Satkara (Citrus macroptera) Fruit Protects against Acetaminophen-Induced Hepatorenal Toxicity in Rats.

Although Citrus macroptera (Rutaceae), an indigenous fruit in Bangladesh, has long been used in folk medicine, however, there is a lack of information concerning its protective effects against oxidative damage. The protective effects of an ethanol extract of Citrus macroptera (EECM) against acetaminophen-induced hepatotoxicity and nephrotoxicity were investigated in rats. Rats (treatment groups) were pretreated with EECM at doses of 250, 500, and 1000 mg/kg, respectively, orally for 30 days followed by acetaminophen administration. Silymarin (100 mg/kg) was administered as a standard drug over a similar treatment period. Our findings indicated that oral administration of acetaminophen induced severe hepatic and renal injuries associated with oxidative stress, as observed by 2-fold higher lipid peroxidation (TBARS) compared to control. Pretreatment with EECM prior to acetaminophen administration significantly improved all investigated biochemical parameters, that is, transaminase activities, alkaline phosphatase, lactate dehydrogenase, γ-glutamyl transferase activities and total bilirubin, total cholesterol, triglyceride and creatinine, urea, uric acid, sodium, potassium and chloride ions, and TBARS levels. These findings were confirmed by histopathological examinations. The improvement was prominent in the group that received 1000 mg/kg EECM. These findings suggested that C. macroptera fruit could protect against acetaminophen-induced hepatonephrotoxicity, which might be via the inhibition of lipid peroxidation.

1. Introduction

Complex redox reactions occur in the human body. Consequently, free radical formation is counteracted by specific endogenous enzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, and by exogenous antioxidants from plant sources [1, 2]. Citrus fruits contain many pharmaceutically important bioactive compounds that are the main contributors to their inherent antioxidant properties [3].

Citrus macroptera var. annamensis (family, Rutaceae) is locally known as “Satkara” in Bengali and “Wild orange” in English [4]. The semiwild species is native to regions of Malesia and Melanesia [5]. The C. macroptera plant is grown in the yard of most homesteads and hill tracts of the Sylhet division of Bangladesh. The fruit is typically used during cooking and for pickle preparation and is popular for its medicinal purposes in Assam, India [6]. It is also used by locals in Northeast India as medicine for stomach pain and alimentary disorders [7].

The C. macroptera fruit has significant cytotoxic, antimicrobial [8], antihypertensive, antipyretic, and appetite stimulant potentials [9, 10]. Additionally, significant hypoglycemic and neuropharmacological effects were confirmed in a rat model [11, 12]. The antioxidant constituents in the C. macroptera fruit include phenolics, flavonoids, tannins, ascorbic acid, and proteins, and significant radical scavenging activity was confirmed by an in vitro study [13]. Therefore, this fruit is postulated to play a therapeutic role in reducing the risk of some forms of fatal oxidative stress disorders, such as liver and kidney dysfunction, cardiovascular disease, and stroke [8, 14, 15].

The liver is a vital organ involved in the detoxification and elimination of toxic substances. The liver is often distressed by a large number of environmental pollutants and drugs, all of which burden, damage, or weaken it, ultimately leading to diseases such as hepatitis and cirrhosis [16]. Drug-induced toxicity of vital organs, including the liver and kidney, is frequently observed worldwide [17, 18]. Paracetamol (acetaminophen or N-acetyl-p-aminophenol; APAP) is a widely used over-the-counter analgesic and antipyretic drug [19]; APAP overdose can cause severe hepatocyte injury. APAP-induced hepatotoxicity is attributed to its reactive metabolite N-acetyl-p-benzoquinone imine (NAPQI), which is generated through cytochrome p450 and causes oxidative stress due to its ability to covalently react with proteins and nucleic acids and to deplete glutathione (GSH) [20-22]. There is also subtle evidence that APAP can cause harmful effects to the kidneys, which are important for drug elimination [23].

Interestingly, there is a plausible metabolic and pathophysiological link between the kidneys and the liver [24]. Both hepatotoxicity and nephrotoxicity are potential complications of APAP overdose, making the assessment of APAP-related toxicity indispensable [25]. There is particular interest in APAP-induced toxicity due to its overuse in Bangladesh, where no strong monitoring system is in place to regulate the utilization of over-the-counter drugs, such as APAP. Therefore, APAP-induced toxicity is a concern that affects many people.

Searching for novel medicinal plants with greater safety and efficacy has become the primary goal of medicinal chemists. We postulate that the high antioxidant potential of C. macroptera may confer protective effects when administered. Therefore, this study was designed to investigate the pharmaceutical effects of C. macroptera against APAP-induced hepatorenal toxicity in a rat model of liver and kidney diseases.

2. Materials and Methods

2.1. Chemicals

Acetaminophen was provided as a gift from Eskayef Bangladesh Limited (Dhaka, Bangladesh). 1,1,3,3-Tetraethoxypropane was purchased from NacalaiTesque, Inc. (Kyoto, Japan). Silymarin was obtained from Square Pharmaceuticals Ltd. (Bangladesh). All chemicals and reagents were of analytical grade.

2.2. Sample Collection

Fresh, mature C. macroptera fruit samples were collected from Sylhet district of Bangladesh in June 2014. The identification of the fruit was authenticated by Professor Nuhu Alam from the Botany Department, Jahangirnagar University. A voucher specimen (Acc. number 38619) was deposited in the Bangladesh National Herbarium for future reference.

2.3. Extract Preparation

The fresh, mature C. macroptera fruit samples were rinsed thoroughly under cold running water. The fruit pulp was separated from the peel and cut into small pieces using a sterile smooth steel knife and completely dried under sunlight for 28 h. Then, the dried samples were combined using a blender (Jaipan Commando, Mumbai-63, India). The blended samples were soaked in pure ethanol (100%) for 24 h and shaken (3 g) at 30°C for 72 h. Then, the extract was filtered through a cotton plug and then through Whatman No. 1 filters. The crude extract was evaporated under reduced pressure (100 psi) at a controlled temperature (40°C) and stored at −20°C prior to analysis.

2.4. Animals

Male Wistar Albino rats aged 12–14 weeks (140–150 g) were used in this study. The animals were bred and housed in an animal facility at the Department of Biochemistry and Molecular Biology, Jahangirnagar University, at a constant temperature of 25 ± 2°C with humidity ranging between 40% and 70%. The rats were housed in sterile plastic cages with soft wood-chip bedding and a natural 12 h day-night cycle. The animals had ad libitum access to standard food and water. The experiments were conducted according to the ethical guidelines approved by the Bangladesh Association for Laboratory Animal Science and the Biosafety, Biosecurity, and Ethical Committee of Jahangirnagar University [Approval number BBEC, JU/M2015 (2)].

2.5. Experimental Design

The animal experiments were designed based on the findings of the effective dose of acetaminophen as an agent for liver damage at subacute exposure while the outcomes of the study are the effects of C. macroptera investigated at multiple doses with some modifications (Figure 1) [13, 26]. Briefly, the animals were randomly divided into seven groups with six rats in each group. Group 1 was administered with normal saline, a solution of 0.90% of sodium chloride (5 mL/kg) perorally (p.o.) once daily for 30 days, and served as the “saline control” group. Group 2, the “EECM control” group, was treated with 1000 mg/kg EECM p.o. once daily for 30 days. Group 3, the “APAP control” group, received normal saline (5 mL/kg, p.o.) once daily for 30 days as well as 500 mg/kg APAP suspended in normal saline p.o. daily for the last 7 days. Groups 4, 5, and 6 received EECM at doses of 250, 500, and 1000 mg/kg p.o., respectively, for 30 days once a day and followed by administration of 500 mg/kg APAP p.o. daily for the last 7 days of the experiment; these groups were named the “T 250,” “T 500,” and “T 1000” groups, respectively. Group 7 was treated with a standard drug suspended in normal saline (silymarin, 100 mg/kg, p.o.) once daily for 30 days along with APAP (500 mg/kg, p.o.) for the last 7 days; this group was named the “silymarin” group.

Figure 1

Schematic diagram of the experimental design of the study.

At the end of the experimental period, the rats in each group were deeply anaesthetized with a ketamine hydrochloride injection (100 mg/kg) and sacrificed prior to dissection. Blood samples (5 mL) were collected from the inferior vena cava, and liver and kidney tissue samples were collected from each rat and stored in specimen containers (Thermo Scientific, USA) at −20°C prior to analysis.

The changes in body weight (BW) and in absolute and relative liver and kidney weights were recorded. BW gain was calculated using the following formula:

2.6. Serum Preparation

Blood samples (3 mL) were collected in clot activator plastic tubes and allowed to coagulate at ambient temperature for 30 min prior to centrifugation at 358 g for 10 min to separate the serum. The serum was stored at −20°C for biochemical analysis.

2.7. Tissue Homogenate Preparation

The liver and kidney samples were homogenized in phosphate-buffered saline (25 mM, pH 7.4) to produce an approximately 10% (w/v) homogenate. The homogenate was centrifuged at 259 g for 10 min. The supernatant was collected and stored at −20°C prior to biochemical analysis. A portion of each liver and kidney sample was stored in 10% formalin for histopathological examination.

2.8. Biochemical Analysis

Biochemical parameters in serum, such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), γ-glutamyl transferase (GGT), total protein (TP), albumin (ALB), total bilirubin (TB), total cholesterol (TC), triglyceride (TG), creatinine (CRE), urea, uric acid (UA), sodium (Na+), potassium (K+), and chloride (Cl−), were estimated following standard protocols using an automated chemistry analyzer (Dimension EXL with LM Integrated Chemistry System, Siemens Medical Solutions Inc., USA). Tissue TP levels were determined according to the method established by Lowry et al. [27]. Malondialdehyde (MDA) levels were investigated for products of lipid peroxidation (LPO) in the liver and kidney tissues. MDA, which is referred to as thiobarbituric acid reactive substance (TBARS), was measured at 532 nm according to the method described by Ohkawa et al. [28]. TBARS levels were expressed as nmol of TBARS per mg of protein.

2.9. Histopathological Examination

The liver and kidney tissues were dissected, fixed in 10% formalin, dehydrated in a graded ethanol series (50–100%), cleared in xylene, and embedded in paraffin wax. The tissues were sectioned at 5 μm thicknesses using a rotary microtome and then stained with hematoxylin and eosin for observation under a light microscope (MZ3000 Micros, St. Veit/Glan, Austria). The pathologist performing the histopathological evaluation was blinded to the treatment assignment of the different study groups.

2.10. Statistical Analysis

Data are presented as the mean ± standard deviation (SD). The data were analyzed using one-way analysis of variance (ANOVA), and the differences between groups were determined using Tukey's HSD post hoc test within Statistical Package for Social Sciences (SPSS) software version 13.0 (IBM Corporation, NY, USA) and Microsoft Excel 2007 (Redmond, WA, USA). A p value < 0.05 was considered statistically significant.

3. Results

The effects of oral EECM administration on liver function were investigated by measuring serum ALT, GGT, AST, ALP, and LDH activities as well as TP and ALB levels. Serum ALT and GGT activities were significantly higher in the APAP-treated group (Group 3) compared to the saline control group (p < 0.05). EECM pretreatment at 250, 500, and 1000 mg/kg significantly lowered ALT and GGT levels compared to the APAP control group (p < 0.05). A significant reduction in serum ALT levels was also observed in Groups 4, 5, and 6. Silymarin treatment significantly reduced ALT levels but not GGT levels. The rats in the EECM control group showed no significant differences in ALT and GGT activities compared to the saline control group (Figure 2).

Figure 2

The effects of EECM and APAP on serum ALT and GGT activities. The results are presented as the mean ± SD (n = 6). In each dataset, each letter indicates a significant difference between two groups. a: a significant difference between saline control and APAP control groups, b: a significant difference between APAP control and T 250 groups, c: a significant difference between APAP control and T 500 groups, d: a significant difference between APAP control and T 1000 groups, e: a significant difference between APAP control and silymarin groups, f: a significant difference between T 250 and T 500 groups, and g: a significant difference between T 500 and T 1000 groups, respectively, at p < 0.05.

Figure 3 shows the significant increases in serum AST, ALP, and LDH activities in the APAP control group compared to the saline control group. Pretreatment with EECM at 250, 500, and 1000 mg/kg and silymarin significantly decreased the levels of the diagnostic markers compared to treatment with APAP alone (Group 3). Marked differences in serum AST and ALP levels were also found between Groups 4 and 6 and Groups 5 and 6, respectively, while LDH levels were significantly different among these three groups. Significant (p < 0.05) improvements in serum ALP and LDH activities were observed in the EECM control group compared to the saline control group.

Figure 3

The effects of EECM and APAP on serum AST, ALP, and LDH activities. The results are presented as the mean ± SD (n = 6). In each dataset, each letter indicates a significant difference between two groups. a: a significant difference between saline control and APAP control groups, b: a significant difference between APAP control and T 250 groups, c: a significant difference between APAP control and T 500 groups, d: a significant difference between APAP control and T 1000 groups, e: a significant difference between APAP control and silymarin groups, f: a significant difference between T 250 and T 500 groups, g: a significant difference between T 500 and T 1000 groups, h: a significant difference between T 250 and T 1000 groups, and i: a significant difference between saline control and EECM control groups, respectively, at p < 0.05.

Treatment with APAP increased serum TB levels compared to the saline control, while pretreatment with 1000 mg/kg EECM (T 1000 group) significantly (p < 0.05) decreased this parameter compared to the APAP control group. Silymarin and EECM pretreatment at doses of 500 and 1000 mg/kg significantly (p < 0.05) reduced serum ALB levels compared to treatment with APAP alone (Group 3); serum ALB levels in the APAP control group remained unchanged compared to the saline control group. A comparison of the different treatment groups showed that serum TP levels remained almost unchanged following APAP and EECM treatment (Table 1).

Table 1

The effects of EECM and APAP on serum TP, ALB, and TB levels.

Group	Parameters
	TP (g/L)	ALB (g/L)	TB (mg/dL)
Saline control	60.00 ± 1.67	11.00 ± 0.63	0.12 ± 0.04
EECM control	61.83 ± 1.83	11.00 ± 0.89	0.12 ± 0.04
APAP control	60.83 ± 0.75	11.50 ± 0.54	0.18 ± 0.04a
T 250	59.54 ± 1.50	12.33 ± 0.52	0.15 ± 0.05
T 500	59.83 ± 1.72	10.83 ± 0.75c,f	0.13 ± 0.05
T 1000	62.12 ± 1.76	9.43 ± 0.89d,g	0.10 ± 0.00d
Silymarin	61.22 ± 1.47	10.00 ± 0.89e	0.12 ± 0.04

The data are presented as the mean ± SD (n = 6).

In each column, each letter indicates a significant difference between two groups.

a indicates a significant difference between saline control and APAP control group.

c indicates a significant difference between APAP control and T 500 groups.

d indicates a significant difference between APAP control and T 1000 groups.

e indicates a significant difference between APAP control and silymarin groups.

f indicates a significant difference between T 250 and T 500 groups and

g indicates a significant difference between T 500 and T 1000 groups, respectively, at p < 0.05.

The effects of EECM and APAP on serum TC and TG levels are shown in Figure 4. Animals in the APAP control group showed a significant increase in TC and TG levels compared to the saline control group. However, the animals in the EECM pretreatment at 500 and 1000 mg/kg and silymarin groups exhibited significantly decreased TG and TC levels. Rats treated with EECM at 1000 mg/kg alone (Group 2) showed significantly higher TC levels and lower TG levels compared to saline control rats.

Figure 4

The effects of EECM and APAP on serum TC and TG levels. The results are presented as the mean ± SD (n = 6). In each dataset, each letter indicates a significant difference between two groups. a: a significant difference between saline control and APAP control groups, b: a significant difference between APAP control and T 250 groups, c: a significant difference between APAP control and T 500 groups, d: a significant difference between APAP control and T 1000 groups, e: a significant difference between APAP control and silymarin groups, f: a significant difference between T 250 and T 500 groups, g: a significant difference between T 500 and T 1000 groups, h: a significant difference between T 250 and T 1000 groups, and i: a significant difference between saline control and EECM control groups, respectively, at p < 0.05.

The effects of EECM and APAP on renal function were investigated by measuring serum CRE, urea, UA, Na+, K+, and Cl− levels (Table 2). There were significant increases in CRE, urea, UA, Na+, and K+ levels and decreases in serum Cl− levels among the APAP-treated animals (Group 3) compared to the saline control animals. However, the serum levels of CRE, urea, UA, Na+, K+, and Cl− were improved in animals that received EECM at both 500 and 1000 mg/kg doses (Groups 5 and 6, resp.).

Table 2

The effects of EECM and APAP on serum CRE, urea, UA, Na+, K+, and Cl− levels.

Group	Parameters
	CRE (mmol/L)	Urea (mmol/L)	UA (mmol/L)	Na+ (mmol/L)	K+ (mmol/L)	Cl− (mmol/L)
Saline control	48.58 ± 2.38	4.79 ± 0.07	40.33 ± 1.37	138.67 ± 2.73	3.60 ± 0.18	101.83 ± 1.33
EECM control	45.39 ± 2.85	5.27 ± 0.44	38.00 ± 2.00	142.83 ± 4.40	4.05 ± 0.05i	103.00 ± 1.79
APAP control	61.00 ± 2.28a	6.94 ± 0.41a	58.50 ± 2.26a	150.33 ± 2.66a	4.60 ± 0.28a	96.00 ± 3.35a
T 250	50.33 ± 2.88b	6.42 ± 0.12	51.33 ± 1.21b	143.17 ± 1.17b	3.42 ± 0.33b	99.33 ± 1.51
T 500	44.83 ± 1.72c,f	5.75 ± 0.36c	39.92 ± 2.46c,f	140.70 ± 4.38c	3.38 ± 0.12c	100.33 ± 3.20c
T 1000	31.88 ± 1.10d,g	4.99 ± 0.30d,g	37.95 ± 2.21d	141.80 ± 3.27d	3.52 ± 0.08d	103.17 ± 3.13d
Silymarin	41.33 ± 2.25e	5.77 ± 0.49	27.50 ± 1.64e	140.67 ± 1.03e	3.80 ± 0.09e	101.67 ± 1.37e

The data are presented as the mean ± SD (n = 6).

In each column, each letter indicates a significant difference between two groups.

a indicates a significant difference between saline control and APAP control groups.

b indicates a significant difference between APAP control and T 250 groups.

c indicates a significant difference between APAP control and T 500 groups.

d indicates a significant difference between APAP control and T 1000 groups.

e indicates a significant difference between APAP control and silymarin groups.

f indicates a significant difference between T 250 and T 500 groups.

g indicates a significant difference between T 500 and T 1000 groups.

i indicates a significant difference between saline control and EECM control groups, respectively, at p < 0.05.

Based on the investigation of oxidative stress biomarkers, there was a significant increase in LPO levels in the animals treated with APAP alone (Group 3), as evidenced by the increase in liver MDA levels compared to the saline control group (Group 1). However, EECM tended to confer a protective effect because the animals that were pretreated with EECM at 250, 500, and 1000 mg/kg had significantly lower MDA levels compared to the APAP control. Significantly reduced LPO levels were observed in both liver and kidney tissues from the rats treated with 1000 mg/kg EECM (Group 6) compared to those in Group 4. Treatment with silymarin also decreased LPO levels compared to APAP control treatment. No significant difference was observed between the saline control and EECM control groups (Figure 5).

Figure 5

The effects of EECM and APAP on tissue MDA levels in rats. The results are presented as the mean ± SD (n = 6). In each dataset, each letter indicates a significant difference between two groups. a: a significant difference between saline control and APAP control groups, b: a significant difference between APAP control and T 250 groups, c: a significant difference between APAP control and T 500 groups, d: a significant difference between APAP control and T 1000 groups, e: a significant difference between APAP control and silymarin groups, f: a significant difference between T 250 and T 500 groups, g: a significant difference between T 500 and T 1000 groups, and h: a significant difference between T 250 and T 1000 groups, respectively, at p < 0.05.

Microscopic examination of the liver and kidney tissues revealed that the livers of the animals in Groups 1 and 2 had a normal hepatocyte arrangement, radiating from the central vein to the periphery of the lobule. The hepatocyte nuclei also exhibited normal vesicular structure with a normal and uniform cytoplasm (Figures 6(a) and 6(b)). In contrast, the livers of the animals in Groups 3 to 7 exhibited histopathological changes. The livers of the animals in Group 3 showed some degenerative changes, including inflammatory cell infiltration, vascular congestion, hepatocyte necrosis, and edema at different locations in the lobule (Figures 6(c) and 6(d)). The livers of the animals in Groups 4 to 7 showed improvements in all of the histopathological features (Figures 6(e)–6(h)), with a moderate to mild degree of hepatocyte degeneration, inflammatory cell infiltration, vascular congestion, and edema at all investigated doses (Table 3).

Figure 6

Liver sections from the experimental animals in (a) Group 1 (saline control) showing a normal liver with a hepatic lobule and a uniform pattern of polyhedral hepatocytes radiating from the central vein (CV) towards the periphery, (b) Group 2 (EECM control) showing a normal appearance of hepatocytes surrounding the CV, and (c) Group 3 (APAP control) demonstrating a disrupted arrangement of hepatocytes around the CV. There was also marked hepatocyte necrosis at the periphery of the CV (red arrow), inflammatory cell infiltration (green arrow), edema at different locations (black arrow), and severe congestion of the CV (d). (e–h) Groups 4, 5, 6 (T 250, T 500, and T 1000 groups, resp.), and 7 (silymarin control) showing a remarkable degree of preservation of the cellular arrangement with only mild inflammation [magnification: 40x; scale bar: 20 μm].

Table 3

Semiquantitative scoring of the architectural changes evidenced by histopathological examination of the rats' livers and kidneys.

Scoring parameter	Group
	1	2	3	4	5	6	7
	Liver
Degeneration of hepatocytes	—	—	+++	++	++	+	+
Inflammatory cell infiltration	—	—	+++	++	++	+	+
Vascular congestion	—	—	+++	++	+	—	+
Edema	—	—	+++	++	++	+	+
	Kidney
Tubular necrosis	—	—	+++	++	++	+	+
Vacuolization	—	—	+++	+	++	+	+
Glomerular necrosis	—	—	+++	++	++	+	++

Scoring was performed as follows: none (—), mild (+), moderate (++), and severe (+++).

Group 1 = control; Group 2 = EECM; Group 3 = APAP; Group 4 = T 250; Group 5 = T 500; Group 6 = T 1000; and Group 7 = silymarin.

The saline control rats (Group 1) and those treated with EECM at 1000 mg/kg alone (Group 2) showed normal renal tubules and glomeruli (Figures 7(a) and 7(b)). However, rats treated with APAP (Group 3) showed severe tubular desquamation of the renal epithelium, cell necrosis, and vacuolization with the presence of intraluminal casts (Figures 7(c) and 7(d)). In contrast, rats treated with APAP and EECM at each of the three doses (Groups 4, 5, and 6) showed significant preservation of glomeruli architecture compared to rats treated with APAP alone (Group 3), although mild tubular degeneration and epithelial vacuolization were still present (Figures 7(e)–7(h)). Only mild to moderate degeneration of the tubular epithelium, vacuolization, and glomerular necrosis were observed (Table 3).

Figure 7

Kidney sections from the experimental animals in (a) Group 1 (saline control) showing a normal morphology of renal parenchyma with well-defined glomeruli and tubules; (b) Group 2 (EECM control) showing a normal appearance of the renal parenchyma; (c and d) Group 3 (APAP control) demonstrating marked degeneration of the tubular epithelium (red arrow), vacuolization (green arrow), and severe glomerular necrosis (black arrow); and (e–h) Groups 4, 5, 6 (T 250, T 500, and T 1000 groups, resp.), and 7 (silymarin control) showing a remarkable degree of morphological preservation with only moderate to mild inflammation [magnification: 40x; scale bar: 20 μm].

4. Discussion

Our study is the first to report the protective effects of C. macroptera against hepatonephrotoxicity induced by APAP in rats. The improvements in the biochemical parameters of the liver (i.e., ALT, AST, ALP, GGT, LDH, TB, TP, ALB, TC, and TG) and kidney (i.e., CRE, urea, UA, Na+, K+, and Cl−) at the three different doses were supported by the inhibition of LPO and were confirmed histopathologically.

Investigation of the livers and kidneys of the experimental animals revealed a nonsignificant increase in both absolute and relative weight following APAP administration, although BW remained relatively unchanged.

Treatment with APAP for 7 consecutive days resulted in a profound increase in serum ALT, ALP, AST, GGT, and LDH activities that could potentially be attributed to hepatic injury and disturbances in the biosynthesis of these enzymes. The disruption of hepatocyte membrane permeability by APAP intoxication allows these enzymes to leak out from the liver cytosol into the blood circulation, thus inducing necrosis and inflammatory responses [25, 29]. Our findings are consistent with those of some previous studies [25, 26]. Pretreatment with EECM tended to alleviate the activities of the serum transaminases, ALP and LDH, thereby demonstrating that EECM maintained membrane integrity and restricted the leakage of hepatic enzymes via a mechanism that is not yet completely understood. Additionally, the rise in the TB level is an important clinical indicator of the severity of necrosis; TB accumulation is indicative of the binding, conjugation, and excretory capacity of hepatic cells [25, 30]. Treatment with 1000 mg/kg EECM restored all of the above diagnostic markers, thereby demonstrating its protective role in the liver.

Serum levels of TC and TG were also increased in the APAP-treated rats, suggesting that APAP affects liver cell membrane permeability. Additionally, blockage of liver bile ducts and the subsequent decreased secretion of cholesterol into the intestine may result in the elevation of serum cholesterol, which is another sign of liver damage [31, 32]. Elevated TG provides further evidence of increased hepatic glyceride synthesis that is directly proportional to the concentration of fatty acids and glycerophosphate [33] and may contribute to the increased VLDL-C involved in the transport of hepatic triglycerides to extrahepatic tissues [34]. Pretreatment with EECM ameliorated TC and TG levels, indicating its hepatoprotective effects.

The possible protective roles of EECM regarding oxidative damage generated by APAP-induced nephrotoxicity were confirmed by examining kidney histopathology. The considerable production of reactive NAPQI due to APAP overdose can result in covalent binding to macromolecules on cellular proteins, leading to the disruption of homeostasis, apoptosis, tissue necrosis, and, ultimately, organ dysfunction [35, 36]. In our study, treatment with APAP alone resulted in a marked elevation of serum CRE, urea, and UA levels that were indicative of decreased glomerular filtration and disrupted synthetic function in the kidney [37, 38]. Moreover, alterations in serum Na+, K+, and Cl− levels in APAP-treated rats compared to saline control rats demonstrated the deterioration of renal function. These findings were consistent with those of previous studies that involved treating rats with APAP [25, 36]. However, EECM treatment ameliorated the kidney biomarkers, restored serum electrolytes, and restabilized the homeostatic function of the kidneys.

Oxidative injury in the liver and kidney was further evidenced by the elevation of LPO, which was suggestive of APAP-related tissue damage. LPO represents one of the most frequently measured parameters resulting from free radical attacks on biological structures due to the consequent perturbation of biochemical and physiological functions [8, 39]. Our results revealed that EECM pretreatment significantly protected the liver and kidney from LPO, as evidenced by reduced MDA levels in both liver and kidney tissues. It is plausible that the antioxidants in C. macroptera [8], including phenolic acids, flavonoids, and tannins, act synergistically through free radical scavenging, hydrogen donation, singlet oxygen quenching, metal ion chelating, and neutralization of free radical reactions [38, 40] to combat oxidative damage.

The APAP-induced liver and renal damage was consistent with subacute hepatic and tubular necrosis, respectively. Hepatocyte degeneration and necrosis, inflammatory cell infiltration, and vascular congestion with edematous spaces were frequently observed in APAP-intoxicated rat livers. Moreover, epithelial degeneration, necrosis, and localized vacuolization were also found in kidney tissues from rats treated with APAP alone. In the present study, our histopathological findings provided clear evidence of hepatonephrotoxicity following the subacute overdose of APAP. The histopathological changes in the liver and kidney tissues of APAP-treated rats indicated reduced oxygen perfusion that further progressed as a function of the rate of cell death [25]. These findings are in agreement with previous investigations into liver and renal histological alterations following APAP overdose [25, 36]. The hepatorenal protective properties of EECM were further confirmed by the significant improvements in liver and kidney architecture. The best protection was achieved when rats were treated with 1000 mg/kg EECM, while mild or moderate effects were observed in rats treated with 250 or 500 mg/kg EECM, respectively. It is plausible that the protective action against APAP-induced histopathological alterations conferred by phenolics, flavonoids, and other antiradicals/antioxidants [8] may be due to the scavenging of free radicals and inhibition of oxidative damage and the consequent degeneration and necrosis of liver and kidney tissues, which is consistent with our biochemical findings. Further study to elucidate the exact mechanism underlying the hepato- and nephroprotection of C. macroptera and to identify the types of antioxidants present in C. macroptera is warranted.

5. Conclusion

To the best of our knowledge, our study is the first to report on the hepato- and nephroprotective effects of the C. macroptera fruit against acetaminophen-induced oxidative damage in animal model. The protective effects were confirmed at three different doses. Treatment with 1000 mg/kg EECM was the most effective based on the biochemical and histological findings. It is plausible that C. macroptera fruit improves the structural integrity of the cell membrane via inhibition of lipid peroxidation while ameliorating the histopathological changes and biochemical perturbations. Therefore, C. macroptera is a useful inexpensive food product that can be consumed on a daily basis as a prophylaxis because it confers some protection against toxin-induced hepatotoxicity and nephrotoxicity.