JAHP_13_s1_939-944

Introduction

Furfuraldehyde (C5H4O2), a colorless, sweet-smelling liquid, is a major chemical compound in the industries like lubricants, polishes, cutting oils, fungicides, acetal resins, perfume fixatives, floor-sealing materials, and roofing materials. Humans are most likely exposed to furfuraldehyde by ingestion, inhalation, and contact with skin. It is evident that this highly toxic compound has contributed to excessive concern regarding human health, particularly in occupational and environmental settings, based on the findings of its neurotoxic, hepatotoxic, and genotoxic characteristics, as well as its contribution to Alzheimer’s, Parkinson’s, and Huntington’s diseases (LoPachin and Gavin, 2014).

From the toxicological standpoint, the various issues associated with furfuraldehyde that will be discussed arises from its ability to generate significant quantities of reactive and often toxic aldehyde metabolites. It will be seen that the different toxicological effects seem to reflect not only the molecular/biochemical site(s) of interaction between the aldehydic xenobiotics and biological endogenous molecules, but also on the ‘rate’ at which these events occur in the course of furfuraldehyde metabolism/clearance. This, in turn, is likely to depend on the route and concentration of furfuraldehyde exposure. This comprehensive examination of the toxicological effects of furfuraldehyde and the contemporary chemical and biochemical evidence detailing related reactions also encompasses an elucidation of the insidious nature of the harmful effects engendered by this aliphatic aldehyde. An understanding of the mechanistic framework underlying these adverse physiological effects is essential to fully appreciate why there is now a widely recognized need to implement strategies to control the increasing exposure of furfuraldehyde under many circumstances (Grootveld, 2022).

Furfural is a compound that was first discovered in a variety of heat-treated food products; in small amounts, it is found in products such as coffee, fruit juices and baked goods. It is also used in the manufacturing of Fabricated metal products, except machinery and equipment; Public administration and safety; Non-metallic mineral products; Wood and paper products; and Chemicals. It is primarily used in the manufacture of printing inks and in the production of synthetic resins, as a cleaning agent and to produce other chemicals. There is evidence suggesting that increased concentrations of furfuraldehyde in the urban environment to which the general population is exposed results in high man-made chemical concentration in urban air. Therefore, it is important to investigate the inhalation toxicity of furfuraldehyde along with the influence of exposure on the antioxidant defense of L-carnitine, an important antioxidant in the respiratory system (Park et al., 2024).

Rapid industrial consumption of wood leads to the production and accumulation of a large amount of wood processing waste, which is not only a waste of resources, but also a serious pollution of the environment and a waste of energy. Furfuraldehyde, as a model of wood processing waste, enters the human body through the environmental environment, resulting in a variety of diseases. Therefore, the furfuraldehyde metabolism process in the human body and the oxidative stress mechanism are crucial to the prevention and control of furfuraldehyde pollution from wood processing waste (Jamshidzadeh et al., 2017).

Furfuraldehyde, a water solubility and colorless flammable liquid with a special almond scent, is a product of pentose dehydration, and is widely used in the industry of fiber, film, coconut shell activated carbon, plastics, rubber, pesticides, medicine, and solvents. In recent years, the consumption of furfural in the world increased continuously, and it is notable that the consumption will be larger and larger based on it, especially for health. Furfural has duality, on the one hand, it is an intermediate product in the biosynthesis of various biological substances, so the human body is necessary and to make the person energetic, healthy, and longevity; on the other hand, it is an important cancer-causing substance, which also includes the mutational substance of the genetic material, whereby the heredity comes true and the species develop. The curiosity about the timeout of the furfural-a haze of scientific research has risen (Andrés et al., 2023).

L-Carnitine is a natural occurring compound that attracts the attention of many scientists due to its role in the metabolism of fatty acid. Fatty acids are digested to acyl-CoA, which enters cells and mitochondria with the help of carnitine. Carnitine serves an important function in the energy production of mammalian cells by converting fatty acids into acyl-carnitine esters and transporting them across the mitochondrial matrix. Carnitine also has a beneficial impact beyond cellular energy producing processes; however, it has been reported that carnitine has antioxidant properties, for example (Li and Zhao, 2021).

In the 4 Cs of nutritional supplementation, carnitine has shown that it can act in the case of staving off the entry into consumption of various toxins; however, the effect of L-carnitine for the regulation of food contaminants like furfuraldehyde (FAL), a common toxin to degrade of certain types of food. L-Carnitine is commonly synthesized in the body, and it can also be obtained from a wide range of foods, such as meat, fish, and dairy products. Due to genetic restrictions, endogenous synthesis, or a low-carnitine diet, the consumption of carnitine through food and dietary supplements is necessary for many people (Rosaria-Carillo et al., 2020).

To evaluate the biochemical alterations induced by prolonged exposure to furfuraldehyde in male rats as animal model, with a focus on liver and kidney function markers, this study investigates the toxicopathological changes in vital organs (liver and kidney) following chronic exposure to furfuraldehyde.

Materials and Methods

Experimental design

Low-dose FA group (Group 2): Throughout the entire study period animals received daily oral doses of FA at 20 mg/kg body weight. High-dose FA group (Group 3): For the entire study period researchers gave animals daily oral doses of 40 mg/kg FA. Low-dose FA + L-carnitine group (Group 4): Through gavage administration the animals received daily oral doses consisting of 20 mg/kg FA with an additional 200 mg/kg L-carnitine. High-dose FA + L-carnitine group (Group 5): The subjects received daily oral gavage doses of 40 mg/kg FA mixed with 200 mg/kg L-carnitine. Existing toxicity research determined FA doses whereas the L-carnitine dose was based on its established antioxidant and cytoprotective properties. The research team monitored animals for a total of 90 days and completed their evaluations on both the 45th and 90th days.

Biochemical assays

Evaluated oxidative stress markers through enzymatic assays performed on liver and kidney tissue homogenates (Zhang at el., 2021).

Reactive oxygen species (ROS) measurement

The reactive oxygen species (ROS) production rate was determined by conducting a dichlorofluorescein diacetate (DCFDA) fluorescence assay. Tissue homogenates received an incubation treatment with 10 µM DCFDA for 30 minutes at 37 °C and the fluorescence was measured using a microplate reader at excitation/emission wavelengths of 488/525 nm. The study quantified ROS levels based on the fluorescence measurement of each milligram of protein present.

Lipid peroxidation (MDA Assay)

Malondialdehyde (MDA), an indicator of lipid peroxidation, was quantified using the thiobarbituric acid reactive substances (TBARS) assay. Briefly, 0.5 mL of tissue homogenate was mixed with 2.5 mL of thiobarbituric acid (TBA) reagent, boiled at 95°C for 15 minutes, cooled on ice, and centrifuged at 3,000 rpm for 10 minutes. The absorbance was measured at 532 nm, and MDA levels were expressed as nmol/mg protein.

Catalase (CAT) activity assay

Catalase activity was measured spectrophotometrically at 240 nm following the decomposition of hydrogen peroxide (H₂O₂). The reaction mixture contained 0.5 mL of tissue homogenate and 1 mL of 10 mM H₂O₂. Absorbance was recorded every 15 seconds for 3 minutes, and catalase activity was expressed as µmol H₂O₂ decomposed per minute per mg of protein.

Histopathological analysis

Liver and kidney samples were collected, fixed in 10% neutral-buffered formalin, and processed for histopathological examination. Paraffin-embedded sections (5 µm) were stained with hematoxylin and eosin (HandE) and observed under a light microscope (Leica, Germany) for structural changes, including necrosis, vacuolization, and inflammatory infiltration.

Statistical analysis

All statistical analyses were conducted using SPSS (Version 25.0, IBM, USA). The Kolmogorov-Smirnov test was used to check data normality. One-way ANOVA followed by Tukey’s post hoc test was performed to analyze group differences. Gene expression data (RT-PCR analysis) were normalized to β-actin and analyzed using the 2^(-ΔΔCt) method. All values were expressed as mean ± standard deviation (SD), and a p-value of <0.05 was considered statistically significant. Graphical representations were created using GraphPad Prism 9.0 (GraphPad Software, USA).

Results

Biochemical analysis

Reactive oxygen species (ROS) levels

FA exposure significantly increased ROS levels in liver and kidney tissues compared to the control group (p < 0.05). The high-dose FA group showed the highest ROS accumulation. L-carnitine supplementation significantly reduced ROS levels in both FA-treated groups, confirming its antioxidant properties (Figure 1).

Lipid peroxidation (MDA levels)

MDA levels were significantly elevated in FA-exposed groups, indicating increased lipid peroxidation (p < 0.01). The high-dose FA group exhibited the most pronounced increase in MDA, while L-carnitine co-protective significantly reduced MDA levels, restoring them closer to control levels (Figure 2).

Catalase (CAT) activity

Catalase activity was initially increased in FA-exposed groups (compensatory response to oxidative stress) but declined over time due to enzymatic exhaustion. L-carnitine protective restored CAT activity, preventing oxidative stress-related enzyme depletion (Figure 3).

Histopathological analysis

Histopathological evaluation of liver and kidney tissues in FA-exposed rats revealed severe necrosis, vacuolization, and inflammatory infiltration. FA exposure also caused mitochondrial abnormalities, as seen in TEM images (Figure 4 and 5. L-carnitine-treated groups exhibited reduced tissue damage, with preserved cellular integrity.

Discussion

The results of this study demonstrate that FA exposure significantly alters biochemical markers associated with oxidative stress. Increased ROS production and lipid peroxidation in FA-exposed groups confirm that oxidative stress is a key mechanism underlying FA toxicity (Kaltsas, 2023). The upregulation of catalase activity in the early phase of FA exposure suggests a compensatory response to oxidative stress. However, the subsequent depletion of catalase at later time points indicates enzymatic exhaustion, further exacerbating oxidative damage (Wang et al., 2018).

The toxic effects of FA on liver and kidney tissues received confirmation through histopathological findings. The presence of inflammation, necrosis and mitochondrial abnormalities in FA-exposed groups confirms earlier research which identified aldehyde toxicity as a significant factor in tissue damage (Benvenga et al., 2019). The study by Mantle and Hargreaves (2022) found that L-carnitine supplementation reduced pathological alterations by restoring mitochondrial integrity and preventing apoptosis caused by oxidative stress.

L-carnitine protects cells through its role in fatty acid transport and mitochondrial structure stabilization. Doseděl et al. (2021) found that L-carnitine protects against oxidative stress-induced lipid peroxidation by enhancing β-oxidation while simultaneously reducing reactive oxygen species generation to preserve cellular function. L-carnitine delivers therapeutic advantages through its capability to manage antioxidant enzyme activity while stopping enzymatic exhaustion (Pagliai et al., 2020).

Findings demonstrate oxidative stress as the main factor in FA toxicity while showing L-carnitine protects cells from aldehyde-induced damage. Scientists need to investigate wider uses of this therapy for eliminating industrial toxins and cleansing environmental contaminants.

Conclusions

The study results reveal the biochemical mechanisms of FA toxicity and propose L-carnitine as a potential protective for oxidative stress caused by FA. Future studies need to investigate the clinical potential of the agent to reduce aldehyde-induced toxicity.

ACKNOWLEDGEMENTS

We extend sincere thanks to the faculty and staff of Department of Pathology and Poultry Diseases, College of Veterinary Medicine, University of Baghdad, Iraq for providing the facilities and assistance that made this work possible. Our heartfelt appreciation goes to my colleagues and friends for their encouragement, cooperation, and for making the research journey a pleasant experience.

Novelty Statement

This study provides novel insights into the toxicopathological consequences of prolonged exposure to furfuraldehyde, a widely used industrial aldehyde with limited in vivo toxicological documentation. Unlike previous studies that focused mainly on acute or short-term exposure, this work investigates chronic biochemical and histopathological alterations in male rats. Furthermore, the study highlights, for the first time, the protective efficacy of L-carnitine against furfuraldehyde-induced toxicity. By demonstrating its role in mitigating oxidative stress, restoring biochemical parameters, and improving tissue architecture, this research suggests the potential of L-carnitine as a therapeutic strategy against aldehyde-related toxicity.

Author’s Contribution

Samer Riyadh Fadhil conceived and designed the study, supervised the experimental work, performed data interpretation, and wrote the original manuscript draft.

Salema Lafta Hassan carried out the laboratory experiments, collected samples, performed biochemical and histopathological analyses, and contributed to data analysis.

Both authors reviewed, edited, and approved the final version of the manuscript.

Generative AI and AI-assisted technology statement

The authors declare that no generative artificial intelligence (AI) or AI-assisted technologies were used in the study design, data collection, data analysis, or interpretation of results. AI tools were used solely for language editing and improving grammar and clarity, without affecting the scientific content, data integrity, or conclusions of the manuscript.

Conflict of interest

The authors have declared no conflict of interest.

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