Ramon Trullas

Copper (Cu) is an essential trace metal; however, its dysregulation promotes oxidative stress and contributes to neurodegeneration. Astrocytes are central to neuronal homeostasis, in part through extracellular vesicle (EV)-mediated communication, yet they are particularly vulnerable to metal-induced oxidative damage. Under pathological conditions, astrocyte-derived EVs can acquire neurotoxic properties, thereby amplifying neuronal injury. However, the mechanisms governing neuron–glia crosstalk under Cu overload remain incompletely defined. Here, we show that sublethal Cu exposure induces mitochondrial oxidative stress in astrocytes, leading to redox-dependent reprogramming of cholesterol metabolism and alterations in EV release. EVs derived from Cu-overloaded astrocytes propagate oxidative damage to neurons, establishing a ROS-driven pathway of glia-to-neuron communication. Notably, activation of insulin-like growth factor 1 (IGF-1) signaling—via recombinant protein or adenoviral delivery—attenuates Cu-induced oxidative stress, partially restores cholesterol metabolic homeostasis, and reprograms astrocyte-derived EVs toward a non-cytotoxic phenotype. Collectively, these findings identify astrocyte-derived EVs as key mediators of Cu-induced neuronal injury and highlight IGF-1 signaling as a potential therapeutic strategy to preserve astrocyte oxidative resilience and neuroprotective function.

A significant body of evidence suggests that mitochondrial dysfunction plays a key role in the development and progression of Alzheimer’s disease (AD). However, the absence of peripheral biomarkers for mitochondrial dysfunction limits its clinical applicability. Mitochondrial DNA (mtDNA) copy number, a proxy for mitochondrial function, has shown promise in detecting early stages of AD and predicting AD risk in cerebrospinal fluid (CSF) and blood, respectively. Surprisingly, recent studies have identified mtDNA molecules in human saliva, but their relationship with AD remains unexplored. Here, we investigated potential associations between salivary mtDNA copy number and cortical amyloid-β (Aβ) load measured with PET, and blood AD markers measured with ultrasensitive single molecule array (SIMOA) assays, in cognitively normal older adults. We found that salivary mtDNA copy number was positively correlated with cortical Aβ burden and plasma levels of tau phosphorylated at threonine 181 (pTau-181), and negatively correlated with general cognitive ability. It is worth noting that salivary mtDNA was not significantly associated with other blood-based AD biomarkers, including Aβ_1-40, Aβ_1-42, neurofilament-light chain (NfL), or glial fibrillary acidic protein (GFAP). Additionally, plasma pTau-181 levels moderated the association between salivary mtDNA and Aβ accumulation in the inferior temporal lobe, while Aβ load in the occipital cortex mediated the association between plasma pTau-181 and salivary mtDNA. Together, these findings represent the first evidence linking salivary mtDNA to well-established AD biomarkers in normal aging, suggesting that salivary mtDNA may serve as a potential non-invasive biomarker for identifying individuals at risk for developing AD in the general population.

A shared hallmark of age-related neurodegenerative diseases is the chronic activation of innate immune cells, which actively contributes to the neurodegenerative process. In Alzheimer’s disease, this inflammatory milieu exacerbates both amyloid and tau pathology. A similar abnormal inflammatory response has been reported in Parkinson’s disease, with elevated levels of cytokines and other inflammatory intermediates derived from activated glial cells, which promote the progressive loss of nigral dopaminergic neurons. Understanding the causes that support this aberrant inflammatory response has become a topic of growing interest and research in neurodegeneration, with high translational potential. It has been postulated that the phenotypic shift of immune cells towards a proinflammatory state combined with the presence of immunogenic cell death fuels a vicious cycle in which mitochondrial dysfunction plays a central role. Mitochondria and mitochondria-generated reactive oxygen species are downstream effectors of different inflammatory signaling pathways, including inflammasomes. Dysfunctional mitochondria are also recognized as important producers of damage-associated molecular patterns, which can amplify the immune response. Here, we review the major findings highlighting the role of mitochondria as a checkpoint of neuroinflammation and immunogenic cell deaths in neurodegenerative diseases. The knowledge of these processes may help to find new druggable targets to modulate the inflammatory response.

Epithelial cells comprising the choroid plexus (CP) form a crucial barrier between the blood and the cerebrospinal fluid, thereby assuming a central position in brain homeostasis and signaling. Mounting evidence suggests that the impairment of CP function may be a significant contributor to Alzheimer’s disease (AD) pathogenesis. CP function relies on the expression of specific receptors, and the potential involvement of olfactory receptors (ORs) and taste receptors (TASRs) in chemical surveillance within the CP is being investigated. Previous studies have implicated ORs and TASRs in neurodegenerative disorders like AD, although the direct evidence of their expression in the human CP remains to be established. In this study, we conducted a transcriptomic analysis encompassing eleven ORs and TASRs in the CP, comparing samples from healthy age-matched controls to those from patients with AD spanning Braak stages I to VI. Among these receptors, a striking finding emerged—OR2K2 exhibited robust expression, with a statistically significant upregulation noted at Braak stage I. Surprisingly, at the protein level, OR2K2 showed a significant decrease in both Braak stage I and VI. Additionally, we identified CP epithelial cells as the source of OR2K2 expression, where it colocalized with autophagy markers LC3 and p62. We postulate that OR2K2 could be subjected to degradation by autophagy in the early stages of AD, triggering a compensatory mechanism that leads to increased OR2K2 mRNA transcription. This study uncovers a potential role for OR2K2 in AD pathogenesis, offering a novel perspective on the intricate dynamics at play in this neurodegenerative disorder.

Background: Necroptosis has been reported in post‐mortem Alzheimer’s disease (AD) brains, but still, the events that trigger or regulate this type of inflammatory cell death in AD are not fully known. Oxidative stress may be determinant as to whether a cell initiates necroptosis; Therefore, it is, likely that mitochondrial dysfunction, observed in the early stages of AD, might favor cells to undergo necroptosis. Previous studies from our group have shown that high intracellular cholesterol levels deplete the mitochondrial pool of GSH, thus sensitizing neurons against amyloid‐beta (Ab)‐induced mitochondrial oxidative stress. The present study is aimed to evaluate whether cholesterol can regulate the necroptotic pathway using both APP‐PSEN1 mice that overexpress the cholesterol‐related transcription factor SREBF2 and cholesterol‐enriched SH‐SY5Y cells.Method: Cholesterol enrichment was assessed by incubating the cells with soluble cholesterol:methyl‐cyclodextrin complex (50 mg/ml) for 1 h followed by 4 h recovery. To induce necroptosis, cells were treated with TLQ [TNFa (10 ng/ml) plus the SMAC mimetic (LCL‐161, 10 mM) and the pan‐caspase inhibitor qVD‐OPH (10 mM)] for 24 h.Results: Brains from APP‐PSEN1‐SREBF2 mice show up‐regulated expression of the necroptosis‐related proteins RIPK3 and MLKL, which together with RIPK1 accumulated in the urea‐soluble protein fraction, indicative of necrosome assembly. Moreover, western blot analyses of brain extracts from triple transgenic mice also showed high levels of c‐FLIP, the natural inhibitor of caspase‐8, further pointing to a cholesterol‐regulated engagement of the necroptotic pathway. In SH‐SY5Y cells, cholesterol enrichment resulted in enhanced cell death after exposure to TLQ, which was prevented by RIPK1 and RIPK3 inhibitors (Necrostatin and GSK’872, respectively). Similar protection against TLQ‐induced necroptosis was achieved when mitochondrial GSH levels were recovered by GSH ethyl ester. Intriguingly, cholesterol also regulated the intracellular localization of RIPK3 and MLKL. Confocal microscopy showed an increased presence of nuclear RIPK3 and MLKL in cholesterol‐enriched cells, recently described as a requirement for the subsequent necrosome formation in the cytosol.Conclusion: Overall, these findings indicate that high intracellular cholesterol levels compromise neuronal viability, promoting oxidative stress and subsequent necroptosis, a pro‐inflammatory type of cell death, which ultimately may contribute to chronic neuroinflammation in AD.

Circulating tumor DNA (ctDNA) has recently emerged as a real-time prognostic and predictive biomarker for monitoring cancer patients. Here, we aimed to ascertain whether tumor-agnostic ctDNA testing would be a feasible strategy to monitor disease progression and therapeutic response in muscle-invasive bladder cancer (MIBC) patients after radical cystectomy (RC). Forty-two MIBC patients who underwent RC were prospectively included. Blood samples from these patients were collected at different follow-up time points. Two specific mutations (TERT c.1-124C>T and ATM c.1236-2A>T) were analyzed in the patients’ plasma samples by droplet digital PCR to determine their ctDNA status. During a median follow-up of 21 months, 24% of patients progressed in a median of six months. ctDNA status was identified as a prognostic biomarker of tumor progression before RC and 4 and 12 months later (HR 6.774, HR 3.673, and HR 30.865, respectively; p < 0.05). Lastly, dynamic changes in ctDNA status between baseline and four months later were significantly associated with patient outcomes (p = 0.045). In conclusion, longitudinal ctDNA analysis using a tumor-agnostic approach is a potential tool for monitoring MIBC patients after RC. The implementation of this testing in a clinical setting could improve disease management and patients’ outcomes.

Uniparental inheritance of mitochondrial DNA (mtDNA) is an evolutionary trait found in nearly all eukaryotes. In many species, including humans, the sperm mitochondria are introduced to the oocyte during fertilization^1,2. The mechanisms hypothesized to prevent paternal mtDNA transmission include ubiquitination of the sperm mitochondria and mitophagy^3,4. However, the causative mechanisms of paternal mtDNA elimination have not been defined^5,6. We found that mitochondria in human spermatozoa are devoid of intact mtDNA and lack mitochondrial transcription factor A (TFAM)—the major nucleoid protein required to protect, maintain and transcribe mtDNA. During spermatogenesis, sperm cells express an isoform of TFAM, which retains the mitochondrial presequence, ordinarily removed upon mitochondrial import. Phosphorylation of this presequence prevents mitochondrial import and directs TFAM to the spermatozoon nucleus. TFAM relocalization from the mitochondria of spermatogonia to the spermatozoa nucleus directly correlates with the elimination of mtDNA, thereby explaining maternal inheritance in this species.