity of lycopene is related to its scavenging of free radicals as evidenced by its direct action to eliminate H₂O₂, NO and  hydroxyl  OH  radicals and its capability to inhibit lipid peroxidation (Ilhane et al., 2022; Juan et al., 2021).
       
Lycopene down-regulates gene expression of iNOS, decreases NO level and increases tissue glutathione (GSH) (Leh and Lee, 2022; Grabowska et al., 2019; Kiran et al., 2023). In addition, it prevents oxidative stress-induced apoptosis (Francenia et al., 2019). Under the circumstances of oxidative stress, Lycopene elevates the total antioxidant status. Lycopene could enhance the activities of all antioxidant enzymes including catalase, superoxide dismutase and glutathione peroxidase and   inhibit oxidative enzymes (Bin-Jumah et al.,  2022; Świątkiewicz et al., 2023). It reduces the level of malondialdehyde (MDA) and reduces the synthesis of ROS in general. Lycopene reduces the mitochondrial and intracellular concentrations of ROS. Through these activities, lycopene could   protect   proteins, DNA and lipids against oxidative damage.
       
It was concluded that lycopene as a carotenoid could counteract and prevent the progression of the effects of ROS. Lycopene acts through diverse mechanistic pathway to alleviate ROS-induced oxidative damage (Rejali et al., 2022; Abir et al., 2023).
       
The present results are in accordance with those of the relevant published studies (Przybylska, 2020; Guo et al., 2023) as evidenced by the currently recorded   improved levels of antioxidant markers (total thiols, glutathione, catalase and TAC in rats exposed to cadmium  and had access to Lycopene. These findings may confirm the positive effect of lycopene on the activity of these antioxidant molecules and consequently reinforcing significant effect on endogenous antioxidant capacity.
       
The significant decrease in cadmium blood levels in presently cadmium-intoxicated rats and administered lycopene may be interpreted by cadmium chelation. Chelation is one of the postulated roles of lycopene to mitigate the damaging effects induced by chemical toxins   (Nadeem et al., 2019; Hedayati et al., 2019). Cadmium is the trigger of oxidative overload and decreasing its level in the blood greatly limiting the initiation of oxidative stress   and thus helps recover the endogenous antioxidant system. The currently assayed haematological and biochemical parameters in rats exposed to cadmium and treated with lycopene  revealed  improvements  toward the control levels. These results may reinforce the proposed synergistic antioxidant role of lycopene in alleviating cadmium-induced oxidative stress.

The present investigation might represent evidence of the antioxidant efficiency of lycopene in countering the outstanding oxidative stress induced by cadmium toxicity. However, detailed research work is recommended to highlight the molecular mechanisms that could explain   clearly the antioxidant properties of lycopene in heavy   metal-induced oxidative stress. The current findings provide evidence of the efficient antioxidant activity of lycopene. However, further investigation is recommended to reveal the detailed molecular mechanisms through   which lycopene exerts its antioxidant properties.

This work was funded by Researchers Supporting Project number (RSP2025R26), King Saud University, Riyadh, Saudi Arabia. This work was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project number (PNURSP2025R62), Princess Nourah bint Abdulrahman University, Riyadh, Saudi Arabia.

The views and conclusions expressed in this article are solely those of the authors and do not necessarily represent the views of their affiliated institutions. The authors are responsible for the accuracy and completeness of the information provided, but do not accept any liability for any direct or indirect losses resulting from the use of this content.

All animal procedures for experiments were approved by the Committee of Experimental Animal care and handling techniques were approved by the University of Animal Care Committee.