Prkdc participates in mitochondrial genome maintenance and prevents Adriamycin-induced nephropathy in mice

PPAR-α Insufficiency Enhances Doxorubicin-Induced Nephropathy in PPAR-α Knockout Mice and a Murine Podocyte Cell Line

Peroxisome proliferator-activated receptor-alpha (PPAR-α) and its exogenous activators (fibrates) promote autophagy. However, whether the deleterious effects of PPAR-α deficiency on doxorubicin (DOX)-induced podocytopathy are associated with reduced autophagy remains to be clarified. We investigated the mechanisms of PPAR-α in DOX-induced podocytopathy and tubular injury in PPAR-α knockout (PAKO) mice and in a murine podocyte cell line. DOX-treated PAKO mice showed higher serum levels of triglycerides and non-esterified fatty acids and more severe podocytopathy than DOX-treated wild-type mice, as evidenced by higher urinary levels of proteins and podocalyxin at 3 days to 2 weeks and higher blood urea nitrogen and serum creatinine levels at 4 weeks. Additionally, there was an increased accumulation of p62, a negative autophagy marker, in the glomerular and tubular regions in DOX-treated PAKO mice at Day 9. Moreover, DOX-treated PAKO mice showed more severe glomerulosclerosis and tubular damage and lower podocalyxin expression in the kidneys than DOX-treated control mice at 4 weeks. Furthermore, DOX treatment increased p-p53, an apoptosis marker, and cleaved the caspase-3 levels and induced apoptosis, which was ameliorated by fenofibrate, a PPAR-α activator. Fenofibrate further enhanced AMPK activation and autophagy under fed and fasting conditions. Conclusively, PPAR-α deficiency enhances DOX-induced podocytopathy, glomerulosclerosis, and tubular injury, possibly by reducing autophagic activity in mouse kidneys.

Development and Characterization of a Novel FVB-PrkdcR2140C Mouse Model for Adriamycin-Induced Nephropathy

The Adriamycin (ADR) nephropathy model, which induces podocyte injury, is limited to certain mouse strains due to genetic susceptibilities, such as the PrkdcR2140C polymorphism. The FVB/N strain without the R2140C mutation resists ADR nephropathy. Meanwhile, a detailed analysis of the progression of ADR nephropathy in the FVB/N strain has yet to be conducted. Our research aimed to create a novel mouse model, the FVB-PrkdcR2140C, by introducing PrkdcR2140C into the FVB/NJcl (FVB) strain. Our study showed that FVB-PrkdcR2140C mice developed severe renal damage when exposed to ADR, as evidenced by significant albuminuria and tubular injury, exceeding the levels observed in C57BL/6J (B6)-PrkdcR2140C. This indicates that the FVB/N genetic background, in combination with the R2140C mutation, strongly predisposes mice to ADR nephropathy, highlighting the influence of genetic background on disease susceptibility. Using RNA sequencing and subsequent analysis, we identified several genes whose expression is altered in response to ADR nephropathy. In particular, Mmp7, Mmp10, and Mmp12 were highlighted for their differential expression between strains and their potential role in influencing the severity of kidney damage. Further genetic analysis should lead to identifying ADR nephropathy modifier gene(s), aiding in early diagnosis and providing novel approaches to kidney disease treatment and prevention.

Differences in susceptibility to ADR nephropathy among C57BL/6 substrains

Adriamycin (ADR) nephropathy is the most widely used nephropathy model to study the pathophysiological mechanisms of chronic kidney disease (CKD) in mice. However, its application is limited to a few mouse strains such as the BALB/c strain; the standard strain, C57BL/6J (B6J), does not develop ADR nephropathy. Nevertheless, Arif et al. reported that C57BL/6N (B6N), another standard strain, is ADR-susceptible. Since then, no follow-up reports or other studies have been published on ADR nephropathy in B6N mice. Therefore, the goal of this study was to determine whether B6N mice are indeed susceptible to ADR nephropathy and whether there are differences in ADR susceptibility among the substrains of C57BL/6NCrl (NCrl) and C57BL/6NJcl (NJcl). NCrl mice showed marked albuminuria and mesangial cell proliferation, which are associated with mild ADR nephropathy, confirming that NCrl mice were susceptible to ADR nephropathy. On the other hand, NJcl mice did not exhibit these symptoms. ADR nephropathy models are usually generated by administering ADR through the tail vein, but Arif et al. administered ADR through the orbital vein. Therefore, we investigated the effect of the route of administration on ADR nephropathy. The degree of ADR nephropathy was found to vary based on the route of administration: more severe nephropathy was observed upon administration through the tail vein than through the orbital vein. Therefore, we conclude that NCrl mice are susceptible to ADR nephropathy, and the severity of ADR-induced nephropathy through orbital vein administration is relatively lower than that through the tail vein.

Female but Not Male Mice Deficient in Soluble IgM Are Susceptible to Chemically Induced Glomerular Injury

B cell-targeted therapies are effective for treating multiple different kidney diseases in humans and also protect mice from Adriamycin nephropathy. Because glomerular IgM is frequently seen in both humans and mice with "nonimmune" forms of glomerular disease, we hypothesized that natural IgM binds to epitopes displayed in the injured glomerulus, exacerbating injury. To test this hypothesis, we induced Adriamycin nephropathy in BALB/C mice that cannot secrete soluble IgM (sIgM-/- mice) and compared them with BALB/C controls. Contrary to our prediction, we found that female sIgM-/- mice developed higher mortality and more severe kidney injury after injection of Adriamycin. The absence of soluble IgM did not reduce glomerular complement activation, and IgG was seen deposited within the injured glomeruli. Furthermore, we discovered that female sIgM-/- mice have higher levels of anti-cardiolipin IgG, and that IgG from these mice binds to epitopes in the injured kidney. These findings indicate that natural IgM may prevent generation of autoreactive IgG. Circulating levels of anti-cardiolipin IgG decreased after induction of kidney injury in female mice, consistent with deposition of the Abs in injured tissues. Better understanding of the mechanisms by which the immune system modulates and amplifies kidney injury may enable the development of targeted therapies to slow kidney disease progression.

Induce male sterility by CRISPR/Cas9-mediated mitochondrial genome editing in tobacco

Genome editing has become more and more popular in animal and plant systems following the emergence of CRISPR/Cas9 technology. However, target sequence modification by CRISPR/Cas9 has not been reported in the plant mitochondrial genome, mtDNA. In plants, a type of male sterility known as cytoplasmic male sterility (CMS) has been associated with certain mitochondrial genes, but few genes have been confirmed by direct mitochondrial gene-targeted modifications. Here, the CMS-associated gene (mtatp9) in tobacco was cleaved using mitoCRISPR/Cas9 with a mitochondrial localization signal. The male-sterile mutant, with aborted stamens, exhibited only 70% of the mtDNA copy number of the wild type and exhibited an altered percentage of heteroplasmic mtatp9 alleles; otherwise, the seed setting rate of the mutant flowers was zero. Transcriptomic analyses showed that glycolysis, tricarboxylic acid cycle metabolism and the oxidative phosphorylation pathway, which are all related to aerobic respiration, were inhibited in stamens of the male-sterile gene-edited mutant. In addition, overexpression of the synonymous mutations dsmtatp9 could restore fertility to the male-sterile mutant. Our results strongly suggest that mutation of mtatp9 causes CMS and that mitoCRISPR/Cas9 can be used to modify the mitochondrial genome of plants.

Molecular and Pathological Analyses of IARS1-Deficient Mice: An IARS Disorder Model

Most mitochondrial diseases are hereditary and highly heterogeneous. Cattle born with the V79L mutation in the isoleucyl-tRNA synthetase 1 (IARS1) protein exhibit weak calf syndrome. Recent human genomic studies about pediatric mitochondrial diseases also identified mutations in the IARS1 gene. Although severe prenatal-onset growth retardation and infantile hepatopathy have been reported in such patients, the relationship between IARS mutations and the symptoms is unknown. In this study, we generated hypomorphic IARS1^V79L mutant mice to develop an animal model of IARS mutation-related disorders. We found that compared to wild-type mice, IARS^V79L mutant mice showed a significant increase in hepatic triglyceride and serum ornithine carbamoyltransferase levels, indicating that IARS1^V79L mice suffer from mitochondrial hepatopathy. In addition, siRNA knockdown of the IARS1 gene decreased mitochondrial membrane potential and increased reactive oxygen species in the hepatocarcinoma-derived cell line HepG2. Furthermore, proteomic analysis revealed decreased levels of the mitochondrial function-associated protein NME4 (mitochondrial nucleoside diphosphate kinase). Concisely, our mutant mice model can be used to study IARS mutation-related disorders.

DNA-PKcs and ATM modulate mitochondrial ADP-ATP exchange as an oxidative stress checkpoint mechanism

DNA-PKcs is a key regulator of DNA double-strand break repair. Apart from its canonical role in the DNA damage response, DNA-PKcs is involved in the cellular response to oxidative stress (OS), but its exact role remains unclear. Here, we report that DNA-PKcs-deficient human cells display depolarized mitochondria membrane potential (MMP) and reoriented metabolism, supporting a role for DNA-PKcs in oxidative phosphorylation (OXPHOS). DNA-PKcs directly interacts with mitochondria proteins ANT2 and VDAC2, and formation of the DNA-PKcs/ANT2/VDAC2 (DAV) complex supports optimal exchange of ADP and ATP across mitochondrial membranes to energize the cell via OXPHOS and to maintain MMP. Moreover, we demonstrate that the DAV complex temporarily dissociates in response to oxidative stress to attenuate ADP-ATP exchange, a rate-limiting step for OXPHOS. Finally, we found that dissociation of the DAV complex is mediated by phosphorylation of DNA-PKcs at its Thr2609 cluster by ATM kinase. Based on these findings, we propose that the coordination between the DAV complex and ATM serves as a novel oxidative stress checkpoint to decrease ROS production from mitochondrial OXPHOS and to hasten cellular recovery from OS.

Protective effect of the tunneling nanotube-TNFAIP2/M-sec system on podocyte autophagy in diabetic nephropathy

Podocyte injury leading to albuminuria is a characteristic feature of diabetic nephropathy (DN). Hyperglycemia and advanced glycation end products (AGEs) are major determinants of DN. However, the underlying mechanisms of podocyte injury remain poorly understood. The cytosolic protein TNFAIP2/M-Sec is required for tunneling nanotubes (TNTs) formation, which are membrane channels that transiently connect cells, allowing organelle transfer. Podocytes express TNFAIP2 and form TNTs, but the potential relevance of the TNFAIP2-TNT system in DN is unknown. We studied TNFAIP2 expression in both human and experimental DN and the renal effect of tnfaip2 deletion in streptozotocin-induced DN. Moreover, we explored the role of the TNFAIP2-TNT system in podocytes exposed to diabetes-related insults. TNFAIP2 was overexpressed by podocytes in both human and experimental DN and exposre of podocytes to high glucose and AGEs induced the TNFAIP2-TNT system. In diabetic mice, tnfaip2 deletion exacerbated albuminuria, renal function loss, podocyte injury, and mesangial expansion. Moreover, blockade of the autophagic flux due to lysosomal dysfunction was observed in diabetes-injured podocytes both in vitro and in vivo and exacerbated by tnfaip2 deletion. TNTs allowed autophagosome and lysosome exchange between podocytes, thereby ameliorating AGE-induced lysosomal dysfunction and apoptosis. This protective effect was abolished by tnfaip2 deletion, TNT inhibition, and donor cell lysosome damage. By contrast, Tnfaip2 overexpression enhanced TNT-mediated transfer and prevented AGE-induced autophagy and lysosome dysfunction and apoptosis. In conclusion, TNFAIP2 plays an important protective role in podocytes in the context of DN by allowing TNT-mediated autophagosome and lysosome exchange and may represent a novel druggable target.Abbreviations: AGEs: advanced glycation end products; AKT1: AKT serine/threonine kinase 1; AO: acridine orange; ALs: autolysosomes; APs: autophagosomes; BM: bone marrow; BSA: bovine serum albumin; CTSD: cathepsin D; DIC: differential interference contrast; DN: diabetic nephropathy; FSGS: focal segmental glomerulosclerosis; HG: high glucose; KO: knockout; LAMP1: lysosomal-associated membrane protein 1; LMP: lysosomal membrane permeabilization; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; PI3K: phosphoinositide 3-kinase; STZ: streptozotocin; TNF: tumor necrosis factor; TNFAIP2: tumor necrosis factor, alpha-induced protein 2; TNTs: tunneling nanotubes; WT: wild type.

Genetic background strongly influences the transition to chronic kidney disease of adriamycin nephropathy in mice

Animal models of podocytopathy and chronic kidney diseases (CKD) help elucidate these pathologies. Adriamycin (ADR)-induced nephropathy is a common rodent model of podocytopathy. BALB/c mice are sensitive to ADR, whereas C57BL/6 (B6) mice, the most commonly used strain, are resistant to ADR. Therefore, mouse strains with the B6 genetic background cannot be used as an ADR nephropathy model. We previously generated DNA-dependent protein kinase catalytic subunit (Prkdc) mutant B6 mice (B6-Prkdc^R2140C) carrying the R2140C mutation that causes ADR nephropathy. However, whether ADR nephropathy in the novel strain progresses to CKD after ADR administration has not been evaluated. Therefore, we examined whether the B6-Prkdc^R2140C mice develop CKD after ADR administration. We also evaluated whether differences existed in the genetic background in ADR nephropathy by comparing the B6-Prkdc^R2140C mice with BALB/c mice. Our findings demonstrated that B6-Prkdc^R2140C progresses to CKD and is resistant to nephropathy compared with the BALB/c mice. The B6-Prkdc^R2140C and BALB/c mice differed in the expression of genes related to inflammatory mediators, and further analysis is required to identify factors that contribute to resistance to nephropathy.

Anti-ANGPTL3-FLD monoclonal antibody treatment ameliorates podocyte lesions through attenuating mitochondrial damage

Proteinuria, an indication of kidney disease, is caused by the malfunction of podocytes, which play a key role in maintaining glomerular filtration. Angiopoietin-like 3 (ANGPTL3) has been documented to have a cell-autonomous involvement in podocytes, and deletion of Angptl3 in podocytes reduced proteinuria in adriamycin-induced nephropathy. Here, we developed a monoclonal antibody (mAb) against ANGPTL3 to investigate its effects on podocyte injury in an ADR nephropathy mouse model and puromycin (PAN) induced podocyte damage in vitro. The mAb against the human ANGPTL3-FLD sequence (5E5F6) inhibited the binding of ANGPTL3-FLD to integrin β3. Treatment with the 5E5F6 mAb in ADR nephropathy mice mitigated proteinuria and led to a significant decline in podocyte apoptosis, reactive oxygen species (ROS) generation and mitochondrial fragmentation. In PAN-induced podocyte damage in vitro, the 5E5F6 mAb blocked the ANPGPLT3-mediated activation of integrin αvβ3 and Rac1, which regulated the mitochondrial homeostasis. Altogether, anti-ANGPLT3-FLD mAb attenuates proteinuria and podocyte lesions in ADR mice models, as well as PAN-induced podocyte damage, in part through regulating mitochondrial functions. Our study provides a therapeutic approach for targeting ANGPTL3 in proteinuric kidney disease.

Systemic gene therapy with thymosin β4 alleviates glomerular injury in mice

Plasma ultrafiltration in the kidney occurs across glomerular capillaries, which are surrounded by epithelial cells called podocytes. Podocytes have a unique shape maintained by a complex cytoskeleton, which becomes disrupted in glomerular disease resulting in defective filtration and albuminuria. Lack of endogenous thymosin β4 (TB4), an actin sequestering peptide, exacerbates glomerular injury and disrupts the organisation of the podocyte actin cytoskeleton, however, the potential of exogenous TB4 therapy to improve podocyte injury is unknown. Here, we have used Adriamycin (ADR), a toxin which injures podocytes and damages the glomerular filtration barrier leading to albuminuria in mice. Through interrogating single-cell RNA-sequencing data of isolated glomeruli we demonstrate that ADR injury results in reduced levels of podocyte TB4. Administration of an adeno-associated viral vector encoding TB4 increased the circulating level of TB4 and prevented ADR-induced podocyte loss and albuminuria. ADR injury was associated with disorganisation of the podocyte actin cytoskeleton in vitro, which was ameliorated by treatment with exogenous TB4. Collectively, we propose that systemic gene therapy with TB4 prevents podocyte injury and maintains glomerular filtration via protection of the podocyte cytoskeleton thus presenting a novel treatment strategy for glomerular disease.

Adriamycin-Induced Nephropathy is Robust in N and Modest in J Substrain of C57BL/6

Adriamycin (ADR)-induced nephropathy remains the leading model to study human primary focal segmental glomerulosclerosis (FSGS), a common pathway for podocyte damage and glomerular loss of function that leads to chronic kidney disease. However, the use of this model for reverse genetics is limited by historical categorization of C57BL/6 mice as an ADR-resistant strain, which is also the most common genetically modified strain. Additionally, conflicting reports exist utilizing C57BL/6 for ADR-nephrosis due to lack of understanding of substrain differences (J/N) and variability in ADR dosage, timing, and frequency to induce damage. We have undertaken a systematic approach to elucidate the specifics of ADR-nephrosis in C57BL/6 N and J substrains. We induced nephropathy with 2 doses of ADR, and measured albuminuria for 6 weeks and performed histological evaluations. Our findings revealed induction of robust and modest proteinuria in N and J substrains, respectively. The serum creatinine levels were elevated in N, but not J substrain. Both the substrains showed reduction in body weight with N greater than J, although mortality remained at 0% in both substrains. Histological analysis showed worse renal lesions in the N than the J substrain. Podocyte markers synaptopodin, nephrin, podocin, and WT1 were reduced to a greater extent in the N than the J substrain. In summary, we provide the nephrology community with a reproducible mouse model for FSGS, in a strain otherwise assumed to be ADR-resistant and highlight the differences between J and N substrains. This enables future studies, especially concerning genetically manipulated animal models in C57BL/6.

Myeloid-derived Growth Factor Deficiency Exacerbates Mitotic Catastrophe of Podocytes in Glomerular Disease

Podocytes are unique, highly specialized, terminally differentiated cells, which are restricted in a post-mitotic state with limited ability to repair or regenerate. Re-entering mitotic phase causes podocyte mitotic catastrophe, thereby leading to podocyte death and glomerular injury. Myeloid-derived growth factor (MYDGF) is a novel secreted protein and plays an important role on the regulation of cardiovascular function. However, whether MYDGF is expressed in kidney parenchymal cells and whether it has biological functions in the kidney remain unknown. Here, we found that MYDGF was expressed in kidney parenchymal cells and was significantly reduced in podocytes from mice with models of focal segmental glomerulosclerosis and diabetic kidney disease. Podocyte-specific deletion of MYDGF in mice exacerbated podocyte injury and proteinuria in both disease models. Functionally, MYDGF protected podocytes against mitotic catastrophe by reducing accumulation of podocytes in S phase, a portion of the cell cycle in which DNA is replicated. Mechanistically, MYDGF regulates the expression of the transcription factor RUNX2 which mediates part of MYDGF effects. Importantly, a significant reduction of MYDGF was found in glomeruli from patients with glomerular disease due to focal segmental glomerulosclerosis and diabetic kidney disease and the level of MYDGF was correlated with glomerular filtration rate, serum creatinine and podocyte loss. Thus, our studies indicate that MYDGF may be an attractive therapeutic target for glomerular disease.

Rodent models to study sodium retention in experimental nephrotic syndrome

Sodium retention and edema are hallmarks of nephrotic syndrome (NS). Different experimental rodent models have been established for simulating NS, however, not all of them feature sodium retention which requires proteinuria to exceed a certain threshold. In rats, puromycin aminonucleoside nephrosis (PAN) is a classic NS model introduced in 1955 that was adopted as doxorubicin-induced nephropathy (DIN) in 129S1/SvImJ mice. In recent years, mice with inducible podocin deletion (Nphs2^Δipod ) or podocyte apoptosis (POD-ATTAC) have been developed. In these models, sodium retention is thought to be caused by activation of the epithelial sodium channel (ENaC) in the distal nephron through aberrantly filtered serine proteases or proteasuria. Strikingly, rodent NS models follow an identical chronological time course after the development of proteinuria featuring sodium retention within days and spontaneous reversal thereafter. In DIN and Nphs2^Δipod mice, inhibition of ENaC by amiloride or urinary serine protease activity by aprotinin prevents sodium retention, opening up new and promising therapeutic approaches that could be translated into the treatment of nephrotic patients. However, the essential serine protease(s) responsible for ENaC activation is (are) still unknown. With the use of nephrotic rodent models, there is the possibility that this (these) will be identified in the future. This review summarizes the various rodent models used to study experimental nephrotic syndrome and the insights gained from these models with regard to the pathophysiology of sodium retention.

Exploring the cytotoxicity and anticancer effects of doxycycline and azithromycin on human glioblastoma multiforme cells

BACKGROUND

Previous studies had reported on the cytotoxic activities of generic antibiotics such as doxycycline (DOXY) and azithromycin (AZI) in multiple types of human cancers. Given that resistance to standard anti-glioblastoma multiforme (GBM) drug [temozolomide (TMZ)] is common and inevitable, alternative candidates are greatly needed.

PURPOSE AND METHOD

The present study was undertaken to explore the cytotoxicity and anticancer effects of DOXY and AZI on human GBM U87 cells via 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), Hoechst, Annexin V-FITC/PI, and clonogenic assays. CompuSyn software was used to determine the combination index (CI) for DOXY+AZI.

RESULT

Individual treatment with DOXY and AZI decreased U87 cell viability in dose- and time-dependent, and quantitatively comparable to TMZ. Nevertheless, combinations of both antibiotics evidenced antagonistic behaviour in U87 cells. Increased apoptotic event was also observed with the individual treatment of DOXY and AZI. Furthermore, the proliferative and clonogenic capability of 21-day survived U87 cells was completely terminated by DOXY and AZI, but not TMZ.

CONCLUSION

The antiproliferative and apoptosis-inducing activity exhibited by both antibiotics against U87 cells demonstrates their potential as a likely alternative to combat GBM. It would be interesting to find out more about their molecular players and cytotoxic effects in different types of GBM cells, including glioma stem cells (GSCs).

Essential role of DNA-PKcs and plasminogen for the development of doxorubicin-induced glomerular injury in mice

Susceptibility to doxorubicin-induced nephropathy (DIN), a toxic model for the induction of proteinuria in mice, is related to the single-nucleotide polymorphism (SNP) C6418T of the Prkdc gene encoding for the DNA-repair enzyme DNA-PKcs. In addition, plasminogen (Plg) has been reported to play a role in glomerular damage. Here, we investigated the interdependence of both factors for the development of DIN. Genotyping confirmed the SNP of the Prkdc gene in C57BL/6 (Prkdc^C6418/C6418) and 129S1/SvImJ (Prkdc^T6418/T6418) mice. Intercross of heterozygous 129SB6F1 mice led to 129SB6F2 hybrids with Mendelian inheritance of the SNP. After doxorubicin injection, only homozygous F2 mice with Prkdc^T6418/T6418 developed proteinuria. Genetic deficiency of Plg (Plg^−/−) in otherwise susceptible 129S1/SvImJ mice led to resistance to DIN. Immunohistochemistry revealed glomerular binding of Plg in Plg^+/+ mice after doxorubicin injection involving histone H2B as Plg receptor. In doxorubicin-resistant C57BL/6 mice, Plg binding was absent. In conclusion, susceptibility to DIN in 129S1/SvImJ mice is determined by a hierarchical two-hit process requiring the C6418T SNP in the Prkdc gene and subsequent glomerular binding of Plg.

This article has an associated First Person interview with the first author of the paper.

Summary: Susceptibility to doxorubicin-induced nephropathy in 129S1/SvImJ mice is determined by a hierarchical two-hit process requiring the C6418T single-nucleotide polymorphism in the Prkdc gene and subsequent glomerular binding of plasminogen.

Observation of non-glandular gastritis associated with Doxil chemotherapy treatment in NSG™ mice

NSG™ mice are highly immunocompromised thus demonstrate high efficiency engraftment of patient-derived xenografts (PDXs) for pre-clinical oncology research. It has previously been reported that NSG™ mice are hyper-sensitive to doxorubicin due to the impairment of DNA damage repair mechanisms. As such, doxorubicin causes a wide spectrum of toxicities including cardiotoxicity, hepatotoxicity and intestinal toxicity in NSG™ mice. Doxil is an alternative clinical formulation of doxorubicin, where doxorubicin is encapsulated within pegylated liposomes and displays improved toxicity profiles compared to conventional doxorubicin. Doxil was substituted for doxorubicin in our study to determine its toxicity profile in female NSG™ mice. The mice that were treated with Doxil developed dose-dependent histopathological alterations associated with non-glandular gastritis, with non-Helicobacter spp. bacterial infiltrates, as well as oesophagitis. Of note, a study using a dose of 2 mg/kg Doxil was terminated early due to significant weight loss while the use of Doxil at 1 mg/kg allowed for repeated treatment of twice a week for a duration of three weeks. A dose optimised treatment regimen has now been established and can be applied to assess Doxil-related anti-tumour efficacy in a range of PDX-bearing NSG™ mice.

A single amino acid substitution in PRKDC is a determinant of sensitivity to Adriamycin-induced renal injury in mouse

Adriamycin (ADR)-induced nephropathy is frequently utilized in rodent models of podocytopathy. However, the application of this model in mice is limited to a few strains, such as BALB/c mice. The most commonly used mouse strain, C57BL/6 (B6), is resistant to ADR-induced nephropathy, as are all mouse strains with a B6 genetic background. Reportedly, the R2140C variant of the Prkdc gene is the cause of susceptibility to ADR-induced nephropathy in mice. To verify this hypothesis, we produced Prkdc mutant B6 mice, termed B6-Prkdc^R2140C, that possess the R2140C mutation. After administration of ADR, B6-Prkdc^R2140C mice exhibited massive proteinuria and glomerular and renal tubular injuries. In addition, there was no significant difference in the severity between B6-Prkdc^R2140C and BALB/c. These findings demonstrated that B6-Prkdc^R2140C show ADR-induced nephropathy susceptibility at a similar level to BALB/c, and that the PRKDC R2140C variant causes susceptibility to ADR-induced nephropathy. In future studies, ADR-induced nephropathy may become applicable to various kinds of genetically modified mice with a B6 background by mating with B6-Prkdc^R2140C.

Loss of decay-accelerating factor triggers podocyte injury and glomerulosclerosis

Kidney glomerulosclerosis commonly progresses to end-stage kidney failure, but pathogenic mechanisms are still poorly understood. Here, we show that podocyte expression of decay-accelerating factor (DAF/CD55), a complement C3 convertase regulator, crucially controls disease in murine models of adriamycin (ADR)-induced focal and segmental glomerulosclerosis (FSGS) and streptozotocin (STZ)-induced diabetic glomerulosclerosis. ADR induces enzymatic cleavage of DAF from podocyte surfaces, leading to complement activation. C3 deficiency or prevention of C3a receptor (C3aR) signaling abrogates disease despite DAF deficiency, confirming complement dependence. Mechanistic studies show that C3a/C3aR ligations on podocytes initiate an autocrine IL-1β/IL-1R1 signaling loop that reduces nephrin expression, causing actin cytoskeleton rearrangement. Uncoupling IL-1β/IL-1R1 signaling prevents disease, providing a causal link. Glomeruli of patients with FSGS lack DAF and stain positive for C3d, and urinary C3a positively correlates with the degree of proteinuria. Together, our data indicate that the development and progression of glomerulosclerosis involve loss of podocyte DAF, triggering local, complement-dependent, IL-1β–induced podocyte injury, potentially identifying new therapeutic targets.

Dysregulated Dynein-Mediated Trafficking of Nephrin Causes INF2-related Podocytopathy

BACKGROUND

FSGS caused by mutations in INF2 is characterized by a podocytopathy with mistrafficked nephrin, an essential component of the slit diaphragm. Because INF2 is a formin-type actin nucleator, research has focused on its actin-regulating function, providing an important but incomplete insight into how these mutations lead to podocytopathy. A yeast two-hybridization screen identified the interaction between INF2 and the dynein transport complex, suggesting a newly recognized role of INF2 in regulating dynein-mediated vesicular trafficking in podocytes.

METHODS

Live cell and quantitative imaging, fluorescent and surface biotinylation-based trafficking assays in cultured podocytes, and a new puromycin aminoglycoside nephropathy model of INF2 transgenic mice were used to demonstrate altered dynein-mediated trafficking of nephrin in INF2 associated podocytopathy.

RESULTS

Pathogenic INF2 mutations disrupt an interaction of INF2 with dynein light chain 1, a key dynein component. The best-studied mutation, R218Q, diverts dynein-mediated postendocytic sorting of nephrin from recycling endosomes to lysosomes for degradation. Antagonizing dynein-mediated transport can rescue this effect. Augmented dynein-mediated trafficking and degradation of nephrin underlies puromycin aminoglycoside-induced podocytopathy and FSGS in vivo.

CONCLUSIONS

INF2 mutations enhance dynein-mediated trafficking of nephrin to proteolytic pathways, diminishing its recycling required for maintaining slit diaphragm integrity. The recognition that dysregulated dynein-mediated transport of nephrin in R218Q knockin podocytes opens an avenue for developing targeted therapy for INF2-mediated FSGS.

Synaptopodin Is Dispensable for Normal Podocyte Homeostasis but Is Protective in the Context of Acute Podocyte Injury

BACKGROUND

Synaptopodin (Synpo) is an actin-associated protein in podocytes and dendritic spines. Many functions in regulating the actin cytoskeleton via RhoA and other pathways have been ascribed to Synpo, yet no pathogenic mutations in the SYNPO gene have been discovered in patients. Naturally occurring Synpo isoforms are known (Synpo-short and -long), and a novel truncated version (Synpo-T) is upregulated in podocytes from Synpo mutant mice. Synpo-T maintains some Synpo functions, which may prevent a podocyte phenotype from emerging in unchallenged mutant mice.

METHODS

Novel mouse models were generated to further investigate the functions of Synpo. In one, CRISPR/Cas9 deleted most of the Synpo gene, preventing production of any detectable Synpo protein. Two other mutant strains made truncated versions of the protein. Adriamycin injections were used to challenge the mice, and Synpo functions were investigated in primary cultured podocytes.

RESULTS

Mice that could not make detectable Synpo (Synpo ^-/- ) did not develop any kidney abnormalities up to 12 months of age. However, Synpo ^-/- mice were more susceptible to Adriamycin nephropathy. In cultured primary podocytes from mutant mice, the absence of Synpo caused loss of stress fibers, increased the number and size of focal adhesions, and impaired cell migration. Furthermore, loss of Synpo led to decreased RhoA activity and increased Rac1 activation.

CONCLUSIONS

In contrast to previous findings, podocytes can function normally in vivo in the absence of any Synpo isoform. Synpo plays a protective role in the context of podocyte injury through its involvement in actin reorganization and focal adhesion dynamics.

Opa1 Overexpression Protects from Early-Onset Mpv17-/--Related Mouse Kidney Disease

Moderate overexpression of Opa1, the master regulator of mitochondrial cristae morphology, significantly improved mitochondrial damage induced by drugs, surgical denervation, or oxidative phosphorylation (OXPHOS) defects due to specific impairment of a single mitochondrial respiratory chain complex. Here, we investigated the effectiveness of this approach in the Mpv17-/- mouse, characterized by profound, multisystem mitochondrial DNA (mtDNA) depletion. After the crossing with Opa1tg mice, we found a surprising anticipation of the severe, progressive focal segmental glomerulosclerosis, previously described in Mpv17-/- animals as a late-onset clinical feature (after 12-18 months of life). In contrast, Mpv17-/- animals from this new "mixed" strain died at 8-9 weeks after birth because of severe kidney failure However, Mpv17-/-::Opa1tg mice lived much longer than Mpv17-/- littermates and developed the kidney dysfunction much later. mtDNA content and OXPHOS activities were significantly higher in Mpv17-/-::Opa1tg than in Mpv17-/- kidneys and similar to those for wild-type (WT) littermates. Mitochondrial network and cristae ultrastructure were largely preserved in Mpv17-/-::Opa1tg versus Mpv17-/- kidney and isolated podocytes. Mechanistically, the protective effect of Opa1 overexpression in this model was mediated by a block in apoptosis due to the stabilization of the mitochondrial cristae. These results demonstrate that strategies aiming at increasing Opa1 expression or activity can be effective against mtDNA depletion syndromes.

MicroRNA‑145 promotes the apoptosis of leukemic stem cells and enhances drug‑resistant K562/ADM cell sensitivity to adriamycin via the regulation of ABCE1

Leukemia is a type of cancer which originates in blood-forming tissues. MicroRNAs (miRNAs or miRs) have been shown to be involved leukemogenesis. In the present study, following the gain- and loss-function of miR-145 and ATP-binding cassette sub-family E member 1 (ABCE1) in K562 cells and K562 adriamycin-resistant cells (K562/ADM cells), the levels of multidrug resistance protein 1 (MRP1) and P-glycoprotein (P-gp) were measured. The viability of the K562 cells and K562/ADM cells treated with various concentrations of ADM, and cell sensitivity to ADM were measured. The apoptosis of stem cells was detected. K562/ADM cells were transfected with miR-145 mimic or with miR-145 mimic together with ABCE1 overexpression plasmid to examine the effects of ABCE1 on the sensitivity of K562/ADM cells to ADM. The association between miR-145 and ABCE1/MRP1 was then verified. The dose- and time-dependent effects of ADM on the K562 cells and K562/ADM cells were examined. The K562/ADM cells exhibited a greater resistance to ADM, higher levels of MRP1 and P-gp, and a lower miR-145 expression. The K562/ADM cells and stem cells in which miR-145 was overexpressed exhibited a suppressed cell proliferation, decreased MRP1 and P-gp levels, and an increased apoptotic rate. However, K562 cells with a low expression of miR-145 exhibited an increased cell proliferation, increased levels of MRP1 and P-gp, and a suppressed apoptotic rate. Compared with the overexpression of miR-145, the combination of miR-145 and ABCE1 decreased the sensitivity of drug-resistant K562/ADM cells to ADM. The above-mentioned effects of miR-145 were achieved by targeting ABCE1. Taken together, the findings of the present study demonstrate that the overexpression of miR-145 promotes leukemic stem cell apoptosis and enhances the sensitivity of K562/ADM cells to ADM by inhibiting ABCE1.

Epigenetic transcriptional reprogramming by WT1 mediates a repair response during podocyte injury

In the context of human disease, the mechanisms whereby transcription factors reprogram gene expression in reparative responses to injury are not well understood. We have studied the mechanisms of transcriptional reprogramming in disease using murine kidney podocytes as a model for tissue injury. Podocytes are a crucial component of glomeruli, the filtration units of each nephron. Podocyte injury is the initial event in many processes that lead to end-stage kidney disease. Wilms tumor-1 (WT1) is a master regulator of gene expression in podocytes, binding nearly all genes known to be crucial for maintenance of the glomerular filtration barrier. Using murine models and human kidney organoids, we investigated WT1-mediated transcriptional reprogramming during the course of podocyte injury. Reprogramming the transcriptome involved highly dynamic changes in the binding of WT1 to target genes during a reparative injury response, affecting chromatin state and expression levels of target genes.

Mitochondria-Modulating Porous Se@SiO2 Nanoparticles Provide Resistance to Oxidative Injury in Airway Epithelial Cells: Implications for Acute Lung Injury

Background

Mitochondrial dysfunction played a vital role in the pathogenesis of various diseases, including acute lung injury (ALI). However, few strategies targeting mitochondria were developed in treating ALI. Recently, we fabricated a porous Se@SiO₂ nanoparticles (NPs) with antioxidant properties.

Methods

The protective effect of Se@SiO₂ NPs was assessed using confocal imaging, immunoblotting, RNA-seq, mitochondrial respiratory chain (MRC) activity assay, and transmission electron microscopy (TEM) in airway epithelial cell line (Beas-2B). The in vivo efficacy of Se@SiO₂ NPs was evaluated in a lipopolysaccharide (LPS)-induced ALI mouse model.

Results

This study demonstrated that Se@SiO₂ NPs significantly increased the resistance of airway epithelial cells under oxidative injury and shifted lipopolysaccharide-induced gene expression profile closer to the untreated controls. The cytoprotection of Se@SiO₂ was found to be achieved by maintaining mitochondrial function, activity, and dynamics. In an animal model of ALI, pretreated with the NPs improved mitochondrial dysfunction, thus reducing inflammatory responses and diffuse damage in lung tissues. Additionally, RNA-seq analysis provided evidence for the broad modulatory activity of our Se@SiO₂ NPs in various metabolic disorders and inflammatory diseases.

Conclusion

This study brought new insights into mitochondria-targeting bioactive NPs, with application potential in curing ALI or other human mitochondria-related disorders.

A genome-wide analysis of targets of macrolide antibiotics in mammalian cells

Macrolide antibiotics, such as erythromycin and josamycin, are natural polyketide products harboring 14- to 16-membered macrocyclic lactone rings to which various sugars are attached. These antibiotics are used extensively in the clinic because of their ability to inhibit bacterial protein synthesis. More recently, some macrolides have been shown to also possess anti-inflammatory and other therapeutic activities in mammalian cells. To better understand the targets and effects of this drug class in mammalian cells, we used a genome-wide shRNA screen in K562 cancer cells to identify genes that modulate cellular sensitivity to josamycin. Among the most sensitizing hits were proteins involved in mitochondrial translation and the mitochondrial unfolded protein response, glycolysis, and the mitogen-activated protein kinase signaling cascade. Further analysis revealed that cells treated with josamycin or other antibacterial agents exhibited impaired oxidative phosphorylation and metabolic shifts to glycolysis. Interestingly, we observed that knockdown of the mitogen-activated protein kinase kinase kinase 4 (MAP3K4) gene, which contributes to p38 mitogen-activated protein kinase signaling, sensitized cells only to josamycin but not to other antibacterial agents. There is a growing interest in better characterizing the therapeutic effects and toxicities of antibiotics in mammalian cells to guide new applications in both cellular and clinical studies. To our knowledge, this is the first report of an unbiased genome-wide screen to investigate the effects of a clinically used antibiotic on human cells.

Genetic Ablation of Calcium-independent Phospholipase A2γ Exacerbates Glomerular Injury in Adriamycin Nephrosis in Mice

Genetic ablation of calcium-independent phospholipase A₂γ (iPLA₂γ) in mice results in marked damage of mitochondria and enhanced autophagy in glomerular visceral epithelial cells (GECs) or podocytes. The present study addresses the role of iPLA₂γ in glomerular injury. In adriamycin nephrosis, deletion of iPLA₂γ exacerbated albuminuria and reduced podocyte number. Glomerular LC3-II increased and p62 decreased in adriamycin-treated iPLA₂γ knockout (KO) mice, compared with treated control, in keeping with increased autophagy in KO. iPLA₂γ KO GECs in culture also demonstrated increased autophagy, compared with control GECs. iPLA₂γ KO GECs showed a reduced oxygen consumption rate and increased phosphorylation of AMP kinase (pAMPK), consistent with mitochondrial dysfunction. Adriamycin further stimulated pAMPK and autophagy. After co-transfection of GECs with mito-YFP (to label mitochondria) and RFP-LC3 (to label autophagosomes), or RFP-LAMP1 (to label lysosomes), there was greater colocalization of mito-YFP with RFP-LC3-II and with RFP-LAMP1 in iPLA₂γ KO GECs, compared with WT, indicating enhanced mitophagy in KO. Adriamycin increased mitophagy in WT cells. Thus, iPLA₂γ has a cytoprotective function in the normal glomerulus and in glomerulopathy, as deletion of iPLA₂γ leads to mitochondrial damage and impaired energy homeostasis, as well as autophagy and mitophagy.

FGF1ΔHBS ameliorates chronic kidney disease via PI3K/AKT mediated suppression of oxidative stress and inflammation

Currently, there is a lack of effective therapeutic approaches to the treatment of chronic kidney disease (CKD) with irreversible deterioration of renal function. This study aimed to investigate the ability of mutant FGF1 (FGF1^ΔHBS, which has reduced mitogenic activity) to alleviate CKD and to study its associated mechanisms. We found that FGF1^ΔHBS exhibited much weaker mitogenic activity than wild-type FGF1 (FGF1^WT) in renal tissues. RNA-seq analysis revealed that FGF1^ΔHBS inhibited oxidative stress and inflammatory signals in mouse podocytes challenged with high glucose. These antioxidative stress and anti-inflammatory activities of FGF1^ΔHBS prevented CKD in two mouse models: a diabetic nephropathy model and an adriamycin-induced nephropathy model. Further mechanistic analyses suggested that the inhibitory effects of FGF1^ΔHBS on oxidative stress and inflammation were mediated by activation of the GSK-3β/Nrf2 pathway and inhibition of the ASK1/JNK signaling pathway, respectively. An in-depth study demonstrated that both pathways are under control of PI3K/AKT signaling activated by FGF1^ΔHBS. This finding expands the potential uses of FGF1^ΔHBS for the treatment of various kinds of CKD associated with oxidative stress and inflammation.

Knock-In Strategy for Editing Human and Zebrafish Mitochondrial DNA Using Mito-CRISPR/Cas9 System

The mitochondria DNA (mtDNA) editing tool, zinc finger nucleases (ZFNs), transcription activator-like effector nuclease (TALENs), and clustered regularly interspaced short palindromic repeats/CRISPR associated protein 9 (CRISPR/Cas9) system, is a promising approach for the treatment of mtDNA diseases by eliminating mutant mitochondrial genomes. However, there have been no reports of repairing the mutant mtDNA with homologous recombination strategy to date. Here, we show a mito-CRISPR/Cas9 system that mito-Cas9 protein can specifically target mtDNA and reduce mtDNA copy number in both human cells and zebrafish. An exogenous single-stranded DNA with short homologous arm was knocked into the targeting loci accurately, and this mutagenesis could be steadily transmitted to F₁ generation of zebrafish. Moreover, we found some major factors involved in nuclear DNA repair were upregulated significantly by the mito-CRISPR/Cas9 system. Taken together, our data suggested that the mito-CRISPR/Cas9 system could be a useful method to edit mtDNA by knock-in strategy, providing a potential therapy for the treatment of inherited mitochondrial diseases.

Plectin protects podocytes from adriamycin-induced apoptosis and F-actin cytoskeletal disruption through the integrin α6β4/FAK/p38 MAPK pathway

Podocyte injury is an early pathological change characteristic of various glomerular diseases, and apoptosis and F‐actin cytoskeletal disruption are typical features of podocyte injury. In this study, we found that adriamycin (ADR) treatment resulted in typical podocyte injury and repressed plectin expression. Restoring plectin expression protected against ADR‐induced podocyte injury whereas siRNA‐mediated plectin silencing produced similar effects as ADR‐induced podocyte injury, suggesting that plectin plays a key role in preventing podocyte injury. Further analysis showed that plectin repression induced significant integrin α6β4, focal adhesion kinase (FAK) and p38 MAPK phosphorylation. Mutating Y1494, a key tyrosine residue in the integrin β4 subunit, blocked FAK and p38 phosphorylation, thereby alleviating podocyte injury. Inhibitor studies demonstrated that FAK Y397 phosphorylation promoted p38 activation, resulting in podocyte apoptosis and F‐actin cytoskeletal disruption. In vivo studies showed that administration of ADR to rats resulted in significantly increased 24‐hour urine protein levels along with decreased plectin expression and activated integrin α6β4, FAK, and p38. Taken together, these findings indicated that plectin protects podocytes from ADR‐induced apoptosis and F‐actin cytoskeletal disruption by inhibiting integrin α6β4/FAK/p38 pathway activation and that plectin may be a therapeutic target for podocyte injury‐related glomerular diseases.

Molecular and Cellular Mechanisms for Proteinuria in Minimal Change Disease

Minimal Change Disease (MCD) is a clinical condition characterized by acute nephrotic syndrome, no evident renal lesions at histology and good response to steroids. However, frequent recurrence of the disease requires additional therapies associated with steroids. Such multi-drug dependence and frequent relapses may cause disease evolution to focal and segmental glomerulosclerosis (FSGS) over time. The differences between the two conditions are not well defined, since molecular mechanisms may be shared by the two diseases. In some cases, genetic analysis can make it possible to distinguish MCD from FSGS; however, there are cases of overlap. Several hypotheses on mechanisms underlying MCD and potential molecular triggers have been proposed. Most studies were conducted on animal models of proteinuria that partially mimic MCD and may be useful to study glomerulosclerosis evolution; however, they do not demonstrate a clear-cut separation between MCD and FSGS. Puromycin Aminonucleoside and Adriamycin nephrosis are models of glomerular oxidative damage, characterized by loss of glomerular basement membrane polyanions resembling MCD at the onset and, at more advanced stages, by glomerulosclerosis resembling FSGS. Also Buffalo/Mna rats present initial lesions of MCD, subsequently evolving to FSGS; this mechanism of renal damage is clearer since this rat strain inherits the unique characteristic of overexpressing Th2 cytokines. In Lipopolysaccharide nephropathy, an immunological condition of renal toxicity linked to B7-1(CD80), mice develop transient proteinuria that lasts a few days. Overall, animal models are useful and necessary considering that they reproduce the evolution from MCD to FSGS that is, in part, due to persistence of proteinuria. The role of T/Treg/Bcells on human MCD has been discussed. Many cytokines, immunomodulatory mechanisms, and several molecules have been defined as a specific cause of proteinuria. However, the hypothesis of a single cell subset or molecule as cause of MCD is not supported by research and an interactive process seems more logical. The implication or interactive role of oxidants, Th2 cytokines, Th17, Tregs, B7-1(CD80), CD40/CD40L, c-Mip, TNF, uPA/suPAR, Angiopoietin-like 4 still awaits a definitive confirmation. Whole genome sequencing studies could help to define specific genetic features that justify a definition of MCD as a “clinical-pathology-genetic entity.”

Podocytes exhibit a specialized protein quality control employing derlin-2 in kidney disease

Podocytes are terminally differentiated cells of the kidney filtration barrier with a limited proliferative capacity and are the primary glomerular target for various sources of cellular stress. Accordingly, it is particularly important for podocytes to cope with stress efficiently to circumvent cell death and avoid compromising renal function. Improperly folded proteins within the endoplasmic reticulum (ER) are associated with increased cellular injury and cell death. To relieve ER stress, protein quality control mechanisms like ER-associated degradation (ERAD) are initiated. Derlin-2 is an important dislocation channel component in the ERAD pathway, having an indispensable role in clearing misfolded glycoproteins from the ER lumen. With studies linking ER stress to kidney disease, we investigated the role of derlin-2 in the susceptibility of podocytes to injury due to protein misfolding. We show that podocytes employ derlin-2 to mediate the ER quality control system to maintain cellular homeostasis in both mouse and human glomeruli. Patients with focal segmental glomerulosclerosis (FSGS) or diabetic nephropathy (DN) upregulate derlin-2 expression in response to glomerular injury, as do corresponding mouse models. In derlin-2-deficient podocytes, compensatory responses were lost under adriamycin (ADR)-induced ER dysfunction, and severe cellular injury ensued via a caspase-12-dependent pathway. Moreover, derlin-2 overexpression in vitro attenuated ADR-induced podocyte injury. Thus derlin-2 is part of a protein quality control mechanism that can rescue glomerular injury attributable to impaired protein folding pathways in the ER. Induction of derlin-2 expression in vivo may have applications in prevention and treatment of glomerular diseases.

Protein Kinase A/CREB Signaling Prevents Adriamycin-Induced Podocyte Apoptosis via Upregulation of Mitochondrial Respiratory Chain Complexes

Previous work showed that the activation of protein kinase A (PKA) signaling promoted mitochondrial fusion and prevented podocyte apoptosis. The cAMP response element binding protein (CREB) is the main downstream transcription factor of PKA signaling. Here we show that the PKA agonist 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate-cyclic AMP (pCPT-cAMP) prevented the production of adriamycin (ADR)-induced reactive oxygen species and apoptosis in podocytes, which were inhibited by CREB RNA interference (RNAi). The activation of PKA enhanced mitochondrial function and prevented the ADR-induced decrease of mitochondrial respiratory chain complex I subunits, NADH-ubiquinone oxidoreductase complex (ND) 1/3/4 genes, and protein expression. Inhibition of CREB expression alleviated pCPT-cAMP-induced ND3, but not the recovery of ND1/4 protein, in ADR-treated podocytes. In addition, CREB RNAi blocked the pCPT-cAMP-induced increase in ATP and the expression of peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1-α). The chromatin immunoprecipitation assay showed enrichment of CREB on PGC1-α and ND3 promoters, suggesting that these promoters are CREB targets. In vivo, both an endogenous cAMP activator (isoproterenol) and pCPT-cAMP decreased the albumin/creatinine ratio in mice with ADR nephropathy, reduced glomerular oxidative stress, and retained Wilm's tumor suppressor gene 1 (WT-1)-positive cells in glomeruli. We conclude that the upregulation of mitochondrial respiratory chain proteins played a partial role in the protection of PKA/CREB signaling.

Serum Response Factor Is Essential for Maintenance of Podocyte Structure and Function

Podocytes contain an intricate actin cytoskeleton that is essential for the specialized function of this cell type in renal filtration. Serum response factor (SRF) is a master transcription factor for the actin cytoskeleton, but the in vivo expression and function of SRF in podocytes are unknown. We found that SRF protein colocalizes with podocyte markers in human and mouse kidneys. Compared with littermate controls, mice in which the Srf gene was conditionally inactivated with NPHS2-Cre exhibited early postnatal proteinuria, hypoalbuminemia, and azotemia. Histologic changes in the mutant mice included glomerular capillary dilation and mild glomerulosclerosis, with reduced expression of multiple canonical podocyte markers. We also noted tubular dilation, cell proliferation, and protein casts as well as reactive changes in mesangial cells and interstitial inflammation. Ultrastructure analysis disclosed foot process effacement with loss of slit diaphragms. To ascertain the importance of SRF cofactors in podocyte function, we disabled the myocardin-related transcription factor A and B genes. Although loss of either SRF cofactor alone had no observable effect in the kidney, deficiency of both recapitulated the Srf-null phenotype. These results establish a vital role for SRF and two SRF cofactors in the maintenance of podocyte structure and function.

AF1q Contributes to Adriamycin-Induced Podocyte Injury by Activating Wnt/β-Catenin Signaling

BACKGROUND/AIMS

Injury of podocytes plays an important role in decline of glomerular filtration and proteinuria. It is well-known that proteinuria is associated with numerous chronic kidney diseases (CKD). However, the underlying mechanism of podocyte injury remains unclear.

METHODS

We used reverse transcription-quantitative PCR (RT-qPCR) to compare the expression level of the ALL1-fused from the chromosome 1q (AF1q) gene in mice and mouse podocytes (MPC5) with or without Adriamycin (ADR) treatment. The effects of AF1q on Wnt/ β-catenin signaling were investigated by determining the expressions of desmin, snail, WT1, nephrin and E-cadherin using western blotting.

RESULTS

We found that AF1q expression was elevated in podocytes treated with ADR than untreated cells. AF1q overexpression directly led to podocytes injury with increased levels of desmin and snail. Luciferase activity of TOPflash reporter was significantly increased in cells with AF1q overexpression than wild type cells whereas deletion of T-cell-factor-7 (TCF7) eliminated this effect. Immunoprecipitation assay evidenced that AF1q interacted with TCF7 and promoted both transcriptional and translational expressions of TCF7. Overexpression of AF1q increased protein expression of β-catenin. However, in podocytes with deletion of TCF7, AF1q was not able to promote β-catenin expression.

CONCLUSION

Our findings demonstrated that aberrant expression of AF1q may activate Wnt/β-catenin signaling and result in podocyte injury.

Hyperoside alleviates adriamycin-induced podocyte injury via inhibiting mitochondrial fission

Podocyte injury underlies many forms of glomerular diseases. Our previous study showed that hyperoside, a naturally occurring flavonoid, could decrease albuminuria at the early stage of diabetic nephropathy by ameliorating renal damage and podocyte injury. However, its protective mechanism against podocyte injury is unknown. A previous study demonstrated that hyperoside might inhibit amyloid β-protein-induced neurotoxicity by suppressing mitochondrial dysfunction. Both mitochondrial dysfunction and its upstream determinant mitochondrial fission were closely related to podocyte injury. Thus, in the current study, we tested the effect of hyperoside on mitochondrial dysfunction and mitochondrial fission in adriamycin (ADR)-induced podocyte injury. In the mice model of ADR-induced nephropathy, hyperoside treatment inhibited ADR-induced albuminuria and podocyte injury. Meanwhile, hyperoside also blocked ADR-induced mitochondrial dysfunction and mitochondrial fission. Consistently, in cultured human podocytes, hyperoside suppressed ADR-induced podocyte injury, mitochondrial dysfunction and mitochondrial fission. All these results indicated that hyperoside might inhibit ADR-induced mitochondrial dysfunction and podocyte injury through suppressing mitochondrial fission both in vivo and in vitro. The underlying mechanisms which we revealed support the therapeutic effects of hyperoside for a broad range of glomerular diseases.

Chemical Proteomic Approaches Targeting Cancer Stem Cells: A Review of Current Literature

Cancer stem cells (CSCs) have been proposed as central drivers of tumor initiation, progression, recurrence, and therapeutic resistance. Therefore, identifying stem-like cells within cancers and understanding their properties is crucial for the development of effective anticancer therapies. Recently, chemical proteomics has become a powerful tool to efficiently determine protein networks responsible for CSC pathophysiology and comprehensively elucidate molecular mechanisms of drug action against CSCs. This review provides an overview of major methodologies utilized in chemical proteomic approaches. In addition, recent successful chemical proteomic applications targeting CSCs are highlighted. Future direction of potential CSC research by integrating chemical genomic and proteomic data obtained from a single biological sample of CSCs are also suggested in this review.

The potential role of retinoic acid receptor α on glomerulosclerosis in rats and podocytes injury is associated with the induction of MMP2 and MMP9

Retinoic acid receptor α (RARα) plays a crucial role in kidney disease. However, the underlying mechanisms in glomerulosclerosis (GS) is still not clear. The roles of RARα in an adriamycin (ADR)-induced GS rat model and in ADR-induced podocyte injury in vitro were investigated. RARα was over-expressed in GS rats, and serum, urine and kidney samples were collected to detect the induction of the expression of the receptor. RARα expression was inhibited and/or over-expressed in cultured podocytes following injury, as demonstrated by morphometric assays, cell toxicity, and matrix metalloproteinase (MMP) enzymatic activity. RARα displayed a renoprotective role in GS rats, resulting in a lower GS index, podocyte foot process fusion, and proteinuria, reduced serum creatinine and blood urea nitrogen. Further experiments indicated that RARα inhibited the accumulation of TGF-β1, α-smooth muscle actin, collagen IV, and fibronectin, while it induced MMP2 and MMP9 excessive expression in podocytes in vitro. RARα improved the renal function and attenuated the progression of GS that was associated with the over-expression of MMP2 and MMP9.

Exacerbation of spontaneous autoimmune nephritis following regulatory T cell depletion in B cell lymphoma 2-interacting mediator knock-out mice

Regulatory T cells (Tregs ) have been recognized as central mediators for maintaining peripheral tolerance and limiting autoimmune diseases. The loss of Tregs or their function has been associated with exacerbation of autoimmune disease. However, the temporary loss of Tregs in the chronic spontaneous disease model has not been investigated. In this study, we evaluated the role of Tregs in a novel chronic spontaneous glomerulonephritis model of B cell lymphoma 2-interacting mediator (Bim) knock-out mice by transient depleting Tregs . Bim is a pro-apoptotic member of the B cell lymphoma 2 (Bcl-2) family. Bim knock-out (Bim-/- ) mice fail to delete autoreactive T cells in thymus, leading to chronic spontaneous autoimmune kidney disease. We found that Treg depletion in Bim-/- mice exacerbated the kidney injury with increased proteinuria, impaired kidney function, weight loss and greater histological injury compared with wild-type mice. There was a significant increase in interstitial infiltrate of inflammatory cells, antibody deposition and tubular damage. Furthermore, the serum levels of cytokines interleukin (IL)-2, IL-4, IL-6, IL-10, IL-17α, interferon (IFN)-γ and tumour necrosis factor (TNF)-α were increased significantly after Treg depletion in Bim-/- mice. This study demonstrates that transient depletion of Tregs leads to enhanced self-reactive T effector cell function followed by exacerbation of kidney disease in the chronic spontaneous kidney disease model of Bim-deficient mice.

Aging and the Krüppel-like factors

The mammalian Krüppel-like factors (KLFs) are a family of zinc-finger containing transcription factors with diverse patterns of expression and a wide array of cellular functions. While their roles in mammalian physiology are well known, there is a growing appreciation for their roles in modulating the fundamental progression of aging. Here we review the current knowledge of Krüppel-like factors with a focus on their roles in processes regulating aging and age-associated diseases.

Bone marrow-derived immature myeloid cells are a main source of circulating suPAR contributing to proteinuric kidney disease

Excess levels of protein in urine (proteinuria) is a hallmark of kidney disease that typically occurs in conjunction with diabetes, hypertension, gene mutations, toxins or infections but may also be of unknown cause (idiopathic). Systemic soluble urokinase plasminogen activator receptor (suPAR) is a circulating factor implicated in the onset and progression of chronic kidney disease (CKD), such as focal segmental glomerulosclerosis (FSGS). The cellular source(s) of elevated suPAR associated with future and progressing kidney disease is unclear, but is likely extra-renal, as the pathological uPAR is circulating and FSGS can recur even after a damaged kidney is replaced with a healthy donor organ. Here we report that bone marrow (BM) Gr-1^lo immature myeloid cells are responsible for the elevated, pathological levels of suPAR, as evidenced by BM chimera and BM ablation and cell transfer studies. A marked increase of Gr-1^lo myeloid cells was commonly found in the BM of proteinuric animals having high suPAR, and these cells efficiently transmit proteinuria when transferred to healthy mice. In accordance with the results seen in suPAR-associated proteinuric animal models, in which kidney damage is caused not by local podocyte-selective injury but more likely by systemic insults, a humanized xenograft model of FSGS resulted in an expansion of Gr-1^lo cells in the BM, leading to high plasma suPAR and proteinuric kidney disease. Together, these results identify suPAR as a functional connection between the BM and the kidney, and they implicate BM immature myeloid cells as a key contributor to glomerular dysfunction.

Non-Transgenic Mouse Models of Kidney Disease

Animal models are essential tools to understand the mechanisms underlying the development and progression of renal disease and to study potential therapeutic approaches. Recently, interventional models suitable to induce acute and chronic kidney disease in the mouse have become a focus of interest due to the wide availability of genetically engineered mouse lines. These models differ by their damaging mechanism (cell toxicity, immune mechanisms, surgical renal mass reduction, ischemia, hypertension, ureter obstruction etc.), functional and histomorphological phenotype and disease evolution. The susceptibility to a damaging mechanism often depends on strain and gender. The C57BL/6 strain, the most commonly used genetic background of transgenic mice, appears to be relatively resistant against developing glomerulosclerosis, proteinuria and hypertension. This review serves to provide a comprehensive overview of interventional mouse models of acute and chronic kidney disease.

Doxycycline down-regulates DNA-PK and radiosensitizes tumor initiating cells: Implications for more effective radiation therapy

DNA-PK is an enzyme that is required for proper DNA-repair and is thought to confer radio-resistance in cancer cells. As a consequence, it is a high-profile validated target for new pharmaceutical development. However, no FDA-approved DNA-PK inhibitors have emerged, despite many years of drug discovery and lead optimization. This is largely because existing DNA-PK inhibitors suffer from poor pharmacokinetics. They are not well absorbed and/or are unstable, with a short plasma half-life. Here, we identified the first FDA-approved DNA-PK inhibitor by "chemical proteomics". In an effort to understand how doxycycline targets cancer stem-like cells (CSCs), we serendipitously discovered that doxycycline reduces DNA-PK protein expression by nearly 15-fold (> 90%). In accordance with these observations, we show that doxycycline functionally radio-sensitizes breast CSCs, by up to 4.5-fold. Moreover, we demonstrate that DNA-PK is highly over-expressed in both MCF7- and T47D-derived mammospheres. Interestingly, genetic or pharmacological inhibition of DNA-PK in MCF7 cells is sufficient to functionally block mammosphere formation. Thus, it appears that active DNA-repair is required for the clonal expansion of CSCs. Mechanistically, doxycycline treatment dramatically reduced the oxidative mitochondrial capacity and the glycolytic activity of cancer cells, consistent with previous studies linking DNA-PK expression to the proper maintenance of mitochondrial DNA integrity and copy number. Using a luciferase-based assay, we observed that doxycycline treatment quantitatively reduces the anti-oxidant response (NRF1/2) and effectively blocks signaling along multiple independent pathways normally associated with stem cells, including STAT1/3, Sonic Hedgehog (Shh), Notch, WNT and TGF-beta signaling. In conclusion, we propose that the efficacy of doxycycline as a DNA-PK inhibitor should be tested in Phase-II clinical trials, in combination with radio-therapy. Doxycycline has excellent pharmacokinetics, with nearly 100% oral absorption and a long serum half-life (18-22 hours), at a standard dose of 200-mg per day. In further support of this idea, we show that doxycycline effectively inhibits the mammosphere-forming activity of primary breast cancer samples, derived from metastatic disease sites (pleural effusions or ascites fluid). Our results also have possible implications for the radio-therapy of brain tumors and/or brain metastases, as doxycycline is known to effectively cross the blood-brain barrier. Further studies will be needed to determine if other tetracycline family members also confer radio-sensitivity.

A monoclonal antibody raised against bacterially expressed MPV17 sequences shows peroxisomal, endosomal and lysosomal localisation in U2OS cells

Recessive mutations in the MPV17 gene cause mitochondrial DNA depletion syndrome, a fatal infantile genetic liver disease in humans. Loss of function in mice leads to glomerulosclerosis and sensineural deafness accompanied with mitochondrial DNA depletion. Mutations in the yeast homolog Sym1, and in the zebra fish homolog tra cause interesting, but not obviously related phenotypes, although the human gene can complement the yeast Sym1 mutation. The MPV17 protein is a hydrophobic membrane protein of 176 amino acids and unknown function. Initially localised in murine peroxisomes, it was later reported to be a mitochondrial inner membrane protein in humans and in yeast. To resolve this contradiction we tested two new mouse monoclonal antibodies directed against the human MPV17 protein in Western blots and immunohistochemistry on human U2OS cells. One of these monoclonal antibodies showed specific reactivity to a protein of 20 kD absent in MPV17 negative mouse cells. Immunofluorescence studies revealed colocalisation with peroxisomal, endosomal and lysosomal markers, but not with mitochondria. This data reveal a novel connection between a possible peroxisomal/endosomal/lysosomal function and mitochondrial DNA depletion.

Podocytes

Podocytes are highly specialized cells of the kidney glomerulus that wrap around capillaries and that neighbor cells of the Bowman’s capsule. When it comes to glomerular filtration, podocytes play an active role in preventing plasma proteins from entering the urinary ultrafiltrate by providing a barrier comprising filtration slits between foot processes, which in aggregate represent a dynamic network of cellular extensions. Foot processes interdigitate with foot processes from adjacent podocytes and form a network of narrow and rather uniform gaps. The fenestrated endothelial cells retain blood cells but permit passage of small solutes and an overlying basement membrane less permeable to macromolecules, in particular to albumin. The cytoskeletal dynamics and structural plasticity of podocytes as well as the signaling between each of these distinct layers are essential for an efficient glomerular filtration and thus for proper renal function. The genetic or acquired impairment of podocytes may lead to foot process effacement (podocyte fusion or retraction), a morphological hallmark of proteinuric renal diseases. Here, we briefly discuss aspects of a contemporary view of podocytes in glomerular filtration, the patterns of structural changes in podocytes associated with common glomerular diseases, and the current state of basic and clinical research.

The minipig as a new model for the evaluation of doxorubicin-induced chronic toxicity

Doxorubicin can cause life-threatening toxic effects in several organs, with cardiotoxicity being the major concern. Although a large number of animal models have been utilized to study doxorubicin toxicity, several restrictions limit their use. Since the Göttingen minipig is an accepted species for non-clinical safety assessment and translation to man, we aimed at exploring its use as a non-rodent animal model for safety assessment and regulatory toxicity studies using doxorubicin. Three groups of three males and three females adult Göttingen minipigs received 1.5 mg kg(-1) , 3/2.3 mg kg(-1) or vehicle at intervals of 3 weeks for 7 cycles. Doxorubicin treatment resulted in a dose-related decrease in the erythrocytes, hemoglobin and hematocrit count, accompanied by leukopenia and thrombocytopenia. Bone marrow smears revealed dose-related hypocellularity. Urea and creatinine levels were elevated in treated animals, associated with proteinuria and hematuria. Histopathological evaluation detected nephropathy and atrophy of hematopoietic tissues/organs, mucosa of the intestinal tract and male genital tract. Cardiac lesions including chronic inflammation, endocardial hyperplasia, hemorrhage and myxomatous changes were evident in hematoxylin and eosin stains, and evaluation of semi-thin sections showed the presence of dose-related vacuolation in the atrial and ventricular cardiomyocytes. Cardiac troponin levels were increased in the high-dose group, but there was no direct correlation to the severity of the histopathological lesions. This study confirms that the Göttingen minipig has a comparable toxicity profile to humans and considering its anatomical, physiological, genetic and biochemical resemblance to humans, it should be considered as the non-rodent species of choice for studies on doxorubicin toxicity. Copyright © 2015 John Wiley & Sons, Ltd.

Doxycycline and therapeutic targeting of the DNA damage response in cancer cells: old drug, new purpose

There is a small proportion of cells within a tumour with self-renewing properties, which is resistant to conventional therapy, and is responsible for tumour initiation, maintenance and metastasis. These cells are known as cancer stem cells (CSCs) or tumour-initiating cells (TICs) [1]. Recent publications identify several antibiotics, such as salinomycin or doxycycline, as selective CSCs inhibitors [2-4]. However, the mechanisms of action of these antibiotics on CSCs are not fully understood.

Oxidative/Nitrative Stress and Inflammation Drive Progression of Doxorubicin-Induced Renal Fibrosis in Rats as Revealed by Comparing a Normal and a Fibrosis-Resistant Rat Strain

Chronic renal fibrosis is the final common pathway of end stage renal disease caused by glomerular or tubular pathologies. Genetic background has a strong influence on the progression of chronic renal fibrosis. We recently found that Rowett black hooded rats were resistant to renal fibrosis. We aimed to investigate the role of sustained inflammation and oxidative/nitrative stress in renal fibrosis progression using this new model. Our previous data suggested the involvement of podocytes, thus we investigated renal fibrosis initiated by doxorubicin-induced (5 mg/kg) podocyte damage. Doxorubicin induced progressive glomerular sclerosis followed by increasing proteinuria and reduced bodyweight gain in fibrosis-sensitive, Charles Dawley rats during an 8-week long observation period. In comparison, the fibrosis-resistant, Rowett black hooded rats had longer survival, milder proteinuria and reduced tubular damage as assessed by neutrophil gelatinase-associated lipocalin (NGAL) excretion, reduced loss of the slit diaphragm protein, nephrin, less glomerulosclerosis, tubulointerstitial fibrosis and matrix deposition assessed by periodic acid–Schiff, Picro-Sirius-red staining and fibronectin immunostaining. Less fibrosis was associated with reduced profibrotic transforming growth factor-beta, (TGF-β1) connective tissue growth factor (CTGF), and collagen type I alpha 1 (COL-1a1) mRNA levels. Milder inflammation demonstrated by histology was confirmed by less monocyte chemotactic protein 1 (MCP-1) mRNA. As a consequence of less inflammation, less oxidative and nitrative stress was obvious by less neutrophil cytosolic factor 1 (p47^phox) and NADPH oxidase-2 (p91^phox) mRNA. Reduced oxidative enzyme expression was accompanied by less lipid peroxidation as demonstrated by 4-hydroxynonenal (HNE) and less protein nitrosylation demonstrated by nitrotyrosine (NT) immunohistochemistry and quantified by Western blot. Our results demonstrate that mediators of fibrosis, inflammation and oxidative/nitrative stress were suppressed in doxorubicin nephropathy in fibrosis-resistant Rowett black hooded rats underlying the importance of these pathomechanisms in the progression of renal fibrosis initiated by glomerular podocyte damage.