Fine particulate matter contributes to COPD-like pathophysiology: experimental evidence from rats exposed to diesel exhaust particles.

BACKGROUND: Ambient fine particulate matter (PM2.5) is considered a plausible contributor to the onset of chronic obstructive pulmonary disease (COPD). Mechanistic studies are needed to augment the causality of epidemiologic findings. In this study, we aimed to test the hypothesis that repeated exposure to diesel exhaust particles (DEP), a model PM2.5, causes COPD-like pathophysiologic alterations, consequently leading to the development of specific disease phenotypes. Sprague Dawley rats, representing healthy lungs, were randomly assigned to inhale filtered clean air or DEP at a steady-state concentration of 1.03 mg/m3 (mass concentration), 4 h per day, consecutively for 2, 4, and 8 weeks, respectively. Pulmonary inflammation, morphologies and function were examined. RESULTS: Black carbon (a component of DEP) loading in bronchoalveolar lavage macrophages demonstrated a dose-dependent increase in rats following DEP exposures of different durations, indicating that DEP deposited and accumulated in the peripheral lung. Total wall areas (WAt) of small airways, but not of large airways, were significantly increased following DEP exposures, compared to those following filtered air exposures. Consistently, the expression of α-smooth muscle actin (α-SMA) in peripheral lung was elevated following DEP exposures. Fibrosis areas surrounding the small airways and content of hydroxyproline in lung tissue increased significantly following 4-week and 8-week DEP exposure as compared to the filtered air controls. In addition, goblet cell hyperplasia and mucus hypersecretions were evident in small airways following 4-week and 8-week DEP exposures. Lung resistance and total lung capacity were significantly increased following DEP exposures. Serum levels of two oxidative stress biomarkers (MDA and 8-OHdG) were significantly increased. A dramatical recruitment of eosinophils (14.0-fold increase over the control) and macrophages (3.2-fold increase) to the submucosa area of small airways was observed following DEP exposures. CONCLUSIONS: DEP exposures over the courses of 2 to 8 weeks induced COPD-like pathophysiology in rats, with characteristic small airway remodeling, mucus hypersecretion, and eosinophilic inflammation. The results provide insights on the pathophysiologic mechanisms by which PM2.5 exposures cause COPD especially the eosinophilic phenotype.

FUNDC1 collaborates with PINK1 in regulating mitochondrial Fission and compensating for PINK1 deficiency.

Parkinson's disease is presently thought to have its molecular roots in the alteration of PINK1-mediated mitophagy and mitochondrial dynamics. Finding new suppressors of the pathway is essential for developing cutting-edge treatment approaches. Our study shows that FUNDC1 suppressed PINK1 mutant phenotypes in Drosophila. The restoration of PINK1-deficient phenotypes through FUNDC1 is not reliant on its LC3-binding motif Y (18)L (21) or autophagy-related pathway. Moreover, the absence of Drp1 affects the phenotypic restoration of PINK1 mediated by FUNDC1 in flies. In summary, our findings have unveiled a fresh mechanism through which FUNDC1 compensates for the loss of PINK1, operating independently of autophagy but exerting its influence via interaction with Drp1.

PINK1 phosphorylates Drp1S616 to regulate mitophagy-independent mitochondrial dynamics.

Impairment of PINK1/parkin-mediated mitophagy is currently proposed to be the molecular basis of mitochondrial abnormality in Parkinson's disease (PD). We here demonstrate that PINK1 directly phosphorylates Drp1 on S616. Drp1S616 phosphorylation is significantly reduced in cells and mouse tissues deficient for PINK1, but unaffected by parkin inactivation. PINK1-mediated mitochondrial fission is Drp1S616 phosphorylation dependent. Overexpression of either wild-type Drp1 or of the phosphomimetic mutant Drp1S616D , but not a dephosphorylation-mimic mutant Drp1S616A , rescues PINK1 deficiency-associated phenotypes in Drosophila. Moreover, Drp1 restores PINK1-dependent mitochondrial fission in ATG5-null cells and ATG7-null Drosophila. Reduced Drp1S616 phosphorylation is detected in fibroblasts derived from 4 PD patients harboring PINK1 mutations and in 4 out of 7 sporadic PD cases. Taken together, we have identified Drp1 as a substrate of PINK1 and a novel mechanism how PINK1 regulates mitochondrial fission independent of parkin and autophagy. Our results further link impaired PINK1-mediated Drp1S616 phosphorylation with the pathogenesis of both familial and sporadic PD.

Identification of rare RTN3 variants in Alzheimer's disease in Han Chinese.

Reticulon 3 (RTN3) is a neuronally-expressed reticulon family protein that was previously shown to negatively regulate BACE1, a protease that is required for the generation of ß-amyloid peptides (Aß) from amyloid precursor protein. Despite biochemical and morphological evidence that supports a role of RTN3 in the formation of neuritic amyloid plaques, no systematic analyses of RTN3 mutations in patients with Alzheimer's disease (AD) have yet been reported. RTN3 were targeted sequenced in 154 sporadic early-onset and 285 late-onset AD patients. Luciferase reporter assay and kymographs were performed to analysis the expression of RNT3 and BACE1-RFP particle mobility on cells transfected with wild-type or variants RTN3 constructs. We identified heterozygous variants such as c.-8G > T, c.17C > A, c.42C > T, and c.116C > T from patients in the early-onset AD group and c.-8G > T, c.17C > A, from patients in the late-onset AD group. Such variants of RTN3 were not observed in control individuals. Further biochemical studies show that the RTN3 c.-8G > T variant in the 5'-untranslated region appears to cause reduced expression of RTN3. The RTN3 c.116 C > T variant causes a change of codon T39 to M39 (T39 M). Overexpression of RTN3 T39 M in cultured neurons led to impaired axonal transport of BACE1. The variants found in this study are likely genetic modifiers for RTN3-mediated formation of neuritic plaques in AD.

Analyzing modal power in multi-mode waveguide via machine learning.

A machine learning assisted modal power analyzing scheme designed for optical modes in integrated multi-mode waveguides is proposed and studied in this work. Convolutional neural networks (CNNs) are successfully trained to correlate the far-field diffraction intensity patterns of a superposition of multiple waveguide modes with its modal power distribution. In particular, a specialized CNN is trained to analyze thin optical waveguides, which are single-moded along one axis and multi-moded along the other axis. A full-scale CNN is also trained to cross-validate the results obtained from this specialized CNN model. Prediction accuracy for modal power is benchmarked statistically with square error and absolute error distribution. It is found that the overall accuracy of our trained specialized CNN is very satisfactory for thin optical waveguides while that of our trained full-scale CNN remains nearly unchanged but the training time doubles. This approach is further generalized and applied to a waveguide that is multi-moded along both horizontal and vertical axes and the influence of noise on our trained network is studied. Overall, we find that the performance in this general condition keeps nearly unchanged. This new concept of analyzing modal power may open the door for high fidelity information recovery in far field and holds great promise for potential applications in both integrated and fiber-based spatial-division demultiplexing.

High performance ultra-compact SOI waveguide crossing.

Waveguide crossing is an important integrated photonic component that will be routinely used for high-density and large-scale photonic integrated circuits, such as optical switches and routers. Several techniques have been reported in achieving high performance waveguide crossings on a silicon-on-insulator photonic platform, i.e., low-loss and low-crosstalk waveguide crossings based on multimode interference, bi-layer tapering, optical transformation, metamaterials, and subwavelength gratings. Until recently, not much attention has been given to the reduction of the footprint of waveguide crossings. Here we experimentally demonstrate an ultra-compact waveguide crossing on silicon photonic platform with a footprint only ~1 × 1 µm2. Our simulations show that it has a low insertion loss (< 0.175 dB) and low crosstalk (< -37dB) across the whole C-band, while the fabricated one has an insertion loss < 0.28 dB and crosstalk around -30 dB for the C-band.

Trapped modes with extremely high quality factor in a circular array of dielectric nanorods.

In this Letter, we investigate the formation of trapped modes with near-zero group velocities in a ring chain composed of dielectric nanorods. Two kinds of bound modes are successfully identified: the regular below-continuum-resonance (BCR) modes formed at the band edge and importantly the quasi-bound-states-in-the-continuum (BIC) trapped modes (similar to the BIC in the equivalent infinite linear chain). The lowest-order trapped mode possesses the highest Q factor, which scales exponentially with the number of nanorods N as Q∼exp(0.325N) for the BCR and Q∼exp(0.662N) for the quasi-BIC. Interestingly, a moderate high Q factor ∼105 can be obtained for the quasi-BIC mode even with a very small N=8. This suggests that our nanorod-based ring resonator possesses a clear advantage over the linear chain for the same N. Our findings greatly expand the application scope of BIC-based phenomena.

BNIP3 Protein Suppresses PINK1 Kinase Proteolytic Cleavage to Promote Mitophagy.

Mutations in PINK1 (PTEN-induced putative kinase 1) cause early onset familial Parkinson's disease (PD). PINK1 accumulates on the outer membrane of damaged mitochondria followed by recruiting parkin to promote mitophagy. Here, we demonstrate that BCL2/adenovirus E1B 19-kDa interacting protein 3 (BNIP3), a mitochondrial BH3-only protein, interacts with PINK1 to promote the accumulation of full-length PINK1 on the outer membrane of mitochondria, which facilitates parkin recruitment and PINK1/parkin-mediated mitophagy. Inactivation of BNIP3 in mammalian cells promotes PINK1 proteolytic processing and suppresses PINK1/parkin-mediated mitophagy. Hypoxia-induced BNIP3 expression results in increased expression of full-length PINK1 and mitophagy. Consistently, expression of BNIP3 in Drosophila suppresses muscle degeneration and the mitochondrial abnormality caused by PINK1 inactivation. Together, the results suggest that BNIP3 plays a vital role in regulating PINK1 mitochondrial outer membrane localization, the proteolytic process of PINK1 and PINK1/parkin-mediated mitophagy under physiological conditions. Functional up-regulation of BNIP3 may represent a novel therapeutic strategy to suppress the progression of PD.

Taxifolin enhances osteogenic differentiation of human bone marrow mesenchymal stem cells partially via NF-κB pathway.

Taxifolin, a flavonoid compound, has been reported to stimulate osteogenic differentiation in osteoblasts. The present study investigated whether taxifolin affects the osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs) and the molecular mechanisms involved. The proliferation and osteogenic differentiation of hBMSCs in the presence of taxifolin were examined by CCK-8 assay, alkaline phosphatase (ALP) activity, ALP staining and Alizarin red staining. The expression of osteogenic differentiation markers were detected by real-time quantitative PCR (RT-PCR) analysis and western blot assay. The activation of potential related pathways was examined by luciferase reporter assay, immunofluorescence and western blot analysis. Taxifolin treatment increased osteogenic differentiation of hBMSCs without cytotoxicity. Luciferase reporter assay showed that taxifolin could not activate estrogen receptor pathway, but inhibit TNF-α-induced NF-κB signaling pathway activation in osteogenic induction condition. Moreover, the nucleus translocation of NF-κB under TNF-α treatment was inhibited by taxifolin treatment. The taxifolin-induced osteogenic differentiation effects of hBMSCs were abolished by TNF-α treatment. In conclusion, our results suggested that taxifolin could promote osteogenesis of hBMSCs, partially through antagonism of NF-κB signaling pathway.

AK048794 maintains the mouse embryonic stem cell pluripotency by functioning as an miRNA sponge for miR-592.

MiR-592 has been identified as a neural-enriched microRNA, plays an important role in mNPCs differentiation, could induce astrogliogenesis differentiation arrest or/and enhance neurogenesis in vitro Previous studies showed that long noncoding RNAs (lncRNAs) were involved in the neuronal development and activity. To investigate the role of miR-592 in neurogenesis, we described the expression profile of lncRNAs in miR-592 knockout mouse embryonic stem cells (mESCs) and the corresponding normal mESCs by microarray. By the microarray analysis and luciferase reporter assays, we demonstrated that lncRNA - AK048794, regulated by transcription factor GATA1, functioned as a competing endogenous RNA (ceRNA) for miR-592 and led to the de-repression of its endogenous target FAM91A1, which is involved in mESC pluripotency maintenance. Taken together, these observations imply that AK048794 modulated the expression of multiple genes involved in mESC pluripotency maintenance by acting as a ceRNA for miR-592, which may build up the link between the regulatory miRNA network and mESC pluripotency.

Baicalein induces human osteosarcoma cell line MG-63 apoptosis via ROS-induced BNIP3 expression.

Baicalein, a flavonoid compound, is one of the active constituents of the root of Scutellariae Radix. Its antitumor effects have attracted widespread attention worldwide. One of its major functions is to induce the apoptosis of tumor cells, but the antitumor mechanism is currently unclear. In the present study, we found that baicalein increased MG-63 cell mortality in a dose-dependent manner. Meanwhile, baicalein activated apoptosis through induced intracellular reactive oxygen species (ROS) generation, and that ROS scavenger N-acetyl-cysteine (NAC), glutathione (GSH), and superoxide dismutase (SOD) apparently inhibited intracellular ROS production, consequently attenuating the baicalein-induced apoptosis. Baicalein also induce the mitochondrial fragmentation which precedes the cell apoptosis. This morphological alteration is accompanied by an increase in the expression of the protein BNIP3 as well as Mul1 and Drp1. Furthermore, we show that the inhibition of BNIP3 expression can inhibit cell apoptosis by baicalein treatment. Taken together, our results bring the evidence of a mechanism that links apoptosis and ROS-induced BNIP3 expression in MG-63 cells with bacalein treatment and suggest that baicalein has a good potential as an anti-osteosarcoma drug.

Increased expression of reticulon 3 in neurons leads to reduced axonal transport of ß site amyloid precursor protein-cleaving enzyme 1.

BACE1 is the sole enzyme responsible for cleaving amyloid precursor protein at the ß-secretase site, and this cleavage initiates the generation of ß-amyloid peptide (Aß). Because amyloid precursor protein is predominantly expressed by neurons and deposition of Aß aggregates in the human brain is highly correlated with the Aß released at axonal terminals, we focused our investigation of BACE1 localization on the neuritic region. We show that BACE1 was not only enriched in the late Golgi, trans-Golgi network, and early endosomes but also in both axons and dendrites. BACE1 was colocalized with the presynaptic vesicle marker synaptophysin, indicating the presence of BACE1 in synapses. Because the excessive release of Aß from synapses is attributable to an increase in amyloid deposition, we further explored whether the presence of BACE1 in synapses was regulated by reticulon 3 (RTN3), a protein identified previously as a negative regulator of BACE1. We found that RTN3 is not only localized in the endoplasmic reticulum but also in neuritic regions where no endoplasmic reticulum-shaping proteins are detected, implicating additional functions of RTN3 in neurons. Coexpression of RTN3 with BACE1 in cultured neurons was sufficient to reduce colocalization of BACE1 with synaptophysin. This reduction correlated with decreased anterograde transport of BACE1 in axons in response to overexpressed RTN3. Our results in this study suggest that altered RTN3 levels can impact the axonal transport of BACE1 and demonstrate that reducing axonal transport of BACE1 in axons is a viable strategy for decreasing BACE1 in axonal terminals and, perhaps, reducing amyloid deposition.

Depression Accompanied by Hopelessness Is Associated with More Negative Future Thinking.

BACKGROUND: This study aimed to delineate the interplay between depression, hopelessness, and episodic future thinking (EFT), focusing on cognitive biases towards negative future thinking that are central to depressive symptomatically. METHODS: A Japanese university student was utilized to scrutinize divergences in EFT across groups stratified by varying degrees of depression and hopelessness. The research leveraged a modified future thinking task (FTT), the Beck Hopelessness Scale, and the Beck Depression Inventory-II to gauge participants' levels of hopelessness and depressive symptoms. RESULTS: Consistent with prior research, the non-depressed group showed a reduction in positive EFT, reinforcing the idea that diminished positive future thinking is a hallmark of depressive conditions, even in the absence of a clinical diagnosis. Moreover, individuals with comorbid depression and elevated hopelessness demonstrated a significant decrease in positive EFT and an increase in negative EFT, substantiating a distinctive cognitive profile for this subgroup. This finding suggests that the presence of hopelessness exacerbates the negative cognitive biases associated with depression. CONCLUSIONS: The study emphasizes the importance of considering hopelessness as an independent construct when assessing EFT in clinical contexts. The pronounced impact of hopelessness on future thinking in those with depression suggests that targeted interventions, such as future-directed therapy (FDT), may be particularly effective for individuals with hopelessness depression by focusing on modifying negative future thinking patterns and enhancing life quality.

RAB21 controls autophagy and cellular energy homeostasis by regulating retromer-mediated recycling of SLC2A1/GLUT1.

The endosomal system maintains cellular homeostasis by coordinating multiple vesicular trafficking events, and the retromer complex plays a critical role in endosomal cargo recognition and sorting. Here, we demonstrate an essential role for the small GTPase RAB21 in regulating retromer-mediated recycling of the glucose transporter SLC2A1/GLUT1 and macroautophagy/autophagy. RAB21 depletion mis-sorts SLC2A1 to lysosomes and affects glucose uptake, thereby activating the AMPK-ULK1 pathway to increase autophagic flux. RAB21 depletion also increases lysosome function. Notably, RAB21 depletion does not overtly affect retrograde transport of IGF2R/CI-M6PR or WLS from endosomes to the trans-Golgi network. We speculate that RAB21 regulates fission of retromer-decorated endosomal tubules, as RAB21 depletion causes accumulation of the SNX27-containing retromer complex on enlarged endosomes at the perinuclear region. Functionally, RAB21 depletion sensitizes cancer cells to energy stress and inhibits tumor growth in vivo, suggesting an oncogenic role for RAB21. Overall, our study illuminates the role of RAB21 in regulating endosomal dynamics and maintaining cellular energy homeostasis and suggests RAB21 as a potential metabolic target for cancer therapy.

Citrus peel extract protects against diesel exhaust particle-induced chronic obstructive pulmonary disease-like lung lesions and oxidative stress.

Chronic obstructive pulmonary disease (COPD) is the third leading cause of death worldwide and characterized by emphysema, small airway remodeling and mucus hypersecretion. Citrus peels have been widely used as food spices and in traditional Chinese medicine for chronic lung disease. Given that citrus peels are known for containing antioxidants and anti-inflammatory compounds, we hypothesize that citrus peel intake can suppress oxidative stress and inflammatory response to air pollution exposure, thereby alleviating COPD-like pathologies. This study aimed to investigate the efficacy of citrus peel extract, namely Guang Chenpi (GC), in preventing the development of COPD induced by diesel exhaust particles (DEPs) and its potential mechanism. DEP-induced COPD-like lung pathologies, inflammatory responses and oxidative stress with or without GC treatment were examined in vivo and in vitro. Our in vivo study showed that GC was effective in decreasing inflammatory cell counts and inflammatory mediator (IL-17A and TNF-α) concentrations in bronchoalveolar lavage fluid (BALF). Pretreatment with GC extract also significantly decreased oxidative stress in the serum and lung tissue of DEP-induced COPD rats. Furthermore, GC pretreatment effectively reduced goblet cell hyperplasia (PAS positive cells) and fibrosis of the small airways, decreased macrophage infiltration as well as carbon loading in the peripheral lungs, and facilitated the resolution of emphysema and small airway remodeling in DEP-induced COPD rats. An in vitro free radical scavenging assay revealed robust antioxidant potential of GC in scavenging DPPH free radicals. Moreover, GC demonstrated potent capacities in reducing ROS production and enhancing SOD activity in BEAS-2B cells stimulated by DEPs. GC treatment significantly attenuated the increased level of IL-8 and MUC5AC from DEP-treated BEAS-2B cells. Mechanistically, GC treatment upregulated the protein level of Nrf-2 and could function via MAPK/NF-κB signaling pathways by suppressing the phosphorylation of p38, JNK and p65. Citrus peel extract is effective in decreasing oxidative stress and inflammatory responses of the peripheral lungs to DEP exposure. These protective effects further contributed to the resolution of COPD-like pathologies.

Vitamin D-VDR (vitamin D receptor) regulates defective autophagy in renal tubular epithelial cell in streptozotocin-induced diabetic mice via the AMPK pathway.

Diabetic nephropathy (DN) has become a major cause of end-stage renal disease, and autophagy disorder is implicated in the pathogenesis of DN. Our previous studies found that vitamin D (VD) and VDR (vitamin D receptor) played a renoprotective role by inhibiting inflammation and fibrosis. However, whether VD-VDR regulates autophagy disorders in DN remains unclear. In this study, we established a streptozotocin (STZ)-induced diabetic model in vdr knockout (vdr-KO) mice and VDR specifically overexpressed in renal proximal tubular epithelial cells (Vdr-OE) mice. Our results showed that paricalcitol (an activated vitamin D analog) or Vdr-OE could alleviate STZ-induced ALB (albumin) excretion, renal tubule injury and inflammation, while these were worsened in vdr-KO mice. Defective autophagy was observed in the kidneys of STZ mice, which was more pronounced in vdr-KO mice and could be partially restored by paricalcitol or Vdr-OE. In high glucose-induced HK-2 cells, defective autophagy and decreased PRKAA1/AMPK phosphorylation was observed, which could be partially restored by paricalcitol in a VDR-dependent manner. AMPK inhibitor abolished paricalcitol-induced autophagy activation, and AMPK activator restored the defective autophagy in high glucose-induced HK-2 cells. Furthermore, paricalcitol-mediated AMPK activation was abrogated by CAMKK2/CaMKKß inhibition, but not by STK11/LKB1 knockout. Meanwhile, paricalcitol rescued the decreased Ca2+ concentration induced by high glucose. In conclusion, VD-VDR can restore defective autophagy in the kidney of STZ-induced diabetic mice, which could be attributed to the activation of the Ca2+-CAMKK2-AMPK pathway in renal tubular epithelial cells.Abbreviations: ACTB/ß-actin: actin beta;AGE: advanced glycation end-products;AMPK: AMP-activated protein kinase;CAMKK2/CaMKKß: calcium-calmodulin dependent protein kinase kinase 2;CQ: chloroquine;DN: diabetic nephropathy;HG: high levels of glucose;KO: knockout;LG: low levels of glucose;MAP1LC3/LC3: microtubule associated protein 1 light chain 3;NOD2: nucleotide binding oligomerization domain containing 2;OE: overexpression;PAS: periodic acid Schiff; Pari: paricalcitol;PTECs: proximal renal tubule epithelial cells;RT: room temperature;SQSTM1/p62: sequestosome 1;STK11/LKB1: serine/threonine kinase 11;STZ: streptozotocin;TEM: transmission electron microscopy;VD: vitamin D;VDR: vitamin D receptor;WT: wild-type.

PINK1-mediated Drp1S616 phosphorylation modulates synaptic development and plasticity via promoting mitochondrial fission.

Dynamic change of mitochondrial morphology and distribution along neuronal branches are essential for neural circuitry formation and synaptic efficacy. However, the underlying mechanism remains elusive. We show here that Pink1 knockout (KO) mice display defective dendritic spine maturation, reduced axonal synaptic vesicles, abnormal synaptic connection, and attenuated long-term synaptic potentiation (LTP). Drp1 activation via S616 phosphorylation rescues deficits of spine maturation in Pink1 KO neurons. Notably, mice harboring a knockin (KI) phosphor-null Drp1S616A recapitulate spine immaturity and synaptic abnormality identified in Pink1 KO mice. Chemical LTP (cLTP) induces Drp1S616 phosphorylation in a PINK1-dependent manner. Moreover, phosphor-mimetic Drp1S616D restores reduced dendritic spine localization of mitochondria in Pink1 KO neurons. Together, this study provides the first in vivo evidence of functional regulation of Drp1 by phosphorylation and suggests that PINK1-Drp1S616 phosphorylation coupling is essential for convergence between mitochondrial dynamics and neural circuitry formation and refinement.

LC3 promotes the nuclear translocation of the vitamin D receptor and decreases fibrogenic gene expression in proximal renal tubules.

Diabetic nephropathy (DN) is a major cause of end-stage renal disease (ESRD). Vitamin D receptor (VDR) belongs to the nuclear receptor superfamily and exerts a renoprotective effect through inhibiting fibrosis. Microtubule-associated protein 1 light chain 3 (LC3), a key regulator of autophagy, is abundant in the nucleus, although its primary function is in the cytoplasm. The role of nuclear LC3 and the mechanism by which LC3 shuttles between the cytoplasm and nucleoplasm has not been fully elucidated. We found that LC3 binds to VDR in an LC3-interacting region (LIR)-independent manner and promotes the nuclear translocation of VDR. Further study indicated that LC3 promotes the formation of the VDR:retinoid X receptor (RXR) heterodimer and inhibits fibrogenic genes expression in HK-2 cells induced by high glucose. Our result demonstrates that LC3 is a negative regulator of high glucose-induced fibrogenic genes expression through its ability to promote VDR signaling.

Activation of BNIP3-mediated mitophagy protects against renal ischemia-reperfusion injury.

Acute kidney injury (AKI) is a syndrome of abrupt loss of renal functions. The underlying pathological mechanisms of AKI remain largely unknown. BCL2-interacting protein 3 (BNIP3) has dual functions of regulating cell death and mitophagy, but its pathophysiological role in AKI remains unclear. Here, we demonstrated an increase of BNIP3 expression in cultured renal proximal tubular epithelial cells following oxygen-glucose deprivation-reperfusion (OGD-R) and in renal tubules after renal ischemia-reperfusion (IR)-induced injury in mice. Functionally, silencing Bnip3 by specific short hairpin RNAs in cultured renal tubular cells reduced OGD-R-induced mitophagy, and potentiated OGD-R-induced cell death. In vivo, Bnip3 knockout worsened renal IR injury, as manifested by more severe renal dysfunction and tissue injury. We further showed that Bnip3 knockout reduced mitophagy, which resulted in the accumulation of damaged mitochondria, increased production of reactive oxygen species, and enhanced cell death and inflammatory response in kidneys following renal IR. Taken together, these findings suggest that BNIP3-mediated mitophagy has a critical role in mitochondrial quality control and tubular cell survival during AKI.

ATP13A2 facilitates HDAC6 recruitment to lysosome to promote autophagosome-lysosome fusion.

Mutations in ATP13A2 cause Kufor-Rakeb syndrome, an autosomal recessive form of juvenile-onset atypical Parkinson's disease (PD). Recent work tied ATP13A2 to autophagy and other cellular features of neurodegeneration, but how ATP13A2 governs numerous cellular functions in PD pathogenesis is not understood. In this study, the ATP13A2-deficient mouse developed into aging-dependent phenotypes resembling those of autophagy impairment. ATP13A2 deficiency impaired autophagosome-lysosome fusion in cultured cells and in in vitro reconstitution assays. In ATP13A2-deficient cells or Drosophila melanogaster or mouse tissues, lysosomal localization and activity of HDAC6 were reduced, with increased acetylation of tubulin and cortactin. Wild-type HDAC6, but not a deacetylase-inactive mutant, restored autophagosome-lysosome fusion, antagonized cortactin hyperacetylation, and promoted lysosomal localization of cortactin in ATP13A2-deficient cells. Mechanistically, ATP13A2 facilitated recruitment of HDAC6 and cortactin to lysosomes. Cortactin overexpression in cultured cells reversed ATP13A2 deficiency-associated impairment of autophagosome-lysosome fusion. PD-causing ATP13A2 mutants failed to rescue autophagosome-lysosome fusion or to promote degradation of protein aggregates and damaged mitochondria. These results suggest that ATP13A2 recruits HDAC6 to lysosomes to deacetylate cortactin and promotes autophagosome-lysosome fusion and autophagy. This study identifies ATP13A2 as an essential molecular component for normal autophagy flux in vivo and implies potential treatments targeting HDAC6-mediated autophagy for PD.