Lovastatin inhibits oxidized low-density lipoprotein- induced plasminogen activator inhibitor and transforming growth factor-β1 expression via a decrease in Ras/extracellular signal-regulated kinase activity in mesangial cells

Oxidized low-density lipoprotein (Ox-LDL) has been implicated as a contributing factor in the development and progression of renal disease, particularly by promoting pathological changes in glomerular mesangial cells. One of the key responses to Ox-LDL exposure in these cells is the upregulation of plasminogen activator inhibitor-1 (PAI-1), a protein associated with matrix accumulation and fibrosis. This effect is mediated through the transforming growth factor-beta (TGF-β)/Smad signaling pathway and requires the activation of extracellular signal-regulated kinases (ERK).

The synthesis of mevalonate, a precursor in the cholesterol biosynthesis pathway, plays a critical role in post-translational modification of signaling proteins, including Ras, via farnesyl pyrophosphate (FPP)-dependent isoprenylation. Statins, which are inhibitors of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, deplete intracellular mevalonate levels, thereby reducing the availability of FPP and potentially disrupting Ras activation.

In this study, the potential of statins to mitigate Ox-LDL-induced fibrotic signaling in mesangial cells was investigated, with a particular focus on lovastatin. Quiescent mesangial cells were pre-treated with lovastatin for 18 hours prior to exposure to Ox-LDL. The results demonstrated that lovastatin effectively suppressed Ox-LDL-induced activation of ERK1/2, decreased nuclear localization of Smad3, and reduced the mRNA and protein expression of both TGF-β1 and PAI-1. Moreover, the transcriptional activity of the PAI-1 gene, as assessed by luciferase reporter assays, was significantly diminished. These inhibitory effects were largely reversed by the addition of mevalonate or FPP, confirming that the observed effects of lovastatin were mediated through disruption of the mevalonate pathway.

In a parallel experiment, FTI-277, a specific inhibitor of Ras farnesylation, was used to evaluate whether direct interference with Ras function would yield similar outcomes. Consistent with the effects of lovastatin, FTI-277 also attenuated Ox-LDL-induced ERK activation, nuclear Smad3 translocation, and the expression of TGF-β1 and PAI-1. These findings support the hypothesis that Ras activation is a key upstream regulator of ERK and Smad3 signaling in the context of Ox-LDL stimulation.

Collectively, the data indicate that statins, by targeting the Ras/ERK signaling axis, exert an inhibitory effect on TGF-β/Smad3-mediated fibrogenic responses in mesangial cells. This mechanism provides a molecular basis for the antifibrotic properties of statins, extending their therapeutic potential beyond lipid-lowering effects. These results are particularly relevant for the management of chronic kidney disease in patients with underlying dyslipidemia, suggesting that statin therapy may help counteract the deleterious impact of Ox-LDL on renal function through suppression of pro-fibrotic signaling pathways.

At A Glance Commentary

Background
The stimulation of plasminogen activator inhibitor-1 (PAI-1) expression by oxidized low-density lipoprotein (Ox-LDL) in mesangial cells involves activation of the transforming growth factor-beta (TGF-β)/Smad signaling pathway, which in turn requires the involvement of extracellular signal-regulated kinase (ERK). Statins, such as lovastatin, inhibit the enzyme HMG-CoA reductase, leading to reduced synthesis of mevalonate and its downstream product, farnesyl pyrophosphate (FPP), which is necessary for the isoprenylation and activation of Ras. Based on this mechanism, it is proposed that lovastatin may reduce Ox-LDL-induced mesangial matrix accumulation by suppressing the Ras/ERK signaling cascade, thereby downregulating TGF-β target gene expression.

Translational Significance
This study demonstrates that lovastatin effectively blocks the activation of Ras and ERK induced by Ox-LDL in mesangial cells, leading to inhibition of Smad3 signaling and reduced expression of TGF-β-responsive genes such as PAI-1. These findings suggest that statins exert a protective, antifibrotic effect in the kidney through their ability to interfere with TGF-β signaling. This mechanism may be particularly valuable in treating chronic kidney disease associated with dyslipidemia, highlighting an additional therapeutic benefit of statins beyond their lipid-lowering properties.

Introduction

Lipoprotein abnormalities, along with oxidative stress, represent significant contributing factors in the progression of primary glomerular injury toward more severe renal conditions such as glomerulosclerosis. Research has shown that low-density lipoprotein (LDL), when incubated with cultured mesangial cells, undergoes oxidation, a process that is also observed within diseased glomeruli in both humans and rat models. The oxidized form of LDL (Ox-LDL) plays an active role in stimulating the transcription of plasminogen activator inhibitor-1 (PAI-1) within mesangial cells. This stimulation occurs via an autocrine mechanism involving the activation of transforming growth factor-beta (TGF-β) and its downstream Smad signaling pathway. In addition to Smad activation, Ox-LDL–induced TGF-β signaling also triggers phosphorylation of extracellular signal-regulated kinase (ERK). Once activated, ERK contributes to further Smad activation and promotes the expression of the PAI-1 gene. Notably, the maximal activation of Smad proteins requires TGF-β–induced ERK activity, which specifically phosphorylates the linker regions of Smad2 and Smad3 proteins. These TGF-β signaling cascades are believed to play a crucial role in mediating renal matrix expansion, a hallmark feature of progressive glomerular diseases.

Beyond these molecular interactions, the class of drugs known as 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors, commonly referred to as statins, exhibit multiple biological effects that extend well beyond their well-known cholesterol-lowering properties. Statins have demonstrated potential in ameliorating experimental models of renal disease, an effect that may be linked to their ability to reduce inflammatory responses within the glomeruli. Moreover, statins have been shown to decrease renal expression levels of TGF-β mRNA in rat models of diabetic nephropathy, indicating a possible modulatory effect on fibrotic pathways within the kidney.

Mechanistically, the depletion of mevalonate caused by statin treatment leads to reduced cellular levels of specific lipid intermediates, including farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP). These lipid molecules serve as critical posttranslational modifiers, attaching covalently to small guanine nucleotide-binding regulatory proteins—commonly known as G-proteins—belonging to the Ras and Rho families. Typically, Ras proteins undergo farnesylation, a lipid modification essential for their attachment to cellular membranes, which is crucial for their proper function. Small G-proteins cycle between an inactive GDP-bound form located in the cytosol and an active GTP-bound form associated with cellular membranes. This cycling allows them to act as important molecular switches in signal transduction pathways initiated by membrane receptors.

In this context, oxidized LDL has been shown to activate Ras proteins, and Ras activity is essential for TGF-β–mediated activation of ERK signaling pathways. The activation of Ras/ERK mitogen-activated protein (MAP) kinase signaling by TGF-β can further induce the expression of TGF-β1 itself, establishing a positive feedback loop that amplifies the TGF-β signaling response and triggers additional downstream effects. Importantly, statins have been reported to inhibit Ras/MAP kinase activation in mesangial cells stimulated by high glucose levels or fetal calf serum (FCS). For instance, simvastatin suppresses the FCS-induced expression of PAI-1 mRNA without significantly affecting TGF-β mRNA levels. Despite these insights, the precise in vitro effects of statins on the regulation of TGF-β remain not fully elucidated, and the cellular mechanisms by which statins mitigate Ox-LDL–associated glomerular injury continue to be unclear.

Based on these observations, we hypothesize that statins may counteract the harmful effects of Ox-LDL–induced mesangial matrix accumulation by inhibiting the activation of the Ras/ERK signaling cascade, which in turn leads to downregulation of TGF-β target gene expression. To explore this hypothesis, our study examined the effects of lovastatin on several key molecular markers in human mesangial cells cultured in the presence of Ox-LDL. These markers included ERK phosphorylation status, nuclear expression of Smad3, mRNA levels of TGF-β1 and PAI-1, and PAI-1 promoter activity.

Materials and Methods

Reagents

The reagents used in this study included mevalonate, farnesyl pyrophosphate (FPP), and FTI-277, all of which were obtained from Sigma Chemical Company. Lovastatin was supplied by Cheil Jedang in Seoul, Korea. Other reagents and chemicals used throughout the experiments were sourced as previously documented in related studies.

Culture of Human Mesangial Cells

Human mesangial cells were isolated from adult nephrectomy specimens following established protocols. The cells were cultured in Dulbecco’s modified Eagle’s medium (DMEM) supplemented with 20% fetal calf serum (FCS), 200 mM L-glutamine, and appropriate antibiotics to ensure sterile conditions. For all experiments reported here, cells between passages five and seven were utilized to maintain consistent cellular characteristics.

LDL Isolation and Modification

Native human LDL was purified from plasma collected from healthy volunteers using a sequential ultracentrifugation method. The density range for LDL isolation was between 1.019 and 1.063 g/mL. To generate oxidized LDL (Ox-LDL), LDL at a concentration of 1 mg/mL was incubated with 10 µM copper sulfate in phosphate-buffered saline (PBS) at 37°C for 24 hours. This oxidation reaction was halted by adding ethylenediaminetetraacetic acid (EDTA) and butylated hydroxytoluene (BHT), which act as antioxidants. The resulting Ox-LDL contained thiobarbituric acid-reactive substances equivalent to approximately 7 nmol malondialdehyde per milligram of protein, confirming successful oxidation. Electrophoretic analysis demonstrated that Ox-LDL migrated faster than native LDL, consistent with its modified state. Prior to experimental use, Cu++-catalyzed Ox-LDL was dialyzed against PBS and filtered through a 0.2-micron filter to remove any residual contaminants.

Experimental Conditions

Lovastatin stock solution was prepared at 10 mM concentration by dissolving 18 mg of lovastatin in an alcoholic sodium hydroxide mixture, followed by dilution with distilled water and adjustment of the pH to 8.0. For treatment, lovastatin was used at a final concentration of 10 µM. Mevalonate was chemically activated by alkaline hydrolysis, dissolved in PBS, and used at 5 mM. FPP was diluted in PBS and applied at 30 µM. Prior to use, all stock solutions were sterilized through filtration. Human mesangial cells were grown to approximately 80% confluence and synchronized to quiescence by incubation in serum-free DMEM supplemented with insulin-transferrin-selenite for 24 hours. Cells were then pretreated with or without lovastatin for 18 hours before exposure to Ox-LDL at 50 µg/mL for one hour, conditions previously optimized to produce a peak response without cytotoxicity as verified by trypan blue exclusion. In some experiments, mevalonate or FPP were added concurrently with Ox-LDL, while FTI-277-treated cells were incubated with the inhibitor for one hour prior to Ox-LDL treatment. Control cells received only serum-free DMEM.

Preparation of Nuclear Fractions

Nuclear extracts from cultured cells were prepared using a protocol involving cell washing with tris-buffered saline, centrifugation, and resuspension in cold buffers containing nonionic detergent to lyse the cytoplasmic membrane while preserving nuclear integrity. Following centrifugation, the nuclear pellet was collected and resuspended in a second cold buffer. Protein concentrations of nuclear extracts were quantified using the bicinchoninic acid assay with bovine serum albumin as a standard.

Immunoblot Analysis

Proteins from whole-cell lysates or nuclear fractions were separated by electrophoresis on 10% polyacrylamide gels under denaturing conditions and transferred onto nitrocellulose membranes. Membranes were blocked and incubated overnight at 4°C with specific primary antibodies against ERK1/2, phosphorylated ERK1/2, or Smad3. Detection was achieved using horseradish peroxidase-conjugated secondary antibodies and enhanced chemiluminescence reagents. Specificity of antibody binding was confirmed by competition with the immunizing peptide. Membranes were reprobed with anti-p62 antibody to ensure equal loading for Smad3 analysis. Band intensities were quantified by densitometry.

Real-Time Quantitative Reverse Transcription-Polymerase Chain Reaction (RT-PCR)

Total RNA was isolated from mesangial cells and reverse transcribed into complementary DNA (cDNA) using a reverse transcriptase premix kit. Specific oligonucleotide primers were designed for amplification of PAI-1, TGF-β1, and 18S ribosomal RNA as an internal control. Quantitative PCR was performed using SYBR Green dye on an ABI Prism 7000 instrument. Cycling conditions included an initial denaturation followed by 40 amplification cycles. Each sample was analyzed in triplicate and experiments were repeated independently to ensure reproducibility. Relative mRNA expression levels were calculated using the 2^-ΔΔCT method.

Quantification of Secreted TGF-β1 by Enzyme-Linked Immunosorbent Assay (ELISA)

Following experimental treatments, culture supernatants were collected, centrifuged to remove debris, and stored on ice. TGF-β1 levels were measured using a commercially available ELISA kit. Samples underwent acid activation to convert latent TGF-β to its active form prior to incubation on plates coated with monoclonal anti–TGF-β1 antibodies. Detection involved incubation with a rabbit anti-human TGF-β1 antibody followed by a horseradish peroxidase–conjugated secondary antibody. The colorimetric reaction was developed with a peroxidase substrate and stopped with phosphoric acid. Absorbance was read at 450 nm to quantify TGF-β1 concentration.

Quantification of Extracellular Matrix-Associated PAI-1 by ELISA

At the conclusion of treatments, culture medium was removed, and cell monolayers were washed and extracted using a buffer containing Triton X-100. The extract was incubated with tissue-type plasminogen activator to release PAI-1 bound within the extracellular matrix. PAI-1 antigen levels were then quantified using ELISA kits according to the manufacturer’s instructions, providing a measure of matrix-associated PAI-1 protein.

Plasmid Constructs

The PAI-1 reporter vector utilized in this study contained a 740-base pair segment of the PAI-1 promoter region fused upstream of the firefly luciferase reporter gene within a pGL3-basic plasmid backbone. This construct enabled the measurement of PAI-1 promoter activity via luciferase expression.

Transfection and Luciferase Assays

Mesangial cells grown to approximately 80% confluence in six-well plates were transfected with the PAI-1 luciferase reporter plasmid along with a β-galactosidase expression plasmid, used as a control for transfection efficiency. DNA plasmids were complexed with Lipofectamine reagent and incubated with cells for six hours. After transfection, cells were incubated overnight with 10% FCS, then treated with Ox-LDL for one hour. Cells were lysed, and luciferase activity was measured alongside β-galactosidase activity. Luciferase readings were normalized to β-galactosidase to correct for variations in transfection efficiency.

Statistical Analyses

All experimental data were presented as means ± standard deviation. Statistical comparisons involving three or more groups were analyzed using one-way analysis of variance (ANOVA), whereas comparisons between two groups employed the Wilcoxon rank sum test. Differences were considered statistically significant at p-values less than 0.05.

Results

Lovastatin significantly reduces the activation of ERK1/2 induced by oxidized low-density lipoprotein (Ox-LDL). When human mesangial cells were exposed to Ox-LDL at a concentration of 50 micrograms per milliliter for one hour, there was a marked increase in the phosphorylation of ERK1/2, reaching approximately 4.1 times higher than the levels observed in untreated control cells. This finding aligns well with our previously published results. However, treatment with lovastatin at a concentration of 10 micromoles per liter notably inhibited the stimulatory effect of Ox-LDL on ERK1/2 activation. Interestingly, the inhibitory influence of lovastatin on ERK1/2 phosphorylation triggered by Ox-LDL was entirely reversed by the addition of mevalonate at 5 millimoles per liter, a compound whose synthesis is catalyzed by the enzyme HMG CoA reductase, the very target of lovastatin. Furthermore, co-treatment of lovastatin-exposed mesangial cells with farnesyl pyrophosphate (FPP) also significantly counteracted the suppressive effects of lovastatin, reinforcing the involvement of these metabolic intermediates in the pathway.

Lovastatin also markedly diminishes the increase in nuclear Smad3 expression stimulated by Ox-LDL. Exposure of mesangial cells to Ox-LDL for one hour resulted in a 2.1-fold rise in Smad3 protein levels within the nucleus, corroborating earlier studies that demonstrated this upregulation. Lovastatin treatment substantially inhibited this elevation of nuclear Smad3 induced by Ox-LDL. Importantly, the suppressive effect exerted by lovastatin on Smad3 expression was fully reversed upon the addition of either mevalonate or FPP, suggesting that lovastatin’s action involves interference with the mevalonate pathway and its downstream metabolites.

In addition to its effects on protein signaling, lovastatin reduces the messenger RNA expression levels of transforming growth factor-beta 1 (TGF-β1) and plasminogen activator inhibitor-1 (PAI-1) that are stimulated by Ox-LDL in human mesangial cells. Using real-time quantitative reverse transcription PCR, it was observed that one hour after Ox-LDL treatment, TGF-β1 mRNA expression increased dramatically by 27-fold, while PAI-1 mRNA levels rose by 13-fold compared with untreated controls. Lovastatin markedly inhibited these profound increases in TGF-β1 and PAI-1 mRNA expression caused by Ox-LDL. When lovastatin-treated cells were simultaneously exposed to either mevalonate or FPP, the inhibitory effects of lovastatin on these mRNA levels were significantly diminished, highlighting the role of the mevalonate pathway intermediates in regulating gene expression changes induced by Ox-LDL.

Beyond gene expression, lovastatin also attenuates the secretion of TGF-β1 protein induced by Ox-LDL in mesangial cells. Measurements using enzyme-linked immunosorbent assay (ELISA) revealed that Ox-LDL stimulation led to a significant increase in TGF-β1 protein secretion, reaching levels approximately 1.4 times higher than those in control cells. Treatment with lovastatin significantly inhibited this secretion of TGF-β1 protein stimulated by Ox-LDL. This inhibitory effect was almost completely reversed by the addition of mevalonate or FPP, further confirming the crucial involvement of the mevalonate pathway in mediating the response.

Similarly, lovastatin reduces the extracellular matrix (ECM)-associated PAI-1 protein expression induced by Ox-LDL. After one hour of incubation with Ox-LDL, human mesangial cells exhibited a 1.7-fold increase in ECM-associated PAI-1 antigen levels compared to controls, consistent with prior findings. Lovastatin treatment significantly decreased this Ox-LDL–induced elevation in PAI-1 protein. Moreover, the reversal of this lovastatin-mediated inhibition by mevalonate and FPP demonstrates the dependency of this effect on the biosynthesis pathway targeted by lovastatin.

The suppressive effect of lovastatin extends to the activity of the PAI-1 gene promoter that is stimulated by Ox-LDL. Using mesangial cells transfected with a luciferase reporter driven by the PAI-1 promoter (740PAI-1-LUC), it was shown that Ox-LDL significantly increased luciferase activity within one hour of treatment, indicating enhanced promoter activation. Lovastatin markedly inhibited this Ox-LDL-induced promoter activity. The inhibitory action of lovastatin was significantly reduced when mevalonate or FPP was present during treatment, reinforcing the role of isoprenoid intermediates in modulating PAI-1 gene transcription under Ox-LDL stimulation.

To investigate whether these effects of lovastatin on Ox-LDL-induced responses are mediated through inhibition of Ras signaling, an additional experiment was conducted using FTI-277, a specific inhibitor of farnesyltransferase and Ras signaling pathways. Cells treated with 15 micromoles per liter of FTI-277 in combination with Ox-LDL showed effects similar to those observed with lovastatin. Specifically, FTI-277 significantly inhibited Ox-LDL-induced ERK1/2 phosphorylation, nuclear Smad3 expression, TGF-β1 and PAI-1 mRNA and protein expression, as well as PAI-1 gene promoter activity. These findings suggest that the inhibitory actions of lovastatin on Ox-LDL-stimulated pathways in mesangial cells are largely attributable to the suppression of Ras-dependent intracellular signaling cascades.

In summary, lovastatin demonstrates a robust ability to counteract the various molecular and cellular effects induced by Ox-LDL in human mesangial cells, ranging from signal transduction events like ERK1/2 phosphorylation and Smad3 nuclear translocation to gene expression and protein secretion changes involving TGF-β1 and PAI-1. The reversal of lovastatin’s effects by mevalonate and FPP, alongside the mimicking of these effects by a Ras pathway inhibitor, highlights the critical role of the mevalonate-Ras signaling axis in mediating these processes. This comprehensive inhibition of Ox-LDL-induced activation by lovastatin underscores its potential therapeutic value in modulating pathological mechanisms relevant to kidney cell function and disease.

Discussion

This study provides novel evidence, to the best of our knowledge for the first time, that lovastatin effectively inhibits the activation of the Ras/ERK signaling pathway induced by oxidized low-density lipoprotein (Ox-LDL) in human mesangial cells. This inhibition subsequently leads to a reduction in Smad3 activation and downregulation of key fibrotic genes, including plasminogen activator inhibitor-1 (PAI-1) and transforming growth factor-beta 1 (TGF-β1). Our observations revealed that lovastatin significantly decreased the phosphorylation of ERK1/2 stimulated by Ox-LDL, and importantly, this suppressive effect of lovastatin was nearly completely reversed by the addition of mevalonate or farnesyl pyrophosphate (FPP). Since FPP is a major isoprenoid intermediate produced during mevalonate metabolism and is essential for the post-translational isoprenylation of Ras proteins, these findings suggest that lovastatin’s action involves interference with this biochemical pathway. Ras is well established as a critical upstream regulator of ERK and is necessary for transforming growth factor-beta (TGF-β)–mediated ERK activation. Furthermore, our use of FTI-277, a specific inhibitor of Ras farnesylation, demonstrated that blocking Ras activation prevented Ox-LDL–induced ERK phosphorylation, supporting the notion that activated Ras is indispensable for the Ox-LDL-triggered ERK signaling cascade. Collectively, these results indicate that the inhibition of ERK activity in lovastatin-treated cells arises primarily from diminished Ras activity, which is a consequence of restricted availability of farnesol required for Ras isoprenylation.

The TGF-β signaling pathway is initiated when TGF-β binds and activates its cell surface receptors, leading to phosphorylation of receptor-regulated Smads, specifically Smad2 and Smad3. These phosphorylated Smads then form complexes with Smad4 and translocate into the nucleus, where they regulate the transcription of target genes involved in fibrosis and extracellular matrix production. In the present study, lovastatin significantly inhibited the Ox-LDL–induced increase in nuclear Smad3 expression, an effect that was almost entirely reversed by supplementation with mevalonate or FPP. Additionally, FTI-277 blocked the stimulatory influence of Ox-LDL on Smad3 activation. Since maximal Smad activation requires TGF-β–induced ERK activity, and Ox-LDL–mediated TGF-β signaling itself activates ERK leading to Smad3 phosphorylation, it appears that lovastatin impairs Ox-LDL–stimulated nuclear Smad3 expression by reducing Ras/ERK activity.

Moreover, we found that lovastatin substantially inhibited the Ox-LDL–induced increase in PAI-1 promoter activity as assessed by luciferase reporter assays. It is known that Smad3 and Smad4 bind preferentially to specific DNA sequences known as CAGA boxes, which are present in promoters of TGF-β–inducible genes such as PAI-1 and TGF-β1. The activation of ERK is required not only to stimulate PAI-1 promoter activity but also to facilitate the formation of DNA-protein complexes and the activation of Smad3 in mesangial cells treated with Ox-LDL. Therefore, the ability of lovastatin to suppress PAI-1 promoter activity likely stems from its capacity to reduce Smad3 binding to the promoter through inhibition of the Ras/ERK pathway. This decreased promoter activity is consistent with the reductions in PAI-1 mRNA and extracellular matrix-associated PAI-1 protein expression observed in lovastatin-treated cells. The fact that these lovastatin effects were reversed by mevalonate or FPP underscores the involvement of the mevalonate pathway, particularly the farnesylation of Ras, in regulating PAI-1 expression in response to Ox-LDL. These findings align with previous work by Nogaki et al., who demonstrated that simvastatin inhibits PAI-1 mRNA expression in mesangial cells. Our observations with FTI-277 further reinforce the critical role of Ras signaling, as this inhibitor suppressed PAI-1 promoter activity, mRNA expression, and protein levels, and also reduced TGF-β1 mRNA and protein expression, highlighting Ras as a key mediator of Ox-LDL–induced profibrotic gene expression.

In addition, lovastatin significantly diminished Ox-LDL–induced TGF-β1 mRNA and protein expression, and this inhibition was reversed by mevalonate or FPP supplementation. Supporting our findings, some studies have reported that statins downregulate TGF-β mRNA levels in mesangial cells under high-glucose conditions, whereas other reports have shown no change or even an increase in TGF-β expression in various cell types following statin treatment. Given that TGF-β–induced activation of Ras/ERK signaling can itself stimulate TGF-β1 expression, and considering that Smads activated by Ox-LDL or TGF-β may bind directly or in association with other transcription factors to the TGF-β1 promoter, it is plausible that lovastatin’s inhibition of TGF-β1 transcription results from decreased Smad3 binding to its promoter, mediated by suppression of Ras/ERK signaling.

Oxidized LDL or lipid peroxidation products are present in the plasma of patients with chronic renal disease as well as within diseased human glomeruli, highlighting their pathological relevance. Several clinical studies have suggested that statins may slow the progression of chronic renal disease or reduce albuminuria, effects which have been attributed not only to lipid-lowering and anti-inflammatory actions but also potentially to lipid-independent mechanisms. By demonstrating that lovastatin exerts anti-fibrotic effects through inhibition of TGF-β signaling, our study offers a novel mechanistic rationale supporting the use of statins in patients with chronic kidney disease and dyslipidemia.

In summary, our results suggest that the Ox-LDL–induced activation of Ras/ERK signaling and subsequent induction of TGF-β signaling is effectively blocked by lovastatin. This blockade leads to the inhibition of Smad3 activation and downregulation of critical TGF-β target genes such as TGF-β1 and PAI-1 in human mesangial cells. Consequently, statins may alleviate Ox-LDL–induced accumulation of mesangial matrix components through their anti–TGF-β effects, underscoring their potential therapeutic relevance in the management of chronic renal disease complicated by dyslipidemia.