p53-dependent caspase-2 activation in mitochondrial release of apoptosis-inducing factor and its role in renal tubular epithelial cell injury

Piracetam mitigates nephrotoxicity induced by cisplatin via the AMPK-mediated PI3K/Akt and MAPK/JNK/ERK signaling pathways

AIMS

Cisplatin (CDDP) is commonly employed as an antineoplastic agent, but its use is significantly limited by the occurrence of dose-dependent nephrotoxicity, the detailed mechanisms of which remain unclear. This research is aimed to explore the molecular mechanisms of Piracetam (PIR)'s protective effects on nephrotoxicity resulting from CDDP exposure and to elucidate the mechanisms responsible for these effects.

MAIN METHODS

PIR was given in dosages of 100 and 300 mg/kg body weight for a duration of 15 days; concurrently, on the last day, a single 10 mg/kg dose of CDDP was delivered via intraperitoneal injection. Forty-eight hours post-CDDP injection, the animals were sacrificed to assess nephrotoxicity. Blood samples and renal tissues were taken for biochemical and histopathological investigations. Serum creatinine and blood urea nitrogen (BUN) were measured. AMP-activated protein kinase (AMPK), caspase-9 and nuclear factor kappa b p65 (NF-κB p65) were assessed by immunohistochemistry method. Enzyme-linked immunosorbent assay (ELISA) analysis was employed to determine cytochrome c (Cyt. c), Bcl-2-associated X-protein (BAX), caspase-3, nuclear factor erythroid 2-related factor 2 (Nrf2), Heme oxygenase-1 (HO-1), superoxide dismutase (SOD), tumor necrosis factor alpha (TNF-α), myeloperoxidase (MPO), and interleukin-1β (IL-1β) levels in renal tissue homogenates. The mRNA levels of tumor protein P53 (TP53), phosphatidylinositol-3 kinase (PI3K), protein kinase B (Akt), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinases (ERK), and c-Jun N-terminal kinases (JNK) were tested by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, histopathological evaluations of the renal tissues and the binding affinity of PIR to AMPK by molecular docking were also performed.

KEY FINDINGS

Pre-treatment with PIR enhanced renal function markers such as urea and creatinine, mitigated histological damage, and diminished inflammatory cell presence in renal tubules. PIR demonstrated antioxidant effects by reestablishing the equilibrium between pro-oxidants and antioxidants such as MPO, HO-1, Nrf2, as well as SOD. Furthermore, PIR inhibited the inflammatory pathways through the MAPK/NF-κB pathway. Additionally, PIR counteracted the CDDP-induced decline in PI3K/Akt activity and hindered caspase-dependent apoptotic processes.

SIGNIFICANCE

In summary, PIR appears to be an effective therapeutic strategy for reducing CDDP-induced nephrotoxicity, attributed to its antioxidant, anti-inflammatory, and antiapoptotic mechanisms. Consequently, PIR may serve as a complementary treatment alongside CDDP to alleviate nephrotoxicity associated with CDDP.

Cisplatin Nephrotoxicity: Novel Insights Into Mechanisms and Preventative Strategies

Cisplatin is a highly effective chemotherapeutic agent that has been used for more than 50 years for a variety of cancers; however, its use is limited by toxicity, including nephrotoxicity. In this in-depth review, we discuss the incidence of cisplatin-associated acute kidney injury, as well as common risk factors for its development. Cisplatin accumulates in the kidney tubules and causes AKI through various mechanisms, including DNA damage, oxidative stress, and apoptosis. We also discuss the spectrum of nephrotoxicity, including acute and chronic impairment of kidney function, electrolyte disturbances, and thrombotic microangiopathy. We discuss the limited options for the diagnosis, prevention, and management of these complications, along with factors that may impact future therapy with or without cisplatin. We conclude with directions for future research in this expanding and important area.

Mathematical Models of Death Signaling Networks

This review provides an overview of the progress made by computational and systems biologists in characterizing different cell death regulatory mechanisms that constitute the cell death network. We define the cell death network as a comprehensive decision-making mechanism that controls multiple death execution molecular circuits. This network involves multiple feedback and feed-forward loops and crosstalk among different cell death-regulating pathways. While substantial progress has been made in characterizing individual cell death execution pathways, the cell death decision network is poorly defined and understood. Certainly, understanding the dynamic behavior of such complex regulatory mechanisms can be only achieved by applying mathematical modeling and system-oriented approaches. Here, we provide an overview of mathematical models that have been developed to characterize different cell death mechanisms and intend to identify future research directions in this field.

Platinum drugs and taxanes: can we overcome resistance?

Cancer therapy is aimed at the elimination of tumor cells and acts via the cessation of cell proliferation and induction of cell death. Many research publications discussing the mechanisms of anticancer drugs use the terms "cell death" and "apoptosis" interchangeably, given that apoptotic pathways are the most common components of the action of targeted and cytotoxic compounds. However, there is sound evidence suggesting that other mechanisms of drug-induced cell death, such as necroptosis, ferroptosis, autophagy, etc. may significantly contribute to the fate of cancer cells. Molecular cross-talks between apoptotic and nonapoptotic death pathways underlie the successes and the failures of therapeutic interventions. Here we discuss the nuances of the antitumor action of two groups of the widely used anticancer drugs, i.e., platinum salts and taxane derivatives. The available data suggest that intelligent interference with the choice of cell death pathways may open novel opportunities for cancer treatment.

A Switch in p53 Dynamics Marks Cells That Escape from DSB-Induced Cell Cycle Arrest

Cellular responses to stimuli can evolve over time, resulting in distinct early and late phases in response to a single signal. DNA damage induces a complex response that is largely orchestrated by the transcription factor p53, whose dynamics influence whether a damaged cell will arrest and repair the damage or will initiate cell death. How p53 responses and cellular outcomes evolve in the presence of continuous DNA damage remains unknown. Here, we have found that a subset of cells switches from oscillating to sustained p53 dynamics several days after undergoing damage. The switch results from cell cycle progression in the presence of damaged DNA, which activates the caspase-2-PIDDosome, a complex that stabilizes p53 by inactivating its negative regulator MDM2. This work defines a molecular pathway that is activated if the canonical checkpoints fail to halt mitosis in the presence of damaged DNA.

Tsabar et al. show that a subset of cells switches from oscillatory to sustained p53 dynamics more than 24 h after irradiation-induced DNA damage. Switching is maximal at intermediate radiation doses, requires escape from irradiation-induced cell cycle arrest, and is facilitated by caspase-2-PIDDosome-mediated degradation of p53’s inhibitor MDM2.

NAM protects against cisplatin-induced acute kidney injury by suppressing the PARP1/p53 pathway

Cisplatin is a commonly used anti-cancer drug, but it induces nephrotoxicity. As a water-soluble vitamin B family member, nicotinamide (NAM) was recently demonstrated to have beneficial effects for renal injury, but its underlying mechanism remains largely unclear. Here, we suggest that NAM may exert protective effects against cisplatin-induced acute kidney injury (AKI) mainly via suppressing the poly ADP-ribose polymerase 1 (PARP1)/p53 pathway. In our experiment, NAM protected against cisplatin-induced apoptosis both in cultured renal proximal tubular cells and AKI in mice. Mechanistically, NAM suppressed the expression and activation of p53, a known mediator of cisplatin-induced AKI. Upstream of p53, NAM attenuated the induction of γ-H2AX, a hallmark of DNA damage response. Interestingly, PARP1 was activated in cisplatin AKI and this activation was inhibited by NAM. Pharmacological inhibition of PARP1 with PJ34 significantly ameliorated p53 activation and cisplatin-induced cell death in RPTCs and AKI in mice. Thus, NAM may protect against cisplatin-induced AKI by suppressing the PARP1/p53 pathway.

Apoptosis-Inducing Factor, Protein Expression, and Apoptosis Changes with Glutamine in Podocytes Cells Exposed with Cisplatin

Cisplatin is a well-known chemotherapeutic drug. It is one of the most effective anticancer agents and is widely used for the treatment of several types of tumors. However, side effects in normal tissues and organs, such as nephrotoxicity that induces apoptosis in epithelial cells in the kidney, limit the use of cisplatin. Glutamine is a substrate for the synthesis of glutathione as an antioxidant and promotes HSP70 release, protecting cells from apoptosis induced by different stimuli. In the present study, we investigated the protective effect of glutamine on cisplatin nephrotoxicity in the kidney. Mice were divided into three groups such as a group of control (P0), a group of intraperitoneal injection of a single dose cisplatin 20 mg/kg BW at 7th day (P1), and a group of intravenous glutamine injection 100 mg/kg BW at days 1–7 and given an intraperitoneal injection of single dose cisplatin 20 mg/kg BW at 7th day (P2). Measurement of AIF expression and apoptotic cells was carried out by immunohistochemical methods. The number of AIF expressions and apoptotic cells is expressed in the Allred score. AIF expression result is as follows: P0: 3.29 ± 0.79, P1: 5.32 ± 0.68, and P2: 4.49 ± 0.47. Apoptosis result is as follows: P0: 3.04 ± 0.70, P1: 5.26 ± 0.53, and P2: 4.44 ± 0.41. There is a decreased expression of AIF on intravenous glutamine administration, followed by a decrease in apoptosis in the podocyte. In conclusion, glutamine administration might represent the treatment of nephrotoxic-induced cisplatin.

Ferrotoxicity and Its Amelioration by Calcitriol in Cultured Renal Cells

Globally, acute kidney injury (AKI) is associated with significant mortality and an enormous economic burden. Whereas iron is essential for metabolically active renal cells, it has the potential to cause renal cytotoxicity by promoting Fenton chemistry-based oxidative stress involving lipid peroxidation. In addition, 1,25-dihydroxyvitamin D3 (calcitriol), the active form of vitamin D, is reported to have an antioxidative role. In this study, we intended to demonstrate the impact of vitamin D on iron-mediated oxidant stress and cytotoxicity of Vero cells exposed to iohexol, a low osmolar iodine-containing contrast media in vitro. Cultured Vero cells were pretreated with 1,25-dihydroxyvitamin D3 dissolved in absolute ethanol (0.05%, 2.0 mM) at a dose of 1 mM for 6 hours. Subsequently, iohexol was added at a concentration of 100 mg iodine per mL and incubated for 3 hours. Total cellular iron content was analysed by a flame atomic absorption spectrophotometer at 372 nm. Lipid peroxidation was determined by TBARS (thiobarbituric acid reactive species) assay. Antioxidants including total thiol content were assessed by Ellman’s method, catalase by colorimetric method, and superoxide dismutase (SOD) by nitroblue tetrazolium assay. The cells were stained with DAPI (4 ${}^{\prime }$ ,6-diamidino-2-phenylindole), and the cytotoxicity was evaluated by viability assay (MTT assay). The results indicated that iohexol exposure caused a significant increase of the total iron content in Vero cells. A concomitant increase of lipid peroxidation and decrease of total thiol protein levels, catalase, and superoxide dismutase activity were observed along with decreased cell viability in comparison with the controls. Furthermore, these changes were significantly reversed when the cells were pretreated with vitamin D prior to incubation with iohexol. Our findings of this in vitro model of iohexol-induced renotoxicity lend further support to the nephrotoxic potential of iron and underpin the possible clinical utility of vitamin D for the treatment and prevention of AKI.

Prognostic Value of Apoptosis-Inducing Factor (AIF) in Germ Cell Tumors

Simple Summary

Germ cell tumors (GCTs) are the most common solid malignancies in young men. GCTs are extraordinary sensitive to chemotherapy and represent a model of curable cancer. However, in a small proportion of patients the disease progresses or relapses despite administration of salvage chemotherapy. Apoptosis is a form of programmed cell death that occurs in multicellular organisms. It is well established that dysregulation of apoptosis plays an important role in pathogenesis of malignant diseases and may be associated with tumor progression and resistance to cytotoxic treatment. This study aimed to evaluate expression of apoptosis inducing factor (AIF) in GCTs. We observed lower AIF expression in GCTs compared to normal testicular tissue. We also showed prognostic significance of AIF in GCTs. AIF downregulation might represent one of the mechanisms of inhibition of apoptosis with subsequent facilitation of cell survival and metastatic dissemination of GCTs and perhaps could serve as a potential therapeutic target.

Abstract

Apoptosis is a strictly regulated process essential for preservation of tissue homeostasis. This study aimed to evaluate expression of apoptosis inducing factor (AIF) in testicular germ cell tumors (GCTs) and to correlate expression patterns with clinicopathological variables. Formalin-fixed and paraffin-embedded specimens of non-neoplastic testicular tissue and GCTs obtained from 216 patients were included in the study. AIF expression was detected by immunohistochemistry, scored by the multiplicative quickscore method (QS). Normal testicular tissue exhibits higher cytoplasmic granular expression of AIF compared to GCTs (mean QS = 12.77 vs. 4.80, p < 0.0001). Among invasive GCTs, mean QS was the highest in embryonal carcinoma, yolk sac tumor and seminoma, lower in teratoma and the lowest in choriocarcinoma. No nuclear translocation of AIF was observed. Nonpulmonary visceral metastases were associated with lower AIF expression. Metastatic GCTs patients with high AIF expression had better overall survival compared to patients with low AIF expression (HR = 0.26, 95% CI 0.11–0.62, p = 0.048). We observed significantly lower AIF expression in GCTs compared to normal testicular tissue, which is an uncommon finding in malignant tumors. AIF downregulation might represent one of the mechanisms of inhibition of apoptosis and promotion of cell survival in GCTs.

Compound C Protects Against Cisplatin-Induced Nephrotoxicity Through Pleiotropic Effects

AICAR (Acadesine/AICA riboside) as an activator of AMPK, can protect renal tubular cells from cisplatin induced apoptosis. But in our experiment, the dorsomorphin (compound C, an inhibitor of AMPK) also significantly reduced cisplatin induced renal tubular cells apoptosis. Accordingly, we tested whether compound C can protect cisplatin-induced nephrotoxicity and the specific mechanism. Here, we treated Boston University mouse proximal tubular cells (BUMPT-306) with cisplatin and/or different dosages of AICAR (Acadesine/AICA riboside) or compound C to confirm the effect of AICAR and compound C in vitro. The AMPK-siRNA treated cells to evaluate whether the protective effect of compound C was through inhibiting AMPK. Male C57BL/6 mice were used to verify the effect of compound C in vivo. Both compound C and AICAR can reduce renal tubular cells apoptosis in dose-dependent manners, and compound C decreased serum creatinine and renal tubular injury induced by cisplatin. Mechanistically, compound C inhibited P53, CHOP and p-IREα during cisplatin treatment. Our results demonstrated that compound C inhibited AMPK, but the renal protective effects of compound C were not through AMPK. Instead, compound C protected cisplatin nephrotoxicity by inhibiting P53 and endoplasmic reticulum (ER) stress. Therefore, compound C may protect against cisplatin-induced nephrotoxicity through pleiotropic effects.

Ferrotoxicity and Its Amelioration by Calcitriol in Cultured Renal Cells

Globally, acute kidney injury (AKI) is associated with significant mortality and an enormous economic burden. Whereas iron is essential for metabolically active renal cells, it has the potential to cause renal cytotoxicity by promoting Fenton chemistry-based oxidative stress involving lipid peroxidation. In addition, 1,25-dihydroxyvitamin D3 (calcitriol), the active form of vitamin D, is reported to have an antioxidative role. In this study, we intended to demonstrate the impact of vitamin D on iron-mediated oxidant stress and cytotoxicity of Vero cells exposed to iohexol, a low osmolar iodine-containing contrast media in vitro. Cultured Vero cells were pretreated with 1,25-dihydroxyvitamin D3 dissolved in absolute ethanol (0.05%, 2.0 mM) at a dose of 1 mM for 6 hours. Subsequently, iohexol was added at a concentration of 100 mg iodine per mL and incubated for 3 hours. Total cellular iron content was analysed by a flame atomic absorption spectrophotometer at 372 nm. Lipid peroxidation was determined by TBARS (thiobarbituric acid reactive species) assay. Antioxidants including total thiol content were assessed by Ellman's method, catalase by colorimetric method, and superoxide dismutase (SOD) by nitroblue tetrazolium assay. The cells were stained with DAPI (4',6-diamidino-2-phenylindole), and the cytotoxicity was evaluated by viability assay (MTT assay). The results indicated that iohexol exposure caused a significant increase of the total iron content in Vero cells. A concomitant increase of lipid peroxidation and decrease of total thiol protein levels, catalase, and superoxide dismutase activity were observed along with decreased cell viability in comparison with the controls. Furthermore, these changes were significantly reversed when the cells were pretreated with vitamin D prior to incubation with iohexol. Our findings of this in vitro model of iohexol-induced renotoxicity lend further support to the nephrotoxic potential of iron and underpin the possible clinical utility of vitamin D for the treatment and prevention of AKI.

The Role of Caspase-2 in Regulating Cell Fate

Caspase-2 is the most evolutionarily conserved member of the mammalian caspase family and has been implicated in both apoptotic and non-apoptotic signaling pathways, including tumor suppression, cell cycle regulation, and DNA repair. A myriad of signaling molecules is associated with the tight regulation of caspase-2 to mediate multiple cellular processes far beyond apoptotic cell death. This review provides a comprehensive overview of the literature pertaining to possible sophisticated molecular mechanisms underlying the multifaceted process of caspase-2 activation and to highlight its interplay between factors that promote or suppress apoptosis in a complicated regulatory network that determines the fate of a cell from its birth and throughout its life.

LncRNA np_5318 promotes renal ischemia-reperfusion injury through the TGF-β/Smad signaling pathway

Long noncoding (Lnc)RNA np_5318 has been proved to be involved in renal injury, while its functionality in renal ischemia-reperfusion (I/R) injury is unknown. Therefore, the present study aimed to investigate the role of lncRNA np_5318 in the development of renal I/R injury. Renal I/R injury model and I/R cell model were established in vitro. The expression of np_5318 in I/R cell was inhibited by small interfering (si)-np_5318 and increased by pc-np_5318. Renal function was detected and evaluated by automatic biochemical tests. Immunohistochemical staining was performed to detect the expression cluster of differentiation (CD)31, transforming growth factor (TGF)-β1 and (mothers against decapentaplegic homolog 3) Smad3 in renal tissue. The interaction between np_5318 and Smad3 was verified by chromatin immunoprecipitation (ChIP). Western blotting was performed to detect the expression levels of TGF-β1, Smad3 and phosphorylated (p)-Smad3 in renal tissue and renal cells. Expression of np_5318 in renal tissue and renal cells was detected by reverse transcription-quantitative PCR. Relative cell viability was confirmed by MTT assay. Renal function was impaired and pathological changes in renal tissue were observed in the renal I/R injury group, indicating the renal I/R injury model was successfully established. Compared with the sham group, the expression level of np_5318 significantly increased in the renal I/R injury group. ChIP data confirmed the interaction between np_5318 and Smad3. The expression of TGF-β1, Smad3 and p-Smad3 in renal tissue was also significantly increased in the renal I/R injury group. Furthermore, the I/R cell model in vitro was successfully constructed and np_5318 in I/R group was significantly increased compared with the control group. Cell growth was significantly suppressed in the I/R group compared with the control group. Additionally, transfection with pc-np_5318 significantly inhibited cell growth of I/R cells at 48 and 72 h. While inhibition of np_5318 by si-np_5318 significantly increased the cell growth of I/R cells at 48 and 72 h. Moreover, the level of TGF-β1, p-Smad3 and Smad3 was significantly increased in the I/R group compared with the control group, and transfection with pc-np_5318 significantly increased the level of TGF-β1, p-Smad3 and Smad3. While inhibition of np_5318 by si-np_5318 significantly suppressed the level of TGF-β1, p-Smad3 and Smad3.

LncRNA np_5318 may participate in the development of renal I/R injury through TGF-β/Smad signaling pathway.

New Insights in the Pathogenesis of Cisplatin-Induced Nephrotoxicity

Cisplatin (cis-diamminedichloroplatinum II) is a widely used chemotherapeutic agent. However, efficacy and clinical utility of this drug is significantly limited by severe side effects such as nephrotoxicity which develops due to renal accumulation and bio-transformation in proximal tubular epithelial cells. Cisplatin-induced nephrotoxicity can be manifested as acute kidney injury (AKI), or as different types of tubulopathies, salt wasting, loss of urinary concentrating ability, and magnesium wasting. The attenuation of cisplatin-caused AKI is currently accomplished by hydration, magnesium supplementation or mannitol-induced forced diuresis. However, mannitol treatment causes over-diuresis and consequent dehydration, indicating an urgent need for the clinical use of newly designed, safe and efficacious renoprotective drug, as an additive therapy for high dose cisplatin-treated patients. Accordingly, we emphasized current knowledge regarding molecular mechanisms responsible for cisplatin-caused nephrotoxicity and we described in detail the main clinical manifestations of cisplatin-induced renal dysfunction in order to pave the way for the design of new therapeutic approaches that can minimize detrimental effects of cisplatin in the kidneys. Having in mind that most of cisplatin-induced cytotoxic effects against renal cells are, at the same time, involved in anti-tumor activity of cisplatin, new nephroprotective therapeutic strategies have to prevent renal injury and inflammation without affecting cisplatin-induced toxicity against malignant cells.

Decreased expression of apoptosis-inducing factor in renal cell carcinoma is associated with poor prognosis and reduced postoperative survival

Apoptosis-inducing factor (AIF) serves a crucial role in cell death and is involved in several types of cancer, including kidney cancer. The present study aimed to explore the association between AIF expression and patient survival based on tumor grades. AIF expression in 96 patients with renal cell carcinoma (RCC) was investigated using immunohistochemistry. Negative AIF expression was determined in 80 patients (83.3%). mRNA expression of AIF was analyzed in RCC and adjacent tissue samples from 15 patients. AIF mRNA expression in RCC tissues were significantly lower compared with that in adjacent tissues. Analysis of histopathological grades revealed that AIF expression was negatively associated with RCC grade, with AIF expression in Grade II tumors being lower than Grade I types, but higher than Grade III. Finally, 68 patients were followed up for 6-118 months, and it was revealed that the overall postoperative survival rate of patients with negative AIF expression was significantly lower compared with those those with positive AIF expression. These results suggest that decreased AIF expression could be associated with worsening RCC grade. Therefore, reduced AIF expression may potentially help diagnose RCC and distinguish tumor grades.

Has vitamin E any shreds of evidence in cisplatin-induced toxicity

Cisplatin is one of the highly consumed and effective antitumor agents whose clinical application is accompanied by nephrotoxicity adverse reaction. Also, other complications such as ototoxicity and hepatotoxicity are a matter of concern. Today, it is suggested that cisplatin-associated toxicities are mainly induced by free radicals production, which will result in oxidative organ injury. The evidence is growing over the protective effects of antioxidants on cisplatin-induced adverse reactions especially nephrotoxicity. The possible protective effects of vitamin E and its derivative in cisplatin-induced nephrotoxicity and ototoxicity are reviewed here at the light of pertinent results from basic and clinical research. Administration of vitamin E alone or in combination with other antioxidant agents could cause amelioration in oxidative stress biomarkers such as decreasing the level of malondialdehyde, reducing serum urea and creatinine, and also enhancing the activities of renal antioxidant enzymes including renal catalase, glutathione-S-transferase, and superoxide dismutase. Although the data from most of the studies are in favors of protective effects of vitamin E against cisplatin-induced toxicity, more clinical trials are needed to clarify the clinical importance of vitamin E administration as an antioxidant during cisplatin therapy in cancer condition.

Molecular mechanisms of cisplatin-induced nephrotoxicity: a balance on the knife edge between renoprotection and tumor toxicity

Background

Cisplatin (cis-diamminedichloroplatinum II, CDDP) is one of the most effective chemotherapeutic agents. However, its clinical use is limited due to the severe side effects, including nephrotoxicity and acute kidney injury (AKI) which develop due to renal accumulation and biotransformation of CDDP. The alleviation or prevention of CDDP-caused nephrotoxicity is currently accomplished by hydration, magnesium supplementation or mannitol-induced forced diuresis which is considered for high-dose CDDP-treated patients. However, mannitol treatment causes over-diuresis and consequent dehydration in CDDP-treated patients, indicating an urgent need for the clinical use of safe and efficacious renoprotective drug as an additive therapy for high dose CDDP-treated patients.

Main body

In this review article we describe in detail signaling pathways involved in CDDP-induced apoptosis of renal tubular cells, oxidative stress and inflammatory response in injured kidneys in order to pave the way for the design of new therapeutic approaches that can minimize CDDP-induced nephrotoxicity. Most of these molecular pathways are, at the same time, crucially involved in cytotoxic activity of CDDP against tumor cells and potential alterations in their function might mitigate CDDP-induced anti-tumor effects.

Conclusion

Despite the fact that many molecules were designated as potential therapeutic targets for renoprotection against CDDP, modulation of CDDP-induced nephrotoxicity still represents a balance on the knife edge between renoprotection and tumor toxicity.

Matrix metalloproteinase-9 and p53 involved in chronic fluorosis induced blood-brain barrier damage and neurocyte changes

INTRODUCTION

A large number of basic and clinical studies have confirmed that fluoride produces toxic effects on multiple organ systems in the body including the nervous system.

MATERIAL AND METHODS

One hundred twenty Wistar rats were randomly divided into 4 groups with 30 in each group: a high fluoride group (drinking 200 mg/l fluoridated water, 24 weeks); a high fluoride control group (drinking distilled water, 24 weeks); a fluoride removal group (drinking fluoridated water, 12 W; then distilled water, 12 W) and a defluorination control group (drinking distilled water, 24 weeks).

RESULTS

The high fluoride and fluoride removal groups had spinal cord astrocyte edema. The apoptosis rate of spinal nerve cells in the high fluoride group and fluoride removal group were significantly higher (p < 0.01) than in the fluoride control and defluorination control group. The Evans blue (EB) content, matrix metalloproteinase-9 (MMP-9) and p53 expression in the high fluoride group and fluoride removal group were higher (p < 0.01) than in the fluoride control and defluorination control group.

CONCLUSIONS

The apoptosis of spinal cord nerve cells is obviously higher in rats with chronic fluoride exposure. Chronic fluoride exposure leads to high expression of MMP-9, and results in increased damage of the blood-spinal cord barrier. Increased p53 may be one of the factors causing damage. Short-term removal of fluoride has no obvious recovery in apoptosis of spinal cord nerve cells; highly expressed MMP-9 and p53 may be one of the reasons for unrecovered function.

Growth arrest and DNA damage 45γ is required for caspase-dependent renal tubular cell apoptosis

BACKGROUND

Growth Arrest and DNA Damage 45γ (GADD45γ) is a member of the DNA damage-inducible gene family which responds to environmental stresses. Apoptosis is a critical mode of renal tubular cell death in nephrotoxin-induced acute kidney injury. In this study, we investigated the role of GADD45γ in renal tubular cell apoptosis induced by nephrotoxic drugs.

METHODS

Primary human renal tubular epithelial (HRE) cells were used in this study. To derive stable cell lines in which GADD45γ expression was silenced, HRE cells were transduced with a plasmid encoding GADD45γ-specific shRNA. The recombinant adenovirus containing the GADD45γ gene was synthesized to overexpress GADD45γ protein. Cell death was induced by cisplatin and cyclosporine A (CsA). To prevent apoptotic cell death, pan-caspase inhibitor ZVAD-FMK was used. To prevent non-apoptotic cell death, necrostatin-1 and ferrostatin-1 were used. The degree of apoptosis and necrosis of cultured cells were evaluated by flow cytometry.

RESULTS

Expression of the GADD45γ gene was significantly upregulated in response to treatment with CsA and cisplatin. Apoptosis and necrosis induced by these drugs were significantly reduced by silencing of GADD45γ, and significantly augmented by the overexpression of GADD45γ. The activation of caspase-3 and caspase-7 as well as caspase-9 induced by cisplatin or CsA was reduced by silencing of GADD45γ, and was augmented by the overexpression of GADD45γ, indicating that caspase activation is dependent on the expression of GADD45γ. ZVAD-FMK significantly inhibited apoptosis induced by cisplatin or CsA, indicating a role of caspases in mediating apoptotic cell death. ZVAD-FMK was effective to prevent necrosis as well, indicating that the observed necrosis was a secondary event following apoptosis at least in part.

CONCLUSIONS

To our knowledge, this is the first study to show that GADD45γ is required for the caspase-dependent apoptosis of renal tubular cells induced by nephrotoxic drugs.

Aristolochic acid I determine the phenotype and activation of macrophages in acute and chronic kidney disease

Acute and chronic kidney injuries are multifactorial traits that involve various risk factors. Experimental animal models are crucial to unravel important aspects of injury and its pathophysiological mechanisms. Translating knowledge obtained from experimental approaches into clinically useful information is difficult; therefore, significant attention needs to be paid to experimental procedures that mimic human disease. Herein, we compared aristolochic acid I (AAI) acute and chronic kidney injury model with unilateral ischemic-reperfusion injury (uIRI), cisplatin (CP)- or folic acid (FA)-induced renal damage. The administration of AAI showed significant changes in serum creatinine and BUN upon CKD. The number of neutrophils and macrophages were highly increased as well as AAI-induced CKD characterized by loss of tubular epithelial cells and fibrosis. The in vitro and in vivo data indicated that macrophages play an important role in the pathogenesis of AA-induced nephropathy (AAN) associated with an excessive macrophage accumulation and an alternative activated macrophage phenotype. Taken together, we conclude that AA-induced injury represents a suitable and relatively easy model to induce acute and chronic kidney injury. Moreover, our data indicate that this model is appropriate and superior to study detailed questions associated with renal macrophage phenotypes.

Scriptaid overcomes hypoxia-induced cisplatin resistance in both wild-type and mutant p53 lung cancer cells

Non-small cell lung cancer (NSCLC), comprising 85% of lung cancer cases, has been associated with resistance to chemo/radiotherapy. The hypoxic tumor micro-environment, where insufficient vasculature results in poor drug penetrance and sub-optimal chemotherapy in the tumor interiors contributes heavily to this resistance. Additionally, epigenetic changes in tumorigenic cells also change their response to different forms of therapy. In our study, we have investigated the effectiveness of a combination of cisplatin with scriptaid [a pan-Histone Deacetylase inhibitor (HDACi)] in a model that mimics the tumor microenvironment of hypoxia and sub-lethal chemotherapy. Scriptaid synergistically increases the efficacy of cisplatin in normoxia as well as hypoxia, accompanied with reduced metastasis and enhanced DNA damage. Addition of scriptaid also overcomes the cisplatin resistance exhibited in lung cancer cells with stabilized hypoxia inducible factor 1 (HIF1)-α (mutant) and mutant p53. Molecular studies showed that the combination treatment increased apoptotic cell death in both normoxia and hypoxia with a dual role of p38MAPK. Together, our results suggest that the combination of low dose cisplatin and scriptaid is cytotoxic to NSCLC lines, can overcome hypoxia induced resistance and mutant p53- induced instability often associated with this cancer, and has the potential to be an effective therapeutic modality.

HIPK2 polymorphisms rs2058265, rs6464214, and rs7456421 were associated with kidney stone disease in Chinese males not females

BACKGROUND AND AIM

Recent studies have shown that genetic factors are involved in the development of kidney stone disease (KSD). A case-control association analysis was performed to investigate the association between homeodomain-interacting protein kinase 2 (HIPK2; OMIM *606868) polymorphisms and KSD.

METHODS

A total of 890 KSD patients and 920 healthy subjects were analyzed. Polymorphisms were genotyped using SNPscanTM high-throughput SNP classification technology. The genotypic and allelic frequencies in KSD patients and healthy individuals were analyzed using a Chi-square test.

RESULTS

The genotype and allele distributions of the three polymorphisms (rs2058265, rs6464214, and rs7456421 in HIPK2) displayed strong associations with KSD in males (rs2058265: odds ratio [OR] 2.480,95%confidence interval [CI] 1.205-5.106, p = 0.014; rs6464214: OR 2.466, 95%CI 1.198-5.078, p = 0.014; rs7456421: OR 2.846, 95%CI 1.362-5.947, p = 0.005; perallele: r2058265T, OR 1.357, 95%CI 1.073-1.715, p = 0.011; rs6464214G, OR 1.340, 95%CI 1.060-1.693, p = 0.014; rs7456421C, OR 1.356, 95%CI 1.073-1.713, p = 0.011). Patients carrying the T allele of rs2058265, the G allele of rs6464214, or the C allele of rs7456421 showed higher systolic blood pressure, creatinine, and uric acid levels compared with wild-genotype individuals after adjusting for age, gender, and body mass index (p < 0.005).

CONCLUSION

The association of HIPK2 gene polymorphisms with KSD was only observed in males but not in females. HIPK2 gene polymorphisms were also involved in the changes of KSD-related metabolic traits.

Diallyl sulfide alleviates cisplatin-induced nephrotoxicity in rats via suppressing NF-κB downstream inflammatory proteins and p53/Puma signalling pathway

Despite being a potent anticancer drug, nephrotoxicity is an adverse effect which renders the clinical use of cisplatin (Cis) limited. The protective role of diallyl sulfide (DAS); a naturally occurring organo-sulfide, present in garlic, in cisplatin-induced nephrotoxicity has been reported earlier. However, the mechanism through which DAS exerts its nephroprotective activity remains elusive. The aim of the current study was to elucidate the possible mechanisms underlying the reno-protective effect of DAS in cisplatin-induced nephrotoxicity in rats. DAS was given at 2 dose levels; 50 and 100 mg/kg, orally for 4 consecutive days, starting 1 hour after administration of single dose of cisplatin (3.5 mg/kg, intraperitoneally [i.p.]). The Cis-induced elevation in serum urea and creatinine, degree of histopathological alterations was significantly ameliorated in cisplatin groups co-treated with DAS. In addition, DAS significantly restored Cis-depleted glutathione (GSH) content and superoxide dismutase (SOD) activity and attenuated Cis-elevated Malondialdehyde (MDA) level. Also, DAS significantly reduced Cis-increased renal expression of nuclear factor kappa B (NF-κB) and subsequent pro-inflammatory mediators; tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), intercellular adhesion molecule-1 (ICAM-1) and inducible nitric oxide synthase (iNOS) in kidney tissues. Moreover, co-treatment with DAS significantly inhibited Cis-increased caspase-8 and -9 levels. Additionally, DAS significantly mitigated Cis-induced protein expression of p53, Puma, and Bax while, it significantly restored Cis-reduced protein expression of Bcl-xL compared to the Cis group. In conclusion, these results demonstrate that DAS ameliorates cisplatin-induced nephrotoxicity in rats through enhancement of antioxidant defense, reduction of inflammatory cytokine tissue levels as well as inhibition of apoptosis via p53/Puma signalling pathway.

FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury

Cisplatin, a widely used cancer therapy drug, induces nephrotoxicity or acute kidney injury (AKI), but the underlying mechanism remains unclear, and renal protective approaches are not available. Fibroblast growth factor (FGF)21 is an endocrine factor that regulates glucose uptake, metabolism, and energy expenditure. However, recent work has also implicated FGF21 in cellular stress response under pathogenic conditions. The role and regulation of FGF21 in AKI are unclear. Here, we show that FGF21 was dramatically induced during cisplatin treatment of renal tubular cells in vitro and mouse kidneys in vivo. The inductive response was suppressed by pifithrin (a pharmacological inhibitor of P53), suggesting a role of P53 in FGF21 induction. In cultured renal tubular cells, knockdown of FGF21 aggravated cisplatin-induced apoptosis, whereas supplementation of recombinant FGF21 was protective. Consistently, recombinant FGF21 alleviated cisplatin-induced kidney dysfunction, tissue damage, and tubular apoptosis in mice. Mechanistically, FGF21 suppressed P53 induction and activation during cisplatin treatment. Together, these results indicate that FGF21 is induced during cisplatin nephrotoxicity to protect renal tubules, and recombinant FGF21 may have therapeutic potential.-Li, F., Liu, Z., Tang, C., Cai, J., Dong, Z. FGF21 is induced in cisplatin nephrotoxicity to protect against kidney tubular cell injury.

Autophagy: A new treatment strategy for MSC-based therapy in acute kidney injury (Review)

Acute kidney injury (AKI) is a common and serious medical condition associated with poor health outcomes. Autophagy is a conserved multistep pathway that serves a major role in many biological processes and diseases. Recent studies have demonstrated that autophagy is induced in proximal tubular cells during AKI. Autophagy serves a pro‑survival or pro‑death role under certain conditions. Furthermore, mesenchymal stem cells (MSCs) have therapeutic potential in the repair of renal injury. This review summarizes the recent progress on the role of autophagy in AKI and MSCs‑based therapy for AKI. Further research is expected to prevent and treat acute kidney injury.

Tangeretin induces cell cycle arrest and apoptosis through upregulation of PTEN expression in glioma cells

Tangeretin (TANG), present in peel of citrus fruits, has been shown to various medicinal properties such as chemopreventive and neuroprotective. However, the chemopreventive effect of TANG on glioblastoma cells has not been examined. The present study was designed to explore the anticancer potential of TANG in glioblastoma cells and to investigate the related mechanism. Human glioblastoma U-87MG and LN-18 cells were treated with 45μM concentration of TANG and cell growth was measured by MTT assay. The cell cycle distribution and cell death were measured by flow cytometry. The expression of cell cycle and apoptosis related genes were analyzed by quantitative RT-PCR and western blot. The cells treated with TANG were significantly increased cell growth suppression and cell death effects than vehicle treated cells. Further, TANG treatment increases G2/M arrest and apoptosis by modulating PTEN and cell-cycle regulated genes such as cyclin-D and cdc-2 mRNA and protein expressions. Moreover, the ability of TANG to decrease cell growth and to induce cell death was compromised when PTEN was knockdown by siRNA. Taken together, the chemopreventive effect of TANG is associated with regulation of cell-cycle and apoptosis in glioblastoma, thereby attenuating glioblastoma cell growth. Hence, the present findings suggest that TANG may be a therapeutic agent for glioblastoma treatment.

Therapeutic Potential and Molecular Mechanisms of Emblica officinalis Gaertn in Countering Nephrotoxicity in Rats Induced by the Chemotherapeutic Agent Cisplatin

Emblica officinalis Gaertn. belonging to family Euphorbiaceae is commonly known as Indian gooseberry or "Amla" in India. It is used as a 'rejuvenating herb' in traditional system of Indian medicine. It has been shown to possess antioxidant, anti-inflammatory and anti-apoptotic effects. Thus, on the basis of its biological effects, the present study was undertaken to evaluate the protective effect of the dried fruit extract of the E. Officinalis (EO) in cisplatin-induced nephrotoxicity in rats and also to evaluate the mechanism of its nephroprotection. The study was done on male albino Wistar rats. They were divided into six groups (n = 6) viz. control, cisplatin-control, cisplatin and EO (150, 300, and 600 mg/kg; p.o. respectively in different groups) and EO only (600 mg/kg; p.o. only). EO was administered orally to the rats for a period of 10 days and on the 7th day, a single injection of cisplatin (8 mg/kg; i.p.) was administered to the cisplatin-control and EO treatment groups. The rats were sacrificed on the 10th day. Cisplatin-control rats had deranged renal function parameters and the kidney histology confirmed the presence of acute tubular necrosis. Furthermore, there were increased oxidative stress, apoptosis and inflammation along with higher expression of MAPK pathway proteins in the rat kidney from the cisplatin-control group. Contrary to this, EO (600 mg/kg) significantly normalized renal function, bolstered antioxidant status and ameliorated histological alterations. The inflammation and apoptosis were markedly lower in comparison to cisplatin-control rats. Furthermore, EO (600 mg/kg) inhibited MAPK phosphorylation which was instrumental in preserving renal function and morphology. In conclusion, the results of our study demonstrated that EO attenuated cisplatin-induced nephrotoxicity in rats through suppression of MAPK induced inflammation and apoptosis.

Copper induced apoptosis in Caco-2 and Hep-G2 cells: Expression of caspases 3, 8 and 9, AIF and p53

Copper (Cu) is an essential trace metal needed to ensure cell function. However, when present at high concentrations it becomes toxic to organisms. Cell death, induced by toxic levels of copper, was previously observed in in vitro studies. However, there is no consensus about the cell death pathway induced by Cu and it is still not known whether this occurs as a result of the direct action of the metal or by indirect effects. In the present work, we intend to identify the influence of different Cu concentrations in the induction of apoptosis and to explore the potential signaling pathways, using two different in vitro cell culture models (Caco-2 and Hep-G2). Cells were exposed, during 6, 12, 24 and 48h, to Cu concentrations corresponding to IC50 and 1/8 of IC50, according to the viability assays. Then, considering the different apoptosis pathways, the expression of caspases 3, 8 and 9, apoptosis inducing factor (AIF) and p53 genes was analyzed by quantitative real time PCR. The results suggested that different Cu concentrations could trigger different apoptotic pathways, at different times of exposure. In both cell lines, apoptosis seems to be initiated by caspase independent pathway and intrinsic pathway, followed by extrinsic pathway. In conclusion, this study demonstrates that Cu induces the activation of apoptosis through caspase dependent and independent pathways, also suggesting that apoptosis activation mechanism is dependent on the concentration, time of exposure to Cu and cell type.

A Comprehensive Review on the Genetic Regulation of Cisplatin-induced Nephrotoxicity

Cisplatin (CDDP) is a well-known antineoplastic drug which has been extensively utilized over the last decades in the treatment of numerous kinds of tumors. However, CDDP induces a wide range of toxicities in a dose-dependent manner, among which nephrotoxicity is of particular importance. Still, the mechanism of CDDP-induced renal damage is not completely understood; moreover, the knowledge about the role of microRNAs (miRNAs) in the nephrotoxic response is still unknown. miRNAs are known to interact with the representative members of a diverse range of regulatory pathways (including postnatal development, proliferation, inflammation and fibrosis) and pathological conditions, including kidney diseases: polycystic kidney diseases (PKDs), diabetic nephropathy (DN), kidney cancer, and drug-induced kidney injury. In this review, we shed light on the following important aspects: (i) information on genes/proteins and their interactions with previously known pathways engaged with CDDP-induced nephrotoxicity, (ii) information on newly discovered biomarkers, especially, miRNAs for detecting CDDP-induced nephrotoxicity and (iii) information to improve our understanding on CDDP. This information will not only help the researchers belonging to nephrotoxicity field, but also supply an indisputable help for oncologists to better understand and manage the side effects induced by CDDP during cancer treatment. Moreover, we provide up-to-date information about different in vivo and in vitro models that have been utilized over the last decades to study CDDP-induced renal injury. Taken together, this review offers a comprehensive network on genes, miRNAs, pathways and animal models which will serve as a useful resource to understand the molecular mechanism of CDDP-induced nephrotoxicity.

Low expression of PIDD is associated with cell proliferation and apoptosis in hepatocellular carcinoma

p53-induced death domain protein (PIDD) facilitates p53-dependent apoptosis through the interaction with components of the death receptor signaling pathways. However, the role of PIDD in hepatocellular carcinoma (HCC) development remains unknown. In this study, we investigated the expression pattern of PIDD in clinical HCC samples and adjacent non-cancerous tissues using immunohistochemistrical and Western blot analyses. The results showed that PIDD was lowly expressed in HCC tissues and HCC cell lines, compared with the adjacent non-tumorous tissues and LO2 normal hepatocytes. In addition, clinicopathological analysis showed that the expression of PIDD was closely related with multiple clinicopathological variables, such as American Joint Committee on Cancer (AJCC) stage, AFP, and poor prognosis of HCC. Univariate and multivariate survival analyses demonstrated that PIDD could serve as an independent prognostic factor to predict the survival of HCC patients. We used serum starvation-refeeding experiment to explore the involvement of PIDD in HCC cell cycle regulation. We found that PIDD was accumulated in growth-arrested HCC cells and was progressively decreased when cells entered into S phase. Moreover, flow cytometry and cell counting kit-8 (CCK-8) assays indicated that depleting the expression of PIDD could facilitate cell cycle progression and accelerate cell proliferation in HepG2 cells, while overexpression of PIDD could result in cell cycle arrest at G1 phase and hinder the cell proliferation in Hep3B cells. Finally, flow cytometry revealed that overexpression of PIDD slightly increased the apoptosis of HCC cells. Taken together, we concluded that PIDD may be a valuable prognostic marker and promising therapeutic target of HCC.

DNA damage response in cisplatin-induced nephrotoxicity

Cisplatin and its derivatives are widely used chemotherapeutic drugs for cancer treatment. However, they have debilitating side effects in normal tissues and induce ototoxicity, neurotoxicity, and nephrotoxicity. In kidneys, cisplatin preferentially accumulates in renal tubular cells causing tubular cell injury and death, resulting in acute kidney injury (AKI). Recent studies have suggested that DNA damage and the associated DNA damage response (DDR) are an important pathogenic mechanism of AKI following cisplatin treatment. Activation of DDR may lead to cell cycle arrest and DNA repair for cell survival or, in the presence of severe injury, kidney cell death. Modulation of DDR may provide novel renoprotective strategies for cancer patients undergoing cisplatin chemotherapy.

Oxygen regulates molecular mechanisms of cancer progression and metastasis

Oxygen is the basic molecule which supports life and it truly is "god's gift to life." Despite its immense importance, research on "oxygen biology" has never received the light of the day and has been limited to physiological and biochemical studies. It seems that in modern day biology, oxygen research is summarized in one word "hypoxia." Scientists have focused on hypoxia-induced transcriptomics and molecular-cellular alterations exclusively in disease models. Interestingly, the potential of oxygen to control the basic principles of biology like homeostatic maintenance, transcription, replication, and protein folding among many others, at the molecular level, has been completely ignored. Here, we present a perspective on the crucial role played by oxygen in regulation of basic biological phenomena. Our conclusion highlights the importance of establishing novel research areas like oxygen biology, as there is great potential in this field for basic science discoveries and clinical benefits to the society.

An integrated view of cisplatin-induced nephrotoxicity and ototoxicity

Cisplatin is one of the most widely-used drugs to treat cancers. However, its nephrotoxic and ototoxic side-effects remain major clinical limitations. Recent studies have improved our understanding of the molecular mechanisms of cisplatin-induced nephrotoxicity and ototoxicity. While cisplatin binding to DNA is the major cytotoxic mechanism in proliferating (cancer) cells, nephrotoxicity and ototoxicity appear to result from toxic levels of reactive oxygen species and protein dysregulation within various cellular compartments. In this review, we discuss molecular mechanisms of cisplatin-induced nephrotoxicity and ototoxicity. We also discuss potential clinical strategies to prevent nephrotoxicity and ototoxicity and their current limitations.

Zinc deficiency induces apoptosis via mitochondrial p53- and caspase-dependent pathways in human neuronal precursor cells

Previous studies have shown that zinc deficiency leads to apoptosis of neuronal precursor cells in vivo and in vitro. In addition to the role of p53 as a nuclear transcription factor in zinc deficient cultured human neuronal precursors (NT-2), we have now identified the translocation of phosphorylated p53 to the mitochondria and p53-dependent increases in the pro-apoptotic mitochondrial protein BAX leading to a loss of mitochondrial membrane potential as demonstrated by a 25% decrease in JC-1 red:green fluorescence ratio. Disruption of mitochondrial membrane integrity was accompanied by efflux of the apoptosis inducing factor (AIF) from the mitochondria and translocation to the nucleus with a significant increase in reactive oxygen species (ROS) after 24h of zinc deficiency. Measurement of caspase cleavage, mRNA, and treatment with caspase inhibitors revealed the involvement of caspases 2, 3, 6, and 7 in zinc deficiency-mediated apoptosis. Down-stream targets of caspase activation, including the nuclear structure protein lamin and polyADP ribose polymerase (PARP), which participates in DNA repair, were also cleaved. Transfection with a dominant-negative p53 construct and use of the p53 inhibitor, pifithrin-μ, established that these alterations were largely dependent on p53. Together these data identify a cascade of events involving mitochondrial p53 as well as p53-dependent caspase-mediated mechanisms leading to apoptosis during zinc deficiency.

Cisplatin-induced Kidney Dysfunction and Perspectives on Improving Treatment Strategies

Cisplatin is one of the most widely used and highly effective drug for the treatment of various solid tumors; however, it has dose-dependent side effects on the kidney, cochlear, and nerves. Nephrotoxicity is the most well-known and clinically important toxicity. Numerous studies have demonstrated that several mechanisms, including oxidative stress, DNA damage, and inflammatory responses, are closely associated with cisplatin-induced nephrotoxicity. Even though the establishment of cisplatin-induced nephrotoxicity can be alleviated by diuretics and pre-hydration of patients, the prevalence of cisplatin nephrotoxicity is still high, occurring in approximately one-third of patients who have undergone cisplatin therapy. Therefore it is imperative to develop treatments that will ameliorate cisplatin-nephrotoxicity. In this review, we discuss the mechanisms of cisplatin-induced renal toxicity and the new strategies for protecting the kidneys from the toxic effects without lowering the tumoricidal activity.

Regulated cell death in AKI

AKI is pathologically characterized by sublethal and lethal damage of renal tubules. Under these conditions, renal tubular cell death may occur by regulated necrosis (RN) or apoptosis. In the last two decades, tubular apoptosis has been shown in preclinical models and some clinical samples from patients with AKI. Mechanistically, apoptotic cell death in AKI may result from well described extrinsic and intrinsic pathways as well as ER stress. Central converging nodes of these pathways are mitochondria, which become fragmented and sensitized to membrane permeabilization in response to cellular stress, resulting in the release of cell death-inducing factors. Whereas apoptosis is known to be regulated, tubular necrosis was thought to occur by accident until recent work unveiled several RN subroutines, most prominently receptor-interacting protein kinase-dependent necroptosis and RN induced by mitochondrial permeability transition. Additionally, other cell death pathways, like pyroptosis and ferroptosis, may also be of pathophysiologic relevance in AKI. Combination therapy targeting multiple cell-death pathways may, therefore, provide maximal therapeutic benefits.

AIF downregulation and its interaction with STK3 in renal cell carcinoma

Apoptosis-inducing factor (AIF) plays a crucial role in caspase-independent programmed cell death by triggering chromatin condensation and DNA fragmentation. Therefore, it might be involved in cell homeostasis and tumor development. In this study, we report significant AIF downregulation in the majority of renal cell carcinomas (RCC). In a group of RCC specimens, 84% (43 out of 51) had AIF downregulation by immunohistochemistry stain. Additional 10 kidney tumors, including an oxyphilic adenoma, also had significant AIF downregulation by Northern blot analysis. The mechanisms of the AIF downregulation included both AIF deletion and its promoter methylation. Forced expression of AIF in RCC cell lines induced massive apoptosis. Further analysis revealed that AIF interacted with STK3, a known regulator of apoptosis, and enhanced its phosphorylation at Thr180. These results suggest that AIF downregulation is a common event in kidney tumor development. AIF loss may lead to decreased STK3 activity, defective apoptosis and malignant transformation.

Mitochondrial dysregulation and protection in cisplatin nephrotoxicity

Nephrotoxicity is a major side effect of cisplatin in chemotherapy. Pathologically, cisplatin nephrotoxicity is characterized by cell injury and death in renal tubules. The research in the past decade has gained significant understanding of the cellular and molecular mechanisms of tubular cell death, revealing a central role of mitochondrial dysregulation. The pathological changes in mitochondria in cisplatin nephrotoxicity are mainly triggered by DNA damage response, pro-apoptotic protein attack, disruption of mitochondrial dynamics, and oxidative stress. As such, inhibitory strategies targeting these cytotoxic events may provide renal protection. Nonetheless, ideal approaches for renoprotection should not only protect kidneys but also enhance the anticancer efficacy of cisplatin in chemotherapy.

Deletion of p18(INK4c) aggravates cisplatin-induced acute kidney injury

Protection of cyclin-dependent kinase inhibitors (CDKIs) has been demonstrated in acute kidney injury (AKI). However, previous studies on CDKIs have mainly focused on CIP/KIP family members, with INK4 family members rarely being investigated. This study investigated the behaviors of p18(INK4c) (p18) in cisplatin-induced AKI using p18 gene knockout mice (p18-/-). AKI was induced in p18-/- and wild-type (p18+/+) mice after a single cisplatin (12.5 mg/kg) intraperitoneal injection. Protection by p18 was identified by a comparison of survival, renal function and morphological injuries between p18-/- and p18+/+ mice. Further investigation of endoplasmic reticulum stress (ERS) was performed by western blot analysis in p18-/- and p18+/+ kidneys at day 3 after cisplatin injection. The results revealed that after cisplatin injection, the survival of p18-/- mice was significantly shorter than that of p18+/+ mice, accompanied by aggravated renal function and more severe morphological injuries. Deletion of p18 also significantly aggravated ERS in cisplatin-induced AKI. In conclusion, p18 exerts protective effects on cisplatin‑induced AKI, which may be associated with the effect of p18 on cell death pathways, such as the ERS pathway.

Endoplasmic reticulum stress-mediated activation of p38 MAPK, Caspase-2 and Caspase-8 leads to abrin-induced apoptosis

Abrin from Abrus precatorius plant is a potent protein synthesis inhibitor and induces apoptosis in cells. However, the relationship between inhibition of protein synthesis and apoptosis is not well understood. Inhibition of protein synthesis by abrin can lead to accumulation of unfolded protein in the endoplasmic reticulum causing ER stress. The observation of phosphorylation of eukaryotic initiation factor 2α and upregulation of CHOP (CAAT/enhancer binding protein (C/EBP) homologous protein), important players involved in ER stress signaling by abrin, suggested activation of ER stress in the cells. ER stress is also known to induce apoptosis via stress kinases such as p38 MAPK and JNK. Activation of both the pathways was observed upon abrin treatment and found to be upstream of the activation of caspases. Moreover, abrin-induced apoptosis was found to be dependent on p38 MAPK but not JNK. We also observed that abrin induced the activation of caspase-2 and caspase-8 and triggered Bid cleavage leading to mitochondrial membrane potential loss and thus connecting the signaling events from ER stress to mitochondrial death machinery.