Unravelling the Interplay between Extracellular Acidosis and Immune Cells

Calcium phosphates enhanced with liposomes - the future of bone regeneration and drug delivery

Effective healing and regeneration of various bone defects is still a major challenge and concern in modern medicine. Calcium phosphates have emerged as extensively studied bone substitute materials due to their structural and chemical resemblance to the mineral phase of bone, along with their versatile properties. Calcium phosphates present promising biological characteristics that make them suitable for bone substitution, but a critical limitation lies in their low osteoinductivity. To supplement these materials with properties that promote bone regeneration, prevent infections, and cure bone diseases locally, calcium phosphates can be biologically and therapeutically modified. A promising approach involves combining calcium phosphates with drug-containing liposomes, renowned for their high biocompatibility and ability to provide controlled and sustained drug delivery. Surprisingly, there is a lack of research focused on liposome-calcium phosphate composites, where liposomes are dispersed within a calcium phosphate matrix. This raises the question of why such studies are limited. In order to provide a comprehensive overview of existing liposome and calcium phosphate composites as bioactive substance delivery systems, the authors review the literature exploring the interactions between calcium phosphates and liposomes. Additionally, it seeks to identify potential interactions between calcium ions and liposomes, which may impact the feasibility of developing liposome-containing calcium phosphate composite materials. Liposome capacity to protect bioactive compounds and facilitate localized treatment can be particularly valuable in scenarios involving bone regeneration, infection prevention, and the management of bone diseases. This review explores the implications of liposomes and calcium phosphate material containing liposomes on drug delivery, bioavailability, and stability, offering insights into their advantages.

Lysosomal exocytosis: From cell protection to protumoral functions

Lysosomes are single membrane bounded group of acidic organelles that can be involved in a process called lysosomal exocytosis which leads to the extracellular release of their content. Lysosomal exocytosis is required for plasma membrane repair or remodeling events such as bone resorption, antigen presentation or mitosis, and for protection against toxic agents such as heavy metals. Recently, it has been showed that to fulfill this protective role, lysosomal exocytosis needs some autophagic proteins, in an autophagy-independent manner. In addition to these crucial physiological roles, lysosomal exocytosis plays a major protumoral role in various cancers. This effect is exerted through tumor microenvironment modifications, including extracellular matrix remodeling, acidosis, oncogenic and profibrogenic signals. This review provides a comprehensive overview of the different elements released in the microenvironment during lysosomal exocytosis, i.e. proteases, exosomes, and protons, and their effects in the context of tumor development and treatment.

Recent Progress of pH-Responsive Peptides, Polypeptides, and Their Supramolecular Assemblies for Biomedical Applications

Peptides and polypeptides feature a variety of active functional groups on their side chains (including carboxylic acid, hydroxyl, amino, and thiol groups), enabling diverse chemical modifications. This versatility makes them highly valuable in stimuli-responsive systems. Notably, pH-responsive peptides and polypeptides, due to their ability to respond to pH changes, hold significant promise for applications in cellular pathology and tumor targeting. Extensive researches have highlighted the potentials of low pH insertion peptides (pHLIPs), peptide-drug conjugates (PDCs), and antibody-drug conjugates (ADCs) in biomedicine. Peptide self-assemblies, with their structural stability, ease of regulation, excellent biocompatibility, and biodegradability, offer immense potentials in the development of novel materials and biomedical applications. We also explore specific examples of their applications in drug delivery, tumor targeting, and tissue engineering, while discussing future challenges and potential advancements in the field of pH-responsive self-assembling peptide-based biomaterials.

The ADVanced Organ Support (ADVOS) hemodialysis system removes IL-6: an in vitro proof-of-concept study

BACKGROUND

IL-6 is a pleiotropic cytokine modulating inflammation and metabolic pathways. Its proinflammatory effect plays a significant role in organ failure pathogenesis, commonly elevated in systemic inflammatory conditions. Extracorporeal blood purification devices, such as the Advanced Organ Support (ADVOS) multi hemodialysis system, might offer potential in mitigating IL-6's detrimental effects, yet its efficacy remains unreported.

METHODS

We conducted a proof-of-concept in vitro study to assess the ADVOS multi system's efficacy in eliminating IL-6. Varying concentrations of IL-6 were introduced into a swine blood model and treated with ADVOS multi for up to 12 h, employing different blood and concentrate flow rates. IL-6 reduction rate, clearance, and dynamics in blood and dialysate were analyzed.

RESULTS

IL-6 clearance rates of 0.70 L/h and 0.42 L/h were observed in 4 and 12-h experiments, respectively. No significant differences were noted across different initial concentrations. Reduction rates ranged between 40 and 46% within the first 4 h, increasing up to 72% over 12 h, with minimal impact from flow rate variations. Our findings suggest that an IL-6-albumin interaction and convective filtration are implicated in in vitro IL-6 elimination with ADVOS multi.

CONCLUSIONS

This study demonstrates for the first time an efficient and continuous in vitro removal of IL-6 by ADVOS multi at low blood flow rates. Initial concentration-dependent removal transitions to more consistent elimination over time. Further clinical investigations are imperative for comprehensive data acquisition.

Effects of pH on opioid receptor activation and implications for drug design

G-protein-coupled receptors are integral membrane proteins that transduce chemical signals from the extracellular matrix into the cell. Traditional drug design has considered ligand-receptor interactions only under normal conditions. However, studies on opioids indicate that such interactions are very different in diseased tissues. In such microenvironments, protons play an important role in structural and functional alterations of both ligands and receptors. The pertinent literature strongly suggests that future drug design should take these aspects into account in order to reduce adverse side effects while preserving desired effects of novel compounds.

High throughput screening of mesenchymal stromal cell morphological response to inflammatory signals for bioreactor-based manufacturing of extracellular vesicles that modulate microglia

Due to their immunomodulatory function, mesenchymal stromal cells (MSCs) are a promising therapeutic with the potential to treat neuroinflammation associated with neurodegenerative diseases. This function is mediated by secreted extracellular vesicles (MSC-EVs). Despite established safety, MSC clinical translation has been unsuccessful due to inconsistent clinical outcomes resulting from functional heterogeneity. Current approaches to mitigate functional heterogeneity include 'priming' MSCs with inflammatory signals to enhance function. However, comprehensive evaluation of priming and its effects on MSC-EV function has not been performed. Furthermore, clinical translation of MSC-EV therapies requires significant manufacturing scale-up, yet few studies have investigated the effects of priming in bioreactors. As MSC morphology has been shown to predict their immunomodulatory function, we screened MSC morphological response to an array of priming signals and evaluated MSC-EV identity and potency in response to priming in flasks and bioreactors. We identified unique priming conditions corresponding to distinct morphologies. These conditions demonstrated a range of MSC-EV preparation quality and lipidome, allowing us to discover a novel MSC-EV manufacturing condition, as well as gain insight into potential mechanisms of MSC-EV microglia modulation. Our novel screening approach and application of priming to MSC-EV bioreactor manufacturing informs refinement of larger-scale manufacturing and enhancement of MSC-EV function.

Cancer EV stimulate endothelial glycolysis to fuel protein synthesis via mTOR and AMPKα activation

Hypoxia is a common feature of solid tumours and activates adaptation mechanisms in cancer cells that induce therapy resistance and has profound effects on cellular metabolism. As such, hypoxia is an important contributor to cancer progression and is associated with a poor prognosis. Metabolic alterations in cells within the tumour microenvironment support tumour growth via, amongst others, the suppression of immune reactions and the induction of angiogenesis. Recently, extracellular vesicles (EV) have emerged as important mediators of intercellular communication in support of cancer progression. Previously, we demonstrated the pro-angiogenic properties of hypoxic cancer cell derived EV. In this study, we investigate how (hypoxic) cancer cell derived EV mediate their effects. We demonstrate that cancer derived EV regulate cellular metabolism and protein synthesis in acceptor cells through increased activation of mTOR and AMPKα. Using metabolic tracer experiments, we demonstrate that EV stimulate glucose uptake in endothelial cells to fuel amino acid synthesis and stimulate amino acid uptake to increase protein synthesis. Despite alterations in cargo, we show that the effect of cancer derived EV on recipient cells is primarily determined by the EV producing cancer cell type rather than its oxygenation status.

Breast Cancer Treatment Strategies Targeting the Tumor Microenvironment: How to Convert "Cold" Tumors to "Hot" Tumors

Breast cancer characterized as "cold tumors" exhibit low levels of immune cell infiltration, which limits the efficacy of conventional immunotherapy. Recent studies have focused on strategies using nanotechnology combined with tumor microenvironment modulation to transform "cold tumors" into "hot tumors". This approach involves the use of functionalized nanoparticles that target and modify the tumor microenvironment to promote the infiltration and activation of antitumor immune cells. By delivering immune activators or blocking immunosuppressive signals, these nanoparticles activate otherwise dormant immune responses, enhancing tumor immunogenicity and the therapeutic response. These strategies not only promise to increase the response rate of breast cancer patients to existing immunotherapies but also may pave new therapeutic avenues, providing a new direction for the immunotherapy of breast cancer.

Amorphous calcium carbonate as a novel potential treatment for osteoarthritis in dogs: a pilot clinical study

Background

Amorphous calcium carbonate (ACC) is a potential new treatment for canine osteoarthritis (OA) with novel mechanisms based on local pH modulation and targeting bone remodeling, inflammation, and pain. The aim of this pilot exploratory clinical study was to obtain initial data on the potential efficacy and safety of ACC in OA dogs and to determine if further investigation was appropriate using similar assessment methods.

Materials and methods

In this prospective, randomized, double-blind, controlled pilot study, 41 client-owned dogs were allocated in a 2:1 ratio to ACC: placebo given orally for 56 days. Efficacy assessments included improvements in pain and mobility using owner questionnaires [Canine Brief Pain Inventory (CBPI), Client Specific Outcome Measure (CSOM), and Veterinary Orthopedic Scores (VOS)]. Safety in the study population was monitored by veterinary examinations, clinical pathology, and adverse events.

Results

Fifty-three dogs were screened, of which 41 enrolled and served for the safety assessment. Thirty-six dogs were found evaluable for initial efficacy assessment. Three dogs given placebo (21.4%) and one given ACC (4.5%) were removed before day 56 due to owner-perceived pain and were considered treatment failures. There were no serious adverse events or clinically significant treatment-related effects in the study. Overall, ACC was found safe in the small study population. On day 56, proportionally more ACC than placebo dogs were treatment successes based on CBPI (45.5% vs. 21.4%) and CSOM (63.6% vs. 30.8%, respectively); however, these differences were not statistically significant (p = 0.15 and 0.06, respectively). On day 56, within the ACC group but not the placebo group, the CBPI, CSOM, and VOS assessments were lower compared to day 0 and day 14 (p < 0.05).

Limitations

The relatively small number of dogs limited the statistical power of the pilot study in evaluating the efficacy and safety of ACC.

Conclusion

Study results support the conduct of larger, appropriately powered studies using similar assessments to confirm whether ACC may be a safe and effective treatment for OA in dogs.

Unveiling cytokine charge disparity as a potential mechanism for immune regulation

Cytokines are small signaling proteins that regulate the immune responses to infection and tissue damage. Surface charges of cytokines determine their in vivo fate in immune regulation, e.g., half-life and distribution. The overall negative charges in the extracellular microenvironment and the acidosis during inflammation and infection may differentially impact cytokines with different surface charges for fine-tuned immune regulation via controlling tissue residential properties. However, the trend and role of cytokine surface charges has yet to be elucidated in the literature. Interestingly, we have observed that most pro-inflammatory cytokines have a negative charge, while most anti-inflammatory cytokines and chemokines have a positive charge. In this review, we extensively examined the surface charges of all cytokines and chemokines, summarized the pharmacokinetics and tissue adhesion of major cytokines, and analyzed the link of surface charge with cytokine biodistribution, activation, and function in immune regulation. Additionally, we identified that the general trend of charge disparity between pro- and anti-inflammatory cytokines represents a unique opportunity to develop precise immune modulation approaches, which can be applied to many inflammation-associated diseases including solid tumors, chronic wounds, infection, and sepsis.

A novel lactylation-related gene signature for effectively distinguishing and predicting the prognosis of ovarian cancer

Background

Lactylation has been found to regulate several types of biological processes in cancer. However, there is limited research on lactylation-related genes in predicting the prognosis of ovarian cancer (OC). This study aimed to explore the functional roles of lactylation-related genes in OC.

Methods

Based on TCGA database, we obtained RNA sequencing data and clinical characteristics of patients with OC. Fourteen lactylation-related genes were screened for bioinformatic analysis in OC. Tumor classification of OC was constructed via a consistency cluster analysis. We examined the prognosis, immune-cell infiltration, and immunotherapy in relation to a lactylation-related model for OC.

Results

A total of 707 prognostic genes and 14 key lactylation-related genes (SNRPA1, MPHOSPH6, POLDIP3, RB1, AHNAK, MAGOHB, CALM1, EP300, HDAC1, HDAC2, HDAC3, SIRT1, SIRT2, and SIRT3) were identified in TCGA-OC patients. Based on 14 genes involved in lactylation, TCGA-OC patients were split into low-risk (G1) and high-risk (G2) groups. Downregulated differentially expressed genes (DEGs) in the low-risk G1 group were associated with thermogenesis, oxidative phosphorylation, neutrophil extracellular trap formation, and interleukin 17 (IL-17) signaling pathway, whereas upregulated DEGs were associated with proteoglycans in cancer, focal adhesion, Wnt signaling pathway, extracellular matrix (ECM)-receptor interaction, and the adherens junction. The immune activity of the low-risk G1 group was lower than that of the high-risk G2 group. Gemcitabine, bleomycin, and doxorubicin had lower half-maximal inhibitory concentration (IC50) values in the high-risk G2 patients with OC, while cisplatin and paclitaxel had higher IC50 values compared to the low-risk G1 patients. The prognosis of patients with OC was also predicted with the help of an eight-lactylation-related gene prognostic model, comprising SNRPA1, MPHOSPH6, POLDIP3, RB1, HDAC1, CALM1, HDAC2, and SIRT2.

Conclusions

The lactylation-related genes are closely related to tumor classification and immunity in patients with OC. There was good prognostic predictive performance for OC based on a lactylation-related signature. Our findings may offer new insights into the diagnosis and treatment of OC.

Optimizing Early Clinical Investigations in Cancer Immunotherapy: The Translational Journey of RG6292, a Novel, Selective Treg-Depleting Antibody

The multifaceted IL-2/IL-2R biology and its modulation by promising therapeutic agents are highly relevant topics in the cancer immunotherapy field. A novel CD25-Treg-depleting antibody (Vopikitug, RG6292) has been engineered to preserve IL-2 signaling on effector T cells to enhance effector activation and antitumor immunity, and is currently being evaluated in the clinic. The Entry into Human-enabling framework described here investigated the characteristics of RG6292, from in vitro quantification of CD25 and RG6292 pharmacology using human tissues to in vivo assessment of PK/PD/safety relationships in cynomolgus monkeys as non-human primate species (NHP). Fundamental knowledge on CD25 and Treg biology in healthy and diseased tissues across NHP and human highlighted the commonalities between these species in regard to the target biology and demonstrated the conservation of RG6292 properties between NHP and human. The integration of in vitro and in vivo PK/PD/safety data from these species enabled the identification of human relevant safety risks, the selection of the most appropriate safe starting dose and the projection of the pharmacologically-relevant dose range. The first clinical data obtained for RG6292 in patients verified the appropriateness of the described approaches as well as validated the full clinical relevance of the projected safety, PK, and PD profiles from animal to man. This work shows how the integration of mechanistic non-clinical data increases the predictive value for human, allowing efficient transition of drug candidates and optimizations of early clinical investigations.

Amorphous calcium carbonate enhances osteogenic differentiation and myotube formation of human bone marrow derived mesenchymal stem cells and primary skeletal muscle cells under microgravity conditions

Astronauts are exposed to severely stressful physiological conditions due to microgravity and increased space radiation. Space environment affects every organ and cell in the body and the significant adverse effects of long-term weightlessness include muscle atrophy and deterioration of the skeleton (spaceflight osteopenia). Amorphous Calcium Carbonate (ACC) emerges as a promising candidate for prevention of these effects, owing to its unique physicochemical properties and its potential to address the intricately linked nature of bone-muscle crosstalk. Reported here are two studies carried out on the International Space Station (ISS). The first, performed in 2018 as a part of the Ramon-Spacelab project, was a preliminary experiment, in which stromal murine cells were differentiated into osteoblasts when ACC was added to the culture medium. A parallel experiment was done on Earth as a control. The second study was part of Axiom-1's Rakia project mission launched to the ISS on 2022 utilizing organ-on-a-chip methodology with a specially designed autonomous module. In this experiment, human bone-marrow derived mesenchymal stem cells (hBM-MSCs) and human primary muscle cells were cultured in the presence or absence of ACC, in duplicates. The results showed that ACC enhanced differentiation of human primary skeletal muscle cells into myotubes. Similarly, hBM-MSCs were differentiated significantly better into osteocytes in the presence of ACC leading to increased calcium deposits. The results, combined with previous data, support the use of ACC as an advantageous supplement for preventing muscle and bone deterioration in outer space conditions, facilitating extended extraterrestrial voyages and colonization.

Intracellular acidity impedes KCa3.1 activation by Riluzole and SKA-31

Background

The unique microenvironment in tumors inhibits the normal functioning of tumor-infiltrating lymphocytes, leading to immune evasion and cancer progression. Over-activation of KCa3.1 using positive modulators has been proposed to rescue the anti-tumor response. One of the key characteristics of the tumor microenvironment is extracellular acidity. Herein, we analyzed how intra- and extracellular pH affects K+ currents through KCa3.1 and if the potency of two of its positive modulators, Riluzole and SKA-31, is pH sensitive.

Methods

Whole-cell patch-clamp was used to measure KCa3.1 currents either in activated human peripheral lymphocytes or in CHO cells transiently transfected with either the H192A mutant or wild-type hKCa3.1 in combination with T79D-Calmodulin, or with KCa2.2.

Results

We found that changes in the intra- and extracellular pH minimally influenced the KCa3.1-mediated K+ current. Extracellular pH, in the range of 6.0-8.0, does not interfere with the capacity of Riluzole and SKA-31 to robustly activate the K+ currents through KCa3.1. Contrariwise, an acidic intracellular solution causes a slow, but irreversible loss of potency of both the activators. Using different protocols of perfusion and depolarization we demonstrated that the loss of potency is strictly time and pH-dependent and that this peculiar effect can be observed with a structurally similar channel KCa2.2. While two different point mutations of both KCa3.1 (H192A) and its associated protein Calmodulin (T79D) do not limit the effect of acidity, increasing the cytosolic Ca2+ concentration to saturating levels eliminated the loss-of-potency phenotype.

Conclusion

Based on our data we conclude that KCa3.1 currents are not sensitive the either the intracellular or the extracellular pH in the physiological and pathophysiological range. However, intracellular acidosis in T cells residing in the tumor microenvironment could hinder the potentiating effect of KCa3.1 positive modulators administered to boost their activity. Further research is warranted both to clarify the molecular interactions between the modulators and KCa3.1 at different intracellular pH conditions and to define whether this loss of potency can be observed in cancer models as well.

pH-regulated single cell migration

Over the last two decades, extra- and intracellular pH have emerged as fundamental regulators of cell motility. Fundamental physiological and pathological processes relying on appropriate cell migration, such as embryonic development, wound healing, and a proper immune defense on the one hand, and autoimmune diseases, metastatic cancer, and the progression of certain parasitic diseases on the other, depend on surrounding pH. In addition, migrating single cells create their own localized pH nanodomains at their surface and in the cytosol. By this means, the migrating cells locally modulate their adhesion to, and the re-arrangement and digestion of, the extracellular matrix. At the same time, the cytosolic nanodomains tune cytoskeletal dynamics along the direction of movement resulting in concerted lamellipodia protrusion and rear end retraction. Extracellular pH gradients as found in wounds, inflamed tissues, or the periphery of tumors stimulate directed cell migration, and long-term exposure to acidic conditions can engender a more migratory and invasive phenotype persisting for hours up to several generations of cells after they have left the acidic milieu. In the present review, the different variants of pH-dependent single cell migration are described. The underlying pH-dependent molecular mechanisms such as conformational changes of adhesion molecules, matrix protease activity, actin (de-)polymerization, and signaling events are explained, and molecular pH sensors stimulated by H+ signaling are presented.

Novel pH-responsive alginate-stabilized curcumin-selenium-ZIF-8 nanocomposites for synergistic breast cancer therapy

In this study, a novel selenium@zeolitic imidazolate framework core/shell nanocomposite stabilised with alginate was used to improve the anti-tumour activity of curcumin. The developed alginate-stabilised curcumin-loaded selenium@zeolitic imidazolate framework (Alg@Cur@Se@ZIF-8) had a mean diameter of 159.6 nm and polydispersity index < 0.25. The release of curcumin from the nanocarrier at pH 5.4 was 2.69 folds as high as at pH 7.4. The bare nanoparticles showed haemolytic activity of about 12.16% at a concentration of 500 µg/mL while covering their surface with alginate reduced this value to 5.2%. By investigating cell viability, it was found that Alg@Cur@Se@ZIF-8 caused more cell death than pure curcumin. Additionally, in vivo studies showed that Alg@Cur@Se@ZIF-8 dramatically reduced tumour growth compared to free curcumin in 4T1 tumour-bearing mice. More importantly, the histological study confirmed that the developed drug delivery system successfully inhibited lung and liver metastasis while causing negligible toxicity in vital organs. Overall, due to the excellent inhibitory activity on cancerous cell lines and tumour-bearing animals, Alg@Cur@Se@ZIF-8 can be considered promising for breast cancer therapy.

Challenges in developing personalized neoantigen cancer vaccines

The recent success of cancer immunotherapies has highlighted the benefit of harnessing the immune system for cancer treatment. Vaccines have a long history of promoting immunity to pathogens and, consequently, vaccines targeting cancer neoantigens have been championed as a tool to direct and amplify immune responses against tumours while sparing healthy tissue. In recent years, extensive preclinical research and more than one hundred clinical trials have tested different strategies of neoantigen discovery and vaccine formulations. However, despite the enthusiasm for neoantigen vaccines, proof of unequivocal efficacy has remained beyond reach for the majority of clinical trials. In this Review, we focus on the key obstacles pertaining to vaccine design and tumour environment that remain to be overcome in order to unleash the true potential of neoantigen vaccines in cancer therapy.

TCR signaling promotes formation of an STS1-Cbl-b complex with pH-sensitive phosphatase activity that suppresses T cell function in acidic environments

T cell responses are inhibited by acidic environments. T cell receptor (TCR)-induced protein phosphorylation is negatively regulated by dephosphorylation and/or ubiquitination, but the mechanisms underlying sensitivity to acidic environments are not fully understood. Here, we found that TCR stimulation induced a molecular complex of Cbl-b, an E3-ubiquitin ligase, with STS1, a pH-sensitive unconventional phosphatase. The induced interaction depended upon a proline motif in Cbl-b interacting with the STS1 SH3 domain. STS1 dephosphorylated Cbl-b interacting phosphoproteins. The deficiency of STS1 or Cbl-b diminished the sensitivity of T cell responses to the inhibitory effects of acid in an autocrine or paracrine manner in vitro or in vivo. Moreover, the deficiency of STS1 or Cbl-b promoted T cell proliferative and differentiation activities in vivo and inhibited tumor growth, prolonged survival, and improved T cell fitness in tumor models. Thus, a TCR-induced STS1-Cbl-b complex senses intra- or extra-cellular acidity and regulates T cell responses, presenting a potential therapeutic target for improving anti-tumor immunity.

Acidic pH modulates Burkholderia cenocepacia antimicrobial susceptibility in the cystic fibrosis nutritional environment

IMPORTANCE

Burkholderia cenocepacia causes severe infections in cystic fibrosis (CF) patients. CF patients are prone to reoccurring infections due to the accumulation of mucus in their lungs, where bacteria can adhere and grow. Some of the antibiotics that inhibit B. cenocepacia in the laboratory are not effective for CF patients. A major contributor to poor clinical outcomes is that antibiotic testing in laboratories occurs under conditions that are different from those of sputum. CF sputum may be acidic and have increased concentrations of iron and zinc. Here, we used a medium that mimics CF sputum and found that acidic pH decreased the activity of many of the antibiotics used against B. cenocepacia. In addition, we assessed susceptibility to more than 500 antibiotics and found four active compounds against B. cenocepacia. Our findings give a better understanding of the lack of a relationship between susceptibility testing and the clinical outcome when treating B. cenocepacia infections.

Systemic perturbations in amino acids/amino acid derivatives and tryptophan pathway metabolites associated with murine influenza A virus infection

BACKGROUND

Influenza A virus (IAV) is the only influenza virus causing flu pandemics (i.e., global epidemics of flu disease). Influenza (the flu) is a highly contagious disease that can be deadly, especially in high-risk groups. Worldwide, these annual epidemics are estimated to result in about 3 to 5 million cases of severe illness and in about 290,000 to 650,000 respiratory deaths. We intend to reveal the effect of IAV infection on the host's metabolism, immune response, and neurotoxicity by using a mouse IAV infection model.

METHODS

51 metabolites of murine blood plasma (33 amino acids/amino acid derivatives (AADs) and 18 metabolites of the tryptophan pathway) were analyzed by using Ultra-High-Performance Liquid Chromatography-Mass Spectrometry with Electrospray Ionization at the acute (7 days post-infection (dpi)), resolution (14 dpi), and recovery (21 dpi) stages of the virus infection in comparison with controls.

RESULTS

Among the 33 biogenic amino acids/AADs, the levels of five amino acids/AADs (1-methylhistidine, 5-oxoproline, α-aminobutyric acid, glutamine, and taurine) increased by 7 dpi, whereas the levels of ten amino acids/AADs (4-hydroxyproline, alanine, arginine, asparagine, cysteine, citrulline, glycine, methionine, proline, and tyrosine) decreased. By 14 dpi, the levels of one AAD (3-methylhistidine) increased, whereas the levels of five amino acids/AADs (α-aminobutyric acid, aminoadipic acid, methionine, threonine, valine) decreased. Among the 18 metabolites from the tryptophan pathway, the levels of kynurenine, quinolinic acid, hydroxykynurenine increased by 7 dpi, whereas the levels of indole-3-acetic acid and nicotinamide riboside decreased.

CONCLUSIONS

Our data may facilitate understanding the molecular mechanisms of host responses to IAV infection and provide a basis for discovering potential new mechanistic, diagnostic, and prognostic biomarkers and therapeutic targets for IAV infection.

High throughput screening of mesenchymal stromal cell morphological response to inflammatory signals for bioreactor-based manufacturing of extracellular vesicles that modulate microglia

Due to their immunomodulatory function, mesenchymal stromal cells (MSCs) are a promising therapeutic with the potential to treat neuroinflammation associated with neurodegenerative diseases. This function can be mediated by secreted extracellular vesicles (MSC-EVs). Despite established safety, MSC clinical translation has been unsuccessful due to inconsistent clinical outcomes resulting from functional heterogeneity. Current approaches to mitigate functional heterogeneity include 'priming' MSCs with inflammatory signals to enhance function. However, comprehensive evaluation of priming and its effects on MSC-EV function has not been performed. Clinical translation of MSC-EV therapies requires significant manufacturing scale-up, yet few studies have investigated the effects of priming in bioreactors. As MSC morphology has been shown to predict their immunomodulatory function, we screened MSC morphological response to an array of priming signals and evaluated MSC-EV identity and potency in response to priming in flasks and bioreactors. We identified unique priming conditions corresponding to distinct morphologies. These conditions demonstrated a range of MSC-EV preparation quality and lipidome, allowing us to discover a novel MSC-EV manufacturing condition, as well as gain insight into potential mechanisms of MSC-EV microglia modulation. Our novel screening approach and application of priming to MSC-EV bioreactor manufacturing informs refinement of larger-scale manufacturing and enhancement of MSC-EV function.

Improving combination therapies: targeting A2B-adenosine receptor to modulate metabolic tumor microenvironment and immunosuppression

BACKGROUND

We investigated the role of A2B-adenosine receptor in regulating immunosuppressive metabolic stress in the tumor microenvironment. Novel A2B-adenosine receptor antagonist PBF-1129 was tested for antitumor activity in mice and evaluated for safety and immunologic efficacy in a phase I clinical trial of patients with non-small cell lung cancer.

METHODS

The antitumor efficacy of A2B-adenosine receptor antagonists and their impact on the metabolic and immune tumor microenvironment were evaluated in lung, melanoma, colon, breast, and epidermal growth factor receptor-inducible transgenic cancer models. Employing electron paramagnetic resonance, we assessed changes in tumor microenvironment metabolic parameters, including pO2, pH, and inorganic phosphate, during tumor growth and evaluated the immunologic effects of PBF-1129, including its pharmacokinetics, safety, and toxicity, in patients with non-small cell lung cancer.

RESULTS

Levels of metabolic stress correlated with tumor growth, metastasis, and immunosuppression. Tumor interstitial inorganic phosphate emerged as a correlative and cumulative measure of tumor microenvironment stress and immunosuppression. A2B-adenosine receptor inhibition alleviated metabolic stress, downregulated expression of adenosine-generating ectonucleotidases, increased expression of adenosine deaminase, decreased tumor growth and metastasis, increased interferon γ production, and enhanced the efficacy of antitumor therapies following combination regimens in animal models (anti-programmed cell death 1 protein vs anti-programmed cell death 1 protein plus PBF-1129 treatment hazard ratio = 11.74 [95% confidence interval = 3.35 to 41.13], n = 10, P < .001, 2-sided F test). In patients with non-small cell lung cancer, PBF-1129 was well tolerated, with no dose-limiting toxicities; demonstrated pharmacologic efficacy; modulated the adenosine generation system; and improved antitumor immunity.

CONCLUSIONS

Data identify A2B-adenosine receptor as a valuable therapeutic target to modify metabolic and immune tumor microenvironment to reduce immunosuppression, enhance the efficacy of immunotherapies, and support clinical application of PBF-1129 in combination therapies.

Inflammation-responsive drug delivery nanosystems for treatment of bacterial-induced sepsis

Sepsis, a complication of dysregulated host immune systemic response to an infection, is life threatening and causes multiple organ injuries. Sepsis is recognized by WHO as a big contributor to global morbidity and mortality. The heterogeneity in sepsis pathophysiology, antimicrobial resistance threat, the slowdown in the development of antimicrobials, and limitations of conventional dosage forms jeopardize the treatment of sepsis. Drug delivery nanosystems are promising tools to overcome some of these challenges. Among the drug delivery nanosystems, inflammation-responsive nanosystems have attracted considerable interest in sepsis treatment due to their ability to respond to specific stimuli in the sepsis microenvironment to release their payload in a precise, targeted, controlled, and rapid manner compared to non-responsive nanosystems. These nanosystems posit superior therapeutic potential to enhance sepsis treatment. This review critically evaluates the recent advances in the design of drug delivery nanosystems that are inflammation responsive and their potential in enhancing sepsis treatment. The sepsis microenvironment's unique features, such as acidic pH, upregulated receptors, overexpressed enzymes, and enhanced oxidative stress, that form the basis for their design have been adequately discussed. These inflammation-responsive nanosystems have been organized into five classes namely: Receptor-targeted nanosystems, pH-responsive nanosystems, redox-responsive nanosystems, enzyme-responsive nanosystems, and multi-responsive nanosystems. Studies under each class have been thematically grouped and discussed with an emphasis on the polymers used in their design, nanocarriers, key characterization, loaded actives, and key findings on drug release and therapeutic efficacy. Further, this information is concisely summarized into tables and supplemented by inserted figures. Additionally, this review adeptly points out the strengths and limitations of the studies and identifies research avenues that need to be explored. Finally, the challenges and future perspectives on these nanosystems have been thoughtfully highlighted.

Cytocompatibility Evaluation of PEG-Methylsulfone Hydrogels

Methylsulfone derivatized poly(ethylene) glycol (PEG) macromers can be biofunctionalized with thiolated ligands and cross-linked with thiol-based cross-linkers to obtain bioactive PEG hydrogels for in situ cell encapsulation. Methylsulfonyl-thiol (MS-SH) reactions present several advantages for this purpose when compared to other thiol-based cross-linking systems. They proceed with adequate and tunable kinetics for encapsulation, they reach a high conversion degree with good selectivity, and they generate stable reaction products. Our previous work demonstrated the cytocompatibility of cross-linked PEG-MS/thiol hydrogels in contact with fibroblasts. However, the cytocompatibility of the in situ MS-SH cross-linking reaction itself, which generates methylsulfinic acid as byproduct at the cross-linked site, remains to be evaluated. These studies are necessary to evaluate the potential of these systems for in vivo applications. Here we perform an extensive cytocompatibility study of PEG hydrogels during in situ cross-linking by the methylsulfonyl-thiol reaction. We compare these results with maleimide-thiol cross-linked PEGs which are well established for cell culture and in vivo experiments and do not involve the release of a byproduct. We show that fibroblasts and endothelial cells remain viable after in situ polymerization of methylsulfonyl-thiol gels on the top of the cell layers. Cell viability seems better than after in situ cross-linking hydrogels with maleimide-thiol chemistry. The endothelial cell proinflammatory phenotype is low and similar to the one obtained by the maleimide-thiol reaction. Finally, no activation of monocytes is observed. All in all, these results demonstrate that the methylsulfonyl-thiol chemistry is cytocompatible and does not trigger high pro-inflammatory responses in endothelial cells and monocytes. These results make methylsulfonyl-thiol chemistries eligible for in vivo testing and eventually clinical application in the future.

Plasma IL-6, TREM1, uPAR, and IL6/IL8 biomarkers increment further witnessing the chronic inflammation in type 2 diabetes

OBJECTIVES

Type 2 diabetes (T2D) is known to be associated with chronic inflammation, but the inflammatory regulators/markers are not exactly defined and the link between them remains undetermined. The objective of this study is to identify these markers by testing traditional (IL6 & IL8) and non-traditional (TREM1 & uPAR) inflammatory markers.

METHODS

Data and blood samples were obtained from 114 T2D and 74 non-diabetic Kuwaiti subjects attending health facilities in Kuwait. Chemical analyzers were used to measure glycemic and lipid profiles, while ELISA was used to measure plasma levels of insulin and several inflammatory markers.

RESULTS

Showed that the IL-6 and TREM1 were significantly higher in T2D compared to non-diabetic controls, and the uPAR level was borderline higher in T2D but significantly correlated with IL-6 levels. Unexpectedly, IL8 was significantly below normal in T2D and IL6/IL8 ratio was significantly higher in T2D patients. Unlike other tested markers, uPAR was in addition strongly correlated with insulin levels and HOMA-IR index.

CONCLUSIONS

Raised levels of IL6, TREMI, IL6/IL8 ratio, and the strong positive correlation of plasma levels of uPAR with IL-6, insulin, and HOMA-IR index, are reliable spectators of chronic inflammation in T2D patients. The reduced level of IL-8 in T2D was a peculiar observation that needs further explanation. Finally, the consequences and impact of the sustained rise of these inflammatory regulators in diabetic tissues need to be meticulously explored.

Hidden chronic metabolic acidosis of diabetes type 2 (CMAD): Clues, causes and consequences

Interpretation of existing data revealed that chronic metabolic acidosis is a pathognomic feature for type 2 diabetes (T2D), which is described here as "chronic metabolic acidosis of T2D (CMAD)" for the first time. The biochemical clues for the CMAD are summarised in the following; low blood bicarbonate (high anionic gap), low pH of interstitial fluid and urine, and response to acid neutralization, while the causes of extra protons are worked out to be; mitochondrial dysfunction, systemic inflammation, gut microbiota (GM), and diabetic lung. Although, the intracellular pH is largely preserved by the buffer system and ion transporters, a persistent systemic mild acidosis leaves molecular signature in cellular metabolism in diabetics. Reciprocally, there are evidences that CMAD contributes to the initiation and progression of T2D by; reducing insulin production, triggering insulin resistance directly or via altered GM, and inclined oxidative stress. The details about the above clues, causes and consequences of CMAD are obtained by searching literature spanning between 1955 and 2022. Finally, the molecular bases of CMAD are discussed in details by interpretation of an up-to-date data and aid of well constructed diagrams, with a conclusion unravelling that CMAD is a major player in T2D pathophysiology. To this end, the CMAD disclosure offers several therapeutic potentials for prevention, delay or attenuation of T2D and its complications.

Acidosis-induced regulation of adipocyte G0S2 promotes crosstalk between adipocytes and breast cancer cells as well as tumor progression

Bidirectional interactions between cancer cells and their microenvironment govern tumor progression. Among the stromal cells in this microenvironment, adipocytes have been reported to upregulate cancer cell migration and invasion by producing fatty acids. Conversely, cancer cells alter adipocyte phenotype notably via increased lipolysis. We aimed to identify the mechanisms through which cancer cells trigger adipocyte lipolysis and evaluate the functional consequences on cancer progression. Here, we show that cancer cell-induced acidification of the extracellular medium strongly promotes preadipocyte lipolysis through a mechanism that does not involve lipophagy but requires adipose triglyceride lipase (ATGL) activity. This increased lipolysis is triggered mainly by attenuation of the G0/G1 switch gene 2 (G0S2)-induced inhibition of ATGL. G0S2-mediated regulation in preadipocytes affects their communication with breast cancer cells, modifying the phenotype of the cancer cells and increasing their resistance to chemotherapeutic agents in vitro. Furthermore, we demonstrate that the adipocyte-specific overexpression of G0S2 impairs mammary tumor growth and lung metastasis formation in vivo. Our results highlight the importance of acidosis in cancer cell-adipocyte crosstalk and identify G0S2 as the main regulator of cancer-induced lipolysis, regulating tumor establishment and spreading.

Stimulus-Responsive Drug Delivery Nanoplatforms for Osteoarthritis Therapy

Osteoarthritis (OA) is one of the most prevalent age-related degenerative diseases. With an increasingly aging global population, greater numbers of OA patients are providing clear economic and societal burdens. Surgical and pharmacological treatments are the most common and conventional therapeutic strategies for OA, but often fall considerably short of desired or optimal outcomes. With the development of stimulus-responsive nanoplatforms has come the potential for improved therapeutic strategies for OA. Enhanced control, longer retention time, higher loading rates, and increased sensitivity are among the potential benefits. This review summarizes the advanced application of stimulus-responsive drug delivery nanoplatforms for OA, categorized by either those that depend on endogenous stimulus (reactive oxygen species, pH, enzyme, and temperature), or those that depend on exogenous stimulus (near-infrared ray, ultrasound, magnetic fields). The opportunities, restrictions, and limitations related to these various drug delivery systems, or their combinations, are discussed in areas such as multi-functionality, image guidance, and multi-stimulus response. The remaining constraints and potential solutions that are represented by the clinical application of stimulus-responsive drug delivery nanoplatforms are finally summarized.

Extracellular Acidification Augments NLRP3-Mediated Inflammasome Signaling in Macrophages

Inflammation is a series of host defense processes in response to microbial infection and tissue injury. Inflammatory processes frequently cause extracellular acidification in the inflamed region through increased glycolysis and lactate secretion. Therefore, the immune cells infiltrating the inflamed region encounter an acidic microenvironment. Extracellular acidosis can modulate the innate immune response of macrophages; however, its role for inflammasome signaling still remains elusive. In the present study, we demonstrated that macrophages exposed to an acidic microenvironment exhibited enhanced caspase-1 processing and IL-1β secretion compared with those under physiological pH. Moreover, exposure to an acidic pH increased the ability of macrophages to assemble the NLR family pyrin domain containing 3 (NLRP3) inflammasome in response to an NLRP3 agonist. This acidosis-mediated augmentation of NLRP3 inflammasome activation occurred in bone marrow-derived macrophages but not in bone marrow-derived neutrophils. Notably, exposure to an acidic environment caused a reduction in the intracellular pH of macrophages but not neutrophils. Concordantly, macrophages, but not neutrophils, exhibited NLRP3 agonist-mediated translocation of chloride intracellular channel protein 1 (CLIC1) into their plasma membranes under an acidic microenvironment. Collectively, our results demonstrate that extracellular acidosis during inflammation can increase the sensitivity of NLRP3 inflammasome formation and activation in a CLIC1-dependent manner. Thus, CLIC1 may be a potential therapeutic target for NLRP3 inflammasome-mediated pathological conditions.

Understanding the evolution of immune genes in jawed vertebrates

Driven by co-evolution with pathogens, host immunity continuously adapts to optimize defence against pathogens within a given environment. Recent advances in genetics, genomics and transcriptomics have enabled a more detailed investigation into how immunogenetic variation shapes the diversity of immune responses seen across domestic and wild animal species. However, a deeper understanding of the diverse molecular mechanisms that shape immunity within and among species is still needed to gain insight into-and generate evolutionary hypotheses on-the ultimate drivers of immunological differences. Here, we discuss current advances in our understanding of molecular evolution underpinning jawed vertebrate immunity. First, we introduce the immunome concept, a framework for characterizing genes involved in immune defence from a comparative perspective, then we outline how immune genes of interest can be identified. Second, we focus on how different selection modes are observed acting across groups of immune genes and propose hypotheses to explain these differences. We then provide an overview of the approaches used so far to study the evolutionary heterogeneity of immune genes on macro and microevolutionary scales. Finally, we discuss some of the current evidence as to how specific pathogens affect the evolution of different groups of immune genes. This review results from the collective discussion on the current key challenges in evolutionary immunology conducted at the ESEB 2021 Online Satellite Symposium: Molecular evolution of the vertebrate immune system, from the lab to natural populations.

Targeting ASIC1a Promotes Neural Progenitor Cell Migration and Neurogenesis in Ischemic Stroke

Cell replacement therapy using neural progenitor cells (NPCs) has been shown to be an effective treatment for ischemic stroke. However, the therapeutic effect is unsatisfactory due to the imbalanced homeostasis of the local microenvironment after ischemia. Microenvironmental acidosis is a common imbalanced homeostasis in the penumbra and could activate acid-sensing ion channels 1a (ASIC1a), a subunit of proton-gated cation channels following ischemic stroke. However, the role of ASIC1a in NPCs post-ischemia remains elusive. Here, our results indicated that ASIC1a was expressed in NPCs with channel functionality, which could be activated by extracellular acidification. Further evidence revealed that ASIC1a activation inhibited NPC migration and neurogenesis through RhoA signaling-mediated reorganization of filopodia formation, which could be primarily reversed by pharmacological or genetic disruption of ASIC1a. In vivo data showed that the knockout of the ASIC1a gene facilitated NPC migration and neurogenesis in the penumbra to improve behavioral recovery after stroke. Subsequently, ASIC1a gain of function partially abrogated this effect. Moreover, the administration of ASIC1a antagonists (amiloride or Psalmotoxin 1) promoted functional recovery by enhancing NPC migration and neurogenesis. Together, these results demonstrate targeting ASIC1a is a novel strategy potentiating NPC migration toward penumbra to repair lesions following ischemic stroke and even for other neurological diseases with the presence of niche acidosis.

Modulation of T cell function and survival by the tumor microenvironment

Cancer immunotherapy is shifting paradigms in cancer care. T cells are an indispensable component of an effective antitumor immunity and durable clinical responses. However, the complexity of the tumor microenvironment (TME), which consists of a wide range of cells that exert positive and negative effects on T cell function and survival, makes achieving robust and durable T cell responses difficult. Additionally, tumor biology, structural and architectural features, intratumoral nutrients and soluble factors, and metabolism impact the quality of the T cell response. We discuss the factors and interactions that modulate T cell function and survive in the TME that affect the overall quality of the antitumor immune response.

Mirror proteorhodopsins

Proteorhodopsins (PRs), bacterial light-driven outward proton pumps comprise the first discovered and largest family of rhodopsins, they play a significant role in life on the Earth. A big remaining mystery was that up-to-date there was no described bacterial rhodopsins pumping protons at acidic pH despite the fact that bacteria live in different pH environment. Here we describe conceptually new bacterial rhodopsins which are operating as outward proton pumps at acidic pH. A comprehensive function-structure study of a representative of a new clade of proton pumping rhodopsins which we name "mirror proteorhodopsins", from Sphingomonas paucimobilis (SpaR) shows cavity/gate architecture of the proton translocation pathway rather resembling channelrhodopsins than the known rhodopsin proton pumps. Another unique property of mirror proteorhodopsins is that proton pumping is inhibited by a millimolar concentration of zinc. We also show that mirror proteorhodopsins are extensively represented in opportunistic multidrug resistant human pathogens, plant growth-promoting and zinc solubilizing bacteria. They may be of optogenetic interest.

Collagen breaks at weak sacrificial bonds taming its mechanoradicals

Collagen is a force-bearing, hierarchical structural protein important to all connective tissue. In tendon collagen, high load even below macroscopic failure level creates mechanoradicals by homolytic bond scission, similar to polymers. The location and type of initial rupture sites critically decide on both the mechanical and chemical impact of these micro-ruptures on the tissue, but are yet to be explored. We here use scale-bridging simulations supported by gel electrophoresis and mass spectrometry to determine breakage points in collagen. We find collagen crosslinks, as opposed to the backbone, to harbor the weakest bonds, with one particular bond in trivalent crosslinks as the most dominant rupture site. We identify this bond as sacrificial, rupturing prior to other bonds while maintaining the material's integrity. Also, collagen's weak bonds funnel ruptures such that the potentially harmful mechanoradicals are readily stabilized. Our results suggest this unique failure mode of collagen to be tailored towards combatting an early onset of macroscopic failure and material ageing.

Astrocytic Slc4a4 regulates blood-brain barrier integrity in healthy and stroke brains via a NO-CCL2-CCR2 pathway

Astrocytes play vital roles in blood-brain barrier (BBB) maintenance, yet how they support BBB integrity under normal or pathological conditions remains poorly defined. Recent evidence suggests pH homeostasis is a new cellular mechanism important for BBB integrity. In the current study, we investigated the function of an astrocyte-specific pH regulator, Slc4a4, in BBB maintenance and repair. We show that astrocytic Slc4a4 is required for normal astrocyte morphological complexity and BBB function. Multi-omics analyses identified increased astrocytic secretion of CCL2 coupled with dysregulated arginine-NO metabolism after Slc4a4 deletion. Using a model of ischemic stroke, we found that loss of Slc4a4 exacerbates BBB disruption and reactive gliosis, which were both rescued by pharmacological or genetic inhibition of the NO-CCL2 pathway in vivo. Together, our study identifies the astrocytic Slc4a4-NO-CCL2 axis as a pivotal mechanism controlling BBB integrity and repair, while providing insights for a novel therapeutic approach against BBB-related CNS disorders.

Compartment-Specific Activation of the Proton-Sensor GPR65 is Uncoupled from Receptor Trafficking

The canonical view of G protein-coupled receptor (GPCR) function is that receptor trafficking is tightly coupled to signaling. GPCRs remain on the plasma membrane (PM) at the cell surface until they are activated, after which they are desensitized and internalized into endosomal compartments. This canonical view presents an interesting context for proton-sensing GPCRs because they are more likely to be activated in acidic endosomal compartments than at the PM. Here we show that the trafficking of the prototypical proton-sensor GPR65 is fully uncoupled from signaling, unlike that of other known mammalian GPCRs. GPR65 internalized and localized to early and late endosomes, from where they signal at steady state, irrespective of extracellular pH. Acidic extracellular environments stimulated receptor signaling at the PM in a dose-dependent manner, although endosomal GPR65 was still required for a full signaling response. Receptor mutants that were incapable of activating cAMP trafficked normally, internalized, and localized to endosomal compartments. Our results show that GPR65 is constitutively active in endosomes, and suggest a model where changes in extracellular pH reprograms the spatial pattern of receptor signaling and biases the location of signaling to the cell surface.

The mechanisms of alkali therapy in targeting renal diseases

Chronic kidney disease (CKD) is characterized by progressive reduction in kidney function and treatments aiming at stabilizing or slowing its progression may avoid or delay the necessity of kidney replacement therapy and the increased mortality associated with reduced kidney function. Metabolic acidosis, and less severe stages of the acid stress continuum, are common consequences of CKD and some interventional studies support that its correction slows the progression to end-stage kidney disease. This correction can be achieved with mineral alkali in the form of bicarbonate or citrate salts, ingestion of diets with fewer acid-producing food components or more base-producing food components, or a pharmacological approach. In this mini-review article, we summarize the potential mechanisms involved in the beneficial effects of alkali therapy. We also discuss the perspectives in the field and challenges that must be overcome to advance our understanding of such mechanisms.

Acidity-mediated induction of FoxP3+ regulatory T cells

Glucose limitation and increased lactic acid levels are consequences of the elevated glycolytic activity of tumor cells, and constitute a metabolic barrier for the function of tumor infiltrating effector immune cells. The immune-suppressive functions of regulatory T cells (Tregs) are unobstructed in lactic-acid rich environments. However, the impact of lactic acid on the induction of Tregs remains unknown. We observed increased TGFβ-mediated induction of Forkhead box P3⁺ (FoxP3⁺ ) cells in the presence of extracellular lactic acid, in a glycolysis-independent, acidity-dependent manner. These CD4⁺ FoxP3⁺ cells expressed Treg-associated markers, including increased expression of CD39, and were capable of exerting suppressive functions. Corroborating these results in vivo, we observed that neutralizing the tumor pH by systemic administration of sodium bicarbonate (NaBi) decreased Treg abundance. We conclude that acidity augments Treg induction and propose that therapeutic targeting of acidity in the tumor microenvironment (TME) might reduce Treg-mediated immune suppression within tumors.

mTOR inhibitor, gemcitabine and PD-L1 antibody blockade combination therapy suppresses pancreatic cancer progression via metabolic reprogramming and immune microenvironment remodeling in Trp53flox/+LSL-KrasG12D/+Pdx-1-Cre murine models

OBJECTIVE

Resistance to immunotherapy and chemotherapy hinders the prognosis of pancreatic cancer(PC). We hypothesized that the combination of mTOR inhibitor sirolimus and gemcitabine would change the metabolic landscape of PC and enhance the anti-PD-L1 therapy.

METHODS

In KPC mice, the following regimens were administered and tumor growth inhibition rates(TGI%) were calculated: sirolimus(S), PD-L1 antibody(P), gemcitabine(G), sirolimus + PD-L1 antibody(SP), sirolimus + gemcitabine(SG), PD-L1 + gemcitabine(PG) and sirolimus + PD-L1 antibody + gemcitabine(SPG). The metabolic changes of tumors were identified by LC-MS and subpopulations of immune cells were measured by flow cytometry. Sirolimus treated macrophages were co-cultured with PC cells in vitro, and the metabolic changes of macrophages and tumor cells as well as tumor cells' viability were detected.

RESULTS

The monotherapy of S, P and G didn't inhibit tumor growth significantly. The combination of SP, PG and SG didn't improve the TGI% significantly compared with monotherapy. However, the TGI% of SPG combination was higher than other groups. The proportion of CD68⁺ macrophages increased in the peripheral blood and CD8⁺ T cells decreased in the tumor tissues after SPG treatment. LC-MS identified 42 differential metabolites caused by sirolimus in SPG group, among which 10 metabolites had potential effects on macrophages. Sirolimus treated M1 and M2 macrophages inhibited the proliferation of tumor cells and decreased tumor cells' glycolysis. The glycolysis of M2 macrophages was increased by sirolimus.

CONCLUSIONS

mTOR inhibitor can change the immune microenvironment of PC via metabolic reprogramming, thus promoting the efficacy of PD-L1 blockade when combined with gemcitabine.

Lactate: a pearl dropped in the ocean-an overlooked signal molecule in physiology and pathology

Lactate, once recognized as a wasty product from anaerobic glycolysis, is proved to be a pivotal signal molecule. Lactate accumulation occurs in diverse physiological and pathological settings due to the imbalance between lactate production and clearance. Under the condition with drastic changes in local microenvironment, such as tumorigenesis, inflammation, and microbial infection, the glycolysis turns to be active in surrounding cells leading to increased lactate release. Meanwhile, lactate can be utilized by these cells as an energy substrate and acts as a signal molecule to regulate cell functions through receptor-dependent or independent pathways. In this review, we tended to tease out the contribution of lactate in tumor progression and immunomodulation. And we also discussed the accessory role of lactate, beyond as the energy source only, in the growth of invading pathogens.

Intratumoral pro-oxidants promote cancer immunotherapy by recruiting and reprogramming neutrophils to eliminate tumors

Neutrophils have recently gained recognition for their potential in the fight against cancer. Neutrophil plasticity between the N1 anti-tumor and N2 pro-tumor subtypes is now apparent, as is the ability to polarize these individual subtypes by interventions such as intratumoral injection of various agents including bacterial products or pro-oxidants. Metabolic responses and the production of reactive oxygen species (ROS) such as hydrogen peroxide act as potent chemoattractants and activators of N1 neutrophils that facilitates their recruitment and ensuing activation of a toxic respiratory burst in tumors. Greater understanding of the precise mechanism of N1 neutrophil activation, recruitment and regulation is now needed to fully exploit their anti-tumor potential against cancers both locally and at distant sites. This systematic review critically analyzes these new developments in cancer immunotherapy.

Acidosis significantly alters immune checkpoint expression profiles of T cells from oesophageal adenocarcinoma patients

Tumour acidosis contributes to cancer progression by inhibiting anti-tumour immunity. However, the effect of acidosis on anti-tumour T cell phenotypes in oesophageal adenocarcinoma (OAC) is unknown. Therefore, this study investigated the effect of acidosis on anti-tumour T cell profiles and if immune checkpoint blockade (ICB) could enhance anti-tumour T cell immunity under acidosis. Acidic conditions substantially altered immune checkpoint expression profiles of OAC patient-derived T cells, upregulating TIM-3, LAG-3 and CTLA-4. Severe acidosis (pH 5.5) significantly decreased the percentage of central memory CD4⁺ T cells, an effect that was attenuated by ICB treatment. ICB increased T cell production of IFN-γ under moderate acidosis (pH 6.6) but not severe acidosis (pH 5.5) and decreased IL-10 production by T cells under severe acidic conditions only. A link between lactate and metastasis was also depicted; patients with nodal metastasis had higher serum lactate levels (p = 0.07) which also positively correlated with circulating levels of pro-angiogenic factor Tie-2. Our findings establish that acidosis-induced upregulation of immune checkpoints on T cells may potentially contribute to immune evasion and disease progression in OAC. However, acidic conditions curtailed ICB efficacy, supporting a rationale for utilizing systemic oral buffers to neutralize tumour acidity to improve ICB efficacy. Study schematic-PBMCs were isolated from OAC patients (A) and expanded ex vivo for 7 days using anti-CD3/28 +IL-2 T cell activation protocol (B) and further cultured for 48 h under increasing acidic conditions in the absence or presence of immune checkpoint blockade (nivolumab, ipilimumab or dual nivolumab + ipilimumab) (C). Immunophenotyping was then carried out to assess immune checkpoint expression profiles and anti-tumour T cell phenotypes (D). Serum lactate was assessed in OAC patients (E-F) and levels were correlated with patient demographics (G) and the levels of circulating immune/pro-angiogenic cytokines that were determined by multiplex ELISA (H). Key Findings-severe acidic conditions upregulated multiple immune checkpoints on T cells (I). Efficacy of ICB was curtailed under severe acidic conditions (J). Circulating lactate levels positively correlated with circulating levels of pro-angiogenic factor tie-2 and higher serum lactate levels were found in patients who had nodal metastasis (K).

An in silico model to study the impact of carbonic anhydrase IX expression on tumour growth and anti-PD-1 therapy

Immune checkpoint inhibitors (ICIs) are revolutionary cancer treatments. However, the mechanisms behind their effectiveness are not yet fully understood. Here, we aimed to investigate the role of the pH-regulatory enzyme carbonic anhydrase IX (CAIX) in ICI success. Consequently, we developed an in silico model of the tumour microenvironment. The hybrid model consists of an agent-based model of tumour-immune cell interactions, coupled with a set of diffusion-reaction equations describing substances in the environment. It is calibrated with data from the literature, enabling the study of its qualitative behaviour. In our model, CAIX-expressing tumours acidified their neighbourhood, thereby reducing immune infiltration by 90% (p < 0.001) and resulting in a 25% increase in tumour burden (p < 0.001). Moreover, suppression of CAIX improved the response to anti-PD-1 (23% tumour reduction in CAIX knockouts and 6% in CAIX-expressing tumours, p < 0.001), independently of initial PD-L1 expression. Our simulations suggest that patients with CAIX-expressing tumours could respond favourably to combining ICIs with CAIX suppression, even in the absence of pre-treatment PD-L1 expression. Furthermore, when calibrated with tumour-type-specific data, our model could serve as a high-throughput tool for testing the effectiveness of such a combinatorial approach.

Hypothesis: inflammatory acid-base disruption underpins Long Covid

The mechanism of Long Covid (Post-Acute Sequelae of COVID-19; PASC) is currently unknown, with no validated diagnostics or therapeutics. SARS-CoV-2 can cause disseminated infections that result in multi-system tissue damage, dysregulated inflammation, and cellular metabolic disruptions. The tissue damage and inflammation has been shown to impair microvascular circulation, resulting in hypoxia, which coupled with virally-induced metabolic reprogramming, increases cellular anaerobic respiration. Both acute and PASC patients show systemic dysregulation of multiple markers of the acid-base balance. Based on these data, we hypothesize that the shift to anaerobic respiration causes an acid-base disruption that can affect every organ system and underpins the symptoms of PASC. This hypothesis can be tested by longitudinally evaluating acid-base markers in PASC patients and controls over the course of a month. If our hypothesis is correct, this could have significant implications for our understanding of PASC and our ability to develop effective diagnostic and therapeutic approaches.

Manipulating T-cell metabolism to enhance immunotherapy in solid tumor

Cellular metabolism is not only essential for tumor cells to sustain their rapid growth and proliferation, but also crucial to maintain T cell fitness and robust immunity. Dysregulated metabolism has been recognized as a hallmark of cancer, which provides survival advantages for tumor cells under stress conditions. Also, emerging evidence suggests that metabolic reprogramming impacts the activation, differentiation, function, and exhaustion of T cells. Normal stimulation of resting T cells promotes the conversion of catabolic and oxidative metabolism to aerobic glycolysis in effector T cells, and subsequently back to oxidative metabolism in memory T cells. These metabolic transitions profoundly affect the trajectories of T-cell differentiation and fate. However, these metabolic events of T cells could be dysregulated by their interplays with tumor or the tumor microenvironment (TME). Importantly, metabolic competition in the tumor ecosystem is a new mechanism resulting in strong suppression of effector T cells. It is appreciated that targeting metabolic reprogramming is a promising way to disrupt the hypermetabolic state of tumor cells and enhance the capacity of immune cells to obtain nutrients. Furthermore, immunotherapies, such as immune checkpoint inhibitor (ICI), adoptive cell therapy (ACT), and oncolytic virus (OV) therapy, have significantly refashioned the clinical management of solid tumors, they are not sufficiently effective for all patients. Understanding how immunotherapy affects T cell metabolism provides a bright avenue to better modulate T cell anti-tumor response. In this review, we provide an overview of the cellular metabolism of tumor and T cells, provide evidence on their dynamic interaction, highlight how metabolic reprogramming of tumor and T cells regulate the anti-tumor responses, describe T cell metabolic patterns in the context of ICI, ACT, and OV, and propose hypothetical combination strategies to favor potent T cell functionality.

Exploiting the Acidic Extracellular pH: Evaluation of Streptococcus salivarius M18 Postbiotics to Target Cancer Cells

Previously, we showed that the growth, antibiotic resistance, and biofilm formation properties of the pathogens Pseudomonas aeruginosa and Klebsiella pneumonia were tremendously inhibited by the cell-free supernatant of the oral probiotic Streptococcus salivarius M18. These anti-pathogenic activities of the supernatant were more efficient under acidic conditions. The present approach takes advantage of the acidic nature of the tumor microenvironment to evaluate the effect of the S. salivarius M18 postbiotics on colon cancer cells. In both two-dimensional (2D) and three-dimensional (3D) cell culture models, S. salivarius M18 cell-free supernatant showed anti-cancer actions in the pH conditions mimicking the acidity of the tumor. The inhibitory effect was more prominent when the colon cancer cells have been treated with the cell-free supernatant obtained from the inulin incubated S. salivarius M18. The results of this study point out the potential of the S. salivarius M18 functional probiotic products to be used for targeting low pH environments including the unique acidic microenvironment of tumors.

The promising therapeutic effects of metformin on metabolic reprogramming of cancer-associated fibroblasts in solid tumors

Tumor-infiltrated lymphocytes are exposed to many toxic metabolites and molecules in the tumor microenvironment (TME) that suppress their anti-tumor activity. Toxic metabolites, such as lactate and ketone bodies, are produced mainly by catabolic cancer-associated fibroblasts (CAFs) to feed anabolic cancer cells. These catabolic and anabolic cells make a metabolic compartment through which high-energy metabolites like lactate can be transferred via the monocarboxylate transporter channel 4. Moreover, a decrease in molecules, including caveolin-1, has been reported to cause deep metabolic changes in normal fibroblasts toward myofibroblast differentiation. In this context, metformin is a promising drug in cancer therapy due to its effect on oncogenic signal transduction pathways, leading to the inhibition of tumor proliferation and downregulation of key oncometabolites like lactate and succinate. The cross-feeding and metabolic coupling of CAFs and tumor cells are also affected by metformin. Therefore, the importance of metabolic reprogramming of stromal cells and also the pivotal effects of metformin on TME and oncometabolites signaling pathways have been reviewed in this study.

LDHA: The Obstacle to T cell responses against tumor

Immunotherapy has become a successful therapeutic strategy in certain solid tumors and hematological malignancies. However, this efficacy of immunotherapy is impeded by limited success rates. Cellular metabolic reprogramming determines the functionality and viability in both cancer cells and immune cells. Extensive research has unraveled that the limited success of immunotherapy is related to immune evasive metabolic reprogramming in tumor cells and immune cells. As an enzyme that catalyzes the final step of glycolysis, lactate dehydrogenase A (LDHA) has become a major focus of research. Here, we have addressed the structure, localization, and biological features of LDHA. Furthermore, we have discussed the various aspects of epigenetic regulation of LDHA expression, such as histone modification, DNA methylation, N6-methyladenosine (m6A) RNA methylation, and transcriptional control by noncoding RNA. With a focus on the extrinsic (tumor cells) and intrinsic (T cells) functions of LDHA in T-cell responses against tumors, in this article, we have reviewed the current status of LDHA inhibitors and their combination with T cell-mediated immunotherapies and postulated different strategies for future therapeutic regimens.

pH variation in medical implant biofilms: Causes, measurements, and its implications for antibiotic resistance

The advent of implanted medical devices has greatly improved the quality of life and increased longevity. However, infection remains a significant risk because bacteria can colonize device surfaces and form biofilms that are resistant to antibiotics and the host's immune system. Several factors contribute to this resistance, including heterogeneous biochemical and pH microenvironments that can affect bacterial growth and interfere with antibiotic biochemistry; dormant regions in the biofilm with low oxygen, pH, and metabolites; slow bacterial growth and division; and poor antibody penetration through the biofilm, which may also be regions with poor acid product clearance. Measuring pH in biofilms is thus key to understanding their biochemistry and offers potential routes to detect and treat latent infections. This review covers the causes of biofilm pH changes and simulations, general findings of metabolite-dependent pH gradients, methods for measuring pH in biofilms, effects of pH on biofilms, and pH-targeted antimicrobial-based approaches.

Advancements in antimicrobial nanoscale materials and self-assembling systems

Antimicrobial resistance is directly responsible for more deaths per year than either HIV/AIDS or malaria and is predicted to incur a cumulative societal financial burden of at least $100 trillion between 2014 and 2050. Already heralded as one of the greatest threats to human health, the onset of the coronavirus pandemic has accelerated the prevalence of antimicrobial resistant bacterial infections due to factors including increased global antibiotic/antimicrobial use. Thus an urgent need for novel therapeutics to combat what some have termed the 'silent pandemic' is evident. This review acts as a repository of research and an overview of the novel therapeutic strategies being developed to overcome antimicrobial resistance, with a focus on self-assembling systems and nanoscale materials. The fundamental mechanisms of action, as well as the key advantages and disadvantages of each system are discussed, and attention is drawn to key examples within each field. As a result, this review provides a guide to the further design and development of antimicrobial systems, and outlines the interdisciplinary techniques required to translate this fundamental research towards the clinic.