Cell-specific Delivery of a Transforming Growth Factor-beta Type I Receptor Kinase Inhibitor to Proximal Tubular Cells for the Treatment of Renal Fibrosis

Purpose  Activation of tubular epithelial cells by transforming growth factor-beta (TGF-β) plays an important role in the pathogenesis of renal tubulointerstitial fibrosis. We developed a renally accumulating conjugate of a TGF-β type-I receptor kinase inhibitor (TKI) and evaluated its efficacy in vitro and in vivo. Methods  TKI was conjugated to the protein Lysozyme (LZM) via a platinum-based linker. TKI-LZM was evaluated in human tubular cells (HK-2) for its anti-fibrotic activity. Plasma, kidney and urine drug levels after a single intravenous dose of TKI-LZM in rats were determined by HPLC or immunodetection. Anti-fibrotic effects of TKI-LZM were examined in the unilateral ureteral obstruction (UUO) model. Results  TKI-LZM conjugate was successfully synthesized at an 1:1 drug/carrier ratio, and inhibited TGF-β1-induced procollagen-1α1 gene expression in HK-2 cells. In vivo, TKI-LZM accumulated rapidly in tubular cells and provided a local depot for 3 days. Interestingly, a single dose of TKI-LZM inhibited the activation of tubular cells and fibroblasts in UUO rats and reduced renal inflammation. In contrast, free TKI at an equimolar (low) dosage exhibited little effects. Conclusions  Inhibition of TGF-beta signaling by local drug delivery is a promising antifibrotic strategy, and demonstrated the important role of tubular activation in renal fibrosis.     

酪氨酸激酶抑制剂类新药的研发现状

蛋白激酶在多种疾病,特别是肿瘤发生发展过程中起重要作用,以其为药物靶点的激酶抑制剂则成为近年药物研发的热点。目前已有11个小分子激酶抑制剂上市,其中9个为酪氨酸激酶抑制剂。激酶抑制剂具有高选择性、副作用少的特点。已上市药物已经在慢性粒细胞白血病、非小细胞肺癌、肾细胞癌等多种疾病的治疗中显示出其较传统治疗药物的优越性,部分已成为治疗肿瘤的一线用药。本文对小分子酪氨酸激酶抑制剂类新药的研发现状进行综述。     

p38 Inhibitors: beyond pyridinylimidazoles

Since the discovery of p38 mitogen-activated protein kinase (MAPK) as a potential intracellular modulator that regulates the crucial biosynthesis and functions of pro-inflammatory cytokines (e.g., TNF-α and IL-1β), numerous groups have disclosed their efforts to find small-molecule p38 inhibitors as potential therapeutic agents for the treatment of inflammatory diseases such as rheumatoid arthritis (RA), Crohn’s disease (CD) and psoriasis. Although greater selectivity has been achieved with these newly disclosed series, their safety profile after chronic treatment remains a question to be answered in human clinical trials. The p38 inhibitors that have been disclosed in the recent patent literature (2000 – 2004) are summarised here. These compounds will be classified into series based on their intrinsic structures and by their binding modes, as revealed by either crystallography or molecular modelling.     

Renal specific delivery of sulfamethoxazole in the rat by coupling to the low molecular weight protein lysozyme via an acid-sensitive linker

Sulfamethaxazole (SM) was converted to a renal specific drug targeting preparation by coupling the drug to egg-white lysozyme via an acid-sensitive cis-aconityl linker (1:1). Due to this chemical manipulation SM was rapidly distributed to the kidney. Both in vitro and in vivo data indicate that SM was uncoupled from the carrier by chemical hydrolysis in the lysosomes of proximal tubular cells, resulting in parent active drug at the target site. This concept is applicable to other drug-polypeptide conjugates which rapidly distribute to the kidney and might enable selective manipulation of renal (patho)physiology.     

Drug targeting to the kidney: Advances in the active targeting of therapeutics to proximal tubular cells

Activated signaling cascades in the proximal tubular cells of the kidneys play a crucial role in the development of tubulointerstitial fibrosis. Inhibition of these signaling cascades with locally delivered therapeutics is an attractive approach to minimize the risk of unwanted side effects and to enhance their efficacy within the renal tissue.This review describes the potential avenues to actively target drugs to proximal tubular cells by recognition of internalizing receptors and how drug carriers can reach this cell type from either the apical or basolateral side. Important characteristics of drug carrier systems such as size and charge are discussed, as well as linking technologies that have been used for the coupling of drugs to the presented carrier systems. Lastly, we discuss the cellular handling of drugs by proximal tubular cells after their delivery to the kidneys.     

Gene deficiency or pharmacological inhibition of PDCD4-mediated FGR signaling protects against acute kidney injury

Recent studies have shown that programmed cell death 4 (PDCD4) modulates distinct signal transduction pathways in different pathological conditions. Despite acute and chronic immune responses elicited by ischemia contributing to the functional deterioration of the kidney, the contributions and mechanisms of PDCD4 in acute kidney injury (AKI) have remained unclear. Using two murine AKI models including renal ischemia/reperfusion injury (IRI) and cisplatin-induced AKI, we found that PDCD4 deficiency markedly ameliorated renal dysfunction and inflammatory responses in AKI mice. Consistently, upregulation of PDCD4 was also confirmed in the kidneys from patients with biopsy confirmed acute tubular necrosis from a retrospective cohort study. Moreover, we found that overexpression of Fgr, a member of the tyrosine kinase family, dramatically aggravated renal injury and counteracted the protective effects of PDCD4 deficiency in AKI mice. We discovered that FGR upregulated NOTCH1 expression through activating STAT3. Most importantly, we further found that systemic administration of ponatinib, a tyrosine kinase inhibitor, significantly ameliorated AKI in mice. In summary, we identified that PDCD4 served as an important regulator, at least in part, of FGR/NOTCH1-mediated tubular apoptosis and inflammation in AKI mice. Furthermore, our findings suggest that ponatinib-mediated pharmacologic targeting of this pathway had therapeutic potential for mitigating AKI.     

Specific delivery of kinase inhibitors in nonmalignant and malignant diseases

Introduction: Kinase inhibitors have been hailed as a breakthrough in the treatment of cancer. Extensive research is now being devoted to the development of kinase inhibitors as a treatment for many nonmalignant diseases. However, the use of kinase inhibitors in both malignant and nonmalignant diseases is also associated with side effects and the development of resistance. It may be worthwhile to explore whether cell-specific delivery of kinase inhibitors improves therapeutic efficacy and reduces side effects.

Areas covered: This review aims to provide an overview of the preclinical studies performed to examine the specific targeting of kinase inhibitors in vitro and in vivo. It gives an introduction to kinase signaling pathways induced during disease, along with the possible problems associated with their inhibition. It also discusses the studies on specific delivery and shows that altering the specificity of kinase inhibitors by targeting methods improves their effectivity and safety.

Expert opinion: Compared with the delivery of cytotoxic compounds, the specific delivery of kinase inhibitors has not yet been studied extensively. The studies discussed in this review provide an insight into methods used to target kinase inhibitors to different organs. The targeting of different kinase inhibitors has improved their therapeutic possibilities, but many questions still remain to be studied.     

KF-1607, a Novel Pan Src Kinase Inhibitor,Attenuates Obstruction-Induced Tubulointerstitial Fibrosis in Mice

Src family kinases (SFKs), an important group of non-receptor tyrosine kinases, are suggested to be excessively activated during various types of tissue fibrosis. The present study investigated the effect of KF-1607, an orally active and a newly synthesized Src kinase inhibitor (SKI) with proposed low toxicity, in preventing the progression of renal interstitial fibrosis. Unilateral ureteral obstruction (UUO) surgery was performed in 6-week-old male C57BL/6 mice to induce renal interstitial fibrosis. Either KF-1607 (30 mg/kg, oral gavage) or PP2 (2 mg/kg, intraperitoneal injection), a common experimental SKI, was administered to mice for seven days, started one day prior to surgery. UUO injury-induced SFK expression, including Src, Fyn, and Lyn kinase. SFK inhibition by KF-1607 prevented the progression of tubular injury in UUO mice, as indicated by decreases in albuminuria, urinary KIM-1 excretion, and kidney NGAL protein expression. Renal tubulointerstitial fibrosis was attenuated in response to KF-1607, as shown by decreases in α-SMA, collagen I and IV protein expression, along with reduced Masson’s trichrome and collagen-I staining in kidneys. KF-1607 also inhibited inflammation in the UUO kidney, as exhibited by reductions in F4/80 positive-staining and protein expression of p-NFκB and ICAM. Importantly, the observed effects of KF-1607 were similar to those of PP2. A new pan Src kinase inhibitor, KF-1607, is a potential pharmaceutical agent to prevent the progression of renal interstitial fibrosis.     

New inhibitors of p38 kinase

In the short time since the 1994 report that the molecular target for the 4-aryl-5-pyridin-4-yl imidazole class of cytokine suppressive anti-inflammatory agents (exemplified by SB-203580) was the human homologue of the stress-induced kinase p38, there has been an explosion of patent literature disclosing related inhibitor analogues. These compounds fall into the general structural class of vicinal aryl/pyridin-4-yl heterocycles. Compounds of this class have been claimed as p38 inhibitors or inhibitors of cytokine biosynthesis. Since cytokines mediate a variety of disease processes, inhibition of cytokine biosynthesis has potential as a therapeutic target. The SAR of binding to p38 for this intensively studied class of compounds is now understandable on the basis of recent x-ray crystallographic and mutagenesis studies. The inhibitors can be sub-classified based upon a variety of structural characteristics. Recently new inhibitor structural classes have been disclosed. Although distinctly different structurally, several of these new compounds appear to bind with the same key interactions as the vicinal aryl/pyridin-4-yl heterocycles.     

LRRK2 Kinase Inhibition as a Therapeutic Strategy for Parkinson’s Disease,Where Do We Stand?

One of the most promising therapeutic targets for potential diseasemodifying treatment of Parkinson’s disease (PD) is leucine-rich repeat kinase 2 (LRRK2). Specifically, targeting LRRK2’s kinase function has generated a lot of interest from both industry and academia. This work has yielded several published studies showing the feasibility of developing potent, selective and brain permeable LRRK2 kinase inhibitors. The availability of these experimental drugs is contributing to filling in the gaps in our knowledge on the safety and efficacy of LRRK2 kinase inhibition. Recent studies of LRRK2 kinase inhibition in preclinical models point to potential undesired effects in peripheral tissues such as lung and kidney. Also, while strategies are now emerging to measure target engagement of LRRK2 inhibitors, there remains an important need to expand efficacy studies in preclinical models of progressive PD. Future work in the LRRK2 inhibition field must therefore be directed towards developing molecules and treatment regimens which demonstrate efficacy in mammalian models of disease in conditions where safety liabilities are reduced to a minimum.     

Rho-kinase inhibitors decrease TGF-β-stimulated VEGF synthesis through stress-activated protein kinase/c-Jun N-terminal kinase in osteoblasts

We have previously reported that transforming growth factor-β (TGF-β) stimulates the synthesis of vascular endothelial growth factor (VEGF) through p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In order to investigate whether Rho-kinase is involved in the TGF-β-stimulated VEGF synthesis in these cells we examined the effects of Rho-kinase inhibitors on the VEGF synthesis. TGF-β time-dependently induced the phosphorylation of myosin phosphatase targeting subunit (MYPT-1) which is a well known substrate of Rho-kinase. Y27632 and fasudil, Rho-kinase inhibitors, significantly reduced the TGF-β-stimulated VEGF synthesis as well as the MYPT-1 phosphorylation. Y27632 and fasudil failed to affect the TGF-β-induced phosphorylation of p44/p42 MAP kinase, p38 MAP kinase or Smad2. On the contrary, Y27632 as well as fasudil markedly suppressed the TGF-β-induced phosphorylation of SAPK/JNK. Taken together, our results strongly suggest that Rho-kinase regulates TGF-β-stimulated VEGF synthesis via SAPK/JNK activation in osteoblasts.     

Indoxyl Sulfate Contributes to mTORC1-Induced Renal Fibrosis via The OAT/NADPH Oxidase/ROS Pathway

Activation of mTORC1 (mechanistic target of rapamycin complex 1) in renal tissue has been reported in chronic kidney disease (CKD)-induced renal fibrosis. However, the molecular mechanisms responsible for activating mTORC1 in CKD pathology are not well understood. The purpose of this study was to identify the uremic toxin involved in mTORC1-induced renal fibrosis. Among the seven protein-bound uremic toxins, only indoxyl sulfate (IS) caused significant activation of mTORC1 in human kidney 2 cells (HK-2 cells). This IS-induced mTORC1 activation was inhibited in the presence of an organic anion transporter inhibitor, a NADPH oxidase inhibitor, and an antioxidant. IS also induced epithelial–mesenchymal transition of tubular epithelial cells (HK-2 cells), differentiation of fibroblasts into myofibroblasts (NRK-49F cells), and inflammatory response of macrophages (THP-1 cells), which are associated with renal fibrosis, and these effects were inhibited in the presence of rapamycin (mTORC1 inhibitor). In in vivo experiments, IS overload was found to activate mTORC1 in the mouse kidney. The administration of AST-120 or rapamycin targeted to IS or mTORC1 ameliorated renal fibrosis in Adenine-induced CKD mice. The findings reported herein indicate that IS activates mTORC1, which then contributes to renal fibrosis. Therapeutic interventions targeting IS and mTORC1 could be effective against renal fibrosis in CKD.     

Rho/Rho kinase as a potential target for the treatment of renal disease

The small G-protein Rho and its downstream effector Rho kinase constitute important mediators not only of vascular contraction but also of actin cytoskeleton reorganization, cellular morphology, motility, adhesion and proliferation. The Rho/Rho kinase pathway plays an important role in the structure and function of various kidney cells including tubular epithelial cells, mesangial cells and podocytes. The Rho/Rho kinase pathway also regulates glomerular blood flow and glomerular filtration rate by modulating renal arteriolar contractility. Potent and specific inhibitors of Rho kinase have recently been developed and their therapeutic effects on a variety of renal injury models have been examined. In the rat models of hypertensive glomerulosclerosis, unilateral ureteral obstruction (for interstitial renal fibrosis) and ischemia/reperfusion acute renal failure, treatment with novel Rho kinase inhibitors attenuates the development of renal damage. Although human data connecting the activation of Rho/Rho kinase pathway and kidney disease are still lacking, these studies have provided compelling evidence for the renoprotective effects of Rho kinase inhibitors.     

阿魏酸钠对UUO大鼠肾脏保护作用的实验研究

目的探讨阿魏酸钠对UUO大鼠肾脏保护作用及其可能的机制。方法将SD大鼠随机分为假手术组、UUO模型组、阿魏酸钠治疗组,每组20只。术后14 d处死动物并取梗阻侧肾脏,比较病理改变;采用免疫组化法检测3组大鼠肾小管上皮细胞TGF-β1、p-p38、α-SMA的表达。处死大鼠同时心脏取血,检测3组血清肌酐、尿素氮及光抑素C水平。结果与假手术组比较,模型组TGF-β1、p-p38、α-SMA的表达显著升高(P<0.05)。与模型组比较,治疗组血清肌酐、尿素氮及光抑素C水平明显降低(P<0.05);而肾小管上皮细胞TGF-β1、p-p38、α-SMA的表达显著降低(P<0.05)。结论阿魏酸钠可能通过下调肾小管上皮细胞TGF-β1、p-p38及α-SMA的表达,起到延缓肾间质纤维化进程及保护肾功能的作用。     

The roles of CYP450 epoxygenases and metabolites, epoxyeicosatrienoic acids, in cardiovascular and malignant diseases

Cytochrome P450 (CYP) epoxygenases metabolize arachidonic acid to biologically active eicosanoids. The primary epoxidation products are four regioisomers of cis-epoxyeicosatrienoic acid (EET): 5,6-, 8,9-, 11,12-, and 14,15-EET. CYP2J2, CYP2C8, and CYP2C9 are the predominant epoxygenase isoforms involved in EET formation. CYP2J and CYP2C gene families in humans are abundantly expressed in the endothelium, myocardium, and kidney. The cardiovascular effects of CYP epoxygenases and EETs range from vasodilation, anti-hypertension, pro-angiogenesis, anti-atherosclerosis, and anti-inflammation to anti-injury caused by ischemia-reperfusion. Using transgenic animals for in vivo analyses of CYP epoxygenases revealed comprehensive and marked cardiovascular protective effects. In contrast, CYP epoxygenases and their metabolites, EETs, are upregulated in human tumors and promote tumor progression and metastasis. These biological effects result from the anti-apoptosis, pro-mitogenesis, and anti-migration roles of CYP epoxygenases and EETs at the cellular level. Importantly, soluble epoxide hydrolase (sEH) inhibitors are anti-hypertensive and anti-inflammatory and, therefore, protect the heart from damage, whereas the terfenadine-related, specific inhibitors of CYP2J2 exhibit strong anti-tumor activity in vitro and in vivo. Thus, CYP2J2 and arachidonic acid-derived metabolites likely play important roles in regulating cardiovascular functions and malignancy under physiological and/or pathological conditions. Moreover, although challenges remain to improving the drug-like properties of sEH inhibitors and identifying efficient ways to deliver sEH inhibitors, sEH will likely become an important therapeutic target for cardiovascular diseases. In addition, CYP2J2 may be a therapeutic target for treating human cancers and leukemia.     

MKK4 is a novel target for the inhibition of tumor necrosis factor-α-induced vascular endothelial growth factor expression by myricetin

Tumor necrosis factor-α (TNF-α) is a mediator of multiple inflammatory diseases. Vascular endothelial growth factor (VEGF) plays a critical role in TNF-α-mediated diseases. We investigated the inhibitory effects of 3,3′,4′,5,5′,7-hexahydroxyflavone (myricetin), an abundant natural flavonoid, on TNF-α-induced VEGF upregulation and the underlying molecular mechanism. Myricetin is a direct inhibitor of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) kinase 1 (MEK1) and inhibits neoplastic cell transformation. We found that myricetin inhibited TNF-α-induced VEGF expression in JB6 P+ mouse epidermal cells by targeting MAPK kinase 4 (MKK4), as well as MEK1. The activation of activator protein-1 by TNF-α was inhibited by myricetin in a dose-dependent manner. The phosphorylation of c-Jun N-terminal kinase (JNK) and ERK was inhibited by myricetin, but not the phosphorylation of their upstream kinases MKK4 and MEK1. TNF-α-induced VEGF expression was inhibited by SP600125 and U0126, which are inhibitors of JNK and MEK, respectively. Myricetin inhibited TNF-α-induced MKK4 activity and bound glutathione S-transferase-MKK4 directly by competing with ATP. Computer modeling suggested that myricetin docks onto the ATP-binding site in MKK4, which is located between the N- and C-lobes of the kinase domain. Overall, our results indicate that myricetin has potent chemopreventive effects against TNF-α-related disease, mainly by targeting MKK4 and MEK1.     

On the nanotoxicity of PAMAM dendrimers: Superfect stimulates the EGFR–ERK1/2 signal transduction pathway via an oxidative stress-dependent mechanism in HEK 293 cells

Polyamidoamine (PAMAM) dendrimers are cationic branch-like macromolecules that may serve as drug delivery systems for gene-based therapies such as RNA interference. For their safe use in the clinic, they should ideally only enhance drug delivery to target tissues and exhibit no adverse effects. However, little is known about their toxicological profiles in terms of their interactions with cellular signal transduction pathways such as the epidermal growth factor receptor (EGFR). The EGFR is an important signaling cascade that regulates cell growth, differentiation, migration, survival and apoptosis. Here, we investigated the impact of naked, unmodified Superfect (SF), a commercially available generation 6 PAMAM dendrimer, on the epidermal growth factor receptor (EGFR) tyrosine kinase–extracellular-regulated kinase 1/2 (ERK1/2) signaling pathway in human embryonic kidney (HEK 293) cells. At concentrations routinely used for transfection, SF exhibited time and dose-dependent stimulation of EGFR and ERK1/2 phosphorylation whereas AG1478, a selective EGFR tyrosine kinase antagonist, inhibited EGFR–ERK1/2 signaling. SF-induced phosphorylation of EGFR for 1 h was partly reversible upon removal of the dendrimer and examination of cells 24 later. Co-treatment of SF with epidermal growth factor (EGF) ligand resulted in greater EGFR stimulation than either agent alone implying that the stimulatory effects of SF and the ligand are synergistic. Dendrimer-induced stimulation of EGFR–ERK1/2 signaling could be attenuated by the antioxidants apocynin, catalase and tempol implying that an oxidative stress dependent mechanism was involved. These results show for the first time that PAMAM dendrimers, aside from their ability to improve drug delivery, can modulate the important EGFR–ERK1/2 cellular signal transduction pathway – a novel finding that may have a bearing on their safe application as drug delivery systems.     

Drug Discovery for Overcoming Chronic Kidney Disease (CKD): Pharmacological Effects of Mineralocorticoid-Receptor Blockers

There is increasing evidence demonstrating that the renoprotective effects of mineralocorticoid receptor (MR) blockade are independent of the effects exerted by renin-angiotensin inhibitors. MR is expressed not only in tubular cells but also in other renal cells including glomerular mesangial cells, podocytes, and renal interstitial fibroblasts. Animal experiments have shown that MR blockers prevent aldosterone-induced proteinuria, glomerular injury, and tubulointerstitial fibrosis. In vitro studies have also demonstrated that MR blockers inhibit aldosterone-induced renal cell damage. Recent clinical studies have shown that treatment with MR blockers attenuates the development of proteinuria in patients with chronic kidney disease (CKD) and hypertension, independent of changes in blood pressure. In some cases, MR blockers elicit potent renoprotective effects in conditions where aldosterone levels are not elevated. These data suggest that treatment with MR blockers may possibly present an effective therapeutic strategy for patients with CKD.