Ras antagonist farnesylthiosalicylic acid (FTS) reduces glomerular cellular proliferation and macrophage number in rat thy-1 nephritis

Loss of HNRNPU in Skeletal Muscle Increases Intramuscular Infiltration of Ly6C Positive Cells, leading to Muscle Atrophy through Activation of NF-κB Signaling

Heterogeneous nuclear ribonucleoprotein U (hnRNPU) is known to play multiple biological roles by regulating transcriptional expression, RNA splicing, RNA stability, and chromatin structure in a tissue-dependent manner. The role of hnRNPU in skeletal muscle development and maintenance has not been previously evaluated. In this study, skeletal muscle specific hnRNPU knock out mice is utilized and evaluated skeletal muscle mass and immune cell infiltration through development. By 4 weeks, muscle-specific hnRNPU knockout mice revealed Ly6C+ monocyte infiltration into skeletal muscle, which preceded muscle atrophy. Canonical NF-kB signaling is activated in a myofiber-autonomous manner with hnRNPU repression. Inducible hnRNPU skeletal muscle knockout mice further demonstrated that deletion of hnRNPU in adulthood is sufficient to cause muscle atrophy, suggesting that hnRNPU's role in muscle maintenance is not during development alone. Treatment with salirasib, to inhibit proliferation of immune cells, prevents muscle atrophy in muscle-specific hnRNPU knock out mice, indicating that immune cell infiltration plays causal role in muscle atrophy of hnRNPU knock out mice. Overall, the findings suggest that loss of hnRNPU triggers muscle inflammation and activates NF-κB signaling in a cell-autonomous manner, culminating in muscle atrophy.

Application of nanoparticles in the diagnosis and treatment of chronic kidney disease

With the development of nanotechnology, nanoparticles have been used in various industries. In medicine, nanoparticles have been used in the diagnosis and treatment of diseases. The kidney is an important organ for waste excretion and maintaining the balance of the internal environment; it filters various metabolic wastes. Kidney dysfunction may result in the accumulation of excess water and various toxins in the body without being discharged, leading to complications and life-threatening conditions. Based on their physical and chemical properties, nanoparticles can enter cells and cross biological barriers to reach the kidneys and therefore, can be used in the diagnosis and treatment of chronic kidney disease (CKD). In the first search, we used the English terms "Renal Insufficiency, Chronic" [Mesh] as the subject word and terms such as "Chronic Renal Insufficiencies," "Chronic Renal Insufficiency," "Chronic Kidney Diseases," "Kidney Disease, Chronic," "Renal Disease, Chronic" as free words. In the second search, we used "Nanoparticles" [Mesh] as the subject word and "Nanocrystalline Materials," "Materials, Nanocrystalline," "Nanocrystals," and others as free words. The relevant literature was searched and read. Moreover, we analyzed and summarized the application and mechanism of nanoparticles in the diagnosis of CKD, application of nanoparticles in the diagnosis and treatment of renal fibrosis and vascular calcification (VC), and their clinical application in patients undergoing dialysis. Specifically, we found that nanoparticles can detect CKD in the early stages in a variety of ways, such as via breath sensors that detect gases and biosensors that detect urine and can be used as a contrast agent to avoid kidney damage. In addition, nanoparticles can be used to treat and reverse renal fibrosis, as well as detect and treat VC in patients with early CKD. Simultaneously, nanoparticles can improve safety and convenience for patients undergoing dialysis. Finally, we summarize the current advantages and limitations of nanoparticles applied to CKD as well as their future prospects.

Immunosuppressants Tacrolimus and Sirolimus revert the cardiac antifibrotic properties of p38-MAPK inhibition in 3D-multicellular human iPSC-heart organoids

Cardiac reactive fibrosis is a fibroblast-derived maladaptive process to tissue injury that exacerbates an uncontrolled deposition of large amounts of extracellular matrix (ECM) around cardiomyocytes and vascular cells, being recognized as a pathological entity of morbidity and mortality. Cardiac fibrosis is partially controlled through the sustained activation of TGF-β1 through IL-11 in fibroblasts. Yet, preclinical studies on fibrosis treatment require human physiological approaches due to the multicellular crosstalk between cells and tissues in the heart. Here, we leveraged an iPSC-derived multi-lineage human heart organoid (hHO) platform composed of different cardiac cell types to set the basis of a preclinical model for evaluating drug cardiotoxicity and assessing cardiac fibrosis phenotypes. We found that the inhibition of the p38-MAPK pathway significantly reduces COL1A1 depositions. Yet, concomitant treatment with organ-rejection immunosuppressant drugs Tacrolimus or Sirolimus reverts this effect, opening new questions on the clinical considerations of combined therapies in reducing fibrosis after organ transplantation.

Stimulated phosphorylation of ERK in mouse kidney mesangial cells is dependent upon expression of Cav3.1

Background

T-type calcium channels (TTCC) are low voltage activated channels that are widely expressed in the heart, smooth muscle and neurons. They are known to impact on cell cycle progression in cancer and smooth muscle cells and more recently, have been implicated in rat and human mesangial cell proliferation. The aim of this study was to investigate the roles of the different isoforms of TTCC in mouse mesangial cells to establish which may be the best therapeutic target for treating mesangioproliferative kidney diseases. 

Methods

In this study, we generated single and double knockout (SKO and DKO) clones of the TTCC isoforms Ca_V3.1 and Ca_V3.2 in mouse mesangial cells using CRISPR-cas9 gene editing. The downstream signals linked to this channel activity were studied by ERK1/2 phosphorylation assays in serum, PDGF and TGF-β1 stimulated cells. We also examined their proliferative responses in the presence of the TTCC inhibitors mibefradil and TH1177.

Results

We demonstrate a complete loss of ERK1/2 phosphorylation in response to multiple stimuli (serum, PDGF, TGF-β1) in Ca_V3.1 SKO clone, whereas the Ca_V3.2 SKO clone retained these phospho-ERK1/2 responses. Stimulated cell proliferation was not profoundly impacted in either SKO clone and both clones remained sensitive to non-selective TTCC blockers, suggesting a role for more than one TTCC isoform in cell cycle progression. Deletion of both the isoforms resulted in cell death.

Conclusion

This study confirms that TTCC are expressed in mouse mesangial cells and that they play a role in cell proliferation. Whereas the Ca_V3.1 isoform is required for stimulated phosphorylation of ERK1/2, the Ca _V3.2 isoform is not. Our data also suggest that neither isoform is necessary for cell proliferation and that the anti-proliferative effects of mibefradil and TH1177 are not isoform-specific. These findings are consistent with data from in vivo rat mesangial proliferation Thy1 models and support the future use of genetic mouse models to test the therapeutic actions of TTCC inhibitors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02844-1.

The role of endothelin and RAS/ERK signaling in immunopathogenesis-related fibrosis in patients with systemic sclerosis: an updated review with therapeutic implications

Systemic sclerosis (SSc) is a disease of connective tissue with high rate of morbidity and mortality highlighted by extreme fibrosis affecting various organs such as the dermis, lungs, and heart. Until now, there is no specific cure for the fibrosis occurred in SSc disease. The SSc pathogenesis is yet unknown, but transforming growth factor beta (TGF-β), endothelin-1 (ET-1), and Ras-ERK1/2 cascade are the main factors contributing to the tissue fibrosis through extracellular matrix (ECM) accumulation. Several studies have hallmarked the association of ET-1 with or without TGF-β and Ras-ERK1/2 signaling in the development of SSc disease, vasculopathy, and fibrosis of the dermis, lungs, and several organs. Accordingly, different clinical and experimental studies have indicated the potential therapeutic role of ET-1 and Ras antagonists in these situations in SSc. In addition, ET-1 and connective tissue growth factor (CTGF) as a cofactor of the TGF-β cascade play a substantial initiative role in inducing fibrosis. Once initiated, TGF-β alone or in combination with ET-1 and CTGF can activate several kinase proteins such as the Ras-ERK1/2 pathway that serve as the fundamental factor for developing fibrosis. Furthermore, Salirasib is a synthetic small molecule that is able to inhibit all Ras forms. Therefore, it can be used as a potent therapeutic factor for fibrotic disorders. So, this review discusses the role of TGF-β/ET-1/Ras signaling and their involvement in SSc pathogenesis, particularly in its fibrotic situation.

Farnesylthiosalicylic Acid-Loaded Albumin Nanoparticle Alleviates Renal Fibrosis by Inhibiting Ras/Raf1/p38 Signaling Pathway

Background

Renal fibrosis is the common pathway in chronic kidney diseases progression to end-stage renal disease, but to date, no clinical drug for its treatment is approved. It has been demonstrated that the inhibitor of proto-oncogene Ras, farnesylthiosalicylic acid (FTS), shows therapeutic potential for renal fibrosis, but its application was hindered by the water-insolubility and low bioavailability. Hence, in this study, we improved these properties of FTS by encapsulating it into bovine serum albumin nanoparticles (AN-FTS) and tested its therapeutic effect in renal fibrosis.

Methods

AN-FTS was developed using a classic emulsification-solvent ultrasonication. The pharmacokinetics of DiD-loaded albumin nanoparticle were investigated in SD rats. The biodistribution and therapeutic efficacy of AN-FTS was assessed in a mouse model of renal fibrosis induced by unilateral ureteral obstruction (UUO).

Results

AN-FTS showed a uniform spherical shape with the size of 100.6 ± 1.12 nm and PDI < 0.25. In vitro, AN-FTS displayed stronger inhibitory effects on the activation of renal fibroblasts cells NRK-49F than free FTS. In vivo, AN-FTS showed significantly higher peak concentration and area under the concentration-time curve. After intravenous administration to UUO-induced renal fibrosis mice, AN-FTS accumulated preferentially in the fibrotic kidney, and alleviated renal fibrosis and inflammation significantly more than the free drug. Mechanistically, the improved anti-fibrosis effect of AN-FTS was associated with greater inhibition in renal epithelial-to-mesenchymal transformation process via Ras/Raf1/p38 signaling pathway.

Conclusion

The study reveals that AN-FTS is capable of delivering FTS to fibrotic kidney and showed superior therapeutic efficacy for renal fibrosis.

Effect of mesenchymal stem cells on anti-Thy1,1 induced kidney injury in albino rats

OBJECTIVE

To evaluate the effect of mesenchymal stem cells (MSCs) in rats with anti-Thy1,1 nephritis.

METHODS

Female albino rats were divided into three groups, control group, anti-Thy1,1 group and treatment with i.v. MSCs group. MSCs were derived from bone marrow of male albino rats, Y-chromosome gene was detected by polymerase chain reaction in the kidney. Serum urea and creatinine were estimated for all groups. Kidney of all studied groups was examined histologically and histochemically (total carbohydrates and total proteins). DNA fragmentation and expression of α-SMA were detected.

RESULTS

Kidney of animals injected with anti-Thy1,1 showed inflammatory leucocytic infiltration, hypertrophied glomeruli, tubular necrosis and congestion in the renal blood vessels. The kidney tissue also showed reduction of carbohydrates and total proteins together with increase in apoptosis and in expression of α-SMA. Moreover, the levels of urea and creatinine were elevated. Treating animals with MSCs revealed that kidney tissue displayed an improvement in the histological and histochemical changes. Apoptosis and α-SMA expression were decreased, and the levels of urea and creatinine decreased.

CONCLUSIONS

The obtained results demonstrated the potential of MSCs to ameliorate the structure and function of the kidney in rats with anti-Thy1,1 nephritis possibly through the release of paracrine growth factor(s).

Kindlin-2 regulates renal tubular cell plasticity by activation of Ras and its downstream signaling

Kindlin-2 is an adaptor protein that contributes to renal tubulointerstitial fibrosis (TIF). Epithelial-to-mesenchymal transition (EMT) in tubular epithelial cells was regarded as one of the key events in TIF. To determine whether kindlin-2 is involved in the EMT process, we investigated its regulation of EMT in human kidney tubular epithelial cells (TECs) and explored the underlying mechanism. In this study, we found that overexpression of kindlin-2 suppressed epithelial marker E-cadherin and increased the expression of fibronectin and the myofibroblast marker α-smooth muscle actin (SMA). Kindlin-2 significantly activated ERK1/2 and Akt, and inhibition of ERK1/2 or Akt reversed kindlin-2-induced EMT in human kidney TECs. Mechanistically, kindlin-2 interacted with Ras and son of sevenless (Sos)-1. Furthermore, overexpression of kindlin-2 increased Ras activation through recruiting Sos-1. Treatment with a Ras inhibitor markedly repressed kindlin-2-induced ERK1/2 and Akt activation, leading to restraint of EMT. We further demonstrated that knockdown of kindlin-2 inhibited EGF-induced Ras-Sos-1 interaction, resulting in reduction of Ras activation and suppression of EMT stimulated by EGF. Importantly, we found that depletion of kindlin-2 significantly inhibited activation of ERK1/2 and Akt signaling in mice with unilateral ureteral obstruction. We conclude that kindlin-2, through activating Ras and the downstream ERK1/2 and Akt signaling pathways, plays an important role in regulating renal tubular EMT and could be a potential therapeutic target for the treatment of fibrotic kidney diseases.

Ras chaperones: new targets for cancer and immunotherapy

The Ras inhibitor S-trans,trans-farnesylthiosalicylic acid (FTS, Salirasib®) interferes with Ras membrane interactions that are crucial for Ras-dependent signaling and cellular transformation. FTS had been successfully evaluated in clinical trials of cancer patients. Interestingly, its effect is mediated by targeting Ras chaperones that serve as key coordinators for Ras proper folding and delivery, thus offering a novel target for cancer therapy. The development of new FTS analogs has revealed that the specific modifications to the FTS carboxyl group by esterification and amidation yielded compounds with improved growth inhibitory activity. When FTS was combined with additional therapeutic agents its activity toward Ras was significantly augmented. FTS should be tested not only in cancer but also for genetic diseases associated with abnormal Ras signaling, as well as for various inflammatory and autoimmune disturbances, where Ras plays a major role. We conclude that FTS has a great potential both as a safe anticancer drug and as a promising immune modulator agent.

Anti-proliferative actions of T-type calcium channel inhibition in Thy1 nephritis

Aberrant proliferation of mesangial cells (MCs) is a key finding in progressive glomerular disease. TH1177 is a small molecule that has been shown to inhibit low-voltage activated T-type Ca(2+) channels (TCCs). The current study investigates the effect of TH1177 on MC proliferation in vitro and in vivo. The effect of Ca(2+) channel inhibition on primary rat MC proliferation in vitro was studied using the microculture tetrazolium assay and by measuring bromodeoxyuridine incorporation. In vivo, rats with Thy1 nephritis were treated with TH1177 or vehicle. Glomerular injury and average glomerular cell number were determined in a blinded fashion. Immunostaining for Ki-67 and phosphorylated ERK were also performed. The expression of TCC isoforms in healthy and diseased tissue was investigated using quantitative real-time PCR. TCC blockade caused a significant reduction in rat MC proliferation in vitro, whereas L-type inhibition had no effect. Treatment of Thy1 nephritis with TH1177 significantly reduced glomerular injury (P < 0.005) and caused a 49% reduction in glomerular cell number (P < 0.005) compared to the placebo. TH1177 also reduced Ki-67-positive and pERK-positive cells per glomerulus by 52% (P < 0.01 and P < 0.005, respectively). These results demonstrate that TH1177 inhibits MC proliferation in vitro and in vivo, supporting the hypothesis that TCC inhibition may be a useful strategy for studying and modifying MC proliferative responses to injury.

PEG-farnesylthiosalicylate conjugate as a nanomicellar carrier for delivery of paclitaxel

S-trans, trans-farnesylthiosalicylic acid (FTS) is a synthetic small molecule that acts as a potent and especially nontoxic Ras antagonist. It inhibits both oncogenically activated Ras and growth factor receptor-mediated Ras activation, resulting in the inhibition of Ras-dependent tumor growth. In this work, an FTS conjugate with poly(ethylene glycol) (PEG) through a labile ester linkage, PEG5K-FTS2(L), was developed. PEG5K-FTS2 conjugate readily forms micelles in aqueous solutions with a critical micelle concentration of 0.68 μM, and hydrophobic drugs such as paclitaxel (PTX) could be effectively loaded into these particles. Both drug-free and PTX-loaded micelles were spherical in shape with a uniform size of 20-30 nm. The release of PTX from PTX-loaded PEG5K-FTS2 micelles was significantly slower than that from Taxol formulation. In vitro cytotoxicity studies with several tumor cell lines showed that PEG5K-FTS2(L) was comparable to FTS in antitumor activity. Western immunoblotting showed that total Ras levels were downregulated in several cancer cell lines treated with FTS or PEG5K-FTS2(L). The micellar formulation of PTX exhibited more in vitro cytotoxic activity against several tumor cell lines compared with free PTX, suggesting a possible synergistic effect between the carrier and the codelivered drug. The antitumor activity of the PTX loaded PEG5K-FTS2(L) micelles in a syngeneic murine breast cancer model was found to be significantly higher than that of Taxol, which may be attributed to their preferential tumor accumulation and a possible synergistic effect between PEG5K-FTS2 carrier and loaded PTX.

Prevention of induced colitis in mice by the ras antagonist farnesylthiosalicylic acid

BACKGROUND

Ras proteins are crucial for cell differentiation and proliferation. Targeting Ras with farnesylthiosalicylic acid (FTS), a Ras antagonist, has been suggested as a therapeutic strategy in proliferative and inflammatory diseases.

AIMS

To examine the role of Ras and the therapeutic potential of FTS in experimental colitis.

METHODS

Colitis was induced in 26 mice by adding 2.5% dextran sodium sulfate to their drinking water for 7 days during which 12 study mice were treated with FTS and 14 control mice were given normal saline. Two additional controls included 10 naïve mice treated with FTS and 7 naïve non-treated mice. The animals were followed clinically and sacrificed after 7 days. Their colons were isolated for histological assessment and for measurement of myeloperoxidase activity (MPO), tumor necrosis factor-α(TNF-α), and interleukin-1β(Il-1β) levels. Ras and activated Ras expression was determined by immunoblotting assays. T cell populations in the colon and spleen were analyzed by flow-cytometry.

RESULTS

FTS induced a 2.1-fold reduction in activated Ras levels (P < 0.004). FTS-treated mice had lower disease activity scores (3.9 ± 1.7 vs. 7.5 ± 2.3, P < 0.001), and lower levels of MPO activity (1.65 ± 0.6 vs. 2.6 ± 0.8 units/g, P < 0.007), Il-1β (2.4 ± 3.6 vs. 24.3 ± 17.5 pg/mg, P < 0.01) and TNF-α (0.63 ± 0.5 vs. 1.9 ± 1 pg/mg, P < 0.04). FTS increased regulatory T cell population in the spleen (1.9 ± 0.4-fold, P < 0.04), and decreased effector T cell populations in the colon and spleen by 24 ± 3% (P < 0.03) and 27 ± 1% (P < 0.02), respectively. FTS had no remarkable side effects.

CONCLUSIONS

Ras is involved in the inflammatory processes of induced colitis in mice and its inhibition by FTS ameliorates the severity of the inflammation.

Antisense knockdown of Kras inhibits fibrosis in a rat model of unilateral ureteric obstruction

Tubulointerstitial fibrosis is the hallmark of chronic kidney disease and is characterized by an increase in the number and activity of interstitial fibroblasts and by excessive matrix deposition. Ras is an intracellular signaling molecule involved in cell proliferation and differentiation. It has recently been implicated in the pathogenesis of renal fibrosis. Of the three different isoforms of Ras (Kirsten, Harvey, and Neural), we previously demonstrated that the Kirsten isoform is key in the control of renal fibroblast proliferation in vitro. In this study, we used gene therapy in the form of antisense oligonucleotides (ASOs) specifically to silence Kras (alias Ki-ras) expression in a rat model of renal fibrosis caused by unilateral ureteric obstruction. We demonstrate that renal Kras expression increases by 70% in this model compared with sham-operated animals and that treatment with ASOs can reduce total renal Kras by >90% to levels well below basal. This silencing is associated with a dramatic inhibition of interstitial fibrosis, a fivefold reduction in α-smooth muscle actin expression, and a 2.4-fold reduction in collagen I deposition. This inhibition was observed despite histologic evidence of marked interstitial inflammation. These findings demonstrate that silencing Kras expression can markedly inhibit renal fibrosis. This strategy should be considered as a new potential therapeutic avenue.

The Ras antagonist, farnesylthiosalicylic acid (FTS), decreases fibrosis and improves muscle strength in dy/dy mouse model of muscular dystrophy

The Ras superfamily of guanosine-triphosphate (GTP)-binding proteins regulates a diverse spectrum of intracellular processes involved in inflammation and fibrosis. Farnesythiosalicylic acid (FTS) is a unique and potent Ras inhibitor which decreased inflammation and fibrosis in experimentally induced liver cirrhosis and ameliorated inflammatory processes in systemic lupus erythematosus, neuritis and nephritis animal models. FTS effect on Ras expression and activity, muscle strength and fibrosis was evaluated in the dy^2J/dy^2J mouse model of merosin deficient congenital muscular dystrophy. The dy^2J/dy^2J mice had significantly increased RAS expression and activity compared with the wild type mice. FTS treatment significantly decreased RAS expression and activity. In addition, phosphorylation of ERK, a Ras downstream protein, was significantly decreased following FTS treatment in the dy^2J/dy^2J mice. Clinically, FTS treated mice showed significant improvement in hind limb muscle strength measured by electronic grip strength meter. Significant reduction of fibrosis was demonstrated in the treated group by quantitative Sirius Red staining and lower muscle collagen content. FTS effect was associated with significantly inhibition of both MMP-2 and MMP-9 activities. We conclude that active RAS inhibition by FTS was associated with attenuated fibrosis and improved muscle strength in the dy^2J/dy^2J mouse model of congenital muscular dystrophy.

The Ras inhibitor farnesylthiosalicylic acid (Salirasib) disrupts the spatiotemporal localization of active Ras: a potential treatment for cancer

Chronic activation of Ras proteins by mutational activation or by growth factor stimulation is a common occurrence in many human cancers and was shown to induce and be required for tumor growth. Even if additional genetic defects are present, "correction" of the Ras defect has been shown to reverse Ras-dependent tumorigenesis. One way to block Ras protein activity is by interfering with their spatiotemporal localization in cellular membranes or in membrane microdomains, a prerequisite for Ras signaling and biological activity. Detailed reports describe the use of this method in studies employing farnesylthiosalicylic acid (FTS, Salirasib), a Ras farnesylcysteine mimetic, which selectively disrupts the association of chronically active Ras proteins with the plasma membrane. FTS competes with Ras for binding to Ras-escort proteins, which possess putative farnesyl-binding domains and interact only with the activated form of Ras proteins, thereby promoting Ras nanoclusterization in the plasma membrane and robust signals. This chapter presents three-dimensional time-lapse images that track the FTS-induced inhibition of membrane-activated Ras in live cells on a real-time scale. It also describes a mechanistic model that explains FTS selectivity toward activated Ras. Selective blocking of activated Ras proteins results in the inhibition of Ras transformation in vitro and in animal models, with no accompanying toxicity. Phase I clinical trials have demonstrated a safe profile for oral FTS, with minimal side effects and promising activity in hematological malignancies. Salirasib is currently undergoing trials in patients with pancreatic cancer and with nonsmall cell lung cancer, with or without identified K-Ras mutations. The findings might indicate whether with the disruption of the spatiotemporal localization of oncogenic Ras proteins and the targeting of prenyl-binding domains by anticancer drugs is worth developing as a means of cancer treatment.

Role of ERK1/2 and PI3-K in the regulation of CTGF-induced ILK expression in HK-2 cells

BACKGROUND

Previous studies revealed that integrin-linked kinase (ILK), an intracellular serine/threonine protein kinase, is a critical mediator for tubular epithelial to mesenchymal transition (EMT), and likely plays an important role in the pathogenesis of chronic kidney fibrosis. However, the exact signal pathway has not been well understood. In this study, we investigated the role of extracellular regulating kinase 1/2 (ERK1/2) and phosphatidylinositol 3-kinase (PI3-K) in the regulation of ILK expression by connective tissue growth factor (CTGF) in HK-2 cells.

METHODS

Experiments were performed on transformed (human kidney cell (HKC)-clone 2) human proximal tubular epithelial cells (PTECs). Induction of ILK in response to CTGF was studied at the mRNA level by real-time PCR and protein by immunoblotting. Chemical inhibitors were used to assess the role of MEK/ERK1/2, PI3-K, and P38 MAPK signaling pathways in induction of ILK by CTGF.

RESULTS

CTGF induced ILK protein expression in HK-2 cells in a time- and dose-dependent manner. There was a 5.638-fold (control: 1.000+/-0.290, 50 ng/ml: 5.638+/-1.200; *P<0.05 vs. control) and 5.740-fold (0 h: 1.000+/-0.498, 48 h: 5.740+/-1.465, *P<0.05 vs. control) increase compared to control respectively. CTGF-induced ILK expression was partially reduced by inhibiting ERK1/2 and PI3-K activation. There was no influence of ILK expression by inhibiting P38 MAPK activation when cells treated with CTGF.

CONCLUSION

CTGF induces the expression of ILK protein in HK-2 cells. This induction is partially dependent on MEK/ERK1/2 and PI3-K signaling pathways. Inhibiting CTGF-induced ILK by targeting PI3-K and/or MEK/ERK1/2 signaling pathways could be of therapeutic value in renal fibrosis.

ANCA-associated vasculitis: new options beyond steroids and cytotoxic drugs

Small vessel vasculitic syndromes--Wegener's granulomatosis, microscopic polyangiitis and renal limited vasculitis (which are associated with circulating antineutrophil cytoplasmic autoantibodies)--are an important cause of renal failure. Present immunosuppressive regimens that are based on cyclophosphamide have significantly increased survival rates. However, these treatments are toxic, increase the risk of infection and do not cure disease. Therefore, newer approaches are required. Understanding disease pathogenesis has allowed rational use for newer therapies such as rituximab, which depletes B cells. Unfortunately, blockade of promising targets such as TNF-alpha, which was thought to be a pivotal cytokine in inflammation, has not shown benefit in a randomised controlled trial. Better understanding of the pathogenesis of the disease is the key to the development of novel targeted therapies, which are urgently required to improve patient prognosis. Gene therapy with targeted delivery of specific proteins is an exciting future prospect.

The role of geranylgeranylated proteins in human mesangial cell proliferation

The Rho family of guanine 5'-triphosphatases (GTPases) play a key role in regulating cell proliferation, tubulointerstitial fibrosis, and glomerular hemodynamics. The post-translational prenylation of RhoGTPases by the addition of a geranylgeranyl moiety is critical for cellular localization and signaling activity. This study investigates the effects of (i) inhibiting geranylgeranylation (GG) in human mesangial cell (HMC) proliferation and apoptosis, using GGTI 298, a specific inhibitor of GG and (ii) lovastatin, an HMG-coacetyl A-reductase inhibitor, which depletes the availability of prenylation substrates. HMC proliferation was assessed using an assay of viable cell number and measuring bromodeoxyuridine (BrdU) incorporation. Hoechst 33342 staining was used to determine apoptosis. Extracellular signal-regulated protein kinase (Erk)1/2 and Akt activation were analysed by Western blotting. Rho activation was determined using the Rhotekin pull-down assay. Immunocytochemistry was performed to study the effects on the actin cytoskeleton and RhoA localization. GGTI 298 (10-20 muM) and lovastatin (5-10 muM) potently inhibited platelet-derived growth factor and serum-stimulated HMC proliferation and induced apoptosis. These effects of lovastatin were attenuated by co-incubation with geranylgeranylpyrophosphate. C3 exoenzyme, a clostridial toxin that specifically targets Rho also inhibited BrdU incorporation and promoted apoptosis. GGTI 298 increased cytosolic expression of RhoA, prevented RhoA activation, and inhibited the activation of Erk1/2 and the survival protein Akt. GGTI 298, lovastatin, and C3 exoenzyme inhibit HMC proliferation and promote apoptosis. Inhibiting GG increases cytosolic RhoA expression, disrupts the actin cytoskeleton, and inhibits RhoA activation. These results suggest that targeting geranylgeranylated proteins with statins or GGTI 298 is a promising therapeutic strategy in human mesangioproliferative renal disease.

PDGF receptor tyrosine kinase inhibitor suppresses mesangial cell proliferation involving STAT3 activation

Proliferation of mesangial cells is a hallmark of glomerular disease, and understanding the regulatory mechanisms is critically important. The purpose of this study was to examine the relationship between mesangial cell proliferation and phosphorylated signal transducer and activator of transcription (STAT) 3 and to determine whether the PDGF receptor tyrosine kinase inhibitor STI 571 inhibited mesangial cell proliferation via modulation of STAT3. In this study, we investigated for the first time, the glomerular expression of phosphorylated STAT3 in paraffin sections from animals with experimental mesangial proliferative glomeronephritis. Phosphorylated STAT3 colocalized with many proliferating mesangial cells. We also demonstrated that treatment with STI 571 reduced mesangial cell proliferation and phosphorylated STAT3 signalling both in vitro and in vivo. In vivo, STI 571 treatment reduced the number of glomerular mesangial cells positive for both phosphorylated STAT3 and proliferating cell nuclear antigen. In summary, phosphorylated STAT3 is strongly expressed during mesangial cell proliferation and STI 571 induced suppression of mesangial cell proliferation involves inhibition of phosphorylated STAT3 signalling.

Simvastatin protection against acute immune-mediated glomerulonephritis in mice

In addition to cholesterol lowering, 3-hydroxy-3-nethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors limit inflammatory changes associated with atherosclerosis. There is also support for their use as inhibitors of progression in chronic renal disease, irrespective of cause. In this study, their capacity to limit acute renal inflammation was evaluated. For this purpose, mice were treated with Simvastatin either prior to, at the time of, or shortly after induction of nephrotoxic nephritis. The severity of disease was determined by evaluation of blood urea nitrogen (BUN), proteinuria, and renal histologic changes. The reversibility of benefit was evaluated by the administration of mevalonic acid along with nephrotoxic serum (NTS) and Simvastatin The severity of the acute nephritis, including proteinuria, elevated BUN, and histologic changes, was ameliorated in a dose-dependent manner, when Simvastatin was administered either prior to NTS injection or at the time of NTS injection. By contrast, Simvastatin did not alter the course of established nephritis. Coadministration of mevalonic acid, the immediate substrate following HMG-CoA reductase, abolished Simvastatin's renoprotective effect, indicating that the benefit is, at least in part, due to interference with HMG-CoA reductase and biosynthetic substrates downstream from the enzyme. These findings provide the rationale for the evaluation of the efficacy of HMG-CoA reductase inhibitors in patients with recurrent forms of renal inflammation, to limit the severity of acute exacerbations of disease, prevent renal scarring and slow the rate of progression.

Therapeutics in renal disease: the road ahead for antiproliferative targets

Discovery into the molecular basis of renal disease is occurring at an unprecedented rate. With the advent of the NIH Roadmap, there is a greater expectation of translating this knowledge into new treatments. Here, we review the therapeutic strategy to preserve renal function in proliferative renal diseases by directly inhibiting the mitogenic pathways within renal parenchymal cells that promote G0 to G1/S cell-cycle phase progression. Reductionist methodologies have identified several antiproliferative molecular targets, and promising preclinical testing of leading small-molecule drugs to modulate these targets has now led to landmark clinical trials. Yet, this advancement into targeted therapy highlights important differences between the therapeutic goals of molecular nephrology versus molecular oncology and, by extension, the poorly understood role of alternative target activity in drug efficacy. Systems research to clarify these issues should accelerate the development of this promising therapeutic strategy.

Antiphospholipid antibodies, thrombin and LPS activate brain endothelial cells and Ras-dependent pathways through distinct mechanisms

BACKGROUND

The antiphospholipid syndrome (APS) commonly affects the central nervous system through mechanisms that may include small vessel pathology and activation of thrombin. Antiphospholipid antibodies (aPL) activate endothelial cells but the specific activation of brain vascular endothelial cells (BVEC) and the receptors and signaling pathways involved have not been fully characterized.

OBJECTIVE

To examine whether aPL, the inflammatory stimulant lipopolysacharide (LPS) and thrombin activate BVECs through a Ras-dependent pathway.

METHODS

Rat BVEC (G8) were grown to confluence on 24-well plates. IgG was purified from 8 APS patients on a protein G column. Phosphorylation of ERK in the BVEC was measured by immunoblot utilizing a specific antibody.

RESULTS

Significant phosphorylation of ERK was measured following exposure of the cells to LPS and thrombin and this was blocked by the Ras inhibitor farnesylthiosalicylate (FTS). aPL IgG (1:100 relative to serum) from 7/8 patients also induced phosphorylation of ERK.

CONCLUSIONS

Activation of the Ras-ERK pathway is an effect of both APS IgG and thrombin. This pathway is potentially amenable to drugs such as FTS and may serve as a therapeutic target in APS.

Effect of inhibition of farnesylation and geranylgeranylation on renal fibrogenesis in vitro

BACKGROUND

The Ras and Rho family of GTPases serve as essential molecular switches in the downstream signalling of many cytokines involved in the regulation of renal fibroblast activity. Prenylation is a post-translational process critical to the membrane localization and function of these GTPases. We studied the effects of a farnesyltransferase inhibitor BMS-191563 and geranylgeranyltransferase inhibitor GGTI-298 on renal fibrogenesis in vitro.

METHODS

Functional studies examined the effects of BMS-191563 and GGTI-298 on rat renal fibroblast kinetics, collagen synthesis and collagen gel contraction. Pro-collagen alpha1(I) mRNA expression was measured by Northern analysis and CTGF expression by Western blotting.

RESULTS

Fibroblast proliferation was significantly reduced by both agents. Exposure of fibroblasts to BMS-191563 resulted in a significant reduction in total collagen production and pro-collagen alpha1(I) mRNA expression, an effect also observed but to a lesser degree with GGTI-298. Both agents significantly reduced CTGF protein expression. Fibroblast-mediated collagen I lattice contraction was decreased at 48 h by GGTI-298, an effect not observed with BMS-191563. Consistent with this finding, marked actin filament disassembly was evident by phalloidin staining of fibroblasts exposed to GGTI-298.

CONCLUSION

BMS-191563 and GGTI-298 exhibit different effects on renal fibroblast function reflecting their predominant roles in inhibiting prenylation of Ras or Rho proteins respectively. Further studies are warranted to establish their potential therapeutic application in the treatment of progressive renal disease.

The inhibition of human mesangial cell proliferation by S-trans, trans-farnesylthiosalicylic acid

BACKGROUND

Many of the proliferative cytokines implicated in human mesangial cell (HMC) proliferation signal through the superfamily of Ras GTPases. The Ras antagonist, S-trans, trans- farnesylthiosalicylic acid (FTS), was used to investigate the effects of the inhibition of Ras signaling on HMC proliferation.

METHODS

Ras expression and membrane localization, MAPK, and Akt activation were analyzed by Western blotting. Ras activation was determined with a pull-down assay using the Ras-binding domain of Raf. HMC growth curves were assessed using the MTS assay of viable cell number, while DNA synthesis was measured with BrdU incorporation. Hoechst 33342 staining was used to determine apoptosis.

RESULTS

FTS reduced the membrane localization of Ras in both serum and platelet-derived growth factor (PDGF). FTS (7.5-20 micromol/L) potently inhibited PDGF-induced HMC proliferation but had no effect on serum-induced proliferation. FTS (10-20 micromol/L) inhibited both Ras and phospho-MAPK activation by serum and PDGF. Furthermore, FTS (10-20 micromol/L) increased HMC apoptosis in the presence of PDGF but not in serum. Moreover, PDGF-stimulated activation of the survival protein Akt was inhibited by FTS. In contrast, serum-stimulated activation of Akt was unaffected by FTS.

CONCLUSION

FTS (5-20 micromol/L) inhibits PDGF-induced but not serum-induced HMC proliferation. FTS (10-20 micromol/L) also promotes HMC apoptosis in the presence of PDGF but not serum. These effects appear to be mediated by inhibitory effects on Ras-dependent signaling that occur as a result of the dislodgment of Ras from its membrane-anchorage sites by FTS. The selectivity of FTS toward PDGF-driven HMC proliferation suggests that FTS may be a valuable therapeutic in mesangioproliferative renal disease.

TGF-β1-Induced Connective Tissue Growth Factor (CCN2) Expression in Human Renal Proximal Tubule Epithelial Cells Requires Ras/MEK/ERK and Smad Signalling

BACKGROUND

Connective tissue growth factor (CTGF, CCN2) plays a fundamental role in the development of tissue fibrosis by stimulating matrix deposition and mediating many of the pro-fibrotic effects of transforming growth factor (TGF)-beta. CCN2 induction by TGF-beta in renal proximal tubule epithelial cells (PTECs) is likely to play an important role in the development of tubulointerstitial fibrosis. In this study, we investigated the induction of CCN2 by TGF-beta1 and the possible mechanisms of this induction in human PTECs.

METHODS

Experiments were performed on primary and transformed (human kidney cell (HKC)-clone 8) human PTECs. Induction of CCN2 in response to TGF-beta1 was studied at the gene promoter level by reporter gene assay, mRNA by semi-quantitative RT-PCR and protein by immunoblotting. While chemical inhibitors were used to assess the role of Ras/MEK/ERK1,2 signalling, an HKC cell line over-expressing Smad7 was used to assess the role of Smad signalling in induction of CCN2 by TGF-beta1.

RESULTS

TGF-beta1 induced CCN2 promoter activity, mRNA and protein in human PTECs. TGF-beta1-dependent CCN2 promoter activity was reduced by inhibiting Ras and MEK activation. MEK inhibition also resulted in inhibition of the TGF-beta1-induced secreted CCN2 protein. There was no significant increase in CCN2 gene promoter activity or protein by TGF-beta1 in Smad7 over-expressing HKCs.

CONCLUSIONS

TGF-beta1 induces the expression of CCN2 in human PTECs. This induction is dependent on Ras/MEK/ERK and Smad signalling. Inhibiting TGF-beta induced CCN2 by targeting Smad and/or Ras/MEK/ERK1,2 signalling pathways could be of therapeutic value in renal fibrosis.

Subcellular distribution of Ras GTPase isoforms in normal human kidney

BACKGROUND

Ras GTPase isoforms have been implicated in proliferative renal disease and are known to have differential cellular expression in kidney. However, their exact subcellular location in various cells is unknown.

METHODS

Immunogold labelling for Ras isoforms (Harvey, Kirsten and Neural) was performed for subcellular localization under electron microscopy in fresh normal kidney specimens, obtained from the opposite pole of kidneys removed for renal cell cancer.

RESULTS

There was prominent staining shown by Ha-Ras only on the glomerular foot processes as compared with basement membrane or the endothelial cells. Mesangial cells showed intense staining in the cytosol with Ha-Ras (absent in the nucleus), minimal staining with Ki-Ras and none with N-Ras. In both the proximal and distal convoluted tubules, there was a clear staining of the mitochondria with Ha-Ras, with mild cytosolic staining with all of the isoforms.

CONCLUSIONS

Ras isoforms have distinct and separate subcellular distributions in normal kidney cells. Understanding the functional aspects of this distribution pattern is essential if Ras is to be targeted by genetic or molecular therapeutic tools.