Endogenous NAMPT dampens chemokine expression and apoptotic responses in stressed tubular cells.

Diabetic nephropathy (DN) is the most common cause of end-stage renal disease and identification of new therapeutic targets is needed. Nicotinamide phosphoribosyltransferase (NAMPT) is both an extracellular and intracellular protein. Circulating NAMPT is increased in diabetics and in chronic kidney disease patients. The role of NAMPT in renal cell biology is poorly understood. NAMPT mRNA and protein were increased in the kidneys of rats with streptozotocin-induced diabetes. Immunohistochemistry localized NAMPT to glomerular and tubular cells in diabetic rats. The inflammatory cytokine TNFα increased NAMPT mRNA, protein and NAD production in cultured kidney human tubular cells. Exogenous NAMPT increased the mRNA expression of chemokines MCP-1 and RANTES. The NAMPT enzymatic activity inhibitor FK866 prevented these effects. By contrast, FK866 boosted TNFα-induced expression of MCP-1 and RANTES mRNA and endogenous NAMPT targeting by siRNA also had a proinflammatory effect. Furthermore, FK866 promoted tubular cell apoptosis in an inflammatory milieu containing the cytokines TNFα/IFNγ. In an inflammatory environment FK866 promoted tubular cell expression of the lethal cytokine TRAIL. These data are consistent with a role of endogenous NAMPT activity as an adaptive, protective response to an inflammatory milieu that differs from the proinflammatory activity of exogenous NAMPT. Thus, disruption of endogenous NAMPT function in stressed cells promotes tubular cell death and chemokine expression. This information may be relevant for the design of novel therapeutic strategies in DN.

TNF-related weak inducer of apoptosis (TWEAK) regulates junctional proteins in tubular epithelial cells via canonical NF-κB pathway and ERK activation.

The tubular epithelium may be intrinsically involved in promoting kidney injury by junctional instability, epithelial-mesenchymal transition (EMT) and extracellular matrix remodelling. In this work, we investigated whether the pleiotropic and proinflammatory cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK), could be able to disturb junctional protein expression and to induce EMT of tubular cells. In cultured murine proximal tubular cells TWEAK induced phenotypic changes that were accompanied by F-actin redistribution, loss of epithelial adherent (E-cadherin, Cadherin-16, ß-catenin) and tight junction (ZO-1) proteins, and re-expression of the mesenchymal protein Vimentin. The transcriptional repressors Snail and HNF1ß were also modulated by TWEAK. In a murine model of obstructive renal pathology, TWEAK expression correlated with the appearance of the mesenchymal marker αSMA in kidney tubular cells. Mechanistically, the epithelial changes induced by TWEAK, including loss of epithelial integrity and EMT, via Fn14 were TGF-ß1 independent, but mediated by several intracellular signaling systems, including the canonical NF-κB, ERK activation and the vitamin D receptor modulation. These results highlight potential contributions of TWEAK-induced inflammatory mechanisms that could unveil new pathogenic effects of TWEAK starting tubulointerstitial damage and fibrosis.

Biocompatibility reduces inflammation-induced apoptosis in mesothelial cells exposed to peritoneal dialysis fluid.

BACKGROUND/AIMS: Peritonitis is a major complication that arises out of peritoneal dialysis (PD), leading to death and loss of mesothelium and peritoneal injury, which may impede PD. We studied the combined impact of inflammatory mediators and PD fluids on mesothelial cell death. METHODS: Cultured human mesothelial cells. RESULTS: Inflammatory cytokines (TNF-α and interferon-γ) cooperate with bioincompatible PD fluids containing high glucose degradation product (GDP) concentrations to promote mesothelial cell death. Thus, the inflammatory cytokine cocktail induced a higher rate of death in cells cultured in high GDP PD fluid than in low GDP PD fluid or cell culture medium (cell death expressed as % hypodiploid cells: TNF-α and interferon-γ in RPMI: 14.15 ± 1.68, TNF-α and interferon-γ in 4.25% low GDP PD fluid 13.16 ± 3.29, TNF-α and interferon-γ in 4.25% high GDP PD fluid 25.88 ± 2.18%, p < 0.05 vs. the other two groups). BclxL BH4 peptides, Apaf-1 inhibition or caspase inhibition failed to protect from apoptosis induced by the combination of inflammatory cytokines and bioincompatible PD fluids, although they protected from other forms of mesothelial cell apoptosis. CONCLUSION: Inflammation cooperates with high GDP PD fluids to promote mesothelial cell death, which is resistant to several therapeutic approaches. This information provides a framework for selection of PD fluid during peritonitis.

TNF-related weak inducer of apoptosis (TWEAK) promotes kidney fibrosis and Ras-dependent proliferation of cultured renal fibroblast.

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) regulates apoptosis, proliferation and inflammation in renal epithelial cells and plays a role in acute kidney injury. However, there is little information on the chronic effects of TWEAK. We hypothesized that TWEAK may influence renal fibrosis and regulate kidney fibroblast biology, in part, through Ras pathway. We studied a chronic model of experimental unilateral ureteral obstruction in wild type and TWEAK deficient mice, and a murine model of systemic TWEAK overexpression. TWEAK actions were also explored in cultured renal and embryonic fibroblasts. TWEAK and TWEAK receptor expression was increased in the obstructed kidneys. The absence of TWEAK decreased early kidney tubular damage, inflammatory infiltrates and myofibroblast number. TWEAK deficient mice had decreased renal fibrosis 21days after obstruction, as assessed by extracellular matrix staining. In mice without prior underlying kidney disease, systemic overexpression of TWEAK induced kidney inflammation and fibrosis. In cultured fibroblasts, TWEAK induced proliferation through activation of the Ras/ERK pathway. TWEAK also activated nuclear factor κB (NFκB)-dependent inflammatory chemokine production in murine renal fibroblasts. In conclusion, lack of TWEAK reduces renal fibrosis in a model of persistent kidney insult and overexpression of TWEAK led to renal fibrosis. TWEAK actions on renal fibroblasts may contribute to the in vivo observations, as TWEAK promotes inflammatory activity and proliferation in fibroblast cultures.

TWEAK and the progression of renal disease: clinical translation.

Tumour necrosis factor-like weak inducer of apoptosis (TWEAK) activates the fibroblast growth factor-inducible-14 (Fn14) receptor. TWEAK has actions on intrinsic kidney cells and on inflammatory cells of potential pathophysiological relevance. The effects of TWEAK in tubular cells have been explored in most detail. In cultured murine tubular cells TWEAK induces the expression of inflammatory cytokines, downregulates the expression of Klotho, is mitogenic, and in the presence of sensitizing agents promotes apoptosis. Similar actions were observed on glomerular mesangial cells. In vivo TWEAK actions on healthy kidneys mimic cell culture observations. Increased expression of TWEAK and Fn14 was reported in human and experimental acute and chronic kidney injury. The role of TWEAK/Fn14 in kidney injury has been demonstrated in non-inflammatory compensatory renal growth, acute kidney injury and chronic kidney disease of immune and non-immune origin, including hyperlipidaemic nephropathy, lupus nephritis (LN) and anti-GBM nephritis. The nephroprotective effect of TWEAK or Fn14 targeting in immune-mediated kidney injury is the result of protection from TWEAK-induced injury of renal intrinsic cells, not from interference with the immune response. A phase I dose-ranging clinical trial demonstrated the safety of anti-TWEAK antibodies in humans. A phase II randomized placebo-controlled clinical trial exploring the efficacy, safety and tolerability of neutralizing anti-TWEAK antibodies as a tissue protection strategy in LN is ongoing. The eventual success of this trial may expand the range of kidney diseases in which TWEAK targeting should be explored.

Facts and Hopes on Cancer Immunotherapy for Small Cell Lung Cancer.

Platinum-based chemotherapy plus PD1 axis blockade is the standard of care in the first-line treatment of extensive-stage small cell lung cancer (SCLC). Despite the robust and consistent increase in long-term survival with PD1 axis inhibition, the magnitude of the benefit from immunotherapy seems lower than that for other solid tumors. Several immune evasive mechanisms have been shown to be prominently altered in human SCLC, including T-cell exclusion, downregulation of components of the MHC class I antigen processing and presentation machinery, or upregulation of macrophage inhibitory checkpoints, among others. New immunotherapies aiming to target some of these dominant immune suppressive features are being intensively evaluated preclinically and clinically in SCLC. They include strategies to enhance the efficacy and/or reverse features that promote intrinsic resistance to PD1 axis inhibition (e.g., restoring MHC class I deficiency and targeting DNA damage response) and novel immunomodulatory agents beyond T-cell checkpoint blockers (e.g., T cell-redirecting strategies, antibody-drug conjugates, or macrophage checkpoint blockers). Among them, delta-like ligand 3-targeted bispecific T-cell engagers have shown the most compelling preliminary evidence of clinical efficacy and hold promise as therapies that might contribute to further improve patient outcomes in this disease. In this study, we first provide a brief overview of key tumor microenvironment features of human SCLC. Then, we update the current clinical evidence with immune checkpoint blockade and review other emerging immunotherapy strategies that are gaining increasing attention in SCLC. We finally summarize our future perspective on immunotherapy and precision oncology for this disease.

Spatially Preserved Multi-Region Transcriptomic Subtyping and Biomarkers of Chemoimmunotherapy Outcome in Extensive-Stage Small Cell Lung Cancer.

PURPOSE: Transcriptomic subtyping holds promise for personalized therapy in extensive-stage small cell lung cancer (ES-SCLC). In this study, we aimed to assess intratumoral transcriptomic subtype diversity and to identify biomarkers of long-term chemoimmunotherapy benefit in human ES-SCLC. EXPERIMENTAL DESIGN: We analyzed tumor samples from 58 patients with ES-SCLC enrolled in two multicenter single-arm phase IIIb studies evaluating frontline chemoimmunotherapy in Spain: n = 32 from the IMfirst trial and n = 26 from the CANTABRICO trial. We used the GeoMx Digital Spatial Profiler system to perform multi-region transcriptomic analysis. For subtype classification, we performed hierarchical clustering using the relative expression of ASCL1 (SCLC-A), NEUROD1 (SCLC-N), POU2F3 (SCLC-P), and YAP1 (SCLC-Y). RESULTS: Subtype distribution was found to be similar between bothcohorts, except for SCLC-P, which was not identified in the CANTABRICO_DSP cohort. A total of 44% of the patients in both cohorts had tumors with multiple coexisting transcriptional subtypes. Transcriptional subtypes or subtype heterogeneity was not associated with outcomes. Most potential targets did not show subtype-specific expression. Consistently in both cohorts, tumors from patients with long-term benefit (time to progression ≥12 months) contained an IFNγ-dominated mRNA profile, including enhanced capacity for antigen presentation. Hypoxia and glycolytic pathways were associated with resistance to chemoimmunotherapy. CONCLUSIONS: This work suggests that intratumoral heterogeneity, inconsistent association with outcome, and unclear subtype-specific target expression might be significant challenges for subtype-based precision oncology in SCLC. Preexisting IFNγ-driven immunity and mitochondrial metabolism seem to be correlates of long-term efficacy in this study, although the absence of a chemotherapy control arm precludes concluding that these are predictive features specific for immunotherapy.

At the crossroads of immunotherapy for oncogene-addicted subsets of NSCLC.

Non-small-cell lung cancer (NSCLC) has become a paradigm of precision medicine, with the discovery of numerous disease subtypes defined by specific oncogenic driver mutations leading to the development of a range of molecularly targeted therapies. Over the past decade, rapid progress has also been made in the development of immune-checkpoint inhibitors (ICIs), especially antagonistic antibodies targeting the PD-L1-PD-1 axis, for the treatment of NSCLC. Although many of the major oncogenic drivers of NSCLC are associated with intrinsic resistance to ICIs, patients with certain oncogene-driven subtypes of the disease that are highly responsive to specific targeted therapies might also derive benefit from immunotherapy. However, the development of effective immunotherapy approaches for oncogene-addicted NSCLC has been challenged by a lack of predictive biomarkers for patient selection and limited knowledge of how ICIs and oncogene-directed targeted therapies should be combined. Therefore, whether ICIs alone or with chemotherapy or even in combination with molecularly targeted agents would offer comparable benefit in the context of selected oncogenic driver alterations to that observed in the general unselected NSCLC population remains an open question. In this Review, we discuss the effects of oncogenic driver mutations on the efficacy of ICIs and the immune tumour microenvironment as well as the potential vulnerabilities that could be exploited to overcome the challenges of immunotherapy for oncogene-addicted NSCLC.

Combination therapy with an angiotensin II receptor blocker and an HMG-CoA reductase inhibitor in experimental subtotal nephrectomy.

BACKGROUND: Angiotensin receptor 1 blockers (ARB) are standard nephroprotective drugs in chronic kidney disease. There is less evidence for a nephroprotective effect of HMG-CoA reductase inhibitors (statins) and much less is known about potential benefits of combination therapy. We evaluated the therapeutic potential of a statin alone or in combination with an ARB in experimental chronic kidney disease. METHODS: Subtotally nephrectomized (5/6 Nx) rats were treated early with vehicle, losartan, cerivastatin or losartan/cerivastatin. Expression of messenger RNA (mRNA) was assessed by real-time reverse transcription-polymerase chain reaction. Tissue proteins were localized by immunohistochemistry. Nuclear factor-κB (NF-κB) activation was measured in whole kidneys. RESULTS: In contrast to the sham group, at 6 weeks, vehicle-treated 5/6 Nx rats displayed renal lesions, albuminuria and increased blood pressure, serum creatinine and total kidney NF-κB p65 DNA-binding activity and preproendothelin-1, fibronectin and type I and III collagen mRNA. NF-κB activation correlated with albuminuria and histological renal injury. Losartan or combination therapy preserved renal function, abrogated albuminuria and improved glomerular and interstitial histology. Cerivastatin alone preserved renal function and improved interstitial injury but did not influence albuminuria, glomerular histology or NF-κB activation. Losartan/cerivastatin normalized kidney NF-κB activation and extracellular matrix mRNA expression pattern. The effect of losartan alone on these parameters was less intense. All treatments decreased preproendothelin-1 mRNA and preserved interstitial capillaries. CONCLUSIONS: In a chronic kidney disease model, early treatment with either an ARB or a statin preserved renal function although the mechanisms differed. Combination therapy with an ARB and a statin did not confer clear-cut advantages on biochemical and histological parameters over ARB alone, although it further improved the kidney NF-κB and gene expression profile.

Correction: Alfaro-Arnedo et al. IGF1R as a Potential Pharmacological Target in Allergic Asthma. Biomedicines 2021, 9, 912.

In the original article [...].

Comprehensive Characterization of Human Lung Large Cell Carcinoma Identifies Transcriptomic Signatures with Potential Implications in Response to Immunotherapy.

Lung cancer is the leading cause of cancer mortality worldwide, with non-small cell lung cancer (NSCLC) being the most prevalent histology. While immunotherapy with checkpoint inhibitors has shown outstanding results in NSCLC, the precise identification of responders remains a major challenge. Most studies attempting to overcome this handicap have focused on adenocarcinomas or squamous cell carcinomas. Among NSCLC subtypes, the molecular and immune characteristics of lung large cell carcinoma (LCC), which represents 10% of NSCLC cases, are not well defined. We hypothesized that specific molecular aberrations may impact the immune microenvironment in LCC and, consequently, the response to immunotherapy. To that end, it is particularly relevant to thoroughly describe the molecular genotype-immunophenotype association in LCC-to identify robust predictive biomarkers and improve potential benefits from immunotherapy. We established a cohort of 18 early-stage, clinically annotated, LCC cases. Their molecular and immune features were comprehensively characterized by genomic and immune-targeted sequencing panels along with immunohistochemistry of immune cell populations. Unbiased clustering defined two novel subgroups of LCC. Pro-immunogenic tumors accumulated certain molecular alterations, showed higher immune infiltration and upregulated genes involved in potentiating immune responses when compared to pro-tumorigenic samples, which favored tumoral progression. This classification identified a set of biomarkers that could potentially predict response to immunotherapy. These results could improve patient selection and expand potential benefits from immunotherapy.

IGF1R as a Potential Pharmacological Target in Allergic Asthma.

BACKGROUND: Asthma is a chronic lung disease characterized by reversible airflow obstruction, airway hyperresponsiveness (AHR), mucus overproduction and inflammation. Although Insulin-like growth factor 1 receptor (IGF1R) was found to be involved in asthma, its pharmacological inhibition has not previously been investigated in this pathology. We aimed to determine if therapeutic targeting of IGF1R ameliorates allergic airway inflammation in a murine model of asthma. METHODS: C57BL/6J mice were challenged by house dust mite (HDM) extract or PBS for four weeks and therapeutically treated with the IGF1R tyrosine kinase inhibitor (TKI) NVP-ADW742 (NVP) once allergic phenotype was established. RESULTS: Lungs of HDM-challenged mice exhibited a significant increase in phospho-IGF1R levels, incremented AHR, airway remodeling, eosinophilia and allergic inflammation, as well as altered pulmonary surfactant expression, all of being these parameters counteracted by NVP treatment. HDM-challenged lungs also displayed augmented expression of the IGF1R signaling mediator p-ERK1/2, which was greatly reduced upon treatment with NVP. CONCLUSIONS: Our results demonstrate that IGF1R could be considered a potential pharmacological target in murine HDM-induced asthma and a candidate biomarker in allergic asthma.

TNF superfamily: a growing saga of kidney injury modulators.

Members of the TNF superfamily participate in kidney disease. Tumor necrosis factor (TNF) and Fas ligand regulate renal cell survival and inflammation, and therapeutic targeting improves the outcome of experimental renal injury. TNF-related apoptosis-inducing ligand (TRAIL and its potential decoy receptor osteoprotegerin are the two most upregulated death-related genes in human diabetic nephropathy. TRAIL activates NF-kappaB in tubular cells and promotes apoptosis in tubular cells and podocytes, especially in a high-glucose environment. By contrast, osteoprotegerin plays a protective role against TRAIL-induced apoptosis. Another family member, TNF-like weak inducer of apoptosis (TWEAK induces inflammation and tubular cell death or proliferation, depending on the microenvironment. While TNF only activates canonical NF-kappaB signaling, TWEAK promotes both canonical and noncanonical NF-kappaB activation in tubular cells, regulating different inflammatory responses. TWEAK promotes the secretion of MCP-1 and RANTES through NF-kappaB RelA-containing complexes and upregulates CCl21 and CCL19 expression through NF-kappaB inducing kinase (NIK-) dependent RelB/NF-kappaB2 complexes. In vivo TWEAK promotes postnephrectomy compensatory renal cell proliferation in a noninflammatory milieu. However, in the inflammatory milieu of acute kidney injury, TWEAK promotes tubular cell death and inflammation. Therapeutic targeting of TNF superfamily cytokines, including multipronged approaches targeting several cytokines should be further explored.

Taming apoptosis in peritoneal dialysis.

Excessive, insufficient, or untimely apoptosis may result in disorders of cell numbers. Peritoneal demesothelization is an example of disease by decreased cell number; untimely leukocyte apoptosis impairs peritoneal defense. Conventional peritoneal dialysis solutions accelerate neutrophil apoptosis. Glucose degradation products such as 3,4-dideoxyglucosone-3-ene (3,4-DGE) decisively contribute to apoptosis induced by these solutions, in both leukocytes and mesothelial cells and in both culture and peritoneal dialysis patients. Pan-caspase inhibition retards neutrophil apoptosis and improves peritoneal clearance of Staphylococcus aureus in animal models. However, regulation of apoptosis in mesothelial cells is more complex than in leukocytes, and caspase inhibitors may not be the optimal drugs to modulate apoptosis in these cells. In this regard, Bax antagonistic peptides protect mesothelial cells from 3,4-DGE. In addition, novel molecular targets have been identified. Short-term modulation of apoptosis may be useful to accelerate recovery and to prevent irreversible peritoneal injury following peritonitis.

The death ligand TRAIL in diabetic nephropathy.

Apoptotic cell death contributes to diabetic nephropathy (DN), but its role is not well understood. The tubulointerstitium from DN biopsy specimens was microdissected, and expression profiles of genes related to apoptosis were analyzed. A total of 112 (25%) of 455 cell death-related genes were found to be significantly differentially regulated. Among those that showed the greatest changes in regulation were two death receptors, OPG (the gene encoding osteoprotegerin) and Fas, and the death ligand TRAIL. Glomerular and proximal tubular TRAIL expression, assessed by immunohistochemistry, was higher in DN kidneys than controls and was associated with clinical and histologic severity of disease. In vitro, proinflammatory cytokines but not glucose alone regulated TRAIL expression in the human proximal tubular cell line HK-2. TRAIL induced tubular cell apoptosis in a dosage-dependant manner, an effect that was more marked in the presence of high levels of glucose and proinflammatory cytokines. TRAIL also activated NF-kappaB, and inhibition of NF-kappaB sensitized cells to TRAIL-induced apoptosis. It is proposed that TRAIL-induced cell death could play an important role in the progression of human DN.

Fra-2-expressing macrophages promote lung fibrosis in mice.

Idiopathic Pulmonary Fibrosis (IPF) is a deadly disease with limited therapies. Tissue fibrosis is associated with Type 2 immune response, although the causal contribution of immune cells is not defined. The AP-1 transcription factor Fra-2 is upregulated in IPF lung sections and Fra-2 transgenic mice (Fra-2tg) exhibit spontaneous lung fibrosis. Here we show that Bleomycin-induced lung fibrosis is attenuated upon myeloid-inactivation of Fra-2 and aggravated in Fra-2tg bone marrow chimeras. Type VI collagen (ColVI), a Fra-2 transcriptional target, is up-regulated in three lung fibrosis models, and macrophages promote myofibroblast activation in vitro in a ColVI- and Fra-2-dependent manner. Fra-2 or ColVI inactivation does not affect macrophage recruitment and alternative activation, suggesting that Fra-2/ColVI specifically controls the paracrine pro-fibrotic activity of macrophages. Importantly, ColVI knock-out mice (KO) and ColVI-KO bone marrow chimeras are protected from Bleomycin-induced lung fibrosis. Therapeutic administration of a Fra-2/AP-1 inhibitor reduces ColVI expression and ameliorates fibrosis in Fra-2tg mice and in the Bleomycin model. Finally, Fra-2 and ColVI positively correlate in IPF patient samples and co-localize in lung macrophages. Therefore, the Fra-2/ColVI pro-fibrotic axis is a promising biomarker and therapeutic target for lung fibrosis, and possibly other fibrotic diseases.

TWEAKing renal injury.

TWEAK is a recently identified cytokine of the TNF superfamiliy. Through activation of the Fn14 receptor, TWEAK regulates cell proliferation, cell death and inflammation. Recent studies show increased TWEAK and Fn14 expression in tubular cells during acute kidney injury as well as elevated urinary TWEAK levels in patients with active lupus nephritis. Furthermore, glomerular mesangial cells and renal tubular epithelial cells express the Fn14 receptor under the regulation of proinflammatory cytokines. TWEAK weakly increases cell death and promotes secretion of inflammatory mediators in non-stimulated mesangial cells. In addition, in a proinflammatory milieu, TWEAK induces apoptosis of mesangial and tubular cells. The available data suggest that TWEAK is a new player in kidney injury both at the glomerular and tubulointerstitial levels and might be a target for therapeutic intervention.

3,4-Dideoxyglucosone-3-ene as a mediator of peritoneal demesothelization.

BACKGROUND: The mesothelium contributes significantly to the functional, structural and homeostatic properties of the peritoneum. Bioincompatible peritoneal dialysis solutions contribute to mesothelial cell loss during chronic peritoneal dialysis. Cell death has been implicated in mesothelial cell loss, but the molecular mechanisms have not been adequately characterized. We now report the modulation of mesothelial cell death by the glucose degradation product 3,4-dideoxyglucosone-3-ene (3,4-DGE). METHODS: Human mesothelial cells were cultured from the effluents of stable dialysis patients. Apoptosis was quantified in cultured mesothelial cells and in peritoneal effluents. Confocal microscopy and inhibitors were used to assess molecular mechanisms. RESULTS: Peritoneal dialysis solutions with a high content of both glucose and glucose degradation products, but not those with low glucose degradation product content, induced mesothelial cell apoptosis and loss of cell viability in culture and in vivo. 3,4-DGE also induced mesothelial cell apoptosis. Apoptosis induced by peritoneal dialysis solutions and 3,4-DGE was associated with oligomerization of Bax at mitochondria and caspase activation. Bax antagonism prevented caspase activation, apoptosis and cell death. The pancaspase inhibitor zVAD was also protective. CONCLUSION: 3,4-DGE and peritoneal dialysis solutions with a high content in glucose degradation products induce mesothelial cell apoptosis by a Bax-dependent mechanism. This could contribute to chronic demesothelization in peritoneal dialysis.

Bcl-xL prevents peritoneal dialysis solution-induced leukocyte apoptosis.

Conventional glucose-containing peritoneal dialysis solutions (PDS) with a high glucose degradation product content accelerate leukocyte apoptosis and impair peritoneal defense. Mononuclear cells are less sensitive than neutrophils to PDS-induced apoptosis, suggesting that they may express antiapoptotic molecules. Since apoptosis induced by PDS requires Bax, we explored the role of an antiapoptotic protein of the same family, Bcl-xL, in PDS-induced apoptosis in cultured peripheral blood mononuclear cells and monocytic THP-1 cells. In these cells, conventional PDS decreased the expression of Bcl-xL protein with a temporal pattern compatible with their lethal effect. Inhibition of Bcl-xL also induced mononuclear cell apoptosis. A cell-permeable TAT-BH4 peptide that contains the BH4 domain of Bcl-xL prevented mononuclear cell apoptosis induced by PDS. These data suggest that Bcl-xL protects mononuclear cells from apoptosis induced by bioincompatible PDS and that Bcl-xL-like molecules should be explored to prolong leukocyte survival and potentiate peritoneal defense during peritonitis.

A versatile drug delivery system targeting senescent cells.

Senescent cells accumulate in multiple aging-associated diseases, and eliminating these cells has recently emerged as a promising therapeutic approach. Here, we take advantage of the high lysosomal ß-galactosidase activity of senescent cells to design a drug delivery system based on the encapsulation of drugs with galacto-oligosaccharides. We show that gal-encapsulated fluorophores are preferentially released within senescent cells in mice. In a model of chemotherapy-induced senescence, gal-encapsulated cytotoxic drugs target senescent tumor cells and improve tumor xenograft regression in combination with palbociclib. Moreover, in a model of pulmonary fibrosis in mice, gal-encapsulated cytotoxics target senescent cells, reducing collagen deposition and restoring pulmonary function. Finally, gal-encapsulation reduces the toxic side effects of the cytotoxic drugs. Drug delivery into senescent cells opens new diagnostic and therapeutic applications for senescence-associated disorders.