Inhibition of p38-MAPK potentiates cisplatin-induced apoptosis via GSH depletion and increases intracellular drug accumulation in growth-arrested kidney tubular epithelial cells

The Interplay between the DNA Damage Response (DDR) Network and the Mitogen-Activated Protein Kinase (MAPK) Signaling Pathway in Multiple Myeloma

The DNA damage response (DDR) network and the mitogen-activated protein kinase (MAPK) signaling pathway are crucial mechanisms for the survival of all living beings. An accumulating body of evidence suggests that there is crosstalk between these two systems, thus favoring the appropriate functioning of multi-cellular organisms. On the other hand, aberrations within these mechanisms are thought to play a vital role in the onset and progression of several diseases, including cancer, as well as in the emergence of drug resistance. Here, we provide an overview of the current knowledge regarding alterations in the DDR machinery and the MAPK signaling pathway as well as abnormalities in the DDR/MAPK functional crosstalk in multiple myeloma, the second most common hematologic malignancy. We also present the latest advances in the development of anti-myeloma drugs targeting crucial DDR- and MAPK-associated molecular components. These data could potentially be exploited to discover new therapeutic targets and effective biomarkers as well as for the design of novel clinical trials. Interestingly, they might provide a new approach to increase the efficacy of anti-myeloma therapy by combining drugs targeting the DDR network and the MAPK signaling pathway.

Eucalyptol alleviates cisplatin-induced kidney damage in rats

This study was aimed to explore the therapeutic effect of eucalyptol on cisplatin induced kidney damage in Wistar albino rats. The animals were divided into four groups: sham (S), eucalyptol (E), cisplatin (C), and cisplatin + eucalyptol (CE) randomly, six animals in each group. Groups C and CE were received cisplatin (12 mg/kg, a single dose, intraperitoneally (i.p.)). Groups E and CE were treated with eucalyptol (100 mg/kg, for seven days, orally). The blood samples and kidney tissues were collected following sacrification and analyzed histopathologically and biochemically. Histopathological results revealed tubular degeneration and necrosis, inflammatory cell infiltration, tubular lumen dilatation, enlargement of bowman's space and hyaline cast were significantly irregular in the group C than group S. However, eucalyptol treatment (CE) modulated the alterations in the group C. Serum levels of blood urea nitrogen (BUN) and creatinine (CRE) were considerably higher in the group C compared to the other groups. There was no significant difference among the other groups statistically (except group C) in terms of BUN and CRE values. Eucalyptol treatment (at 100 mg/kg, for seven days) decreased the cisplatin induced increase in serum BUN and CRE levels and restored the reduced Vit C level and CAT activity of kidneys caused by cisplatin. Thus, eucalyptol's antioxidative, nephroprotective, and curative effects indicated the potential for future drug development.

Identification of Renoprotective Phytosterols from Mulberry (Morus alba) Fruit against Cisplatin-Induced Cytotoxicity in LLC-PK1 Kidney Cells

The aim of this study was to explore the protective effects of bioactive compounds from the fruit of the mulberry tree (Morus alba L.) against cisplatin-induced apoptosis in LLC-PK1 pig kidney epithelial cells. Morus alba fruit is a well-known edible fruit commonly used in traditional folk medicine. Chemical investigation of M. alba fruit resulted in the isolation and identification of six phytosterols (1-6). Their structures were determined as 7-ketositosterol (1), stigmast-4-en-3β-ol-6-one (2), (3β,6α)-stigmast-4-ene-3,6-diol (3), stigmast-4-ene-3β,6β-diol (4), 7β-hydroxysitosterol 3-O-β-d-glucoside (5), and 7α-hydroxysitosterol 3-O-β-d-glucoside (6) by analyzing their physical and spectroscopic data as well as liquid chromatography/mass spectrometry data. All compounds displayed protective effects against cisplatin-induced LLC-PK1 cell damage, improving cisplatin-induced cytotoxicity to more than 80% of the control value. Compound 1 displayed the best effect at a relatively low concentration by inhibiting the percentage of apoptotic cells following cisplatin treatment. Its molecular mechanisms were identified using Western blot assays. Treatment of LLC-PK1 cells with compound 1 decreased the upregulated phosphorylation of p38 and c-Jun N-terminal kinase (JNK) following cisplatin treatment. In addition, compound 1 significantly suppressed cleaved caspase-3 in cisplatin-induced LLC-PK1 cells. Taken together, these findings indicated that cisplatin-induced apoptosis was significantly inhibited by compound 1 in LLC-PK1 cells, thereby supporting the potential of 7-ketositosterol (1) as an adjuvant candidate for treating cisplatin-induced nephrotoxicity.

Protective Effect of Panaxynol Isolated from Panax vietnamensis against Cisplatin-Induced Renal Damage: In Vitro and In Vivo Studies

Polyacetylenic compounds isolated from Panax species are comprised of non-polar C17 compounds, exhibiting anti-inflammatory, antitumor, and antifungal activities. Panaxynol represents the major component of the essential oils of ginseng. We investigated whether panaxynol isolated from Panax vietnamensis (Vietnamese ginseng, VG) could prevent cisplatin-induced renal damage induced in vitro and in vivo. Cisplatin-induced apoptotic cell death was observed by staining with annexin V conjugated with Alexa Fluor 488, and western blotting evaluated the molecular mechanism. Panaxynol at concentrations above 0.25 μM prevented cisplatin-induced LLC-PK1 porcine renal proximal tubular cell death. LLC-PK1 cells treated with cisplatin demonstrated an increase in apoptotic cell death, whereas pretreatment with 2 and 4 μM panaxynol decreased this effect. Cisplatin demonstrated a marked increase in the phosphorylation of c-Jun N-terminal kinase (JNK), P38, and cleaved caspase-3. However, pretreatment with 2 and 4 μM panaxynol reversed the upregulated phosphorylation of JNK, P38, and the expression of cleaved caspase-3. We confirmed that the protective effect of panaxynol isolated from P. vietnamensis in LLC-PK1 cells was at least partially mediated by reducing the cisplatin-induced apoptotic damage. In the animal study, panaxynol treatment ameliorated body weight loss and blood renal function markers and downregulated the mRNA expression of inflammatory mediators.

Comprehensive review on how platinum- and taxane-based chemotherapy of ovarian cancer affects biology of normal cells

One of the most neglected aspects of chemotherapy are changes, and possible consequences of these changes, that occur in normal somatic cells. In this review, we summarize effects of selected drugs used to treat ovarian cancer (platin derivatives-cisplatin and carboplatin; and taxanes-paclitaxel and docetaxel) on cellular metabolism, acquisition of reactive stroma features, cellular senescence, inflammatory reactions, apoptosis, autophagy, mitophagy, oxidative stress, DNA damage, and angiogenesis in various types of normal cells, including fibroblasts, epithelial cells, endothelial cells, and neurons. The activity of these drugs against the normal cells is presented from a broader perspective of their desirable anti-tumoral effects.

Cisplatin based therapy: the role of the mitogen activated protein kinase signaling pathway

Cisplatin is a widely used chemotherapeutic agent for treatment of various cancers. However, treatment with cisplatin is associated with drug resistance and several adverse side effects such as nephrotoxicity, reduced immunity towards infections and hearing loss. A Combination of cisplatin with other drugs is an approach to overcome drug resistance and reduce toxicity. The combination therapy also results in increased sensitivity of cisplatin towards cancer cells. The mitogen activated protein kinase (MAPK) pathway in the cell, consisting of extracellular signal regulated kinase, c-Jun N-terminal kinase, p38 kinases, and downstream mediator p90 ribosomal s6 kinase (RSK); is responsible for the regulation of various cellular events including cell survival, cell proliferation, cell cycle progression, cell migration and protein translation. This review article demonstrates the role of MAPK pathway in cisplatin based therapy, illustrates different combination therapy involving cisplatin and also shows the importance of targeting MAPK family, particularly RSK, to achieve increased anticancer effect and overcome drug resistance when combined with cisplatin.

Beneficial Effects of Bioactive Compounds in Mulberry Fruits against Cisplatin-Induced Nephrotoxicity

Mulberry, the fruit of white mulberry tree (Morus alba L., Moraceae), is commonly used in traditional Chinese medicines as a sedative, tonic, laxative, and emetic. In our continuing research of the bioactive metabolites from mulberry, chemical analysis of the fruits led to the isolation of five compounds, 1–5. The compounds were identified as butyl pyroglutamate (1), quercetin 3-O-β-d-glucoside (2), kaempferol 3-O-β-d-rutinoside (3), rutin (4), and 2-phenylethyl d-rutinoside (5) by spectroscopic data analysis, comparing their nuclear magnetic resonance (NMR) data with those in published literature, and liquid chromatography–mass spectrometry analysis. The isolated compounds 1–5 were evaluated for their effects on anticancer drug-induced side effects by cell-based assays. Compound 1 exerted the highest protective effect against cisplatin-induced kidney cell damage. This effect was found to be mediated through the attenuation of phosphorylation of c-Jun N-terminal kinase, extracellular signal-regulated kinase, p38, mitogen-activated protein kinase, and caspase-3 in cisplatin-induced kidney cell damage.

Chemical Characterization of a Renoprotective Metabolite from Termite-Associated Streptomyces sp. RB1 against Cisplatin-Induced Cytotoxicity

Platinum-based anticancer drug therapies can cause renal damage and apoptotic kidney cell damage. The development of reno- and kidney-protective molecules is therefore urgently required. To address this challenge, we explored secondary metabolites of termite-associated Streptomyces sp. RB1 isolated from the cuticle of the South African termite, Macrotermes natalensis for their renoprotective ability using bioassay-guided fractionation and LLC-PK1 cells. Chemical investigation of the MeOH extract of Streptomyces sp. RB1 resulted in the isolation and identification of a renoprotective metabolite, 1-O-(2-aminobenzoyl)-α-l-rhamnopyranoside (ABR) (1) from the active fraction, which ameliorated cisplatin-induced cytotoxicity to 80% of the control value at 25 μM. Upregulated phosphorylation of c-Jun N-terminal kinases (JNK) and p38 following cisplatin treatment was markedly decreased after pre-treatment of cells with ABR. In addition, levels of cleaved caspase-3 and the percentage of apoptotic cells were also significantly reduced after pre-treatment with ABR. These findings provide experimental evidence that blocking the MAPK signaling cascade plays a critical role in mediating the renoprotective effect of ABR, which may inspire the development of novel therapeutic substances to prevent anticancer drug-induced nephrotoxicity.

Identification of noninvasive biomarkers for nephrotoxicity using HK-2 human kidney epithelial cells

The kidney is an important site of xenobiotic-induced toxicity. Because the traditional markers of renal injury indicate only severe renal damage, new biomarkers are needed for a more sensitive and reliable evaluation of renal toxicity. This study was designed to identify in vitro noninvasive biomarkers for efficient assessment of nephrotoxicity by using cisplatin as a model of nephrotoxic compounds. To this end, a comparative proteomic analysis of conditioned media from HK-2 human kidney epithelial cells treated with cisplatin was performed. Here, we identified pyruvate kinase M1/M2 isoform M2 (PKM2) and eukaryotic translation elongation factor 1 gamma (EF-1γ) as potential biomarker candidates for evaluation of nephrotoxicity. PKM2 and EF-1γ were increased by cisplatin in a kidney cell-specific manner, most likely due to cisplatin-induced apoptosis. The increase of PKM2 and EF-1γ levels in conditioned media was also observed in the presence of other nephrotoxic agents with different cytotoxic mechanisms such as CdCl2, HgCl2, and cyclosporine A. Rats treated with cisplatin, CdCl2, or HgCl2 presented increased levels of PKM2 and EF-1γ in the urine and kidney tissue. Taken together, this study identified two noninvasive biomarker candidates, PKM2 and EF-1γ, by comparative proteomic analysis. These new biomarkers may offer an alternative to traditional renal markers for efficient evaluation of nephrotoxicity.

Loss of α(E)-catenin potentiates cisplatin-induced nephrotoxicity via increasing apoptosis in renal tubular epithelial cells

Cisplatin is one of the most potent and widely used antitumor drugs. However, the use of cisplatin is limited by its side effect, nephrotoxicity. Evidence has shown an increased incidence and severity of acute kidney injury (AKI) in the elderly. Previous studies from our laboratory demonstrate a decrease in α(E)-catenin expression in aged kidney. In this study, we investigated whether the loss of α(E)-catenin may increase cisplatin nephrotoxicity. To study the effects of reduced α(E)-catenin, a cell line with stable knockdown of α(E)-catenin (C2 cells) was used; NT3 is nontargeted control. C2 cells exhibited a significant loss of viability as determined by MTT assay compared with NT3 cells after cisplatin challenge, but showed no difference in lactate dehydrogenase (LDH) leakage. Increased caspase 3/7 activation and PARP cleavage was observed in C2 cells after cisplatin treatment. Z-VAD, a pan-caspase inhibitor, abolished the difference in susceptibility between NT3 and C2 cells. Interestingly, the expression of α(E)-catenin was further decreased after cisplatin treatment. Furthermore, in vivo data demonstrated a significant increase in serum creatinine at 72 h after a single dose of cisplatin in 24-month-old rats, but not in 4-month-old rats. Increased expression of KIM-1 and in situ apoptosis were also detected in aged kidney after cisplatin challenge. Taken together, these data suggest that loss of α(E)-catenin increases apoptosis of tubular epithelial cells which may contribute to the increased nephrotoxicity induced by cisplatin in aged kidney.

Bone marrow-derived mesenchymal stem cells protect against cisplatin-induced acute kidney injury in rats by inhibiting cell apoptosis

Acute kidney injury (AKI) is a common syndrome with a high mortality and morbidity rate. Recent developments in stem cell research have shown great promise for the treatment of AKI. The aim of this study was to investigate the therapeutic potential and anti-apoptotic mechanisms of action of bone marrow-derived mesenchymal stem cells (BM-MSCs) in the treatment of AKI induced by cisplatin in vivo and in vitro. In vivo, adult male Sprague-Dawley rats (n=24) were administered BM-MSCs intravenously one day after cisplatin injection. The rats were sacrificed four days after the cisplatin injection and the effects of BM-MSCs on cisplatin-induced AKI, as well as the anti-apoptotic mechanisms involved were investigated. In vitro, NRK-52E cells, a rat renal proximal tubular cell line, were incubated in conditioned medium or complete medium in the presence or absence of cisplatin, followed by cell proliferation and apoptosis assays. The infusion of BM-MSCs preserved renal function, ameliorated renal tubular lesions, reduced apoptosis and accelerated tubular cell regeneration in the rats with cisplatin-induced AKI. The infusion of BM-MSCs also inhibited the activation of two mitogen-activated protein kinases, p38 and ERK, downregulated the expression of Bax and cleaved caspase-3, and upregulated the expression of Bcl-2. BM-MSC-conditioned medium improved NRK-52E cell viability and inhibited apoptosis. In conclusion, our results demonstrate that injecting rats with BM-MSCs protects renal function and structure in cisplatin-induced AKI by inhibiting cell apoptosis in vivo. BM-MSC-conditioned medium protects renal cells from apoptosis induced by cisplatin in vitro. Hence, the infusion of BM-MSCs should be considered as a possible therapeutic strategy for the treatment of AKI.

MK5 is degraded in response to doxorubicin and negatively regulates doxorubicin-induced apoptosis in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. The mechanisms by which hepatoma cells resist apoptosis induced by doxorubicin are largely unknown. MAPKAPK5 (MK5), also named as p38-regulated/activated protein kinase (PRAK), has been identified as a crucial mediator of skin tumorigenesis in mouse and colon cancerogenesis in human. Here, we describe a novel role of MK5 in doxorubicin-induced apoptosis in human hepatoma cells. Expression of MK5 was highly upregulated in hepatoma cell lines. Doxorubicin rather than other chemotherapeutic drugs reduced MK5 protein level in a time- and concentration-dependent manner in hepatoma cells (HepG2 and Hep3B). We further showed that MK5 degradation induced by doxorubicin was via the 26S proteasome. Remarkably, stable overexpression of MK5 led to decreased cleavage of caspase-3 and PARP and attenuated doxorubicin-induced apoptosis, while stable knockdown of endogenous MK5 sensitized hepatoma cells to doxorubicin, which was coupled with increased cleavage of caspase-3 and PARP. Taken together, our results firstly demonstrate that MK5 is degraded in response to doxorubicin and negatively regulates doxorubicin-induced apoptosis, providing novel insights into the molecular mechanism of doxorubicin resistance in hepatoma cells.

Induction of autophagy in hepatocellular carcinoma cells by SB203580 requires activation of AMPK and DAPK but not p38 MAPK

SB203580 is a well-known inhibitor of p38 mitogen-activated protein kinase (MAPK). However, it can suppress cell proliferation in a p38 MAPK independent manner. The inhibitory mechanism remains unknown. Here, we showed that SB203580 induced autophagy in human hepatocellular carcinoma (HCC) cells. SB203580 increased GFP-LC3-positive cells with GFP-LC3 dots, induced accumulation of autophagosomes, and elevated the levels of microtubule-associated protein light chain 3 and Beclin 1. It stimulated the phosphorylation of adenosine monophosphate-activated protein kinase (AMPK) and p53, but inhibited the phosphorylation of death-associated protein kinase (DAPK). Inhibition of AMPK, p53, or DAPK attenuated SB203580-induced autophagy. AMPK activation appeared to predate the DAPK signal. The activation of both AMPK and DAPK prompted the phosphorylation of p53 and enhanced Beclin 1 expression. Neither the downregulation of p38 MAPK by its siRNA or chemical inhibitor nor the upregulation of p38 MAPK by p38 MAPK DNA transfection affected B203580-induced autophagy. Collectively, the findings demonstrate a novel function of SB203580 to induce autophagy via activating AMPK and DAPK but independent of p38 MAPK. The induction of autophagy can thus account for the antiproliferative effect of SB203580 in HCC cells.

Glutathione homeostasis and functions: potential targets for medical interventions

Glutathione (GSH) is a tripeptide, which has many biological roles including protection against reactive oxygen and nitrogen species. The primary goal of this paper is to characterize the principal mechanisms of the protective role of GSH against reactive species and electrophiles. The ancillary goals are to provide up-to-date knowledge of GSH biosynthesis, hydrolysis, and utilization; intracellular compartmentalization and interorgan transfer; elimination of endogenously produced toxicants; involvement in metal homeostasis; glutathione-related enzymes and their regulation; glutathionylation of sulfhydryls. Individual sections are devoted to the relationships between GSH homeostasis and pathologies as well as to developed research tools and pharmacological approaches to manipulating GSH levels. Special attention is paid to compounds mainly of a natural origin (phytochemicals) which affect GSH-related processes. The paper provides starting points for development of novel tools and provides a hypothesis for investigation of the physiology and biochemistry of glutathione with a focus on human and animal health.

Inhibition of glutathione synthesis reverses Krüppel-like factor 4-mediated cisplatin resistance

PURPOSE

To explore the protective effect of KLF4 against cytotoxicity induced by cisplatin and its possible mechanisms.

METHODS

The expression levels of KLF4 were detected by RT-PCR and western blot in cancer stem-like cells derived from hepatocarcinoma (T3A-A3) and the hepatocarcinoma cell line HepG2. KLF4 was knocked down in T3A-A3 by infection of pLVTHM-shKLF4 lentivirus and ectopic expressed in HepG2 by infection of pWPTS-KLF4 lentivirus. The MTT assay was carried out to determine the impact of KLF4 on cell survival in response to cisplatin. Cisplatin-induced DNA damage was measured by TUNEL staining. Glutathione content was measured by enzymatic assay. Buthionine sulfoximine was used to deplete the content of glutathione. The expression of γ-glutamylcysteine synthetase was analyzed by RT-PCR in HepG2 cells ectopic expressed KLF4.

RESULTS

With a higher level of KLF4, T3A-A3 cells were found to be more resistant to cisplatin than HepG2 cells. KLF4 knockdown was found to reduce cisplatin resistance in T3A-A3 cells. Ectopic expression of KLF4 in HepG2 cells was found to be associated with heightened resistance to DNA damage after exposure to cisplatin. Furthermore, the content of glutathione was found to be higher in T3A-A3 cells than in HepG2 cells. A nearly twofold increase in the cellular level of glutathione was identified in HepG2 cells with ectopic expression of KLF4. This was accompanied by heightened resistance to cisplatin. KLF4-mediated resistance to cisplatin in HepG2 cells was found to be completely abrogated by treatment with buthionine sulfoximine, an inhibitor of glutathione synthesis, which did not affect the expression of KLF4. Moreover, the mRNA expression of γ-glutamylcysteine synthetase, a rate-limiting enzyme of glutathione synthesis was up-regulated by KLF.

CONCLUSION

We conclude that KLF4 regulates the cellular sensitivity to cisplatin in hepatocarcinoma stem-like cells and hepatocarcinoma cells by elevating intracellular glutathione levels.