The role of protein prenylation inhibition through targeting FPPS by zoledronic acid in the prevention of renal fibrosis in rats

Abstract

Renal fibrosis (RF) represents the most widespread pathological condition in chronic kidney disease (CKD). Recently, protein prenylation has been implicated in the fibrosis's progression. The research examined the renoprotective effect of zoledronic acid (ZA) (50 µg/kg/week) in a rat model of carbon tetrachloride (CCl₄)-induced RF through targeting protein prenylation. Forty Wistar male rats were split up into the control group, vehicle-treated group, model-RF group, and RF-ZA group. Mean arterial blood pressure (MBP), BUN, serum creatinine, and urine albumin-creatinine ratio (uACR), protein levels of farnesyl pyrophosphate (FPP), tumour necrosis factor-alpha (TNF-α), transforming growth factor-β (TGF-β), and malondialdehyde (MDA), and catalase and gene expression of farnesyl pyrophosphate synthase (FPPS) and nuclear factor-kB (NF-κB) were measured. Immunohistochemical staining for renal interleukin-6 (IL-6), α-smooth muscle actin (α-SMA), and caspase-3, as well as histopathological alterations, were assessed. ZA considerably ceased the reduction in MBP, markedly reduced uACR, serum creatinine, BUN, and expression of FPPS, FPP, NF-κB, TGF-β, TNF-α, and MDA, and significantly increased catalase levels compared to the model-RF rats. ZA ameliorated the CCl₄-induced histopathological alterations and suppressed the expression of caspase-3, α-SMA, and IL-6. In conclusion, ZA preserved renal function and prevented renal fibrosis in a rat model. These were achieved through targeting protein prenylation mainly by inhibiting FPPS.

Keywords: FPPS; NF-κB; Protein prenylation; Renal fibrosis; Zoledronic acid.

Figure 1

Diagrammatic illustration of the study timeline for drug administration and timing of outcome measures. Wk week, MBP mean blood pressure, ZA zoledronate, CCl₄ carbon tetrachloride, i.p. intraperitoneal injection.

Figure 2

H&E-stained sections X400: (A) control group: the glomerulus (G), parietal layer of Bowman’s capsule (curved arrow), proximal convoluted tubules (PCT), distal convoluted tubules (DCT). (B–D) Model-RF group: the glomerulus (G), parietal layer of bowman’s capsule (curved arrow), disrupted parietal layer of Bowman’s capsule ( >), proximal convoluted tubules (PCT), distal convoluted tubules (DCT), sloughed tubular cells (↑), vacuolated tubular cells (↑↑), mononuclear cell infiltration (*), congested glomerular (▲) and peritubular capillaries (Δ), acidophilic area with pyknotic nuclei (♦). (E,F) RF-ZA group: the glomerulus (G), parietal layer of bowman’s capsule (curved arrow), proximal convoluted tubules (PCT), distal convoluted tubules (DCT), shrunken glomerulus ( >), congested glomerular (▲) and peritubular capillaries (Δ).

Figure 3

Histogram showing the PCT diameter (µm) in different groups.

Figure 4

Picrosirius red X400. (A) Control group: few collagen fibers (↑) around renal corpuscle and renal tubules. (B) Model-RF group: massive collagen fibers (↑) around renal corpuscles and renal tubules. Increased amount of collagen fibers is also seen inside renal glomeruli ( >) (C) RF-ZA group: mild collagen fibers (↑) around renal corpuscle and renal tubules. No collagen fibers inside renal glomeruli.

Figure 5

Histogram showing the mean area % of collagen fibers, caspase-3, IL-6 and α-SMA in different groups.

Figure 6

Caspase 3 Immunohistochemistry X400. (A) Control group: minimal reaction to caspase 3 in some tubular cells. (B) Model-RF Group: intense reaction to caspase 3 in most renal tubules. [(C) RF-ZA group: mild reaction to caspase 3 in some renal tubules.

Figure 7

IL6 Immunohistochemistry X400. (A) Control group: minimal IL6 expression. (B) Model-RF Group: intense IL6 expression. (C) RF-ZA group: mild IL6 expression.

Figure 8

α-SMA Immunohistochemistry X400. (A) Control group: minimal reaction to α-SMA in the wall of blood vessels (↑), negative reaction is seen in the renal glomeruli. (B) Model-RF group: intense reaction to α- SMA in the wall of blood vessels (↑) and inside the glomerulus (▲). (C) RF-ZA group: mild reaction to α-SMA in the wall of blood vessels (↑) and inside the glomerulus (▲).