Inhibition of c-Src/p38 MAPK pathway ameliorates renal tubular epithelial cells apoptosis in db/db mice

Role of renal tubular programed cell death in diabetic kidney disease

The pathogenic mechanism of diabetic kidney disease (DKD) is involved in various functions; however, its inadequate characterisation limits the availability of effective treatments. Tubular damage is closely correlated with renal function and is thought to be the main contributor to the injury observed in early DKD. Programed cell death (PCD) occurs during the biological development of the living body. Accumulating evidence has clarified the fundamental role of abnormalities in tubular PCD during DKD pathogenesis. Among PCD types, classical apoptosis, autophagic cell death, and pyroptosis are the most studied and will be the focus of this review. Our review aims to elucidate the current knowledge of the mechanism of DKD and the potential therapeutic potential of drugs targeting tubular PCD pathways in DKD.

Pan-Src kinase inhibitor treatment attenuates diabetic kidney injury via inhibition of Fyn kinase-mediated endoplasmic reticulum stress

Src family kinases (SFKs) have been implicated in the pathogenesis of kidney fibrosis. However, the specific mechanism by which SFKs contribute to the progression of diabetic kidney disease (DKD) remains unclear. Our preliminary transcriptome analysis suggested that SFK expression was increased in diabetic kidneys and that the expression of Fyn (a member of the SFKs), along with genes related to unfolded protein responses from the endoplasmic reticulum (ER) stress signaling pathway, was upregulated in the tubules of human diabetic kidneys. Thus, we examined whether SFK-induced ER stress is associated with DKD progression. Mouse proximal tubular (mProx24) cells were transfected with Fyn or Lyn siRNA and exposed to high glucose and palmitate (HG-Pal). Streptozotocin-induced diabetic rats were treated with KF-1607, a novel pan-Src kinase inhibitor (SKI) with low toxicity. The effect of KF-1607 was compared to that of losartan, a standard treatment for patients with DKD. Among the SFK family members, the Fyn and Lyn kinases were upregulated under diabetic stress. HG-Pal induced p70S6 kinase and JNK/CHOP signaling and promoted tubular injury. Fyn knockdown but not Lyn knockdown inhibited this detrimental signaling pathway. In addition, diabetic rats treated with KF-1607 showed improved kidney function and decreased ER stress, inflammation, and fibrosis compared with those treated with losartan. Collectively, these findings indicate that Fyn kinase is a specific member of the SFKs implicated in ER stress activation leading to proximal tubular injury in the diabetic milieu and that pan-SKI treatment attenuates kidney injury in diabetic rats. These data highlight Fyn kinase as a viable target for the development of therapeutic agents for DKD.

Insights into a signaling pathway that promotes diabetic kidney disease could lead to new therapies that protect against this major cause of kidney failure. Past studies have suggested that the various Src family kinase (SFK) signaling proteins play a part in the cell death and scar tissue formation associated with diabetic kidney disease. Hunjoo Ha of Ewha Womans University, Seoul, South Korea, and colleagues have now focused on one particular SFK, Fyn, as a direct driver of the kidney damage seen in mouse models of diabetes. Genetic interventions that selectively inhibit Fyn suppressed this damage, as did treatment with an oral drug that broadly inactivates SFKs. This experimental drug proved as effective as controlling inflammation and oxidative damage in the kidney as an already clinically approved treatment, confirming the significance of SFK signaling in this condition.

Src Family Kinases: A Potential Therapeutic Target for Acute Kidney Injury

Src family kinases (SFKs) are non-receptor tyrosine kinases and play a key role in regulating signal transduction. The mechanism of SFKs in various tumors has been widely studied, and there are more and more studies on its role in the kidney. Acute kidney injury (AKI) is a disease with complex pathogenesis, including oxidative stress (OS), inflammation, endoplasmic reticulum (ER) stress, autophagy, and apoptosis. In addition, fibrosis has a significant impact on the progression of AKI to developing chronic kidney disease (CKD). The mortality rate of this disease is very high, and there is no effective treatment drug at present. In recent years, some studies have found that SFKs, especially Src, Fyn, and Lyn, are involved in the pathogenesis of AKI. In this paper, the structure, function, and role of SFKs in AKI are discussed. SFKs play a crucial role in the occurrence and development of AKI, making them promising molecular targets for the treatment of AKI.

Src Activation Aggravates Podocyte Injury in Diabetic Nephropathy via Suppression of FUNDC1-Mediated Mitophagy

Background and purpose: Mitophagy plays a significant role in the progression of diabetic nephropathy (DN), although the regulatory mechanisms remain unclear. Recently, accumulating evidence demonstrated that impaired mitochondrial function and mitophagy are involved in DN. Here, we are aimed to explore the role of c-Src (Src) and FUNDC1-related mitophagy in the development of DN.

Methods: The db/db mice were used to establish a DN mice model. The mice accepted PP2 (Src inhibitor) treatment to study the role of Src in DN. Kidney function was measured via biochemical testing. Renal histopathology and morphometric analysis were conducted via hematoxylin-eosin (HE), periodic acid-Schiff (PAS), Masson’s staining, and transmission electron microscopy (TEM). We measured degree of apoptosis in kidney by TUNEL assay. Indices of mitophagy (LC3 and p62) were evaluated by Western blotting and immunofluorescence. Complementary in vitro assays were conducted using human podocytes subjected to high glucose in combination with PP2 treatment or FUNDC1 small interfering RNAs (siRNAs). Flow cytometry was used to detect the apoptotic cells. Mitochondrial function was evaluated by JC-1 staining. Double immunofluorescence labeling of LC3 and TOMM20 used to assess the degree of mitophagy.

Results: Increased Src activation was detected in the kidneys of db/db mice, and its expression was positively correlated with mitochondrial damage, podocyte apoptosis, and renal dysfunction. Inhibition of Src activation with PP2 protected against mitochondrial damage and podocyte apoptosis. In vitro experiments in podocytes established that high glucose increased Src activation, promoting FUNDC1 phosphorylation and inhibiting mitophagy. Consistent with the mouse model, inhibiting Src activity protected podocytes against mitochondrial damage. FUNDC1 silencing negated the actions of PP2, indicating that FUNDC1-mediated mitophagy is downstream pathway of Src.

Conclusion: In summary, our data indicated that Src is a culprit factor in diabetic renal damage via suppression of FUNDC1-mediated mitophagy, promoting the development of DN.

Inhibition of p38 MAPK decreases hyperglycemia-induced nephrin endocytosis and attenuates albuminuria

Abstract

Chronic hyperglycemia, as in diabetes mellitus, may cause glomerular damage with microalbuminuria as an early sign. Noteworthy, even acute hyperglycemia can increase glomerular permeability before structural damage of the glomerular filter can be detected. Despite intensive research, specific antiproteinuric therapy is not available so far. Thus, a deeper understanding of the molecular mechanisms of albuminuria is desirable. P38 MAPK signaling is involved in the development of hyperglycemia-induced albuminuria. However, the mechanism of increased p38 MAPK activity leading to increased permeability and albuminuria remained unclear. Recently, we demonstrated that acute hyperglycemia triggers endocytosis of nephrin, the key molecule of the slit diaphragm, and induces albuminuria. Here, we identify p38 MAPK as a pivotal regulator of hyperglycemia-induced nephrin endocytosis. Activated p38 MAPK phosphorylates the nephrin c-terminus at serine 1146, facilitating the interaction of PKCα with nephrin. PKCα phosphorylates nephrin at threonine residues 1120 and 1125, mediating the binding of β-arrestin2 to nephrin. β-arrestin2 triggers endocytosis of nephrin by coupling it to the endocytic machinery, leading to increased glomerular permeability. Pharmacological inhibition of p38 MAPK preserves nephrin surface expression and significantly attenuates albuminuria.

Key messages

Acute hyperglycemia triggers endocytosis of nephrin.

Activated p38 MAPK phosphorylates the nephrin c-terminus at serine 1146, facilitating the interaction of PKCα with nephrin.

PKCα phosphorylates nephrin at threonine residues 1120 and 1125, mediating the binding of β-arrestin2 to nephrin.

β-arrestin2 triggers endocytosis of nephrin by coupling it to the endocytic machinery, leading to a leaky glomerular filter.

Pharmacological inhibition of p38 MAPK preserves nephrin surface expression and significantly attenuates albuminuria under hyperglycemic conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00109-022-02184-5.

Blocking REDD1/TXNIP Complex Ameliorates HG-Induced Renal Tubular Epithelial Cell Apoptosis and EMT through Repressing Oxidative Stress

Diabetic nephropathy (DN) has become the most common secondary kidney disease causing end-stage renal disease (ESRD). Nevertheless, the underlying mechanisms responsible for DN remain largely unknown. Regulated in development and DNA damage response 1 (REDD1) is a prooxidative molecule known to contribute to diabetes mellitus and its complications. However, it has not been previously examined whether and how REDD1 can further drive renal tubular epithelial cell (RTEC) apoptosis and epithelial-to-mesenchymal transition in DN. The expression of REDD1 was elevated in the kidneys of DN patients and diabetic mice in this study. By generating the DN model in REDD1 knockout mice, we demonstrated that REDD1 deficiency significantly improved apoptosis and EMT in diabetic mice. In vitro experiments showed that REDD1 generation was induced by high glucose (HG) in HK-2 cells. Similarly, the transfection of REDD1 siRNA plasmid also suppressed HG-induced apoptosis and EMT. Furthermore, we discovered that the inhibition of REDD1 suppressed the expression of Nox4-induced HG and reactive oxygen species (ROS) synthesis in HK-2 cells. In addition, HG could induce endogenous REDD1 and TXNIP to form a powerful complex. In summary, our findings demonstrate that blocking the REDD1/TXNIP complex can prevent HG-induced apoptosis and EMT by inhibiting ROS production, highlighting REDD1 as a valuable therapeutic priority site for DN.

PP2 Ameliorates Renal Fibrosis by Regulating the NF-κB/COX-2 and PPARγ/UCP2 Pathway in Diabetic Mice

Renal fibrosis is characterized by glomerulosclerosis and tubulointerstitial fibrosis in diabetic nephropathy (DN). We aimed to evaluate the effects of PP2 on renal fibrosis of DN. GSE33744 and GSE86300 were downloaded from the GEO database. Firstly, 839 DEGs were identified between nondiabetic and diabetic mice renal glomerular samples. COX-2 was selected to assess the effects of PP2 on renal glomerulosclerosis. In db/db mice, PP2 decreased the expression of COX-2, phosphorylated p65, and fibrotic proteins, accompanied with attenuated renal glomerulosclerosis. In cultured glomerular mesangial cells, high glucose- (HG-) induced p65 phosphorylation and COX-2 expression were attenuated by PP2 or NF-κB inhibitor PDTC. PP2, PDTC, or COX-2 inhibitor NS-398 ameliorated abnormal proliferation and expression of fibrotic proteins induced by HG. Secondly, 238 DEGs were identified between nondiabetic and diabetic mice renal cortex samples. UCP2 was selected to assess the effects of PP2 on renal tubulointerstitial fibrosis. In db/db mice, PP2 decreased the expression of PPARγ and UCP2, accompanied with attenuated renal tubulointerstitial fibrosis and EMT. In cultured proximal tubular cells, HG-induced PPARγ and UCP2 expression was inhibited by PP2 or PPARγ antagonist GW9662. PP2, GW9662, or UCP2 shRNA ameliorated HG-induced EMT. These results indicated that PP2 ameliorated renal fibrosis in diabetic mice.

Recent advances in pharmacological diversification of Src family kinase inhibitors

Background

Src kinase, a nonreceptor protein-tyrosine kinase is composed of 11 members (in human) and is involved in a wide variety of essential functions required to sustain cellular homeostasis and survival.

Main body of the abstract

Deregulated activity of Src family kinase is related to malignant transformation. In 2001, Food and Drug Administration approved imatinib for the treatment of chronic myeloid leukemia followed by approval of various other inhibitors from this category as effective therapeutics for cancer patients. In the past decade, Src family kinase has been investigated for the treatment of diverse pathologies in addition to cancer. In this regard, we provide a systematic evaluation of Src kinase regarding its mechanistic role in cancer and other diseases. Here we comment on preclinical and clinical success of Src kinase inhibitors in cancer followed by diabetes, hypertension, tuberculosis, and inflammation.

Short conclusion

Studies focusing on the diversified role of Src kinase as potential therapeutical target for the development of medicinally active agents might produce significant advances in the management of not only various types of cancer but also other diseases which are in demand for potent and safe therapeutics.

LncRNA TUG1 ameliorates diabetic nephropathy via inhibition of PU.1/RTN1 signaling pathway

Diabetic nephropathy (DN) is a leading cause of end-stage renal failure. The study aimed to investigate whether long noncoding RNA taurine-upregulated gene 1 (TUG1) can ameliorate the endoplasmic reticulum stress (ERS) and apoptosis of renal tubular epithelial cells in DN, and the underlying mechanism. The DN mouse model was established by streptozocin injection, and the human renal tubular epithelial cell line HK-2 was treated with high glucose (HG) to mimic DN in vitro. The molecular mechanism was explored through dual-luciferase activity assay, RNA pull-down assay, RNA immunoprecipitation (RIP), and chromatin immunoprecipitation (CHIP) assay. The expression of TUG1 was significantly decreased in the renal tubules of DN model mice. Overexpression of TUG1 reduced the levels of ERS markers and apoptosis markers by inhibiting reticulon-1 (RTN1) expression in HG-induced HK-2 cells. Furthermore, TUG1 down-regulated RTN1 expression by inhibiting the binding of transcription factor PU.1 to the RTN1 promoter, thereby reducing the levels of ERS markers and apoptosis markers. Meanwhile, TUG1-overexpression adenovirus plasmids injection significantly alleviated tubular lesions, and reduced RTN1 expression, ERS markers and apoptosis markers, whereas these results were reversed by injection of PU.1-overexpression adenovirus plasmids. TUG1 restrains the ERS and apoptosis of renal tubular epithelial cells and ameliorates DN through inhibition of transcription factor PU.1.

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.

Inhibition of Src Family Kinases Ameliorates LPS-Induced Acute Kidney Injury and Mitochondrial Dysfunction in Mice

Acute kidney injury (AKI), a critical syndrome characterized by a rapid decrease of kidney function, is a global health problem. Src family kinases (SFK) are proto-oncogenes that regulate diverse biological functions including mitochondrial function. Since mitochondrial dysfunction plays an important role in the development of AKI, and since unbalanced SFK activity causes mitochondrial dysfunction, the present study examined the role of SFK in AKI. Lipopolysaccharides (LPS) inhibited mitochondrial biogenesis and upregulated the expression of NGAL, a marker of tubular epithelial cell injury, in mouse proximal tubular epithelial (mProx) cells. These alterations were prevented by PP2, a pan SFK inhibitor. Importantly, PP2 pretreatment significantly ameliorated LPS-induced loss of kidney function and injury including inflammation and oxidative stress. The attenuation of LPS-induced AKI by PP2 was accompanied by the maintenance of mitochondrial biogenesis. LPS upregulated SFK, especially Fyn and Src, in mouse kidney as well as in mProx cells. These data suggest that Fyn and Src kinases are involved in the pathogenesis of LPS-induced AKI, and that inhibition of Fyn and Src kinases may have a potential therapeutic effect, possibly via improving mitochondrial biogenesis.

GADD45B Promotes Glucose-Induced Renal Tubular Epithelial-Mesenchymal Transition and Apoptosis via the p38 MAPK and JNK Signaling Pathways

Growth arrest and DNA damage-inducible beta (GADD45B) is closely linked with cell cycle arrest, DNA repair, cell survival, or apoptosis in response to stress and is known to regulate the mitogen-activated protein kinase (MAPK) pathway. Here, using an RNA sequencing approach, we determined that GADD45B was significantly upregulated in diabetic kidneys, which was accompanied by renal tubular epithelial-mesenchymal transition (EMT) and apoptosis, as well as elevated MAPK pathway activation. In vitro, GADD45B expression in cultured human kidney proximal tubular epithelial cells (HK-2 cells) was also stimulated by high glucose (HG). In addition, overexpression of GADD45B in HK-2 cells exacerbated renal tubular EMT and apoptosis and increased p38 MAPK and c-Jun N-terminal kinases (JNK) activation, whereas knockdown of GADD45B reversed these changes. Notably, the activity of extracellular regulated kinase (ERK) was not affected by GADD45B expression. Furthermore, inhibitors of p38 MAPK (SB203580) and JNK (SP600125) alleviated HG‐ and GADD45B overexpression-induced renal tubular epithelial-mesenchymal transition and apoptosis. These findings indicate a role of GADD45B in diabetes-induced renal tubular EMT and apoptosis via the p38 MAPK and JNK pathways, which may be an important mechanism of diabetic kidney injury.

Expression and Function of GABA Receptors in Myelinating Cells

Myelin facilitates the fast transmission of nerve impulses and provides metabolic support to axons. Differentiation of oligodendrocyte progenitor cells (OPCs) and Schwann cell (SC) precursors is critical for myelination during development and myelin repair in demyelinating disorders. Myelination is tightly controlled by neuron-glia communication and requires the participation of a wide repertoire of signals, including neurotransmitters such as glutamate, ATP, adenosine, or γ-aminobutyric acid (GABA). GABA is the main inhibitory neurotransmitter in the central nervous system (CNS) and it is also present in the peripheral nervous system (PNS). The composition and function of GABA receptors (GABARs) are well studied in neurons, while their nature and role in glial cells are still incipient. Recent studies demonstrate that GABA-mediated signaling mechanisms play relevant roles in OPC and SC precursor development and function, and stand out the implication of GABARs in oligodendrocyte (OL) and SC maturation and myelination. In this review, we highlight the evidence supporting the novel role of GABA with an emphasis on the molecular identity of the receptors expressed in these glial cells and the possible signaling pathways involved in their actions. GABAergic signaling in myelinating cells may have potential implications for developing novel reparative therapies in demyelinating diseases.

Sulforaphane protects against skeletal muscle dysfunction in spontaneous type 2 diabetic db/db mice

AIMS

Skeletal muscle diseases have become to be the most common complication in patients with type 2 diabetic mellitus (T2DM). However, the effective therapies against skeletal muscle diseases are not yet available. Sulforaphane (SFN) is an organic isothiocyanate found in cruciferous plants. Our aim was to explore whether SFN could attenuate the skeletal muscle diseases in spontaneous type 2 diabetic db/db mice.

MATERIALS AND METHODS

The db/m and littermate db/db mice were treated with SFN or dimethyl sulfoxide. The grip strength of mice was measured by a grasping forcing machine. The electron transmission microscopy was used to perform the skeletal muscle. The western blot was used to detect the nuclear factor E2-related factor 2/heme oxygenase 1 (Nrf2/HO-1) signal pathway related proteins, and inflammatory and apoptotic associated proteins. The mRNA levels of anti-inflammatory and anti-oxidative relative genes were detected by RT-QPCR.

KEY FINDINGS

We found that SFN could significantly increase the grip strength of the db/db mice. The lean mass and gastrocnemius mass were increased in the db/db mice after administration with SFN. Additionally, the db/db mice restored the skeletal muscle fiber organization after SFN treatment. Mechanistically, SFN could activate the Nrf2/HO-1 signal pathway, and downregulate the expression of inflammatory and apoptotic associated proteins. Furthermore, SFN could also regulate the mRNA levels of anti-inflammatory and anti-oxidative related genes.

SIGNIFICANCE

Our results demonstrated that SFN can protect against skeletal muscle diseases in db/db type 2 diabetic mice and provide a potential drug to prevent skeletal muscle dysfunction in T2DM patients.

Fyn Kinase: A Potential Therapeutic Target in Acute Kidney Injury

Acute kidney injury (AKI) is a common disease with a complex pathophysiology which significantly contributes to the development of chronic kidney disease and end stage kidney failure. Preventing AKI can consequently reduce mortality, morbidity, and healthcare burden. However, there are no effective drugs in use for either prevention or treatment of AKI. Developing therapeutic agents with pleiotropic effects covering multiple pathophysiological pathways are likely to be more effective in attenuating AKI. Fyn, a non-receptor tyrosine kinase, has been acknowledged to integrate multiple injurious stimuli in the kidney. Limited studies have shown increased Fyn transcription level and activation under experimental AKI. Activated Fyn kinase propagates various downstream signaling pathways associated to the progression of AKI, such as oxidative stress, inflammation, endoplasmic reticulum stress, as well as autophagy dysfunction. The versatility of Fyn kinase in mediating various pathophysiological pathways suggests that its inhibition can be a potential strategy in attenuating AKI.

Angiotensin II triggers RIPK3-MLKL-mediated necroptosis by activating the Fas/FasL signaling pathway in renal tubular cells

Our earlier studies proved that RIPK3-mediated necroptosis might be an important mode of renal tubular cell death in rats with chronic renal injury and the necroptotic cell death can be triggered by tumor necrosis factor-α (TNF-α) in vitro, but the triggering role of angiotensin II (AngII), which exerts notable effects on renal cells for the initiation and progression of renal tubulointerstitial fibrosis, is largely unknown. Here, we identified the presence of necroptotic cell death in the tubular cells of AngII-induced chronic renal injury and fibrosis mice and assessed the percentage of necroptotic renal tubular cell death with the disruption of this necroptosis by the addition of necrostatin-1 (Nec-1). Furthermore, the observation was further confirmed in HK-2 cells treated with AngII and RIPK1/3 or MLKL inhibitors. The detection of Fas and FasL proteins led us to investigate the contribution of the Fas/FasL signaling pathway to AngII-induced necroptosis. Disruption of FasL decreased the percentage of necroptotic cells, suggesting that Fas and FasL are likely key signal molecules in the necroptosis of HK-2 cells induced by AngII. Our data suggest that AngII exposure might trigger RIPK3-MLKL-mediated necroptosis in renal tubular epithelial cells by activating the Fas/FasL signaling pathway in vivo and in vitro.

Suppression of HDAC2 by sodium butyrate alleviates apoptosis of kidney cells in db/db mice and HG‑induced NRK‑52E cells

Butyrate is short-chain fatty acid, which is produced by intestinal microbiota metabolizing dietary fibers. Butyrate participates in various physiological processes predominantly by activating G-coupled-receptors, inhibiting histone deacetylases (HDACs) and serving as an energy substrate. Previous studies have shown that butyrate plays a protective role in diabetic nephropathy (DN); however, the exact mechanism remains unclear. The present study identified that providing sodium butyrate (NaBu) by gavage relieved renal damage and apoptosis in db/db mice, which is a widely used type 2 DN model. In vitro, NaBu suppressed high glucose (HG)-induced apoptosis in normal rat kidney tubular epithelial (NRK-52E) cells. Of the eleven HDACs (HDAC1-11) studied, only the mRNA expression of HDAC2 was attenuated by NaBu in NRK-52E cells under the HG condition. Overexpression of HDAC2 offset the anti-apoptotic effect of NaBu. NaBu also suppressed HG-induced oxidative stress. Additionally, H₂O₂ induced an upregulation of HDAC2 in NRK-52E cells, while NaBu inhibited this process. Mechanistically, NaBu acted as an antioxidant in HG-induced NRK-52E cells and suppressed HG-induced apoptosis of NRK-52E cells through inhibiting HDAC2 by virtue of its anti-oxidative property.

Src Tyrosine Kinase Inhibitors: New Perspectives on Their Immune, Antiviral, and Senotherapeutic Potential

Deregulated activity of the Src tyrosine kinases leads to malignant transformation. Since the FDA approval of the tyrosine kinase inhibitor, imatinib, in 2001 for the treatment of chronic myeloid leukemia (CML), the number of these inhibitors together with Src tyrosine kinase inhibitors (STKIs) has increased notably due to their beneficial effects. Dasatinib, a second-generation STKI inhibitor widely studied, proved high efficiency in CML patients resistant to imatinib. In the last decade STKIs have also been implicated and showed therapeutic potential for the treatment of diverse pathologies other than cancer. In this regard, we review the properties of STKIs, dasatinib in particular, including its immunomodulatory role. Similarly, the potential benefits, adverse effects, and safety concerns of these inhibitors regarding viral infections are considered. Moreover, since life expectancy has increased in the last decades accompanied by age-related morbidity, the reduction of undesirable effects associated to aging has become a powerful therapeutic target. Here, we comment on the ability of STKIs to alleviate age-associated physical dysfunction and their potential impact in the clinic.

Natural compound Oblongifolin C confers gemcitabine resistance in pancreatic cancer by downregulating Src/MAPK/ERK pathways

Gemcitabine (GEM)-induced drug resistance is the major reason for the failure of chemotherapy in pancreatic cancer (PC). In this study, we found that Oblongifolin C (OC) efficiently inhibited PC cell proliferation by inducing G0/G1 arrest and apoptosis. Also, our mechanism study demonstrated that OC re-sensitized the GEM-resistant PC cells through the ubiquitin-proteasome-dependent degradation of Src, and then downregulating the MAPK pathway. Knockdown of Src plus OC resulted in a greater inhibitory effect in GEM-resistant PC cells. In contrast, Src overexpression reversed OC-mediated chemosensitization, thereby implicating Src in the action of OC. Moreover, our in vivo study showed that OC suppressed the tumor growth via the downregulation of Src, and enhanced the chemosensitivity of GEM-resistant PC to GEM. Overall, our results have revealed that OC is applicable as a promising agent for overcoming GEM-resistant PC, especially with aberrant Src expression.

Esculin ameliorates cognitive impairment in experimental diabetic nephropathy and induces anti-oxidative stress and anti-inflammatory effects via the MAPK pathway

Esculin is a derivative of coumarin, which is also an active ingredient of ash bark, and has antibacterial, anti-inflammatory, anti‑allergy and skin protective effects. The underlying mechanism and protective effects of esculin on cognitive impairment in experimental diabetic nephropathy (DN) was investigated in the present study. Male C57BL/6J 6‑week‑old mice were injected intravenously with a single dose of streptozotocin (STZ; 30 mg/kg). At 2 weeks after the STZ injection, mice received intravenous injection with 5, 10 or 20 mg/kg esculin for 2 weeks. In the present study, the results of the Morris water maze test demonstrated that esculin significantly improved behavior and recognition memory in STZ‑induced diabetic rats. Furthermore, treatment of STZ‑induced diabetic rats with esculin significantly inhibited tumor necrosis factor‑α, interleukin‑6, malondialdehyde, monocyte chemoattractant protein‑1 and intracellular adhesion molecule‑1 activity levels, and increased the activity of superoxide dismutase, in the kidney, which was determined by ELISA. In addition, esculin treatment significantly suppressed the renal protein expression of activator protein 1, phosphorylated (p)‑p38 mitogen activated protein kinase (MAPK) and p‑c‑Jun N‑terminal kinase, and increased p‑extracellular signal regulated kinase 1/2 protein expression, in STZ‑induced diabetic rats, as determined by western blotting. These results indicate that esculin may ameliorate cognitive impairment in experimental DN, and exert anti‑oxidative stress and anti‑inflammatory effects, via the MAPK signaling pathway. Thus, it may serve as a potential target for cognitive impairment of DN in the future.

Anthocyanins inhibit high glucose-induced renal tubular cell apoptosis caused by oxidative stress in db/db mice

Oxidative stress is an important contributory factor resulting the development of kidney injury in patients with diabetes. Numerous in vitro and in vivo studies have suggested that anthocyanins, natural phenols commonly existing in numerous fruits and vegetables, exhibit important antioxidative, anti‑inflammatory and antihyperlipidemic effects; however, their effects and underlying mechanisms on diabetic nephropathy (DN) have not yet been fully determined. In the present study, the regulation of apoptosis metabolism and antioxidative effects exhibited by anthocyanins [grape seed procyanidin (GSPE) and cyanidin‑3‑O‑β‑glucoside chloride (C3G)] were investigated, and the molecular mechanism underlying this process was investigated in vivo and in vitro. GSPE administration was revealed to suppress renal cell apoptosis, as well as suppress the expression of Bcl‑2 in diabetic mouse kidneys. Furthermore, GSPE administration was demonstrated to suppress the expression of thioredoxin interacting protein (TXNIP), in addition to enhancing p38 mitogen‑activation protein kinase (MAPK) and extracellular signal‑regulated kinase 1/2 (ERK1/2) oxidase activity in diabetic mouse kidneys. In vitro experiments using HK‑2 cells revealed that C3G suppressed the generation of HG‑mediated reactive oxygen species, cellular apoptosis, the expression of cleaved caspase‑3 and the Bax/Bcl‑2 ratio; and enhanced the expression of cytochrome c released from mitochondria. Furthermore, treatment with C3G was revealed to suppress the expression of TXNIP, in addition to the phosphorylation of p38 MAPK and ERK1/2 oxidase activity in HK‑2 cells under HG conditions. In addition, treatment with C3G was revealed to attenuate the HG‑induced suppression of the biological activity of thioredoxin, and to enhance the expression of thioredoxin 2 in HK‑2 cells under HG conditions. In conclusion, the present study demonstrated that anthocyanins may exhibit protective effects against HG‑induced renal injury in DN via antioxidant activity.

Pentosan polysulfate ameliorates apoptosis and inflammation by suppressing activation of the p38 MAPK pathway in high glucose‑treated HK‑2 cells

The apoptosis of tubular epithelial cells in diabetic nephropathy (DN) is commonly observed in human renal biopsies. Inflammation plays a key role in DN, and pentosan polysulfate (PPS) has been shown to largely attenuate the inflammation of nephropathy in aging diabetic mice. p38 mitogen-activated protein kinase (p38 MAPK) plays a crucial role in tissue inflammation and cell apoptosis, and it is activated by hyperglycemia. In the present study, high glucose (HG)-treated human renal proximal tubular epithelial cells (HK-2) were used to examine the protective effects of PPS against HG-stimulated apoptosis and inflammation. The results of the study revealed that PPS markedly suppressed the HG-induced reduction in cell viability. Incubation of HK-2 cells with HG activated the p38 MAPK pathway and, subsequently, as confirmed by western blot analysis and flow cytometry, increased cell apoptosis, which was blocked by PPS. In addition, PPS treatment significantly inhibited HG-stimulated p38 MAPK and nuclear factor-κB activation, and reduced the production of pro-inflammatory cytokines, such as tumor necrosis factor-α, interleukin (IL)-1β and IL-6. In conclusion, PPS ameliorates p38 MAPK-mediated renal cell apoptosis and inflammation. The anti-apoptotic actions and anti-inflammatory effects of PPS prompt further investigation of this compound as a promising therapeutic agent against DN.

Src family kinases in chronic kidney disease

Src family kinases (SFKs) belong to nonreceptor protein tyrosine kinases and have been implicated in the regulation of numerous cellular processes, including cell proliferation, differentiation, migration and invasion, and angiogenesis. The role and mechanisms of SFKs in tumorgenesis have been extensively investigated, and some SFK inhibitors are currently under clinical trials for tumor treatment. Recent studies have also demonstrated the importance of SFKs in regulating the development of various fibrosis-related chronic diseases (e.g., idiopathic pulmonary fibrosis, liver fibrosis, renal fibrosis, and systemic sclerosis). In this article, we summarize the roles of SFKs in various chronic kidney diseases, including glomerulonephritis, diabetic nephropathy, human immunodeficiency virus-associated nephropathy, autosomal dominant form of polycystic kidney disease, and obesity-associated kidney disease, and discuss the mechanisms involved.

Mesenchymal stem cell therapy ameliorates diabetic nephropathy via the paracrine effect of renal trophic factors including exosomes

Bone marrow-derived mesenchymal stem cells (MSCs) have contributed to the improvement of diabetic nephropathy (DN); however, the actual mediator of this effect and its role has not been characterized thoroughly. We investigated the effects of MSC therapy on DN, focusing on the paracrine effect of renal trophic factors, including exosomes secreted by MSCs. MSCs and MSC-conditioned medium (MSC-CM) as renal trophic factors were administered in parallel to high-fat diet (HFD)-induced type 2 diabetic mice and streptozotocin (STZ)-induced insulin-deficient diabetic mice. Both therapies showed approximately equivalent curative effects, as each inhibited the exacerbation of albuminuria. They also suppressed the excessive infiltration of BMDCs into the kidney by regulating the expression of the adhesion molecule ICAM-1. Proinflammatory cytokine expression (e.g., TNF-α) and fibrosis in tubular interstitium were inhibited. TGF-β1 expression was down-regulated and tight junction protein expression (e.g., ZO-1) was maintained, which sequentially suppressed the epithelial-to-mesenchymal transition of tubular epithelial cells (TECs). Exosomes purified from MSC-CM exerted an anti-apoptotic effect and protected tight junction structure in TECs. The increase of glomerular mesangium substrate was inhibited in HFD-diabetic mice. MSC therapy is a promising tool to prevent DN via the paracrine effect of renal trophic factors including exosomes due to its multifactorial action.

Leptin Promotes cPLA₂ Gene Expression through Activation of the MAPK/NF-κB/p300 Cascade

Hyperplasia or hypertrophy of adipose tissues plays a crucial role in obesity, which is accompanied by the release of leptin. Recently, obesity was determined to be associated with various pulmonary diseases including asthma, acute lung injury, and chronic obstructive pulmonary disease. However, how obesity contributes to pulmonary diseases and whether leptin directly regulates lung inflammation remains unclear. We used cell and animal models to study the mechanisms of leptin mediation of pulmonary inflammation. We found that leptin activated de novo synthesis of cytosolic phospholipase A₂-α (cPLA₂-α) in vitro in the lung alveolar type II cells, A549, and in vivo in ICR mice. Upregulated cPLA₂-α protein was attenuated by pretreatment with an OB-R blocking antibody, U0126, SB202190, SP600125, Bay11-7086, garcinol, and p300 siRNA, suggesting roles of p42/p44 MAPK, p38 MAPK, JNK1/2, NF-κB, and p300 in leptin effects. Leptin enhanced the activities of p42/p44 MAPK, p38 MAPK, JNK1/2, and p65 NF-κB in a time-dependent manner. Additional studies have suggested the participation of OB-R, p42/p44 MAPK, and JNK1/2 in leptin-increased p65 phosphorylation. Furthermore, p300 phosphorylation and histone H4 acetylation were reduced by blockage of OB-R, p42/p44 MAPK, p38 MAPK, JNK1/2, and NF-κB in leptin-stimulated cells. Similarly, blockage of the MAPKs/NF-κB/p300 cascade significantly inhibited leptin-mediated cPLA₂-α mRNA expression. Our data as a whole showed that leptin contributed to lung cPLA₂-α expression through OB-R-dependent activation of the MAPKs/NF-κB/p300 cascade.