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Mitochondria contribute to shape intraneuronal Ca 2+ signals. Excessive Ca 2+ taken up by mitochondria could lead to cell death. Amyloid beta (Aβ) causes cytosolic Ca 2+ overload, but the effects of Aβ on mitochondrial Ca 2+ levels in Alzheimer’s disease (AD) remain unclear. Using a ratiometric Ca 2+ indicator targeted to neuronal mitochondria and intravital multiphoton microscopy, we find increased mitochondrial Ca 2+ levels associated with plaque deposition and neuronal death in a transgenic mouse model of cerebral β-amyloidosis. Naturally secreted soluble Aβ applied onto the healthy brain increases Ca 2+ concentration in mitochondria, which is prevented by blockage of the mitochondrial calcium uniporter. RNA-sequencing from post-mortem AD human brains shows downregulation in the expression of mitochondrial influx Ca 2+ transporter genes, but upregulation in the genes related to mitochondrial Ca 2+ efflux pathways, suggesting a counteracting effect to avoid Ca 2+ overload. We propose lowering neuronal mitochondrial Ca 2+ by inhibiting the mitochondrial Ca 2+ uniporter as a novel potential therapeutic target against AD. Calvo-Rodriguez et al. show elevated calcium levels in neuronal mitochondria in a mouse model of cerebral β-amyloidosis after plaque deposition, which precede rare neuron death events in this model. The mechanism involves toxic extracellular Aβ oligomers and the mitochondrial calcium uniporter.

Background Reactive oxidative stress is a critical player in the amyloid beta (Aβ) toxicity that contributes to neurodegeneration in Alzheimer’s disease (AD). Damaged mitochondria are one of the main sources of reactive oxygen species and accumulate in Aβ plaque-associated dystrophic neurites in the AD brain. Although Aβ causes neuronal mitochondria reactive oxidative stress in vitro, this has never been directly observed in vivo in the living mouse brain. Here, we tested for the first time whether Aβ plaques and soluble Aβ oligomers induce mitochondrial oxidative stress in surrounding neurons in vivo, and whether this neurotoxic effect can be abrogated using mitochondrial-targeted antioxidants. Methods We expressed a genetically encoded fluorescent ratiometric mitochondria-targeted reporter of oxidative stress in mouse models of the disease and performed intravital multiphoton microscopy of neuronal mitochondria and Aβ plaques. Results For the first time, we demonstrated by direct observation in the living mouse brain exacerbated mitochondrial oxidative stress in neurons after both Aβ plaque deposition and direct application of soluble oligomeric Aβ onto the brain, and determined the most likely pathological sequence of events leading to oxidative stress in vivo. Oxidative stress could be inhibited by both blocking calcium influx into mitochondria and treating with the mitochondria-targeted antioxidant SS31. Remarkably, the latter ameliorated plaque-associated dystrophic neurites without impacting Aβ plaque burden. Conclusions Considering these results, combination of mitochondria-targeted compounds with other anti-amyloid beta or anti-tau therapies hold promise as neuroprotective drugs for the prevention and/or treatment of AD.

Summary The detection of amyloid beta deposits and neurofibrillary tangles, both hallmarks of Alzheimer’s disease (AD), is key to understanding the mechanisms underlying these pathologies. Luminescent conjugated oligothiophenes (LCOs) enable fluorescence imaging of these protein aggregates. Using LCOs and multiphoton microscopy, individual tangles and amyloid beta deposits were labeled in vivo and imaged longitudinally in a mouse model of tauopathy and cerebral amyloidosis, respectively. Importantly, LCO HS-84, whose emission falls in the green region of the spectrum, allowed for the first time longitudinal imaging of tangle dynamics following a single intravenous injection. In addition, LCO HS-169, whose emission falls in the red region of the spectrum, successfully labeled amyloid beta deposits, allowing multiplexing with other reporters whose emission falls in the green region of the spectrum. In conclusion, this method can provide a new approach for longitudinal in vivo imaging using multiphoton microscopy of AD pathologies as well as other neurodegenerative diseases associated with protein aggregation in mouse models.

Reactive oxidative stress is a critical player in the amyloid beta (A[beta]) toxicity that contributes to neurodegeneration in Alzheimer's disease (AD). Damaged mitochondria are one of the main sources of reactive oxygen species and accumulate in A[beta] plaque-associated dystrophic neurites in the AD brain. Although A[beta] causes neuronal mitochondria reactive oxidative stress in vitro, this has never been directly observed in vivo in the living mouse brain. Here, we tested for the first time whether A[beta] plaques and soluble A[beta] oligomers induce mitochondrial oxidative stress in surrounding neurons in vivo, and whether this neurotoxic effect can be abrogated using mitochondrial-targeted antioxidants. We expressed a genetically encoded fluorescent ratiometric mitochondria-targeted reporter of oxidative stress in mouse models of the disease and performed intravital multiphoton microscopy of neuronal mitochondria and A[beta] plaques. For the first time, we demonstrated by direct observation in the living mouse brain exacerbated mitochondrial oxidative stress in neurons after both A[beta] plaque deposition and direct application of soluble oligomeric A[beta] onto the brain, and determined the most likely pathological sequence of events leading to oxidative stress in vivo. Oxidative stress could be inhibited by both blocking calcium influx into mitochondria and treating with the mitochondria-targeted antioxidant SS31. Remarkably, the latter ameliorated plaque-associated dystrophic neurites without impacting A[beta] plaque burden. Considering these results, combination of mitochondria-targeted compounds with other anti-amyloid beta or anti-tau therapies hold promise as neuroprotective drugs for the prevention and/or treatment of AD.

Summary The detection of amyloid beta deposits and neurofibrillary tangles, both hallmarks of Alzheimer's disease (AD), is key to understanding the mechanisms underlying these pathologies. Luminescent conjugated oligothiophenes (LCOs) enable fluorescence imaging of these protein aggregates. Using LCOs and multiphoton microscopy, individual tangles and amyloid beta deposits were labeled in vivo and imaged longitudinally in a mouse model of tauopathy and cerebral amyloidosis, respectively. Importantly, LCO HS-84, whose emission falls in the green region of the spectrum, allowed for the first time longitudinal imaging of tangle dynamics following a single intravenous injection. In addition, LCO HS-169, whose emission falls in the red region of the spectrum, successfully labeled amyloid beta deposits, allowing multiplexing with other reporters whose emission falls in the green region of the spectrum. In conclusion, this method can provide a new approach for longitudinal in vivo imaging using multiphoton microscopy of AD pathologies as well as other neurodegenerative diseases associated with protein aggregation in mouse models. Keywords: Alzheimer's disease, Amyloid beta plaques, Cerebral amyloid angiopathy, Luminescence, Multiphoton microscopy, Neurofibrillary tangles, Oligothiophenes, Tau

BackgroundReactive oxidative stress is a critical player in the amyloid beta (A beta) toxicity that contributes to neurodegeneration in Alzheimer's disease (AD). Damaged mitochondria are one of the main sources of reactive oxygen species and accumulate in A beta plaque-associated dystrophic neurites in the AD brain. Although A beta causes neuronal mitochondria reactive oxidative stress in vitro, this has never been directly observed in vivo in the living mouse brain. Here, we tested for the first time whether A beta plaques and soluble A beta oligomers induce mitochondrial oxidative stress in surrounding neurons in vivo, and whether this neurotoxic effect can be abrogated using mitochondrial-targeted antioxidants.MethodsWe expressed a genetically encoded fluorescent ratiometric mitochondria-targeted reporter of oxidative stress in mouse models of the disease and performed intravital multiphoton microscopy of neuronal mitochondria and A beta plaques.ResultsFor the first time, we demonstrated by direct observation in the living mouse brain exacerbated mitochondrial oxidative stress in neurons after both A beta plaque deposition and direct application of soluble oligomeric A beta onto the brain, and determined the most likely pathological sequence of events leading to oxidative stress in vivo. Oxidative stress could be inhibited by both blocking calcium influx into mitochondria and treating with the mitochondria-targeted antioxidant SS31. Remarkably, the latter ameliorated plaque-associated dystrophic neurites without impacting A beta plaque burden.ConclusionsConsidering these results, combination of mitochondria-targeted compounds with other anti-amyloid beta or anti-tau therapies hold promise as neuroprotective drugs for the prevention and/or treatment of AD.

Reactive oxidative stress is a critical player in the amyloid beta (Aβ) toxicity that contributes to neurodegeneration in Alzheimer’s disease (AD). Mitochondrial damage, observed in AD, is one of the main sources of reactive oxygen species. Although Aβ causes neuronal mitochondria-associated reactive oxidative stress in vitro, this has never been directly observed in the in vivo living brain. Here, we tested whether Aβ plaques and soluble oligomers induce mitochondrial oxidative stress in surrounding neurons in vivo, and whether the neurotoxic effect can be abrogated using mitochondrial-targeted antioxidants. We expressed a genetically encoded fluorescent ratiometric mitochondria-targeted reporter of oxidative stress in mouse models of the disease, and performed intravital multiphoton microscopy of neuronal mitochondria and Aβ plaques. For the first time, we demonstrated by direct observation exacerbated mitochondrial oxidative stress in neurons after both Aβ plaque deposition and direct application of soluble oligomeric Aβ onto the brain, and determined the most likely pathological sequence of events leading to oxidative stress in vivo. Oxidative stress could be inhibited by both blocking calcium influx into mitochondria and treating with the mitochondria-targeted antioxidant SS31. Considering these results, mitochondria-targeted compounds hold promise as neuroprotective drugs for the prevention and/or treatment of AD.

INTRODUCTION Validation of the primary cognitive composite and baseline cognitive characteristics are presented for the US‐Study‐to‐Protect‐Brain‐Health‐Through‐Lifestyle‐Intervention‐to‐Reduce‐Risk (US POINTER). METHODS US POINTER is a multicenter, randomized clinical trial of two lifestyle interventions testing cognitive benefit in older adults without significant cognitive impairment but at‐risk for decline due to well‐established factors. Cognition is measured using a global cognitive composite (US POINTER modified Neuropsychological Test Battery‐PmNTB). RESULTS The PmNTB is a valid cognitive composite, exhibiting good psychometric properties and tracking with other established outcomes. Among the 2111 enrolled participants (mean age = 68.2 years, 69% women, 31% from race and ethnic minoritized groups), demographic characteristics alone (age, sex, education, race, ethnicity) explained more variance in cognition measured using the PmNTB (25.94%) compared with cardiovascular and family history risk factors combined (added < 3% explained variance). DISCUSSION In a large diverse older adult cohort, demographic features rather than well‐established risks for cognitive decline correlate with baseline global cognition. Clinical trial registration number: NCT03688126 Highlights Demographic characteristics explain baseline cognition in at‐risk older adults. The POINTER Modified Neuropsychological Test Battery (PmNTB) is a valid measure. Worse cognition tracks with E4+, high HbA1c, current smoking, Framingham heart risk.

Despite the importance of bronchiolitis obliterans syndrome (BOS) in lung transplantation, little is known regarding the factors that influence survival after the onset of this condition, particularly among bilateral transplant recipients. To identify factors that influence survival after the onset of BOS among bilateral lung transplant recipients. The effect of demographic or clinical factors, occurring before BOS, upon survival after the onset of BOS was studied in 95 bilateral lung transplant recipient using Cox proportional hazards models. Although many factors, including prior acute rejection or rejection treatments, were not associated with survival after BOS, BOS onset within 2 years of transplantation (early-onset BOS), or BOS onset grade of 2 or 3 (high-grade onset) were predictive of significantly worse survival (early onset P = 0.04; hazard ratio, 1.84; 95% confidence interval, 1.03-3.29; high-grade onset P = 0.003; hazard ratio, 2.40; 95% confidence interval, 1.34-4.32). The effects of both early onset and high-grade onset on survival persisted in multivariable analysis and after adjustment for concurrent treatments. Results suggested an interaction might exist between early onset and high-grade onset. In particular, high-grade onset of BOS, regardless of its timing after transplant, is associated with a very poor prognosis. The course of BOS after bilateral lung transplantation is variable. Distinct patterns of survival after BOS are evident and related to timing or severity of onset. Further characterization of these subgroups should provide a more rational basis from which to design, stratify, and assess response in future BOS treatment trials.

The impact of relative humidity (RH) on organic new particle formation (NPF) from ozonolysis of monoterpenes remains an area of active debate. Previous reports provide contradictory results indicating both depression and enhancement of NPF under conditions of moderate RH, while others do not indicate a potential impact. Only several reports have suggested that the effect may depend on absolute mixing ratio of the precursor volatile organic compound (VOC, ppbv). Herein we report on the impact of RH on NPF from dark ozonolysis of α- and β-pinene at mixing ratios ranging from 0.2 to 80 ppbv. We show that RH enhances NPF (by a factor of eight) at the lowest α-pinene mixing ratio, with a very strong dependence on α-pinene mixing ratio from 4 to 22 ppbv. At higher mixing ratios, the effect of RH plateaus, with resulting modest decreases in NPF. In the case of α- and β-pinene, NPF is enhanced at low mixing ratios due to a combination of chemistry, accelerated kinetics, and reduced partitioning of semi-volatile oxidation products to the particulate phase. Reduced partitioning would limit particle growth, permitting increased gas-phase concentrations of semi- and low-volatility products, which could favor NPF.