Nanoparticle‐mediated lysosomal reacidification restores mitochondrial turnover and function in β cells under lipotoxicity

Assali, Essam A.; Shlomo, Dovi; Zeng, Jialiu; Taddeo, Evan P.; Trudeau, Kyle; Erion, Karel; Colby, Aaron H.; Grinstaff, Mark W.; Liesa, Marc; Las, Guy; Shirihai, Orian S.

doi:10.1096/fj.201801292r

Cited by 34 publications

(41 citation statements)

References 30 publications

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“…For the studies presented here, only the mCherry fluorophore was excited and recorded. 2mtGCaMP6m construct was a generous gift from Diego De Stefani 26 and the adenoviral particles were prepared as described previously 50,52 .…”

Section: Methodsmentioning

confidence: 99%

NCLX prevents cell death during adrenergic activation of the brown adipose tissue

et al. 2020

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A sharp increase in mitochondrial Ca 2+ marks the activation of brown adipose tissue (BAT) thermogenesis, yet the mechanisms preventing Ca 2+ deleterious effects are poorly understood. Here, we show that adrenergic stimulation of BAT activates a PKA-dependent mitochondrial Ca 2+ extrusion via the mitochondrial Na + /Ca 2+ exchanger, NCLX. Adrenergic stimulation of NCLX-null brown adipocytes (BA) induces a profound mitochondrial Ca 2+ overload and impaired uncoupled respiration. Core body temperature, PET imaging of glucose uptake and VO 2 measurements confirm a thermogenic defect in NCLX-null mice. We show that Ca 2+ overload induced by adrenergic stimulation of NCLX-null BAT, triggers the mitochondrial permeability transition pore (mPTP) opening, leading to a remarkable mitochondrial swelling and cell death. Treatment with mPTP inhibitors rescue mitochondrial function and thermogenesis in NCLX-null BAT, while calcium overload persists. Our findings identify a key pathway through which BA evade apoptosis during adrenergic stimulation of uncoupling. NCLX deletion transforms the adrenergic pathway responsible for thermogenesis activation into a death pathway.

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Section: Methodsmentioning

confidence: 99%

NCLX prevents cell death during adrenergic activation of the brown adipose tissue

et al. 2020

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“…Moreover, the restoration of lysosomal pH by lysosome-targeted nanoparticles reinstates mitophagy in pancreatic cells exposed to high concentrations of free fatty acids [32]. These findings indicate that, at least under lipotoxic conditions, mitochondrial dysfunction develops downstream of lysosomal alkalization and that recovery of lysosomal acidity restores MQC [32].…”

Section: Introductionmentioning

confidence: 91%

“…On a similar note, ablation or pharmacological inhibition of apoptosis inducing factor (AIF), OPA1, or phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1) in neurons impairs lysosome activity, thereby causing accrual of autophagic substrates [31]. Moreover, the restoration of lysosomal pH by lysosome-targeted nanoparticles reinstates mitophagy in pancreatic cells exposed to high concentrations of free fatty acids [32]. These findings indicate that, at least under lipotoxic conditions, mitochondrial dysfunction develops downstream of lysosomal alkalization and that recovery of lysosomal acidity restores MQC [32].…”

Section: Introductionmentioning

confidence: 99%

Inter-Organelle Membrane Contact Sites and Mitochondrial Quality Control during Aging: A Geroscience View

Picca

Calvani

Coelho-Júnior

et al. 2020

Cells

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Mitochondrial dysfunction and failing mitochondrial quality control (MQC) are major determinants of aging. Far from being standalone organelles, mitochondria are intricately related with cellular other compartments, including lysosomes. The intimate relationship between mitochondria and lysosomes is reflected by the fact that lysosomal degradation of dysfunctional mitochondria is the final step of mitophagy. Inter-organelle membrane contact sites also allow bidirectional communication between mitochondria and lysosomes as part of nondegradative pathways. This interaction establishes a functional unit that regulates metabolic signaling, mitochondrial dynamics, and, hence, MQC. Contacts of mitochondria with the endoplasmic reticulum (ER) have also been described. ER-mitochondrial interactions are relevant to Ca 2+ homeostasis, transfer of phospholipid precursors to mitochondria, and integration of apoptotic signaling. Many proteins involved in mitochondrial contact sites with other organelles also participate to degradative MQC pathways. Hence, a comprehensive assessment of mitochondrial dysfunction during aging requires a thorough evaluation of degradative and nondegradative inter-organelle pathways. Here, we present a geroscience overview on (1) degradative MQC pathways, (2) nondegradative processes involving inter-organelle tethering, (3) age-related changes in inter-organelle degradative and nondegradative pathways, and (4) relevance of MQC failure to inflammaging and age-related conditions, with a focus on Parkinson's disease as a prototypical geroscience condition.Cells 2020, 9, 598 2 of 18 instability, telomere attrition, epigenetic alterations, deregulated nutrient sensing, and stem cell exhaustion [3]. According to the geroscience hypothesis, perturbations in these mechanisms increase the susceptibility to most chronic diseases, functional loss, and eventually, death [4]. Hence, these biologic pillars represent ideal targets for interventions to foster healthy aging [5,6].Mitochondrial dysfunction has attracted considerable interest as a target for geroprotective interventions. Indeed, mitochondria play sensor-transducer-effector roles in a multitude of biological processes, including integration of cell death signaling and preservation of cell stemness [7,8]. Albeit long considered to be standalone organelles, a great deal of evidence indicates that mitochondria interact physically and functionally with other cellular compartments via membrane contact sites and tethering molecules [9,10]. In particular, mitochondria establish connections with the endosomal compartment [11,12] and lysosomes [13,14]. These interactions support cytosolic shuttle systems of ions and metabolites across organelles [10,15], and participate to the regulation of cellular housekeeping processes [13,14].The mitochondrial-lysosomal axis is a major actor in mitochondrial quality control (MQC), a hierarchical network of pathways that ensure organellar homeostasis through the coordination of mitochondrial proteostasis, dynamics, biogene...

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“…Insulin content was also measured in all the treatment conditions (Figure S3, Supporting Information), and it was not significantly altered between the conditions, indicating that PLGA NPs unlikely affected insulin release from granules. It has been reported that dysfunctional lysosomal acidification in pancreatic beta cells leads to an increase in mitochondrial mass and a decrease in mitochondria turnover and mitochondrial respiratory capacity . This decrease in mitochondrial respiratory results in decreased adenosine triphospate (ATP) production, and eventually leads to decreased GSIS and beta cell dysfunction .…”

Section: Resultsmentioning

confidence: 99%

“…It has been reported that dysfunctional lysosomal acidification in pancreatic beta cells leads to an increase in mitochondrial mass and a decrease in mitochondria turnover and mitochondrial respiratory capacity . This decrease in mitochondrial respiratory results in decreased adenosine triphospate (ATP) production, and eventually leads to decreased GSIS and beta cell dysfunction . Therefore, repairing lysosomal function with PLGA NPs provides an opportunity to restore mitochondrial function with ATP production affording improved GSIS and beta cell function.…”

Section: Resultsmentioning

confidence: 99%

Degradable Nanoparticles Restore Lysosomal pH and Autophagic Flux in Lipotoxic Pancreatic Beta Cells

Grinstaff

2019

Adv Healthcare Materials

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between autophagosome and a sufficiently acidic lysosome (Figure 1). In the insulin secreting pancreatic beta cells (β-cells), chronic exposure to high levels of fatty acids results in lipotoxicity [7,8] and leads to disruption of autophagy concomitant with compromised lysosomal acidity. This autophagic dysfunction affords an increased accumulation of damaged organelles and proteins in the cells, thereby exacerbating the decline in cellular functions which leads to progressive diseases such as Type II diabetes (T2D). [7][8][9][10][11][12][13][14][15] Therefore, addressing the role of impaired acidification in lipotoxic pancreatic β-cells is important for identifying its downstream consequences and for studying the potential benefits of restored acidification on cellular function and autophagy. Given that nanoparticles (NPs) readily accumulate in lysosomes upon exposure to cells, nanoparticle-based strategies that alter the local intracellular lysosomal pH are being explored. For example, NPs that degrade into acidic products [16,17] and activate with light to generate acid [15] are reported. With regards to the former approach, poly(lactic-co-glycolic acid) (PLGA) NPs are able to restore lysosomal pH in retinal pigment epithelium (RPE) cells [16] and ATP13A2 cells, [17] thereby leading to restoration of autophagic flux and cellular function. The current study is the first to report the use of NPs to alter lysosomal dysfunction in pancreatic beta cells under lipotoxicity. Additionally, the biology of the pancreatic beta cell type is different than RPE and ATP13A2 cells, and hence the response(s) to NP treatment will afford new insights. We hypothesize that the PLGA NPs will acidify lysosomes in a NP concentration dependent manner and result in lowering of lysosomal pH, rescuing of autophagic flux, and restoration of glucose stimulated insulin secretion in β-cells, specifically rat pancreatic insulin secreting (INS1) β-cells. Results and Discussion Synthesis and Characterization of PLGA NPsMonodisperse PLGA NPs were formed using a previously reported sonication method using PLGA (Resomer 503 H) with sodium dodecyl sulfate (SDS) as the surfactant. [16] The PLGA NPs exhibit average diameters of 100 nm and polydispersity of 0.13 by dynamic light scattering (DLS) and possess a zeta Chronic exposure to high levels of fatty acids (lipotoxicity) in pancreatic beta cells (β-cells) decreases lysosomal acidity and inhibits autophagic flux. Today, there are a lack of approaches to modify lysosomal acidity to determine whether impaired lysosomal acidification is causally inhibiting autophagic flux and cellular functions. Biodegradable poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) with diameters of ≈100 nm localize to lysosomes and serve as an ideal method to deliver lactic and glycolic acid to lysosomes upon NP polymer degradation. In this study, the ability of PLGA NPs to lower lysosomal pH and restore autophagic flux is investigated in pancreatic insulin secreting (INS1) β-cells. PLGA NPs display a concentration d...

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Nanoparticle‐mediated lysosomal reacidification restores mitochondrial turnover and function in β cells under lipotoxicity

Cited by 34 publications

References 30 publications

NCLX prevents cell death during adrenergic activation of the brown adipose tissue

NCLX prevents cell death during adrenergic activation of the brown adipose tissue

Inter-Organelle Membrane Contact Sites and Mitochondrial Quality Control during Aging: A Geroscience View

Degradable Nanoparticles Restore Lysosomal pH and Autophagic Flux in Lipotoxic Pancreatic Beta Cells

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