Mitochondrial Ca2+-dependent NLRP3 activation exacerbates the Pseudomonas aeruginosa-driven inflammatory response in cystic fibrosis

Mitochondrial calcium uniporter complex: Unveiling the interplay between its regulators and calcium homeostasis

The mitochondrial calcium uniporter complex (MCUc), serving as the specific channel for calcium influx into the mitochondrial matrix, is integral to calcium homeostasis and cellular integrity. Given its importance, ongoing research spans various disease models to understand the properties of the MCUc in pathophysiological contexts, but reported a different conclusion. Therefore, this review delves into the profound connection between MCUc-mediated calcium transients and cellular signaling pathways, mitochondrial dynamics, metabolism, and cell death. Additionally, we shed light on the recent advancements concerning the structural intricacies and auxiliary components of the MCUc in both resting and activated states. Furthermore, emphasis is placed on novel extrinsic and intrinsic regulators of the MCUc and their therapeutic implications across a spectrum of diseases. Meanwhile, we employed molecular docking simulations and identified candidate traditional Chinese medicine components with potential binding sites to the MCUc, potentially offering insights for further research on MCUc modulation.

ER-mitochondria association negatively affects wound healing by regulating NLRP3 activation

Methicillin-resistant Staphylococcus aureus (MRSA) is the most common causative agent of acute bacterial skin and skin-structure infections (ABSSSI), one of the major challenges to the health system worldwide. Although the use of antibiotics as the first line of intervention for MRSA-infected wounds is recommended, important side effects could occur, including cytotoxicity or immune dysregulation, thus affecting the repair process. Here, we show that the oxazolidinone antibiotic linezolid (LZD) impairs wound healing by aberrantly increasing interleukin 1 β (IL-1β) production in keratinocytes. Mechanistically, LZD triggers a reactive oxygen species (ROS)-independent mitochondrial damage that culminates in increased tethering between the endoplasmic reticulum (ER) and mitochondria, which in turn activates the NLR family pyrin domain-containing 3 (NLRP3) inflammasome complex by promoting its assembly to the mitochondrial surface. Downregulation of ER-mitochondria contact formation is sufficient to inhibit the LZD-driven NLRP3 inflammasome activation and IL-1β production, restoring wound closure. These results identify the ER-mitochondria association as a key factor for NLRP3 activation and reveal a new mechanism in the regulation of the wound healing process that might be clinically relevant.

Multifaceted mitochondria in innate immunity

The ability of mitochondria to transform the energy we obtain from food into cell phosphorylation potential has long been appreciated. However, recent decades have seen an evolution in our understanding of mitochondria, highlighting their significance as key signal-transducing organelles with essential roles in immunity that extend beyond their bioenergetic function. Importantly, mitochondria retain bacterial motifs as a remnant of their endosymbiotic origin that are recognised by innate immune cells to trigger inflammation and participate in anti-microbial defence. This review aims to explore how mitochondrial physiology, spanning from oxidative phosphorylation (OxPhos) to signalling of mitochondrial nucleic acids, metabolites, and lipids, influences the effector functions of phagocytes. These myriad effector functions include macrophage polarisation, efferocytosis, anti-bactericidal activity, antigen presentation, immune signalling, and cytokine regulation. Strict regulation of these processes is critical for organismal homeostasis that when disrupted may cause injury or contribute to disease. Thus, the expanding body of literature, which continues to highlight the central role of mitochondria in the innate immune system, may provide insights for the development of the next generation of therapies for inflammatory diseases.

Mitochondrial Cation Signalling in the Control of Inflammatory Processes

Mitochondria are the bioenergetic organelles responsible for the maintenance of cellular homeostasis and have also been found to be associated with inflammation. They are necessary to induce and maintain innate and adaptive immune cell responses, acting as signalling platforms and mediators in effector responses. These organelles are also known to play a pivotal role in cation homeostasis as well, which regulates the inflammatory responses through the modulation of these cation channels. In particular, this review focuses on mitochondrial Ca2+ and K+ fluxes in the regulation of inflammatory response. Nevertheless, this review aims to understand the interplay of these inflammation inducers and pathophysiological conditions. In detail, we discuss some examples of chronic inflammation such as lung, bowel, and metabolic inflammatory diseases caused by a persistent activation of the innate immune response due to a dysregulation of mitochondrial cation homeostasis.

Loss of CFTR function in macrophages alters the cell transcriptional program and delays lung resolution of inflammation

Cystic fibrosis (CF) is an autosomal recessive genetic disorder caused by mutations in the CF Transmembrane-conductance Regulator (CFTR) gene. The most severe pathologies of CF occur in the lung, manifesting as chronic bacterial infection, persistent neutrophilic inflammation, and mucopurulent airway obstruction. Despite increasing knowledge of the CF primary defect and the resulting clinical sequelae, the relationship between the CFTR loss of function and the neutrophilic inflammation remains incompletely understood. Here, we report that loss of CFTR function in macrophages causes extended lung inflammation. After intratracheal inoculation with Pseudomonas aeruginosa, mice with a macrophage-specific Cftr-knockout (Mac-CF) were able to mount an effective host defense to clear the bacterial infection. However, three days post-inoculation, Mac-CF lungs demonstrated significantly more neutrophil infiltration and higher levels of inflammatory cytokines, suggesting that Mac-CF mice had a slower resolution of inflammation. Single-cell RNA sequencing revealed that absence of CFTR in the macrophages altered the cell transcriptional program, affecting the cell inflammatory and immune responses, antioxidant system, and mitochondrial respiration. Thus, loss of CFTR function in macrophages influences cell homeostasis, leading to a dysregulated cellular response to infection that may exacerbate CF lung disease.

Role of NLRP3 inflammasome-mediated neuronal pyroptosis and neuroinflammation in neurodegenerative diseases

BACKGROUND

Neurodegenerative diseases are a common group of neurological disorders characterized by progressive loss of neuronal structure and function leading to cognitive impairment. Recent studies have shown that neuronal pyroptosis mediated by the NLRP3 inflammasome plays a crucial role in the pathogenesis of neurodegenerative diseases.

OBJECTIVE AND METHOD

The NLRP3 inflammasome is a multiprotein complex that, when activated within cells, triggers an inflammatory response, ultimately leading to pyroptotic cell death of neurons. Pyroptosis is a typical pro-inflammatory programmed cell death process occurring downstream of NLRP3 inflammasome activation, characterized by the formation of pores on the cell membrane by the GSDMD protein, leading to cell lysis and the release of inflammatory factors. It has been found that NLRP3 inflammasome-mediated neuronal pyroptosis is closely associated with the development of various neurodegenerative diseases, such as Alzheimer's disease, traumatic brain injury, and Parkinson's disease. Therefore, inhibiting NLRP3 inflammasome activation and attenuating neuronal pyroptosis could potentially serve as novel strategies for the treatment of neurodegenerative diseases.

RESULTS

The aim of this review is to explore the role of NLRP3 activation-mediated neuronal pyroptosis and neuroinflammation in neurodegenerative diseases. Firstly, we extensively discuss the relationship between NLRP3 inflammasome-mediated neuronal pyroptosis and neuroinflammation in various neurodegenerative diseases. Subsequently, we further explore the mechanisms driving NLRP3 activation and assembly, as well as the post-translational modifications regulating NLRP3 inflammasome activation.

CONCLUSION

Understanding these mechanisms will contribute to a deeper understanding of the link between neuronal pyroptosis and neurodegenerative diseases, and hold significant implications for the treatment and prevention of neurodegenerative diseases.

Interrogating the Etiology of Sporadic Alzheimer's Disease Using Aging Rhesus Macaques: Cellular, Molecular, and Cortical Circuitry Perspectives

Aging is the most significant risk factor for neurodegenerative disorders such as Alzheimer's disease (AD) associated with profound socioeconomic and personal costs. Consequently, there is an urgent need for animal models that recapitulate the age-related spatial and temporal complexity and patterns of pathology identical to human AD. Our research in aging nonhuman primate models involving rhesus macaques has revealed naturally occurring amyloid and tau pathology, including the formation of amyloid plaques and neurofibrillary tangles comprising hyperphosphorylated tau. Moreover, rhesus macaques exhibit synaptic dysfunction in association cortices and cognitive impairments with advancing age, and thus can be used to interrogate the etiological mechanisms that generate neuropathological cascades in sporadic AD. Particularly, unique molecular mechanisms (eg, feedforward cyclic adenosine 3',5'-monophosphate [cAMP]-Protein kinase A (PKA)-calcium signaling) in the newly evolved primate dorsolateral prefrontal cortex are critical for persistent firing required for subserving higher-order cognition. For example, dendritic spines in primate dorsolateral prefrontal cortex contain a specialized repertoire of proteins to magnify feedforward cAMP-PKA-calcium signaling such as N-methyl-d-aspartic acid receptors and calcium channels on the smooth endoplasmic reticulum (eg, ryanodine receptors). This process is constrained by phosphodiesterases (eg, PDE4) that hydrolyze cAMP and calcium-buffering proteins (eg, calbindin) in the cytosol. However, genetic predispositions and age-related insults exacerbate feedforward cAMP-Protein kinase A-calcium signaling pathways that induce a myriad of downstream effects, including the opening of K+ channels to weaken network connectivity, calcium-mediated dysregulation of mitochondria, and activation of inflammatory cascades to eliminate synapses, thereby increasing susceptibility to atrophy. Therefore, aging rhesus macaques provide an invaluable model to explore novel therapeutic strategies in sporadic AD.

Ru360 Alleviates Postoperative Cognitive Dysfunction in Aged Mice by Inhibiting MCU-Mediated Mitochondrial Dysfunction

Purpose

Ru360, a selective inhibitor of mitochondrial calcium uptake, maintains mitochondrial calcium homeostasis. To evaluate whether mitochondrial calcium uniporter (MCU)-mediated mitochondrial function is associated with the pathological process of Postoperative cognitive dysfunction (POCD), elucidate its relationship with neuroinflammation, and observe whether the relevant pathological process can be improved with Ru360.

Methods

Aged mice underwent experimental open abdominal surgery after anesthesia. Open field tests, Novel object recognition tests and Y Maze Tests were used to conduct behavioral experiments. The reactive oxygen species (ROS) content, the levels of inflammatory cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), intra-mitochondrial calcium, mitochondrial membrane potential (MMP) and the activity of antioxidant superoxide dismutase (SOD) in the hippocampus of mice were detected using kits. The expression of proteins was detected using Western blot.

Results

After treatment with Ru360, MCU-mediated mitochondrial dysfunction was inhibited, neuroinflammation was reduced, and the learning ability of the mice was improved after surgery.

Conclusion

Our study demonstrated that mitochondrial function plays a crucial role in the pathology of POCD, and using Ru360 to improve mitochondrial function may be a new and necessary direction for the treatment of POCD.

Crosslink between SARS-CoV-2 replication and cystic fibrosis hallmarks

SARS-CoV-2, the etiological cause of the COVID-19 pandemic, can cause severe illness in certain at-risk populations, including people with cystic fibrosis (pwCF). Nevertheless, several studies indicated that pwCF do not have higher risks of SARS-CoV-2 infection nor do they demonstrate worse clinical outcomes than those of the general population. Recent in vitro studies indicate cellular and molecular processes to be significant drivers in pwCF lower infection rates and milder symptoms than expected in cases of SARS-CoV-2 infection. These range from cytokine releases to biochemical alterations leading to morphological rearrangements inside the cells associated with CFTR impairment. Based on available data, the reported low incidence of SARS-CoV-2 infection among pwCF is likely a result of several variables linked to CFTR dysfunction, such as thick mucus, IL-6 reduction, altered ACE2 and TMPRSS2 processing and/or functioning, defective anions exchange, and autophagosome formation. An extensive analysis of the relation between SARS-CoV-2 infection and pwCF is essential to elucidate the mechanisms involved in this lower-than-expected infection impact and to possibly suggest potential new antiviral strategies.

The Tricky Connection between Extracellular Vesicles and Mitochondria in Inflammatory-Related Diseases

Mitochondria are organelles present in almost all eukaryotic cells, where they represent the main site of energy production. Mitochondria are involved in several important cell processes, such as calcium homeostasis, OXPHOS, autophagy, and apoptosis. Moreover, they play a pivotal role also in inflammation through the inter-organelle and inter-cellular communications, mediated by the release of mitochondrial damage-associated molecular patterns (mtDAMPs). It is currently well-documented that in addition to traditional endocrine and paracrine communication, the cells converse via extracellular vesicles (EVs). These small membrane-bound particles are released from cells in the extracellular milieu under physio-pathological conditions. Importantly, EVs have gained much attention for their crucial role in inter-cellular communication, translating inflammatory signals into recipient cells. EVs cargo includes plasma membrane and endosomal proteins, but EVs also contain material from other cellular compartments, including mitochondria. Studies have shown that EVs may transport mitochondrial portions, proteins, and/or mtDAMPs to modulate the metabolic and inflammatory responses of recipient cells. Overall, the relationship between EVs and mitochondria in inflammation is an active area of research, although further studies are needed to fully understand the mechanisms involved and how they may be targeted for therapeutic purposes. Here, we have reported and discussed the latest studies focused on this fascinating and recent area of research, discussing of tricky connection between mitochondria and EVs in inflammatory-related diseases.

Beyond the matrix: structural and physiological advancements in mitochondrial calcium signaling

Mitochondrial calcium (Ca2+) signaling has long been known to regulate diverse cellular functions, ranging from ATP production via oxidative phosphorylation, to cytoplasmic Ca2+ signaling to apoptosis. Central to mitochondrial Ca2+ signaling is the mitochondrial Ca2+ uniporter complex (MCUC) which enables Ca2+ flux from the cytosol into the mitochondrial matrix. Several pivotal discoveries over the past 15 years have clarified the identity of the proteins comprising MCUC. Here, we provide an overview of the literature on mitochondrial Ca2+ biology and highlight recent findings on the high-resolution structure, dynamic regulation, and new functions of MCUC, with an emphasis on publications from the last five years. We discuss the importance of these findings for human health and the therapeutic potential of targeting mitochondrial Ca2+ signaling.

Control of mitochondrial functions by Pseudomonas aeruginosa in cystic fibrosis

Cystic fibrosis (CF) is a genetic disease characterized by mutations of cystic fibrosis transmembrane conductance regulator (CFTR) gene, which lead to a dysfunctional chloride and bicarbonate channel. Abnormal mucus viscosity, persistent infections and hyperinflammation that preferentially affect the airways, referred to the pathogenesis of CF lung disease. It has largely demonstrated that Pseudomonas aeruginosa (P. aeruginosa) represents the most important pathogen that affect CF patients, leading to worsen inflammation by stimulating pro-inflammatory mediators release and tissue destruction. The conversion to mucoid phenotype and formation of biofilms, together with the increased frequency of mutations, are only few changes that characterize the P. aeruginosa's evolution during CF lung chronic infection. Recently, mitochondria received increasing attention due to their involvement in inflammatory-related diseases, including in CF. Alteration of mitochondrial homeostasis is sufficient to stimulate immune response. Exogenous or endogenous stimuli that perturb mitochondrial activity are used by cells, which, through the mitochondrial stress, potentiate immunity programs. Studies show the relationship between mitochondria and CF, supporting the idea that mitochondrial dysfunction endorses the exacerbation of inflammatory responses in CF lung. In particular, evidences suggest that mitochondria in CF airway cells are more susceptible to P. aeruginosa infection, with consequent detrimental effects that lead to amplify the inflammatory signals. This review discusses the evolution of P. aeruginosa in relationship with the pathogenesis of CF, a fundamental step to establish chronic infection in CF lung disease. Specifically, we focus on the role of P. aeruginosa in the exacerbation of inflammatory response, by triggering mitochondria in CF.

SARS-CoV-2-Mediated Lung Edema and Replication Are Diminished by Cystic Fibrosis Transmembrane Conductance Regulator Modulators

Coronaviruses (CoVs) of genera α, β, γ, and δ encode proteins that have a PDZ-binding motif (PBM) consisting of the last four residues of the envelope (E) protein (PBM core). PBMs may bind over 400 cellular proteins containing PDZ domains (an acronym formed by the combination of the first letter of the names of the three first proteins where this domain was identified), making them relevant for the control of cell function. Three highly pathogenic human CoVs have been identified to date: severe acute respiratory syndrome coronavirus (SARS-CoV) and Middle East respiratory syndrome coronavirus (MERS-CoV), and SARS-CoV-2. The PBMs of the three CoVs were virulence factors. SARS-CoV mutants in which the E protein PBM core was replaced by the E protein PBM core from virulent or attenuated CoVs were constructed. These mutants showed a gradient of virulence, depending on whether the alternative PBM core introduced was derived from a virulent or an attenuated CoV. Gene expression patterns in the lungs of mice infected with SARS-CoVs encoding each of the different PBMs were analyzed by RNA sequencing of infected lung tissues. E protein PBM of SARS-CoV and SARS-CoV-2 dysregulated gene expression related to ion transport and cell homeostasis. Decreased expression of cystic fibrosis transmembrane conductance regulator (CFTR) mRNA, essential for alveolar edema resolution, was shown. Reduced CFTR mRNA levels were associated with edema accumulation in the alveoli of mice infected with SARS-CoV and SARS-CoV-2. Compounds that increased CFTR expression and activity, significantly reduced SARS-CoV-2 growth in cultured cells and protected against mouse infection, suggesting that E protein virulence is mediated by a decreased CFTR expression. IMPORTANCE Three highly pathogenic human CoVs have been identified: SARS-CoV, MERS-CoV, and SARS-CoV-2. The E protein PBMs of these three CoVs were virulence factors. Gene expression patterns associated with the different PBM motifs in the lungs of infected mice were analyzed by deep sequencing. E protein PBM motif of SARS-CoV and SARS-CoV-2 dysregulated the expression of genes related to ion transport and cell homeostasis. A decrease in the mRNA expression of the cystic fibrosis transmembrane conductance regulator (CFTR), which is essential for edema resolution, was observed. The reduction of CFTR mRNA levels was associated with edema accumulation in the lungs of mice infected with SARS-CoV-2. Compounds that increased the expression and activity of CFTR drastically reduced the production of SARS-CoV-2 and protected against its infection in a mice model. These results allowed the identification of cellular targets for the selection of antivirals.

SARS-CoV-2 viral entry and replication is impaired in Cystic Fibrosis airways due to ACE2 downregulation

As an inherited disorder characterized by severe pulmonary disease, cystic fibrosis could be considered a comorbidity for coronavirus disease 2019. Instead, current clinical evidence seems to be heading in the opposite direction. To clarify whether host factors expressed by the Cystic Fibrosis epithelia may influence coronavirus disease 2019 progression, here we describe the expression of SARS-CoV-2 receptors in primary airway epithelial cells. We show that angiotensin converting enzyme 2 (ACE2) expression and localization are regulated by Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) channel. Consistently, our results indicate that dysfunctional CFTR channels alter susceptibility to SARS-CoV-2 infection, resulting in reduced viral entry and replication in Cystic Fibrosis cells. Depending on the pattern of ACE2 expression, the SARS-CoV-2 spike (S) protein induced high levels of Interleukin 6 in healthy donor-derived primary airway epithelial cells, but a very weak response in primary Cystic Fibrosis cells. Collectively, these data support that Cystic Fibrosis condition may be at least partially protecting from SARS-CoV-2 infection.

Pseudomonas aeruginosa Cytotoxins: Mechanisms of Cytotoxicity and Impact on Inflammatory Responses

Pseudomonas aeruginosa is one of the most virulent opportunistic Gram-negative bacterial pathogens in humans. It causes many acute and chronic infections with morbidity and mortality rates as high as 40%. P. aeruginosa owes its pathogenic versatility to a large arsenal of cell-associated and secreted virulence factors which enable this pathogen to colonize various niches within hosts and protect it from host innate immune defenses. Induction of cytotoxicity in target host cells is a major virulence strategy for P. aeruginosa during the course of infection. P. aeruginosa has invested heavily in this strategy, as manifested by a plethora of cytotoxins that can induce various forms of cell death in target host cells. In this review, we provide an in-depth review of P. aeruginosa cytotoxins based on their mechanisms of cytotoxicity and the possible consequences of their cytotoxicity on host immune responses.

Targeting the mitochondria in chronic respiratory diseases

Mitochondria are one of the basic essential components for eukaryotic life survival. It is also the source of respiratory ATP. Recently published studies have demonstrated that mitochondria may have more roles to play aside from energy production. There is an increasing body of evidence which suggest that mitochondrial activities involved in normal and pathological states contribute to significant impact to the lung airway morphology and epithelial function in respiratory diseases such as asthma, COPD, and lung cancer. This review summarizes the pathophysiological pathways involved in asthma, COPD, lung cancer and highlights potential treatment strategies that target the malfunctioning mitochondria in such ailments. Mitochondria are responsive to environmental stimuli such as infection, tobacco smoke, and inflammation, which are essential in the pathogenesis of respiratory diseases. They may affect mitochondrial shape, protein production and ultimately cause dysfunction. The impairment of mitochondrial function has downstream impact on the cytosolic components, calcium control, response towards oxidative stress, regulation of genes and proteins and metabolic activities. Several novel compounds and alternative medicines that target mitochondria in asthma and chronic lung diseases have been discussed here. Moreover, mitochondrial enzymes or proteins that may serve as excellent therapeutic targets in COPD are also covered. The role of mitochondria in respiratory diseases is gaining much attention and mitochondria-based treatment strategies and personalized medicine targeting the mitochondria may materialize in the near future. Nevertheless, more in-depth studies are urgently needed to validate the advantages and efficacy of drugs that affect mitochondria in pathological states.

TREM2/β-catenin attenuates NLRP3 inflammasome-mediated macrophage pyroptosis to promote bacterial clearance of pyogenic bacteria

Triggering receptors expressed on myeloid cells 2 (TREM2) is considered a protective factor to protect host from bacterial infection, while how it elicits this role is unclear. In the present study, we demonstrate that deficiency of triggering receptors expressed on myeloid cells 2 (TREM2) significantly enhanced macrophage pyroptosis induced by four common pyogenic bacteria including Staphylococcus aureus, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Escherichia coli. TREM2 deficiency also decreased bacterial killing ratio of macrophage, while Caspase-1 or GSDMD inhibition promoted macrophage-mediated clearance to these bacteria. Further study demonstrated that the effect of TREM2 on macrophage pyroptosis and bacterial eradication mainly dependents on the activated status of NLRP3 inflammasome. Moreover, as the key downstream of TREM2, β-catenin phosphorylated at Ser675 by TREM2 signal and accumulated in nucleus and cytoplasm. β-catenin mediated the effect of TREM2 on NLRP3 inflammasome and macrophage pyroptosis by reducing NLRP3 expression, and inhibiting inflammasome complex assembly by interacting with ASC. Collectively, TREM2/β-catenin inhibits NLRP3 inflammasome to regulate macrophage pyroptosis, and enhances macrophage-mediated pyogenic bacterial clearance.

The Multifaceted Roles of Autophagy in Infectious, Obstructive, and Malignant Airway Diseases

Autophagy is a highly conserved dynamic process by which cells deliver their contents to lysosomes for degradation, thus ensuring cell homeostasis. In response to environmental stress, the induction of autophagy is crucial for cell survival. The dysregulation of this degradative process has been implicated in a wide range of pathologies, including lung diseases, representing a relevant potential target with significant clinical outcomes. During lung disease progression and infections, autophagy may exert both protective and harmful effects on cells. In this review, we will explore the implications of autophagy and its selective forms in several lung infections, such as SARS-CoV-2, Respiratory Syncytial Virus (RSV) and Mycobacterium tuberculosis (Mtb) infections, and different lung diseases such as Cystic Fibrosis (CF), Chronic Obstructive Pulmonary Disease (COPD), and Malignant Mesothelioma (MM).

A Splice Switch in SIGIRR Causes a Defect of IL-37-Dependent Anti-Inflammatory Activity in Cystic Fibrosis Airway Epithelial Cells

Cystic fibrosis (CF) is a hereditary disease typically characterized by infection-associated chronic lung inflammation. The persistent activation of toll-like receptor (TLR) signals is considered one of the mechanisms for the CF hyperinflammatory phenotype; however, how negative regulatory signals of TLRs associate with CF inflammation is still elusive. Here, we showed that the cell surface expression of a single immunoglobulin interleukin-1 receptor (IL-1R)-related molecule (SIGIRR), a membrane protein essential for suppressing TLRs- and IL-1R-dependent signals, was remarkably decreased in CF airway epithelial cells compared to non-CF cells. Notably, CF airway epithelial cells specifically and highly expressed a unique, alternative splice isoform of the SIGIRR that lacks exon 8 (Δ8-SIGIRR), which results in the production of a C-terminal truncated form of the SIGIRR. Δ8-SIGIRR was expressed intracellularly, and its over-expression abolished the cell surface expression and function of the full-length SIGIRR (WT-SIGIRR), indicating its dominant-negative effect leading to the deficiency of anti-inflammatory activity in CF cells. Consistently, IL-37, a ligand for the SIGIRR, failed to suppress viral dsRNA analogue poly(I:C)-dependent JNK activation and IL-8 production, confirming the reduction in the functional WT-SIGIRR expression in the CF cells. Together, our studies reveal that SIGIRR-dependent anti-inflammatory activity is defective in CF airway epithelial cells due to the unique splicing switch of the SIGIRR gene and provides the first evidence of IL-37-SIGIRR signaling as a target of CF airway inflammation.

Mitochondrial calcium uniporter promotes phagocytosis-dependent activation of the NLRP3 inflammasome

Mitochondria, a highly metabolically active organelle, have been shown to play an essential role in regulating innate immune function. Mitochondrial Ca²⁺ uptake via the mitochondrial Ca²⁺ uniporter (MCU) is an essential process regulating mitochondrial metabolism by targeting key enzymes involved in the tricarboxylic acid cycle (TCA). Accumulative evidence suggests MCU-dependent mitochondrial Ca²⁺ signaling may bridge the metabolic reprogramming and regulation of immune cell function. However, the mechanism by which MCU regulates inflammation and its related disease remains elusive. Here we report a critical role of MCU in promoting phagocytosis-dependent activation of NLRP3 (nucleotide-binding domain, leucine-rich repeat containing family, pyrin domain-containing 3) inflammasome by inhibiting phagolysosomal membrane repair. Myeloid deletion of MCU (Mcu^Δmye) resulted in an attenuated phagolysosomal rupture, leading to decreased caspase-1 cleavage and interleukin (IL)-1β release, in response to silica or alum challenge. In contrast, other inflammasome agonists such as adenosine triphosphate (ATP), nigericin, poly(dA:dT), and flagellin induced normal IL-1β release in Mcu^Δmye macrophages. Mechanistically, we demonstrated that decreased NLRP3 inflammasome activation in Mcu^Δmye macrophages was caused by improved phagolysosomal membrane repair mediated by ESCRT (endosomal sorting complex required for transport)-III complex. Furthermore, Mcu^Δmye mice showed a pronounced decrease in immune cell recruitment and IL-1β production in alum-induced peritonitis, a typical IL-1-dependent inflammation model. In sum, our results identify a function of MCU in promoting phagocytosis-dependent NLRP3 inflammatory response via an ESCRT-mediated phagolysosomal membrane repair mechanism.

Activated glia cells cause bioenergetic impairment of neurons that can be rescued by knock-down of the mitochondrial calcium uniporter

Neuroinflammation is a hallmark of various neurological disorders including autoimmune-, neurodegenerative and neuropsychiatric diseases. In neuroinflammation, activated microglia and astrocytes release soluble mediators such as cytokines, glutamate, and reactive oxygen species that negatively affect neuronal function and viability, and thus contribute to neurodegeneration during disease progression. Therefore, the development of neuroprotective strategies might be important in addition to treating inflammation in these diseases. Mitochondria are promising cellular targets for neuroprotective interventions: They are among the first structures affected in many neuroinflammatory diseases, with mitochondrial impairment ranging from impaired respiratory activity and reduced mitochondrial membrane potential to mitochondrial oxidation and fragmentation. Therefore, we developed a cell culture model that resembles an early state of inflammation-induced neuronal mitochondrial dysfunction preceding neuronal cell death, and can be used to test mito- and neuroprotective strategies. Rat primary cortical neurons were challenged with conditioned medium from mixed primary cultures of rat microglia and astrocytes that had been activated with lipopolysaccharide and ATP. When sublethal amounts of glia-conditioned medium were added to neurons for 24 h, mitochondrial membrane potential and ATP levels were decreased, whereas mitochondrial redox state remained unaffected. Effects on mitochondrial membrane potential and ATP levels were ameliorated by knock-down of the mitochondrial calcium uniporter in neurons. This study suggests that neuronal bioenergetic failure is an early event during neuroinflammation and it identifies the mitochondrial calcium uniporter as a candidate target for neuroprotection in this context.

CrkII/Abl phosphorylation cascade is critical for NLRC4 inflammasome activity and is blocked by Pseudomonas aeruginosa ExoT

Type 3 Secretion System (T3SS) is a highly conserved virulence structure that plays an essential role in the pathogenesis of many Gram-negative pathogenic bacteria, including Pseudomonas aeruginosa. Exotoxin T (ExoT) is the only T3SS effector protein that is expressed in all T3SS-expressing P. aeruginosa strains. Here we show that T3SS recognition leads to a rapid phosphorylation cascade involving Abl / PKCδ / NLRC4, which results in NLRC4 inflammasome activation, culminating in inflammatory responses that limit P. aeruginosa infection in wounds. We further show that ExoT functions as the main anti-inflammatory agent for P. aeruginosa in that it blocks the phosphorylation cascade through Abl / PKCδ / NLRC4 by targeting CrkII, which we further demonstrate to be important for Abl transactivation and NLRC4 inflammasome activation in response to T3SS and P. aeruginosa infection.

Pseudomonas aeruginosa secretes the toxin ExoT, which is important for pathogenesis. Here, the authors show that ExoT inhibits NLRC4-dependent inflammatory responses during wound infection.

The Role of NLRP3 Inflammasome in Alzheimer’s Disease and Potential Therapeutic Targets

Alzheimer’s disease (AD) is a common age-related neurodegenerative disease characterized by progressive cognitive dysfunction and behavioral impairment. The typical pathological characteristics of AD are extracellular senile plaques composed of amyloid ß (Aβ) protein, intracellular neurofibrillary tangles formed by the hyperphosphorylation of the microtubule-associated protein tau, and neuron loss. In the past hundred years, although human beings have invested a lot of manpower, material and financial resources, there is no widely recognized drug for the effective prevention and clinical cure of AD in the world so far. Therefore, evaluating and exploring new drug targets for AD treatment is an important topic. At present, researchers have not stopped exploring the pathogenesis of AD, and the views on the pathogenic factors of AD are constantly changing. Multiple evidence have confirmed that chronic neuroinflammation plays a crucial role in the pathogenesis of AD. In the field of neuroinflammation, the nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key molecular link in the AD neuroinflammatory pathway. Under the stimulation of Aβ oligomers and tau aggregates, it can lead to the assembly and activation of NLRP3 inflammasome in microglia and astrocytes in the brain, thereby causing caspase-1 activation and the secretion of IL-1β and IL-18, which ultimately triggers the pathophysiological changes and cognitive decline of AD. In this review, we summarize current literatures on the activation of NLRP3 inflammasome and activation-related regulation mechanisms, and discuss its possible roles in the pathogenesis of AD. Moreover, focusing on the NLRP3 inflammasome and combining with the upstream and downstream signaling pathway-related molecules of NLRP3 inflammasome as targets, we review the pharmacologically related targets and various methods to alleviate neuroinflammation by regulating the activation of NLRP3 inflammasome, which provides new ideas for the treatment of AD.

Neutrophil-derived extracellular vesicles promote feed-forward inflammasome signaling in cystic fibrosis airways

Cystic fibrosis (CF) airways feature high extracellular levels of the IL-1 family of proinflammatory mediators. These mediators are cleavage products of caspase-1, the final protease in the inflammasome cascade. Due to the proven chronic presence of reprogrammed neutrophils in the CF airway lumen, understanding inflammasome signaling in these cells is of great importance to understand how disease is perpetuated in this milieu. Here, we hypothesized that CF airway neutrophils contribute to chronic inflammation, in part, via the packaging of inflammasome-inducing signals in extracellular vesicles (EVs). We confirmed that CF airway fluid is enriched in IL-1α, IL-1β, and IL-18, and that CF airway neutrophils up-regulate the activating receptor IL-1R1. Meanwhile, down-modulatory signals such as IL-1R2 and IL-1RA are unchanged. Active caspase-1 itself is present in CF airway fluid EVs, with neutrophil-derived EVs being most enriched. Using a transmigration model of CF airway inflammation, we show that CF airway fluid EVs are necessary and sufficient to induce primary granule exocytosis by naïve neutrophils (hallmark of reprogramming) and concomitantly activate caspase-1 and IL-1β production by these cells and that the addition of triple-combination highly effective CFTR modulator therapy does not abrogate these effects. Finally, EVs from activated neutrophils can deliver active caspase-1 to primary tracheal epithelial cells and induce their release of IL-1α. These findings support the existence of a feed-forward inflammatory process by which reprogrammed CF airway neutrophils bypass 2-step control of inflammasome activation in neighboring cells (naïve neutrophils and epithelial cells) via the transfer of bioactive EVs.

The Effect of PGC-1alpha-SIRT3 Pathway Activation on Pseudomonas aeruginosa Infection

The innate immune response to P. aeruginosa pulmonary infections relies on a network of pattern recognition receptors, including intracellular inflammasome complexes, which can recognize both pathogen- and host-derived signals and subsequently promote downstream inflammatory signaling. Current evidence suggests that the inflammasome does not contribute to bacterial clearance and, in fact, that dysregulated inflammasome activation is harmful in acute and chronic P. aeruginosa lung infection. Given the role of mitochondrial damage signals in recruiting inflammasome signaling, we investigated whether mitochondrial-targeted therapies could attenuate inflammasome signaling in response to P. aeruginosa and decrease pathogenicity of infection. In particular, we investigated the small molecule, ZLN005, which transcriptionally activates peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a master regulator of mitochondrial biogenesis, antioxidant defense, and cellular respiration. We demonstrate that P. aeruginosa infection promotes the expression of inflammasome components and attenuates several components of mitochondrial repair pathways in vitro in lung epithelial cells and in vivo in an acute pneumonia model. ZLN005 activates PGC-1α and its downstream effector, Sirtuin 3 (SIRT3), a mitochondrial-localized deacetylase important for cellular metabolic processes and for reactive oxygen species homeostasis. ZLN005 also attenuates inflammasome signaling induced by P. aeruginosa in bronchial epithelial cells and this action is dependent on ZLN005 activation of SIRT3. ZLN005 treatment reduces epithelial-barrier dysfunction caused by P. aeruginosa and decreases pathogenicity in an in vivo pneumonia model. Therapies that activate the PGC-1α—SIRT3 axis may provide a complementary approach in the treatment of P. aeruginosa infection.

Alterations in the Ca2+ toolkit in oesophageal adenocarcinoma

Aim:

To investigate alterations in transcription of genes, encoding Ca²⁺ toolkit proteins, in oesophageal adenocarcinoma (OAC) and to assess associations between gene expression, tumor grade, nodal-metastatic stage, and patient survival.

Methods:

The expression of 275 transcripts, encoding components of the Ca²⁺ toolkit, was analyzed in two OAC datasets: the Cancer Genome Atlas [via the University of Alabama Cancer (UALCAN) portal] and the oesophageal-cancer, clinical, and molecular stratification [Oesophageal Cancer Clinical and Molecular Stratification (OCCAMS)] dataset. Effects of differential expression of these genes on patient survival were determined using Kaplan-Meier log-rank tests. OAC grade- and metastatic-stage status was investigated for a subset of genes. Adjustment for the multiplicity of testing was made throughout.

Results:

Of the 275 Ca²⁺-toolkit genes analyzed, 75 displayed consistent changes in expression between OAC and normal tissue in both datasets. The channel-encoding genes, N-methyl-D-aspartate receptor 2D (GRIN2D), transient receptor potential (TRP) ion channel classical or canonical 4 (TRPC4), and TRP ion channel melastatin 2 (TRPM2) demonstrated the greatest increase in expression in OAC in both datasets. Nine genes were consistently upregulated in both datasets and were also associated with improved survival outcomes. The 6 top-ranking genes for the weighted significance of altered expression and survival outcomes were selected for further analysis: voltage-gated Ca²⁺ channel subunit α 1D (CACNA1D), voltage-gated Ca²⁺ channel auxiliary subunit α2 δ4 (CACNA2D4), junctophilin 1 (JPH1), acid-sensing ion channel 4 (ACCN4), TRPM5, and secretory pathway Ca²⁺ ATPase 2 (ATP2C2). CACNA1D, JPH1, and ATP2C2 were also upregulated in advanced OAC tumor grades and nodal-metastatic stages in both datasets.

Conclusions:

This study has unveiled alterations of the Ca²⁺ toolkit in OAC, compared to normal tissue. Such Ca²⁺ signalling findings are consistent with those from studies on other cancers. Genes that were consistently upregulated in both datasets might represent useful markers for patient diagnosis. Genes that were consistently upregulated, and which were associated with improved survival, might be useful markers for patient outcome. These survival-associated genes may also represent targets for the development of novel chemotherapeutic agents.

The Distribution and Role of the CFTR Protein in the Intracellular Compartments

Cystic fibrosis is a hereditary disease that mainly affects secretory organs in humans. It is caused by mutations in the gene encoding CFTR with the most common phenylalanine deletion at position 508. CFTR is an anion channel mainly conducting Cl⁻ across the apical membranes of many different epithelial cells, the impairment of which causes dysregulation of epithelial fluid secretion and thickening of the mucus. This, in turn, leads to the dysfunction of organs such as the lungs, pancreas, kidney and liver. The CFTR protein is mainly localized in the plasma membrane; however, there is a growing body of evidence that it is also present in the intracellular organelles such as the endosomes, lysosomes, phagosomes and mitochondria. Dysfunction of the CFTR protein affects not only the ion transport across the epithelial tissues, but also has an impact on the proper functioning of the intracellular compartments. The review aims to provide a summary of the present state of knowledge regarding CFTR localization and function in intracellular compartments, the physiological role of this localization and the consequences of protein dysfunction at cellular, epithelial and organ levels. An in-depth understanding of intracellular processes involved in CFTR impairment may reveal novel opportunities in pharmacological agents of cystic fibrosis.

Chronic Stress Weakens Connectivity in the Prefrontal Cortex: Architectural and Molecular Changes

Chronic exposure to uncontrollable stress causes loss of spines and dendrites in the prefrontal cortex (PFC), a recently evolved brain region that provides top-down regulation of thought, action, and emotion. PFC neurons generate top-down goals through recurrent excitatory connections on spines. This persistent firing is the foundation for higher cognition, including working memory, and abstract thought. However, exposure to acute uncontrollable stress drives high levels of catecholamine release in the PFC, which activates feedforward calcium-cAMP signaling pathways to open nearby potassium channels, rapidly weakening synaptic connectivity to reduce persistent firing. Chronic stress exposures can further exacerbate these signaling events leading to loss of spines and resulting in marked cognitive impairment. In this review, we discuss how stress signaling mechanisms can lead to spine loss, including changes to BDNF-mTORC1 signaling, calcium homeostasis, actin dynamics, and mitochondrial actions that engage glial removal of spines through inflammatory signaling. Stress signaling events may be amplified in PFC spines due to cAMP magnification of internal calcium release. As PFC dendritic spine loss is a feature of many cognitive disorders, understanding how stress affects the structure and function of the PFC will help to inform strategies for treatment and prevention.

Anti-Inflammatory Effects of RTD-1 in a Murine Model of Chronic Pseudomonas aeruginosa Lung Infection: Inhibition of NF-κB, Inflammasome Gene Expression, and Pro-IL-1β Biosynthesis

Vicious cycles of chronic airway obstruction, lung infections with Pseudomonas aeruginosa, and neutrophil-dominated inflammation contribute to morbidity and mortality in cystic fibrosis (CF) patients. Rhesus theta defensin-1 (RTD-1) is an antimicrobial macrocyclic peptide with immunomodulatory properties. Our objective was to investigate the anti-inflammatory effect of RTD-1 in a murine model of chronic P. aeruginosa lung infection. Mice received nebulized RTD-1 daily for 6 days. Bacterial burden, leukocyte counts, and cytokine concentrations were evaluated. Microarray analysis was performed on bronchoalveolar lavage fluid (BALF) cells and lung tissue homogenates. In vitro effects of RTD-1 in THP-1 cells were assessed using quantitative reverse transcription PCR, enzyme-linked immunosorbent assays, immunoblots, confocal microscopy, enzymatic activity assays, and NF-κB-reporter assays. RTD-1 significantly reduced lung white blood cell counts on days 3 (-54.95%; p = 0.0003) and 7 (-31.71%; p = 0.0097). Microarray analysis of lung tissue homogenates and BALF cells revealed that RTD-1 significantly reduced proinflammatory gene expression, particularly inflammasome-related genes (nod-like receptor protein 3, Mediterranean fever gene, interleukin (IL)-1α, and IL-1β) relative to the control. In vitro studies demonstrated NF-κB activation was reduced two-fold (p ≤ 0.0001) by RTD-1 treatment. Immunoblots revealed that RTD-1 treatment inhibited proIL-1β biosynthesis. Additionally, RTD-1 treatment was associated with a reduction in caspase-1 activation (FC = -1.79; p = 0.0052). RTD-1 exhibited potent anti-inflammatory activity in chronically infected mice. Importantly, RTD-1 inhibits inflammasome activity, which is possibly a downstream effect of NF-κB modulation. These findings support that this immunomodulatory peptide may be a promising therapeutic for CF-associated lung disease.

Mitochondrial Dysfunction in Chronic Respiratory Diseases: Implications for the Pathogenesis and Potential Therapeutics

Mitochondria are indispensable for energy metabolism and cell signaling. Mitochondrial homeostasis is sustained with stabilization of mitochondrial membrane potential, balance of mitochondrial calcium, integrity of mitochondrial DNA, and timely clearance of damaged mitochondria via mitophagy. Mitochondrial dysfunction is featured by increased generation of mitochondrial reactive oxygen species, reduced mitochondrial membrane potential, mitochondrial calcium imbalance, mitochondrial DNA damage, and abnormal mitophagy. Accumulating evidence indicates that mitochondrial dysregulation causes oxidative stress, inflammasome activation, apoptosis, senescence, and metabolic reprogramming. All these cellular processes participate in the pathogenesis and progression of chronic respiratory diseases, including chronic obstructive pulmonary disease, pulmonary fibrosis, and asthma. In this review, we provide a comprehensive and updated overview of the impact of mitochondrial dysfunction on cellular processes involved in the development of these respiratory diseases. This not only implicates mechanisms of mitochondrial dysfunction for the pathogenesis of chronic lung diseases but also provides potential therapeutic approaches for these diseases by targeting dysfunctional mitochondria.

p38 MAPK Activity Is Required to Prevent Hyperactivation of NLRP3 Inflammasome

Inflammation contributes to the pathogenesis and morbidity of wide spectrum of human diseases. The inflammatory response must be actively controlled to prevent bystander damage to tissues. Yet, the mechanisms controlling excessive inflammatory responses are poorly understood. NLRP3 inflammasome plays an important role in innate immune response to cellular infection or stress. Its activation must be tightly regulated because uncontrolled inflammasome activation is associated with a number of human diseases. p38 MAPK signaling plays an essential role in the regulation of inflammation. The role of p38 MAPK in inflammatory response associated with the expression of proinflammatory molecules is known. However, the anti-inflammatory functions of p38 MAPK are largely unknown. In this study, we show that pharmacologic inhibition or genetic deficiency of p38 MAPK leads to hyperactivation of NLRP3 inflammasome, resulting in enhanced Caspase 1 activation and IL-1β and IL-18 production. The deficiency of p38 MAPK activity induced an increase of cytosolic Ca²⁺ and excessive mitochondrial Ca²⁺ uptake, leading to exacerbation of mitochondrial damage, which was associated with hyperactivation of NLRP3 inflammasome. In addition, mice with deficiency of p38 MAPK in granulocytes had evidence of in vivo hyperactivation of NLRP3 inflammasome and were more susceptible to LPS-induced sepsis compared with wild-type mice. Our results suggest that p38 MAPK negatively regulates NLRP3 inflammasome through control of Ca²⁺ mobilization. Hyperactivity of inflammasome in p38-deficient mice causes lung inflammation and increased susceptibility to septic shock.

Airway Administration of Flagellin Regulates the Inflammatory Response to Pseudomonas aeruginosa

Excessive lung inflammation and airway epithelial damage are hallmarks of human inflammatory lung diseases, such as cystic fibrosis (CF). Enhancement of innate immunity provides protection against pathogens while reducing lung-damaging inflammation. However, the mechanisms underlying innate immunity–mediated protection in the lung remain mysterious, in part because of the lack of appropriate animal models for these human diseases. TLR5 (Toll-like receptor 5) stimulation by its specific ligand, the bacterial protein flagellin, has been proposed to enhance protection against several respiratory infectious diseases, although other cellular events, such as calcium signaling, may also control the intensity of the innate immune response. Here, we investigated the molecular events prompted by stimulation with flagellin and its role in regulating innate immunity in the lung of the pig, which is anatomically and genetically more similar to humans than rodent models. We found that flagellin treatment modulated NF-κB signaling and intracellular calcium homeostasis in airway epithelial cells. Flagellin pretreatment reduced the NF-κB nuclear translocation and the expression of proinflammatory cytokines to a second flagellin stimulus as well as to Pseudomonas aeruginosa infection. Moreover, in vivo administration of flagellin decreased the severity of P. aeruginosa–induced pneumonia. Then we confirmed these beneficial effects of flagellin in a pathological model of CF by using ex vivo precision-cut lung slices from a CF pigz model. These results provide evidence that flagellin treatment contributes to a better regulation of the inflammatory response in inflammatory lung diseases such as CF.

mTOR-driven glycolysis governs induction of innate immune responses by bronchial epithelial cells exposed to the bacterial component flagellin

Human bronchial epithelial (HBE) cells play an essential role during bacterial infections of the airways by sensing pathogens and orchestrating protective immune responses. We here sought to determine which metabolic pathways are utilized by HBE cells to mount innate immune responses upon exposure to a relevant bacterial agonist. Stimulation of HBE cells by the bacterial component flagellin triggered activation of the mTOR pathway resulting in an increased glycolytic flux that sustained the secretory activity of immune mediators by HBE cells. The mTOR inhibitor rapamycin impeded glycolysis and limited flagellin-induced secretion of immune mediators. The role of the mTOR pathway was recapitulated in vivo in a mouse model of flagellin-triggered lung innate immune responses. These data demonstrate that metabolic reprogramming via the mTOR pathway modulates activation of the respiratory epithelium, identifying mTOR as a potential therapeutic target to modulate mucosal immunity in the context of bacterial infections.

CFTR chloride channel activity modulates the mitochondrial morphology in cultured epithelial cells

The impairment of the CFTR channel activity, a cAMP-activated chloride (Cl^-) channel responsible for cystic fibrosis (CF), has been associated with a variety of mitochondrial alterations such as modified gene expression, impairment in oxidative phosphorylation, increased reactive oxygen species (ROS), and a disbalance in calcium homeostasis. The mechanisms by which these processes occur in CF are not fully understood. Previously, we demonstrated a reduced MTND4 expression and a failure in the mitochondrial complex I (mCx-I) activity in CF cells. Here we hypothesized that the activity of CFTR might modulate the mitochondrial fission/fusion balance, explaining the decreased mCx-I. The mitochondrial morphology and the levels of mitochondrial dynamic proteins MFN1 and DRP1 were analysed in IB3-1 CF cells, and S9 (IB3-1 expressing wt-CFTR), and C38 (IB3-1 expressing a truncated functional CFTR) cells. The mitochondrial morphology of IB3-1 cells compared to S9 and C38 cells showed that the impaired CFTR activity induced a fragmented mitochondrial network with increased rounded mitochondria and shorter branches. Similar results were obtained by using the CFTR pharmacological inhibitors CFTR(inh)-172 and GlyH101 on C38 cells. These morphological changes were accompanied by modifications in the levels of the mitochondrial dynamic proteins MFN1, DRP1, and p(616)-DRP1. IB3-1 CF cells treated with Mdivi-1, an inhibitor of mitochondrial fission, restored the mCx-I activity to values similar to those seen in S9 and C38 cells. These results suggest that the mitochondrial fission/fusion balance is regulated by the CFTR activity and might be a potential target to treat the impaired mCx-I activity in CF.

Cystic Fibrosis Lung Disease in the Aging Population

The demographics of the population with cystic fibrosis (CF) is continuously changing, with nowadays adults outnumbering children and a median predicted survival of over 40 years. This leads to the challenge of treating an aging CF population, while previous research has largely focused on pediatric and adolescent patients. Chronic inflammation is not only a hallmark of CF lung disease, but also of the aging process. However, very little is known about the effects of an accelerated aging pathology in CF lungs. Several chronic lung disease pathologies show signs of chronic inflammation with accelerated aging, also termed “inflammaging”; the most notable being chronic obstructive pulmonary disease (COPD) and idiopathic pulmonary fibrosis (IPF). In these disease entities, accelerated aging has been implicated in the pathogenesis via interference with tissue repair mechanisms, alterations of the immune system leading to impaired defense against pulmonary infections and induction of a chronic pro-inflammatory state. In addition, CF lungs have been shown to exhibit increased expression of senescence markers. Sustained airway inflammation also leads to the degradation and increased turnover of cystic fibrosis transmembrane regulator (CFTR). This further reduces CFTR function and may prevent the novel CFTR modulator therapies from developing their full efficacy. Therefore, novel therapies targeting aging processes in CF lungs could be promising. This review summarizes the current research on CF in an aging population focusing on accelerated aging in the context of chronic airway inflammation and therapy implications.

Inflammasome Genetic Variants, Macrophage Function, and Clinical Outcomes in Cystic Fibrosis

Cystic fibrosis (CF) is characterized by chronic airway infection, inflammation, and tissue damage that lead to progressive respiratory failure. NLRP3 and NLRC4 are cytoplasmic pattern recognition receptors that activate the inflammasome, initiating a caspase-1-mediated response. We hypothesized that gain-of-function inflammasome responses are associated with worse outcomes in children with CF. We genotyped nonsynonymous variants in NLRP3 and the NLRC4 pathway from individuals in the EPIC (Early Pseudomonas Infection Control) Observational Study cohort and tested for association with CF outcomes. We generated knockouts of NLRP3 and NLRC4 in human macrophage-like cells and rescued knockouts with wild-type or variant forms of NLRP3 and NLRC4. We identified a SNP in NLRP3, p.(Q705K), that was associated with a higher rate of P. aeruginosa colonization (N = 609; P = 0.01; hazard ratio, 2.3 [Cox model]) and worsened lung function over time as measured by forced expiratory volume in 1 second (N = 445; P = 0.001 [generalized estimating equation]). We identified a SNP in NLRC4, p.(A929S), that was associated with a lower rate of P. aeruginosa colonization as part of a composite of rare variants (N = 405; P = 0.045; hazard ratio, 0.68 [Cox model]) and that was individually associated with protection from lung function decline (P < 0.001 [generalized estimating equation]). Rescue of the NLRP3 knockout with the p.(Q705K) variant produced significantly more IL-1β in response to NLRP3 stimulation than rescue with the wild type (P = 0.020 [Student's t test]). We identified a subset of children with CF at higher risk of early lung disease progression. Knowledge of these genetic modifiers could guide therapies targeting inflammasome pathways.

Lateral size of graphene oxide determines differential cellular uptake and cell death pathways in Kupffer cells, LSECs, and hepatocytes

As a representative two-dimensional (2D) nanomaterial, graphene oxide (GO) has shown high potential in many applications due to its large surface area, high flexibility, and excellent dispersibility in aqueous solutions. These properties make GO an ideal candidate for bio-imaging, drug delivery, and cancer therapy. When delivered to the body, GO has been shown to accumulate in the liver, the primary accumulation site of systemic delivery or secondary spread from other uptake sites, and induce liver toxicity. However, the contribution of the GO physicochemical properties and individual liver cell types to this toxicity is unclear due to property variations and diverse cell types in the liver. Herein, we compare the effects of GOs with small (GO-S) and large (GO-L) lateral sizes in three major cell types in liver, Kupffer cells (KCs), liver sinusoidal endothelial cells (LSECs), and hepatocytes. While GOs induced cytotoxicity in KCs, they induced significantly less toxicity in LSECs and hepatocytes. For KCs, we found that GOs were phagocytosed that triggered NADPH oxidase mediated plasma membrane lipid peroxidation, which leads to PLC activation, calcium flux, mitochondrial ROS generation, and NLRP3 inflammasome activation. The subsequent caspase-1 activation induced IL-1β production and GSDMD-mediated pyroptosis. These effects were lateral size-dependent with GO-L showing stronger effects than GO-S. Amongst the liver cell types, decreased cell association and the absence of lipid peroxidation resulted in low cytotoxicity in LSECs and hepatocytes. Using additional GO samples with different lateral sizes, surface functionalities, or thickness, we further confirmed the differential cytotoxic effects in liver cells and the major role of GO lateral size in KUP5 pyroptosis by correlation studies. These findings delineated the GO effects on cellular uptake and cell death pathways in liver cells, and provide valuable information to further evaluate GO effects on the liver for biomedical applications.

Update on Calcium Signaling in Cystic Fibrosis Lung Disease

Cystic fibrosis (CF) is an autosomal recessive disorder characterized by mutations in the cystic fibrosis transmembrane conductance regulator gene, which causes multifunctional defects that preferentially affect the airways. Abnormal viscosity of mucus secretions, persistent pathogen infections, hyperinflammation, and lung tissue damage compose the classical pathological manifestation referred to as CF lung disease. Among the multifunctional defects associated with defective CFTR, increasing evidence supports the relevant role of perturbed calcium (Ca²⁺) signaling in the pathophysiology of CF lung disease. The Ca²⁺ ion is a critical player in cell functioning and survival. Its intracellular homeostasis is maintained by a fine balance between channels, transporters, and exchangers, mediating the influx and efflux of the ion across the plasma membrane and the intracellular organelles. An abnormal Ca²⁺ profile has been observed in CF cells, including airway epithelial and immune cells, with heavy repercussions on cell function, viability, and susceptibility to pathogens, contributing to proinflammatory overstimulation, organelle dysfunction, oxidative stress, and excessive cytokines release in CF lung. This review discusses the role of Ca²⁺ signaling in CF and how its dysregulation in airway epithelial and immune cells contributes to hyperinflammation in the CF lung. Finally, we provide an outlook on the therapeutic options that target the Ca²⁺ signaling to treat the CF lung disease.

Molecular machinery regulating mitochondrial calcium levels: The nuts and bolts of mitochondrial calcium dynamics

Mitochondria play vital role in regulating the cellular energetics and metabolism. Further, it is a signaling hub for cell survival and apoptotic pathways. One of the key determinants that calibrate both cellular energetics and survival functions is mitochondrial calcium (Ca2+) dynamics. Mitochondrial Ca2+ regulates three Ca2+-sensitive dehydrogenase enzymes involved in tricarboxylic acid cycle (TCA) cycle thereby directly controlling ATP synthesis. On the other hand, excessive Ca2+ concentration within the mitochondrial matrix elevates mitochondrial reactive oxygen species (mROS) levels and causes mitochondrial membrane depolarization. This leads to opening of the mitochondrial permeability transition pore (mPTP) and release of cytochrome c into cytosol eventually triggering apoptosis. Therefore, it is critical for cell to maintain mitochondrial Ca2+ concentration. Since cells can neither synthesize nor metabolize Ca2+, it is the dynamic interplay of Ca2+ handling proteins involved in mitochondrial Ca2+ influx and efflux that take the center stage. In this review we would discuss the key molecular machinery regulating mitochondrial Ca2+ concentration. We would focus on the channel complex involved in bringing Ca2+ into mitochondrial matrix i.e. Mitochondrial Ca2+ Uniporter (MCU) and its key regulators Mitochondrial Ca2+ Uptake proteins (MICU1, 2 and 3), MCU regulatory subunit b (MCUb), Essential MCU Regulator (EMRE) and Mitochondrial Ca2+ Uniporter Regulator 1 (MCUR1). Further, we would deliberate on major mitochondrial Ca2+ efflux proteins i.e. Mitochondrial Na+/Ca2+/Li+ exchanger (NCLX) and Leucine zipper EF hand-containing transmembrane1 (Letm1). Moreover, we would highlight the physiological functions of these proteins and discuss their relevance in human pathophysiology. Finally, we would highlight key outstanding questions in the field.

Mitochondrial Oxidative Stress and "Mito-Inflammation": Actors in the Diseases

A decline in mitochondrial redox homeostasis has been associated with the development of a wide range of inflammatory-related diseases. Continue discoveries demonstrate that mitochondria are pivotal elements to trigger inflammation and stimulate innate immune signaling cascades to intensify the inflammatory response at front of different stimuli. Here, we review the evidence that an exacerbation in the levels of mitochondrial-derived reactive oxygen species (ROS) contribute to mito-inflammation, a new concept that identifies the compartmentalization of the inflammatory process, in which the mitochondrion acts as central regulator, checkpoint, and arbitrator. In particular, we discuss how ROS contribute to specific aspects of mito-inflammation in different inflammatory-related diseases, such as neurodegenerative disorders, cancer, pulmonary diseases, diabetes, and cardiovascular diseases. Taken together, these observations indicate that mitochondrial ROS influence and regulate a number of key aspects of mito-inflammation and that strategies directed to reduce or neutralize mitochondrial ROS levels might have broad beneficial effects on inflammatory-related diseases.

STIM1 mediates IAV-induced inflammation of lung epithelial cells by regulating NLRP3 and inflammasome activation via targeting miR-223

AIMS

Influenza A virus (IAV) infection accelerates the inflammatory injury of lung epithelial cells that contributes to pulmonary lesion. Recently, stromal interaction molecule 1 (STIM1) was found to mediate cellular immune response and participated in lung tumorigenesis. Our study aimed to illustrate the function and mechanism of STIM1 in IAV-induced inflammation injury and oxidative stress of lung epithelial cells.

MAIN METHODS

We evaluated the levels of STIM1 in IAV-infected patients' serum and BEAS-2B cells using RT-qPCR, Elisa and western blotting methods. MTT and Elisa were performed to measure cell viability and cytokine contents. Besides, ROS intensity, SOD contents and cell apoptosis were detected based on DCFH-DA probe, colorimetry and cell death kits. A luciferase assay and Pearson's correlation analysis evaluated the associations between target genes.

KEY FINDINGS

STIM1 was dramatically up-regulated in IAV-infected patients' serum and BEAS-2B cells. Silencing STIM1 in vitro inhibited oxidative stress and inflammatory responses induced by IAV, and reversed cell viability and suppressed apoptosis. Moreover, miR-223 and NLRP3 were negatively and positively correlated with STIM1. STIM1 was found to regulate NLRP3 expression by binding the AACUGAC motif in miR-223. STIM1/miR-223/NLRP3 axis modulated IAV-induced inflammation injury of lung epithelial cells.

SIGNIFICANCE

Our evidence indicated that silencing STIM1 alleviated IAV-induced inflammation injury of lung epithelial cells by inactivating NLRP3 and inflammasome via promoting miR-223 expression. These findings may contribute to understand the mechanism of IAV-induced lung injury and help for therapy of IAV infection.

The yin and yang of mitochondrial Ca2+ signaling in cell physiology and pathology

Mitochondria are autonomous and dynamic cellular organelles orchestrating a diverse range of cellular activities. Numerous cell-signaling pathways target these organelles and Ca²⁺ is one of the most significant. Mitochondria are able to rapidly and transiently take up Ca²⁺, thanks to the mitochondrial Ca²⁺ uniporter complex, as well as to extrude it through the Na⁺/Ca²⁺ and H⁺/Ca²⁺ exchangers. The transient accumulation of Ca²⁺ in the mitochondrial matrix impacts on mitochondrial functions and cell pathophysiology. Here we summarize the role of mitochondrial Ca²⁺ signaling in both physiological (yang) and pathological (yin) processes and the methods that can be used to investigate mitochondrial Ca²⁺ homeostasis. As an example of the pivotal role of mitochondria in pathology, we described the state of the art of mitochondrial Ca²⁺ alterations in different pathological conditions, with a special focus on Alzheimer's disease.

A looming role of mitochondrial calcium in dictating the lung epithelial integrity and pathophysiology of lung diseases

With the increasing appreciation of mitochondria in modulating cellular homeostasis, various disease biology researchers have started exploring the detailed role of mitochondria in multiple diseases beyond neuronal and muscular diseases. In this context, emerging shreds of evidence in lung biology indicated the meticulous role of lung epithelia in provoking a plethora of lung diseases in contrast to earlier beliefs. As lung epithelia are ceaselessly exposed to the environment, they need to have multiple protective mechanisms to maintain the integrity of lung structure and function. As ciliated airway epithelium and type 2 alveolar epithelia require intense energy for executing their key functions like ciliary beating and surfactant production, it is no surprise that defects in mitochondrial function in these cells could perturb lung homeostasis and engage in the pathophysiology of lung diseases. On one hand, intracellular calcium plays the central role in executing key functions of lung epithelia, and on the other hand maintenance of intracellular calcium needs the buffering role of mitochondria. Thus, the regulation of mitochondrial calcium in lung epithelia seems to be critical in lung homeostasis and could be decisive in the pathogenesis of various lung diseases.

Mitochondrial dysfunction in lung ageing and disease

Mitochondrial biology has seen a surge in popularity in the past 5 years, with the emergence of numerous new avenues of exciting mitochondria-related research including immunometabolism, mitochondrial transplantation and mitochondria-microbe biology. Since the early 1960s mitochondrial dysfunction has been observed in cells of the lung in individuals and in experimental models of chronic and acute respiratory diseases. However, it is only in the past decade with the emergence of more sophisticated tools and methodologies that we are beginning to understand how this enigmatic organelle regulates cellular homeostasis and contributes to disease processes in the lung. In this review, we highlight the diverse role of mitochondria in individual lung cell populations and what happens when these essential organelles become dysfunctional with ageing and in acute and chronic lung disease. Although much remains to be uncovered, we also discuss potential targeted therapeutics for mitochondrial dysfunction in the ageing and diseased lung.

Mitochondrial Stress Responses and "Mito-Inflammation" in Cystic Fibrosis

Cystic fibrosis (CF) is a genetic disease associated to mutations in the cystic fibrosis transmembrane conductance regulator gene, which results in the alteration of biological fluid and electrolyte homeostasis. The characteristic pathological manifestation is represented by exaggerated proinflammatory response in lung of CF patients, driven by recurrent infections and worsen by hypersecretion of proinflammatory mediators and progressive tissue destruction. Treating inflammation remains a priority in CF. However, current anti-inflammatory treatments, including non-steroidal agents, are poorly effective and present dramatic side effects in CF patients. Different studies suggest an intimate relationship between mitochondria and CF lung disease, supporting the hypothesis that a decline in mitochondrial function endorses the development of the hyperinflammatory phenotype observed in CF lung. This allowed the implementation of a new concept: the "mito-inflammation," a compartmentalization of inflammatory process, related to the role of mitochondria in engage and sustain the inflammatory responses, resulting a druggable target to counteract the amplification of inflammatory signals in CF. Here, we will offer an overview of the contribution of mitochondria in the pathogenesis of CF lung disease, delving into mitochondrial quality control responses, which concur significantly to exacerbation of CF lung inflammatory responses. Finally, we will discuss the new therapeutic avenues that aim to target the mito-inflammation, an alternative therapeutic advantage for mitochondrial quality control that improves CF patient's inflammatory state.

Immune response of polarized cystic fibrosis airway epithelial cells infected with Influenza A virus

BACKGROUND

Cystic fibrosis (CF), a genetic disease caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene, is characterized by dysfunction of the immune response in the airway epithelium that leads to prolonged infection, colonization and exacerbated inflammation. In this study, we determined the gene expression profile of airway epithelial cells knockdown for CFTR (CFTR KD) in response to bacterial and viral challenges.

METHODS

In a first approach, polarized CFTR KD and their control counterpart (CFTR CTL) cells were stimulated with P. aeruginosa-derived virulence factor flagellin. Next, we developed a model of Influenza A virus (IAV) infection in CTL and CFTR KD polarized cells. mRNA was collected for transcriptome analysis.

RESULTS

Beside the expected pro-inflammatory response, Gene Set Enrichment Analysis highlighted key molecular pathways and players involved in IAV and anti-viral interferon signaling. Although IAV replication was similar in both cell types, multiplex gene expression analysis revealed changes of key immune genes dependent on time of infection that were found to be CFTR-dependent and/or IAV-dependent. Interferons are key signaling proteins/cytokines in the antibacterial and antiviral response. To evaluate their impact on the altered gene expression profile in CFTR responses to pathogens, we measured transcriptome changes after exposure to Type I-, Type II- and Type III-interferons.

CONCLUSIONS

Our findings reveal target genes in understanding the defective immune response in the CF airway epithelium in the context of viral infection. Information provided in this study would be useful to understand the dysfunctional immune response of the CF airway epithelium during infection.

Caspase-11 Non-canonical Inflammasomes in the Lung

The airway epithelium and underlying innate immune cells comprise the first line of host defense in the lung. They recognize pathogen-associated molecular patterns (PAMPs) using membrane-bound receptors, as well as cytosolic receptors such as inflammasomes. Inflammasomes activate inflammatory caspases, which in turn process and release the inflammatory cytokines IL-1β and IL-18. Additionally, inflammasomes trigger a form of lytic cell death termed pyroptosis. One of the most important inflammasomes at the host-pathogen interface is the non-canonical caspase-11 inflammasome that responds to LPS in the cytosol. Caspase-11 is important in defense against Gram-negative pathogens, and can drive inflammatory diseases such as LPS-induced sepsis. However, pathogens can employ evasive strategies to minimize or evade host caspase-11 detection. In this review, we present a comprehensive overview of the function of the non-canonical caspase-11 inflammasome in sensing of cytosolic LPS, and its mechanism of action with particular emphasis in the role of caspase-11 in the lung. We also explore some of the strategies pathogens use to evade caspase-11.

Role of Cystic Fibrosis Bronchial Epithelium in Neutrophil Chemotaxis

A hallmark of cystic fibrosis (CF) chronic respiratory disease is an extensive neutrophil infiltrate in the mucosa filling the bronchial lumen, starting early in life for CF infants. The genetic defect of the CF Transmembrane conductance Regulator (CFTR) ion channel promotes dehydration of the airway surface liquid, alters mucus properties, and decreases mucociliary clearance, favoring the onset of recurrent and, ultimately, chronic bacterial infection. Neutrophil infiltrates are unable to clear bacterial infection and, as an adverse effect, contribute to mucosal tissue damage by releasing proteases and reactive oxygen species. Moreover, the rapid cellular turnover of lumenal neutrophils releases nucleic acids that further alter the mucus viscosity. A prominent role in the recruitment of neutrophil in bronchial mucosa is played by CF bronchial epithelial cells carrying the defective CFTR protein and are exposed to whole bacteria and bacterial products, making pharmacological approaches to regulate the exaggerated neutrophil chemotaxis in CF a relevant therapeutic target. Here we revise: (a) the major receptors, kinases, and transcription factors leading to the expression, and release of neutrophil chemokines in bronchial epithelial cells; (b) the role of intracellular calcium homeostasis and, in particular, the calcium crosstalk between endoplasmic reticulum and mitochondria; (c) the epigenetic regulation of the key chemokines; (d) the role of mutant CFTR protein as a co-regulator of chemokines together with the host-pathogen interactions; and (e) different pharmacological strategies to regulate the expression of chemokines in CF bronchial epithelial cells through novel drug discovery and drug repurposing.

Knockout of the Mitochondrial Calcium Uniporter Strongly Suppresses Stimulus-Metabolism Coupling in Pancreatic Acinar Cells but Does Not Reduce Severity of Experimental Acute Pancreatitis

Acute pancreatitis is a frequent disease that lacks specific drug treatment. Unravelling the molecular mechanisms of acute pancreatitis is essential for the development of new therapeutics. Several inducers of acute pancreatitis trigger sustained Ca²⁺ increases in the cytosol and mitochondria of pancreatic acinar cells. The mitochondrial calcium uniporter (MCU) mediates mitochondrial Ca²⁺ uptake that regulates bioenergetics and plays an important role in cell survival, damage and death. Aberrant Ca²⁺ signaling and mitochondrial damage in pancreatic acinar cells have been implicated in the initiation of acute pancreatitis. The primary aim of this study was to assess the involvement of the MCU in experimental acute pancreatitis. We found that pancreatic acinar cells from MCU^-/- mice display dramatically reduced mitochondrial Ca²⁺ uptake. This is consistent with the drastic changes of stimulus-metabolism coupling, manifested by the reduction of mitochondrial NADH/FAD⁺ responses to cholecystokinin and in the decrease of cholecystokinin-stimulated oxygen consumption. However, in three experimental models of acute pancreatitis (induced by caerulein, taurolithocholic acid 3-sulfate or palmitoleic acid plus ethanol), MCU knockout failed to reduce the biochemical and histological changes characterizing the severity of local and systemic damage. A possible explanation of this surprising finding is the redundancy of damaging mechanisms activated by the inducers of acute pancreatitis.