Pinostrobin attenuated cadmium instigated cardiotoxicity in albino rats: A biochemical, inflammatory, apoptotic and histopathological examination

1 Introduction

Cd is considered as one of the most lethal heavy metals and designated a carcinogenic substance that instigates severe health risks to animals and humans (Al Olayan et al., 2020). Cd enters the body predominantly by ingestion, inhalation or dermal contact (Nduka et al., 2019). Moreover, Genchi et al. (2020) elucidated that Cd is extensively used in the manufacturing of various products including batteries, pigments, plastics, cigarette, metal coatings and polyvinyl chloride. People exposed to Cd during various operations such as mining, metal ores, production of nickel–cadmium (Ni-Cd) batteries and electronic devices. Owing to low rate of excretion, Cd accumulates in different organs & instigates various organ damages such as hepatotoxicity, cardiotoxicity and nephrotoxicity (Pi et al., 2015; Oyinloye et al., 2016; Dong, 2014).

The heart is one of the vital organs of body that performs pivotal role in living organisms (Peate, 2021). Cd disrupts the cardiovascular system (CVS) by disrupting cytochrome P450 as well as antioxidant balance in the body. When Cd reaches the cardiac tissues, it prompts oxidative stress as well as DNA damage which ultimately disregulates the normal gene transcription (Guo et al., 2020). The exposure to Cd disruptes the antioxidant defense system that involves neutralization of free radicals by lowering ROS production and protecting the macromolecules (proteins, DNA & lipids) from damage (Jan et al., 2015). Furthermore, Cd intoxication instigates peripheral arterial disease, increased vascular intima media thickness, morphological lesions, disorders of cardiac muscles & myocardial infarction that ultimately leads to congenital heart disease & cardiovascular disease (CVD) (Ray et al., 2023).

Flavonoids are secondary metabolites of plants that are extensively used against various disorders (Juca et al., 2020). Pinostrobin (PSB) is a bioflavonoid which demonstrated various pharmacological abilities including anti-oxidative (Hidajati et al., 2018), antifungal (Kanchanapiboon et al., 2020), anticancer (Sun et al., 2020), antiapoptotic (Jadaun et al., 2019) antiparasitic (Vechi et al., 2021) & anti-inflammatory (Patel et al., 2014). However, the cardioprotective potential of PSB is yet to be reported. Consequently, the current trial was executed to ascertain the ameliorative effect of PSB against Cd-instigated heart damages in rats.

2 Materials & methods

3 Results

3.6

3.6 Effect of PSB on cardiac histopathology

Cd intoxication led to various histopathological disruptions in cardiac tissues such as myocardial damage, focal necrosis, vacuolization of cytoplasm, myofibril disarray, interstitial fibrosis, inflammation, and alterations in cellular morphology in comparison to control group. Nevertheless, PSB supplementation remarkably (p < 0.05) mitigated abovementioned histopathological disruptions prompted by Cd exposure. However, control and PSB only supplemented group showed (Fig. 1).

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Fig. 1

Histopathological analysis of heart tissues. H&E stain; 40X (A) Control group exhibited normal architecture of heart tissues (B) Cd exposed group demonstrated fibrosis, inflammation as well as large interstitial spaces (edema) (C) Cd + PSB group showed a remarkable recovery in contrast to Cd exposed group (D) Only PSB supplemented group showed normal morphology of cardiac tissues as in control group.

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4 Discussion

Cd is one of the most prevalent contaminants with a continuous increasing concentration because of agricultural and industrial activities, causing unavoidable hazards to humans (Wang et al., 2023). Setia et al. (2020) documented that Cd penetrates the body through skin, gastrointestinal & respiratory tract. It is reported that Cd exposure induces various damages such as nephrotoxicity, bone disease, infertility, liver toxicity as well as cardiac damages (Mitra et al., 2022). In cardiac tissues, Cd exposure generates oxidative stress, inflammation, cardiomyocyte apoptosis and histological damage (Alpsoy et al., 2014). Recent literature shows that antioxidants can prevent the body from adverse effects of Cd intoxication. PSB is a poly-phenolic compound that is effective in scavenging free radicals & well-known for its broad range of pharmacological properties (Athapaththu et al., 2023).

Our investigation elucidated that Cd intoxication reduced the activities of antioxidant enzymes while augmenting the levels of oxidative stress markers in cardiac tissues of treated animals. Furthermore, excessive generation of ROS reduced the activities of antioxidant enzymes thereby impairing cellular defense system (Ahmad et al., 2023). Ighodaro and Akinloye (2018) elaborated that SOD transforms superoxide radicals into H₂O₂, whereas CAT utilizes the oxygen as a cofactor and stimulates the degradation of H₂O₂ into H₂O & O₂. GPx reduces oxidative stress by scavenging the hydrogen peroxide. GSH also protects the cells from oxidative stress (OS) by lowering the levels of H₂O₂ and other peroxides. GST participates in cellular detoxification of cytotoxic and genotoxic substances as well as in defending tissues against oxidative damage. (Hayes et al., 1999). Similarly, escalated levels of MDA indicate the onset of lipid peroxidation due to excessive generation of reactive oxygen species (Ijaz et al., 2022). Elsayed et al. (2022) reported that flavonoids can reduce the levels of OS by increasing the activity of antioxidant enzymes. In the current investigation PSB supplementation restored the balance between antioxidant and prooxidants which demonstrates its ROS neutralizing abilities.

Oral administration of Cd led to a remarkable upsurge in the level of cardiac function markers (CK-MB, CPK, LDH & troponin). Troponin, CPK, and CK-MB are the diagnostic biomarkers of cardiotoxicity due to their serum catalytic activity and tissue specificity (Zhang et al., 2015). A previous investigation elucidated that Cd is a cardio-toxic compound having the capability to destroy directly cardiomyocytes & release these cardiac damage biomarkers into the blood stream. Various types of heart injury, including myocarditis, heart failure & myocardial infarction have been associated with elevated levels of these enzymes (Saleh et al., 2017). However, PSB administration notably lowered the level of these enzymes that might be attributed to its cardio-protective ability.

In the current investigation, exposure to Cd instigated an augmentation in the levels of IL-6, TNF-α, NF-κB, IL-1β & COX-2 activity. NF-kB, a cytoplasmic protein complex which is associated with elevated levels of ROS during various disorders (Ali et al., 2022) and its activation ultimately trigger the production of aforementioned inflammatory markers (Somade et al., 2019). Furthermore, COX-2 is an adaptive enzyme that stimulates the complete inflammation state (Kumar et al., 2022). Therefore, inflammatory responses in the cell can be blocked by preventing the activation of NF-κB. However, PSB supplementation reduced the levels of inflammatory biomarkers which is attributed to anti-inflammatory property of PSB.

Cd administration induced a substantial upsurge in the levels of pro-apoptotic markers while downregulating the anti-apoptotic markers. Danial and Korsmeyer (2004) elaborated that Bax works as pro-apoptotic protein that mediates various events of apoptosis while Bcl-2 functions antagonistic to Bax. An escalation in Bax levels & decline in Bcl-2 alters the mitochondrial membrane permeability & triggers the eviction of Cytochrome c into cytoplasmic matrix that in turn activates Caspase-3 to mediate apoptotic pathways (Santana, 2018). Caspase-3 belongs to the cysteine protease family which splits the cellular proteins & making structural variations that led to apoptosis (Hofmann, 2020). However, administration of PSB lowered the levels of pro-apoptotic proteins while elevating the levels of anti-apoptotic markers owing to its anti-apoptotic properties.

The present research demonstrated that Cd intoxication induced adverse histopathological damages in the architecture of cardiac tissues such as focal necrosis, perivascular and interstitial fibrosis, myofibril disarray, alterations in cellular morphology and increased levels of matrix metalloproteinases (MMPs). Our outcomes matched with the investigations of Chou et al. (2023) who stated that Cd exposure instigated various histopathological damages in heart including focal necrosis, myofibril disarray, disorganized sarcomere structures and interstitial & perivascular fibrosis. However, the supplementation of PSB significantly restored all the histopathological damages in the cardiac tissues of rats that might be ascribed to its anti-inflammatory, anti-oxidative & anti-apoptotic nature.

5 Conclusion

Taken together, the current research exposed that Cd intoxication prompted OS in cardiac tissues and disturbed the heart functional enzymes, inflammatory, apoptotic, and biochemical markers along with histopathological profile. However, PSB supplementation significantly restored all the cardiac damages provoked by Cd. As a result, it can be assumed that PSB might be used as a potential therapeutic drug in future to cure cardiac damage. However, further clinical investigations are indispensable to evaluate the efficacy of PSB to cure cardiac damages in humans.