Thunbergia laurifolia leaf extract partially recovers lead-induced renotoxicity through modulating the cell signaling pathways

Abstract

This research investigated the reno-protective effect of Thunbergia laurifolia Linn. (TL) in a lead-induced toxicity test through the modulation of cell signaling pathways. The study carried out to evaluate the effect of TL leaf extracts in Swiss Albino mice exposed to lead acetate (PbAc). Prior to in vivo study, a probable kidney-protective effect of the plant leaf extract was presumed through an activity-specific (PASS) molecular docking analysis. In animal model study, albino mice were divided in seven groups and co-treated with PbAc and TL (100, 200 mg/kgBW) or vitamin E (100 mg/kgBW) for 38 days, whereas the untreated control, TL control, and vehicle control groups received sodium acetate, PbAc, sodium acetate plus mineral oil, respectively. At the end of treatment, blood and kidney tissue were collected for investigating Pb concentration, estimating biochemical profile, evaluating oxidative stress and inflammatory parameters. The histopathological change of kidney along with apoptosis was assessed from kidney sections using H & E staining and TUNEL assay. Pb-exposed mice were found to be increased concentration of Pb in the blood and kidney sample, which further led to increased MDA levels in the plasma, blood, and tissue. Followed by kidney damage, increased expression of TNF-α, iNOS, and COX-2 in kidney tissues were noticed, which were related to elevated TNF-α in the systemic circulation of Pb-treated mice. Co-treatment with TL or vitamin E significantly reduced altered structure and apoptosis of kidney tissues. Downregulation of inflammatory markers especially TNF-α, iNOS, and COX-2 with simultaneous improvement of renal function through reduced plasma BUN and creatinine levels demonstrate that TL act as a potential dietary supplement to detoxify Pb in kidney showing an antioxidant and anti-inflammatory effect.

Keywords: Anti-inflammation; BUN, Blood urea nitrogen; BW, body weight; COX-2, Cyclooxygenase-2; DNA, Deoxyribonucleic acid; ELISA, enzyme-linked immunosorbent assay; GFR, Glomerular filtration rate; H&E, Hematoxylin-Eosin; Lead (Pb); MDA, Malondialdehyde; Oxidative stress; Pb, lead; ROS, reactive oxygen species; Renotoxicity; TBARS, Thiobarbituric acid reactive substances; TBS, Tris phosphate saline; TBST, Tris phosphate buffer saline with Tween 20; TL, Thunbergia laurifolia Linn.; TNF-α, Tumor necrosis factor-alpha; TUNEL, Terminal deoxynucleotidyl transferase dUTP nick end labeling; Thunbergia laurifolia Linn.; iNOS, Inducible nitric oxide synthase.

Graphical abstract

Fig. 1

Effect of TL extract on oxidative stress and antioxidant parameters of PbAc treated mice. Here, (A)- superoxide dismutase (SOD) level, (B)- catalase (CAT) activity, (C-E)- TBARS levels in the plasma, RBC, and kidney tissue, respectively. The values are presented as mean ± SEM (n = 6). The multiple comparisons were analyzed by one-way analysis of variance followed by Newman–Keuls post hoc test. Whereas, a P < 0.05 vs untreated control, b P < 0.05 vs PbAc treated group.

Fig. 2

Effect of TL extract on inflammatory parameters of PbAc treated mice. Here, (A)- TNF-α level in plasma by ELISA assay, (B-D)- protein expression and quantification of TNF-α, COX-2, and iNOS in the kidney, respectively. The values are presented as mean ± SEM (n = 6). The multiple comparisons were analyzed by one-way analysis of variance followed by Newman–Keuls post hoc test. Whereas, a P < 0.05 vs untreated control, b P < 0.05 vs PbAc treated group.

Fig. 3

Histopathological alterations in the kidney of experimental mice. Kidney tissues were stained with hematoxylin and eosin staining. Histological alteration of kidney was mainly observed in the cortex region, both in proximal (PT) and distal tubules (DT). Untreated Control, TL 200 mg/kgBW, and Vehicle Control groups showed normal renal architectures. In contrast, only PbAc exposed group (PbAc 1% in DW) showed the presence of tubular necrosis such as cloudy swelling of PT, shrinkage of both DT and PT. However, co-treatment with TL (100 and 200 mg/kgBW) and vitamin E (100 mg/kgBW) significantly restored the renal alterations compared to only PbAc exposed group (PbAc 1% in DW).

Fig. 4

Evaluation of the kidney apoptosis of PbAc treated mice kidney by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. (A)-Quantification of TUNEL positive cells in the kidney tissue section. The values are presented as mean ± SEM (n = 6). The multiple comparisons were analyzed by one-way analysis of variance followed by Newman–Keuls post hoc test. Whereas, a P ≤0.05 vs untreated control, b P≤0.05 vs PbAc treated group. (B)- TUNEL positive cells were indicated by the red arrow in kidney tissue section (original magnification x400).