Search Results (1,563)

SIRT2 (Sirtuin 2) is an NAD+-dependent deacetylase that exerts crucial regulatory effects on immune homeostasis and macrophage activation. While chronic cold exposure is a known predisposing factor for pulmonary dysfunction, the precise mechanisms by which SIRT2 potentially modulates lung macrophage polarization under cold stress remains poorly understood. In this study, we evaluated the protective capacity of SIRT2 using both wild-type (WT) and Sirt2-knockout (Sirt2−/−) murine models subjected to chronic cold exposure (4 °C for 3 h daily over 21 days). Our results demonstrated that Sirt2 deficiency significantly exacerbated cold-induced pulmonary histopathological damage and increased the secretion of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) (p < 0.05). Furthermore, chronic cold stress triggered a macrophage-centered inflammatory response, a process wherein SIRT2 was found to curtail M1 pro-inflammatory polarization. To further investigate these mechanisms, in vitro experiments were conducted using the mouse alveolar macrophage cell line MH-S. While LPS was utilized as a canonical inflammatory stimulus to mimic the injury environment, SIRT2 overexpression was found to reverse the LPS-induced increase in M1 markers and attenuate inflammatory cytokine secretion. These findings suggest that SIRT2 maintains intracellular homeostasis by modulating macrophage plasticity and plays a protective role in the development of chronic cold stimulus-induced lung injury. Consequently, SIRT2 activation may represent a potential therapeutic pathway for the treatment of environment-related respiratory diseases. Full article

Efferocytosis—the tightly regulated clearance of apoptotic cells by phagocytes—maintains tissue homeostasis and is impaired in chronic obstructive pulmonary disease (COPD), where it contributes to persistent inflammation and increases the risk of comorbidities, including lung cancer. Inhaled corticosteroids (ICS) and long-acting β2 agonists (LABAs) are cornerstones of COPD therapy, but their effects on efferocytosis and on the COPD–lung cancer interface are incompletely understood. The primary objective of this study was to determine whether the ICS fluticasone propionate and the LABA salmeterol xinafoate, alone or in combination at clinically informed concentrations (10⁻⁸–10⁻⁶ M; 10⁻⁴ M reserved for cytotoxicity screening), modulate efferocytic capacity and inflammatory cell survival across diverse phagocyte models. We performed standardized in vitro efferocytosis assays using murine peritoneal and alveolar macrophages, the murine macrophage line J774A.1, PMA-differentiated human THP-1 macrophages, human blood-derived neutrophils, and the human alveolar adenocarcinoma cell line A549. Apoptosis was induced in Jurkat T cells by UV irradiation (100 mJ/cm²) and in murine thymocytes by dexamethasone (1 µM, 4 h); apoptotic and necrotic populations were characterized by annexin-V/propidium iodide and Sytox Green/Hoechst H-33342 staining. Peritoneal macrophages showed the highest efferocytic activity (~75%), followed by J774A.1 (~75% at 24 h), THP-1 (~30% at 2 h; ~60% at 24 h), alveolar macrophages (~40%), and A549 cells (<20%). Neither fluticasone nor salmeterol, individually or in combination, significantly altered efferocytic capacity in any phagocyte tested (all ANOVA p > 0.26). Fluticasone (10⁻⁸ and 10⁻⁶ M) significantly improved 24 h neutrophil survival and reduced early apoptosis (p < 0.05) but did not translate this survival benefit into enhanced efferocytosis. Salmeterol was cytotoxic at 10⁻⁴ M and inactive at 10⁻⁸–10⁻⁶ M. These findings indicate that the established anti-inflammatory benefits of ICS/LABA in COPD do not extend to augmentation of efferocytosis in this acute, serum-free in vitro setting and that pharmacological restoration of efferocytosis in COPD—a defect implicated in the pathogenesis and progression of comorbid lung cancer—will likely require strategies targeting the efferocytic machinery itself (e.g., MerTK, Rac-1, MFG-E8) rather than relying on current inhaled therapy. Full article

Orthodontic tooth movement (OTM) is driven by force-induced alveolar bone remodeling, yet the molecular mechanisms by which periodontal ligament stem cells (PDLSCs) sense and transduce mechanical signals remain incompletely understood. Here, we identify the epigenetic regulator HELLS as a compressive force-responsive gene and investigate its role as a mechanosensitive mediator in human PDLSCs (hPDLSCs). Compressive force downregulated HELLS expression both in vitro and in a mouse OTM model. Functionally, siRNA-mediated HELLS knockdown impaired osteogenic differentiation, as evidenced by reduced Alizarin Red S staining and alkaline phosphatase activity, and induced global transcriptomic changes indicative of altered mechanotransduction pathways. Moreover, HELLS knockdown increased YAP and RANKL expression and potentiated osteoclast differentiation of co-cultured RAW264.7 cells. Finally, we identified E2F1 as a candidate transcription factor mediating the force-induced downregulation of HELLS. Collectively, these findings establish HELLS as a potential mechano-epigenetic regulator in hPDLSCs, and suggest that its force-induced downregulation may contribute to alveolar bone remodeling during OTM by simultaneously attenuating osteogenesis and enhancing pro-osteoclastogenic signaling via transcriptional reprogramming. Full article

African swine fever virus (ASFV) is the causative agent of African swine fever (ASF), a fatal and highly contagious disease, resulting in enormous losses to the global swine industry. No licensed vaccines or effective therapeutics are currently available to control ASFV infection. Interferons (IFNs) serve as key mediators of host antiviral immunity by inducing interferon-stimulated genes (ISGs), but the specific mechanisms by which individual ISGs restrict ASFV replication remain unclear. Interferon-induced protein with tetratricopeptide repeats 3 (IFIT3, also called ISG60) has been shown to exhibit antiviral activity against various viruses, but its role in ASFV infection has not been previously studied. Here, we used porcine alveolar macrophages (PAMs), the primary target cells of ASFV, to investigate IFIT3’s function in ASFV replication. We found that overexpression of IFIT3 inhibited ASFV replication, while its knockdown enhanced viral propagation. Mechanistically, IFIT3 directly blocked ASFV adsorption to host cells, thereby suppressing all subsequent stages of the viral cycle. IFIT3 also specifically interacted with ASFV F334L, an early viral gene product that encodes the small subunit of ribonucleotide reductase, a key enzyme for viral DNA synthesis. Additionally, IFIT3 positively regulated the STAT1/TBK1/IRF3 signaling axis: its overexpression increased phosphorylation of TBK1 and IRF3, as well as the protein level of STAT1, while IFIT3 knockdown attenuated activation of these molecules. Transcriptomic analysis of IFIT3-knockout PAMs revealed significant suppression of innate immune pathways, including type I interferon, JAK-STAT, and RIG-I-like receptor pathways, along with downregulated expression of core antiviral molecules such as ISG15, MX1, and STAT1. Conversely, pathways related to viral adsorption, endocytosis, and cytoskeleton were activated, and pathways involved in protein translation initiation, endoplasmic reticulum stress, and autophagy were dysregulated, creating a favorable intracellular environment for ASFV replication. In conclusion, IFIT3 restricts ASFV replication possibly by inhibiting viral adsorption and promoting innate immune signaling, identifying it as a potential therapeutic target against ASFV. This study’s limitation is its in vitro PAM model; future work will validate IFIT3’s role in vivo and develop targeted inhibitors. Full article

Background: Small cell lung cancer (SCLC) carries a dismal prognosis with limited biomarkers for risk stratification. This study aimed to identify circulating prognostic biomarkers. Methods: We prioritized SCLC risk-associated genes using Summary-data-based Mendelian Randomization of pQTL/eQTL, differential expression, and weighted gene co-expression network analysis. Five machine learning approaches were compared to develop a diagnostic model based on ACE, AGER, and IL18R1, trained on GSE149507 and validated in GSE60052. We conducted single-cell transcriptomic analysis using public datasets (GSE150766 and GSE279570) and peripheral blood mononuclear cells (PBMCs) from our extensive-stage cohort. Finally, prioritizing the lead candidate IL18R1, we enrolled a prospective clinical cohort to assess its prognostic utility. A LASSO–Cox prognostic model incorporating plasma IL18R1 and clinical variables was internally validated (7:3 split) for progression-free survival (PFS) prediction. Results: Integrative multi-omics identified ACE, AGER, and IL18R1 as SCLC-protective genes. Elastic Net machine learning identified a two-gene predictive signature (AGER and IL18R1) with robust diagnostic accuracy. Single-cell RNA sequencing revealed the predominant downregulation of ACE, AGER, and IL18R1 in T cells and alveolar type II cells from SCLC patients. PBMC analysis further supported IL18R1 downregulation in CD8⁺ T cells, NK cells, and dendritic cells. In an independent prospective cohort (n = 300), lower plasma IL18R1 levels were independently associated with shorter PFS (HR = 0.997 per unit increase; 95% CI: 0.995–0.999; and p = 0.003), with time-dependent AUCs of 0.77–0.86. Performance in limited-stage disease was inconsistent and requires further validation. A prognostic model incorporating plasma IL18R1 and 11 clinical parameters stratified patients into distinct risk groups (HR = 5.19), showing a strong discriminative ability in extensive-stage SCLC. Conclusions: We identified ACE, AGER, and IL18R1 as protective factors against SCLC progression. Integration of plasma IL18R1 with clinical parameters provides a prognostic tool for extensive-stage SCLC. Full article

Periodontitis is a chronic inflammatory disease which is initiated by dysbiotic biofilms and maintained by a host who is permissive to inflammation resulting in continuous destruction of periodontal supporting structures. Periodontitis occurs frequently with obesity and type 2 diabetes mellitus and the broader cardiometabolic risk state leading to investigations into the common immunometabolic pathways that link these conditions. Adiponectin, an insulin sensitizing and anti-inflammatory adipokine which can also act as a vasculoprotective and bone-related factor, has been studied as a potential modulator of the relation between periodontal inflammation and systemic metabolic disturbance. This narrative review summarizes the biology of adiponectin and its receptors, human findings relating to both the local and circulating forms of adiponectin in periodontal health and disease, the mechanism in cell and animal models and translational implications and limitations. The literature was reviewed in a narrative manner with particular attention to study quality, compartment-specific biology and any conflicts in evidence and the difference between biological plausibility and clinical relevance. A tendency for a reduction in the circulating, saliva and gingival crevicular fluid levels of adiponectin in periodontitis in human studies, particularly those with co-existing obesity and type 2 diabetes mellitus, can be demonstrated but these finding are often disparate due to variable methods in case definitions, assay techniques, metabolic background of subjects and other confounders. Experimental findings may establish biological plausibility by linking adiponectin signalling with the mechanisms which affect inflammatory responses, endothelial function and matrix homeostasis, osteoclastogenesis and subsequent alveolar bone loss, although adiponectin signalling appears context-specific in its actions and this does not confirm clinical relevance. Evidence suggests adiponectin is a biologically significant, but context-dependent factor within the immunometabolic network which connects periodontal disease with the systemic condition, rather than a sole marker or clinically recognized target for therapeutic intervention. Full article

In recent years, the feasibility of immunotherapy targeting activated fibroblasts in pulmonary fibrosis has received further support. Recent studies have shown that transient FAP-targeted immunotherapy can alleviate pulmonary fibrosis by eliminating excessively activated fibroblasts, improving the aberrant extracellular matrix environment, and promoting alveolar cell lineage remodeling, suggesting that FAP-associated pathological stromal cells are amenable to therapeutic intervention. Based on this, research on FAP-centered engineered cell therapies is being gradually extended from settings such as myocardial fibrosis to pulmonary fibrosis. In this context, primary human NK cells represent a promising effector cell platform, as they are generally associated with a lower risk of severe treatment-related toxicities and relatively limited in vivo persistence, which may confer a more controllable therapeutic window. This feature is particularly important in fibrotic diseases, because long-term and continuous depletion of fibroblast populations may disrupt tissue homeostasis and injury repair. In addition, current studies of FAP-targeted CAR-NK therapy have mainly relied on NK cell lines such as NK-92, but these systems may not fully reflect the functional characteristics, receptor signaling, or clinical potential of primary human NK cells. Based on these considerations, it is necessary to develop a FAP-targeted cell therapy platform with greater clinical relevance for pulmonary fibrosis. In this study, we established a primary human FAP-CAR-NK-cell platform and conducted a proof-of-concept evaluation in pulmonary fibrosis-related models, including in vitro systems, a human pulmonary fibrosis-like organoid model, and an acute in vivo observation model. The main novelty of this study lies in the use of primary human NK cells for FAP-targeted intervention in pulmonary fibrosis-related models. We focused on whether these engineered cells could selectively target and eliminate FAP-positive activated fibroblasts, retain effector function in a fibrotic microenvironment, and show short-term feasibility after adoptive transfer. The study was not intended to assess long-term therapeutic efficacy or systemic safety, but rather to examine the feasibility of FAP-directed fibroblast targeting by primary human CAR-NK cells in pulmonary fibrosis and to provide a basis for further preclinical investigation. Full article

WNT5a is a lipid-modified glycoprotein member of the WNT family of signaling molecules. Two isoforms of WNT5a have been identified that are conserved across mice and humans. These isoforms display specific functions in regulating cancer cell activities. While WNT5a is, indeed, essential for normal lung development and homeostasis, and is dysregulated in multiple lung diseases, little to no information is available regarding the expression or potential function of WNT5a isoforms in normal or diseased lungs. Such information has the potential to help to elucidate the more precise and nuanced functions of WNT5a in various pulmonary conditions. In this study, we characterized the expression of individual Wnt5a isoforms during mouse lung development and compared their expression across major alveolar cell populations. We further investigated the molecular basis of the signaling mechanisms that regulate Wnt5a isoform expression in fibroblasts, the major lung cell type with high-level Wnt5a expression. We present data that reveal a role for the AKT pathway in differentially regulating the expression of Wnt5a isoforms, a novel finding. Furthermore, we demonstrate that Wnt5a isoforms are dysregulated in bleomycin-induced fibrosis and Pseudomonas aeruginosa (PA)-induced acute lung injury and exhibit distinct impacts in Wnt5a isoform expression in response to lung injury. Full article

Concurrent alcohol and cannabis use (“crossfading”) is increasingly prevalent, especially among adolescents, yet its toxicological impact on pulmonary innate immunity remains largely unexplored. Alveolar macrophages (AMs) orchestrate inflammatory responses in the lung, and dysregulated macrophage polarization is a hallmark of alcohol-associated lung disease. Although alcohol and cannabinoids individually modulate immune function, the mechanisms by which their co-exposure alters macrophage activation and inflammatory signaling in the lung are largely unknown. AMs are highly sensitive to xenobiotic exposure and play a central role in regulating inflammatory and cytotoxic responses. In this study, we investigated how acute ethanol exposure, synthetic cannabinoid exposure, and their combined exposure affect macrophage viability, polarization, and the release of inflammatory mediators via cannabinoid receptor (CB1R/CB2R)-dependent pathways. Human THP-1-derived macrophages and KG-1 macrophage-like cells were exposed to ethanol, the CB1/CB2 agonist WIN 55,212-2, or both, with selective pharmacological antagonism of CB1R and CB2R. Ethanol exposure activated and polarized macrophages toward a pro-inflammatory M1 phenotype, accompanied by increased secretion of pro-inflammatory cytokines MCP-1, TGF-α, IFN-β, IL-6, and TNF-α. In contrast, WIN 55,212-2 promoted anti-inflammatory M2 polarization and increased IL-10 and IL-4 production. Notably, co-exposure to ethanol and WIN produced an antagonistic immunomodulatory response, characterized by the suppression of ethanol-induced M1 polarization and attenuation of pro-inflammatory cytokine release. Mechanistically, pharmacological CB1R blockade reduced ethanol-induced M1 polarization and cytokine secretion, whereas CB2R blockade exacerbated these effects, underscoring divergent roles for cannabinoid receptors in regulating pulmonary macrophage responses. This study provides novel findings demonstrating the mechanism by which alcohol–cannabinoid co-use reshapes macrophage immune phenotypes and identifies the endocannabinoid system as a potential therapeutic target for alcohol-related inflammatory lung disease. Full article

A male castrated Shih Tzu was evaluated for recurrent nocturnal episodes of acute respiratory distress accompanied by hemoptysis and transient erythrocytosis. The dog was clinically normal between episodes, but each nighttime event was severe and prompted repeated emergency visits. During each emergency presentation, thoracic radiographs revealed severe diffuse interstitial-to-alveolar pulmonary infiltrates, and packed cell volume showed marked but reversible increases. A stepwise diagnostic evaluation, including serial indirect blood pressure measurement, coagulation assessment, echocardiography, and bronchoscopy with bronchoalveolar lavage, progressively excluded typical infectious, cardiac, structural, and coagulopathic causes of hemoptysis and acute respiratory distress. Given the stereotyped pattern of near-acute crises with diffuse pulmonary infiltrates and hemoptysis, mechanisms analogous to noncardiogenic pulmonary edema or exercise-induced pulmonary hemorrhage were considered. Therapeutic trials with sildenafil and furosemide failed to prevent further nocturnal recurrences. Considering concurrent transient PCV surges and the proposed role of catecholamine-driven splenic contraction as a rapidly mobilizable erythrocyte reservoir, a sympathetically mediated process was suspected, and α₁-adrenergic blockade with prazosin was initiated. Following prazosin therapy, sustained clinical remission was achieved, with no further emergency episodes over a 17.5-month follow-up period. The response may have reflected multiple pharmacological effects of prazosin, including attenuation of sympathetically mediated splenic α₁-adrenergic activity, systemic vasodilation, and reduction in venous return. This unique case suggests that dysregulation of the sympathetic nervous system may have contributed to the recurrent hemoptysis and acute respiratory distress and highlights adrenergic modulation as a potential therapeutic consideration in similar cases. Full article

Fine particulate matter (PM_2.5) can directly impact pulmonary epithelial cells, resulting in lung injury. While it is known that PM_2.5 can alter the expression profile of microRNAs in the lung, its specific role in damaging pulmonary epithelial cells remains unclear. This study, therefore, employed RT-qPCR, Western blotting, and dual luciferase reporter assays to investigate the regulatory role of microRNAs in PM_2.5-induced cellular damage. PM_2.5 exposure induces oxidative stress, autophagy, and ferroptosis in rat lung alveolar epithelial cells (RLE-6TN). Further functional rescue experiments confirm that the ferroptosis-specific inhibitor Fer-1 can block PM_2.5-induced ferroptosis. Bioinformatics analysis and validation indicate that miR-212-5p plays a crucial role by negatively regulating RASSF1 through targeted inhibition. Overexpression of miR-212-5p activates the PI3K/AKT signaling pathway, thereby promoting autophagy and ferroptosis. However, when the expression of both miR-212-5p and RASSF1 is suppressed, PM_2.5-induced autophagy and ferroptosis are significantly alleviated by inhibiting the PI3K/AKT/mTOR signaling pathway. Rescue validation experiments demonstrated that, under PM_2.5 exposure combined with RASSF1 overexpression, miR-212-5p exacerbates the aforementioned cellular damage process. This study reveals that miR-212-5p regulates autophagy and ferroptosis by targeting RASSF1. These findings provide a multi-target intervention strategy for PM_2.5-related lung diseases. Full article

The yak (Bos grunniens), a unique bovine species that is endemic to the Qinghai–Tibet Plateau and adjacent mountainous regions, exhibits remarkable adaptations to chronic high-altitude hypoxia. However, the molecular mechanisms underlying yaks’ adaptation to this extreme environment remain poorly understood. This study aimed to elucidate the spatiotemporal expression dynamics of hypoxia-inducible factor 1α (HIF-1α) and 2α (HIF-2α) in major tissues of yaks across developmental stages (0.5, 1.5, 2.5, and 4.5 years; n = 3 per group). The tissues (heart, liver, spleen, lungs, kidneys, blood vessels and skeletal muscles) were analyzed using hematoxylin and eosin (H&E) staining and immunohistochemistry. The results revealed significant differences in the expression levels of HIF-1α and HIF-2α between tissues and at different ages. In cardiac tissue, both HIF-1α and HIF-2α are localized to the myocardial interstitium, with HIF-1α expression peaking at 1.5–2.5 years and HIF-2α expression reaching its maximum at 2.5 years. Hepatic HIF-1α showed perivenous hepatocytes enrichment and peaked at 2.5 years (p < 0.01 vs. other ages), while HIF-2α was uniformly distributed across lobules without age-related changes. Splenic HIF-1α and HIF-2α levels increased progressively with age, both peaking at 4.5 years (p < 0.01), and age was strongly correlated with expression levels (HIF-1α: r = 0.430; HIF-2α: r = 0.493). In pulmonary tissues, HIF-1α in bronchial smooth muscle peaked at 2.5 years, whereas alveolar septal HIF-2α peaked at 1.5 years (p < 0.05). In the kidney, HIF-1α was primarily localized to tubular epithelial cells and HIF-2α was diffusely distributed in the glomerular interstitium; neither factor showed significant variation across ages. In vascular tissues, HIF-1α expression remained stable across all ages and was predominantly observed in the smooth muscle layer, while HIF-2α exhibited a significant peak in endothelial cells at 2.5 years (p < 0.01). These findings suggest that HIF-1α predominates during early development stages, while HIF-2α becomes dominant as yaks approach maturity. Full article

Purpose: A high-salt extracellular environment promotes fibrosis in multiple organs by inducing oxidative stress, fibroblast activation, and extracellular matrix remodeling. In the lung, sodium accumulation may result from impaired epithelial ion transport. Transforming growth factor-β1 (TGF-β1), a key profibrotic cytokine, downregulates epithelial sodium and chloride channels, promoting sodium retention and fibrotic remodeling. This study investigated whether antifibrotic drugs can prevent TGF-β1-induced suppression of sodium channel expression in the lung epithelium. Methods: Human A549 alveolar epithelial cells and primary alveolar epithelial cells were cultured with or without TGF-β1 in the presence or absence of nintedanib or pirfenidone. Expression of epithelial sodium channel (ENaC) subunits (SCNN1A, SCNN1B, SCNN1G, SCNN1D) and CFTR was analyzed. In vivo, lung tissues from TGF-β1 transgenic mice and wild-type controls were examined following intranasal administration of pirfenidone. Results: TGF-β1 markedly reduced the expression of all ENaC subunits and CFTR in vitro. Nintedanib prevented suppression of SCNN1A, SCNN1D, and SCNN1G, whereas pirfenidone prevented suppression of SCNN1A, SCNN1B, and SCNN1G. In TGF-β1 transgenic mice, Scnn1a, Scnn1b, and Scnn1g expression was significantly decreased compared with wild-type controls. Pirfenidone administration dose-dependently restored expression of these ENaC subunits in vivo. Conclusions: Antifibrotic drugs partially prevent TGF-β1-induced suppression of epithelial sodium channels, preserving epithelial ion homeostasis. Restoration of ENaC expression may represent a novel mechanism by which antifibrotic therapy mitigates sodium-associated lung fibrosis. Full article

Staphylococcus aureus remains a leading cause of morbidity and mortality worldwide, with persistent and relapsing infections posing a major global health threat. Here, we report that baloxavir, an FDA-approved influenza antiviral, exhibits antibacterial activity against S. aureus. Baloxavir demonstrated potent activity against both MSSA and MRSA clinical isolates with MICs of 2–4 μg/mL and exhibited concentration-dependent antibacterial activity in time-kill assays. Notably, baloxavir effectively eliminated intracellular S. aureus in both A549 alveolar epithelial cells and RAW264.7 macrophages at 10 μg/mL and achieved complete eradication in A549 cells at 50 μg/mL. In vivo, baloxavir (20–40 mg/kg) significantly improved survival in MRSA-infected mice from 12.5% to 75–87.5%. Transcriptomic analysis revealed significant downregulation of purine de novo biosynthesis genes, including purF and purK, which was validated by RT-qPCR (r = 0.862, p = 0.027). This study demonstrates for the first time that baloxavir possesses significant antibacterial activity against S. aureus including MRSA, positioning it as a promising repurposed candidate for treating persistent intracellular infections and post-viral superinfections. Full article

Background and Objectives: The integration of chemotherapy (ChT) and immune checkpoint inhibitors (ICIs) has become a standard approach in oncology. Although the addition of ICIs to double-agent ChT regimens has demonstrated clinical benefit in multiple studies, other trials have reported no significant improvement. ChT is hypothesized to potentiate the effects of ICIs through multiple mechanisms, including tumor antigen release and modulation of the tumor microenvironment. This study aimed to evaluate whether nivolumab enhances the cytotoxic effects of cisplatin or paclitaxel in lung adenocarcinoma (A549) cell lines under immune-independent conditions. Materials and Methods: A549 lung alveolar carcinoma cell lines were treated with varying concentrations of nivolumab, cisplatin, and paclitaxel, individually and in combinations. Cytotoxicity and apoptosis were assessed using mitochondrial membrane potential analysis, cell viability assays, and morphological evaluation of cellular and nuclear alterations characteristic of apoptotic cell death. Results: Nivolumab alone exhibited no cytotoxic activity. The combination of cisplatin at its IC₅₀ (half-maximal inhibitory concentration) (3 µg/mL) with 13 µg/mL nivolumab yielded the most pronounced cytotoxicity (89%) compared to cisplatin alone (49%, p < 0.001). Paclitaxel combined with nivolumab increased cytotoxicity to 69% versus 51% for paclitaxel alone (p < 0.05). The enhancement effect was greater with cisplatin than with paclitaxel. Notably, adding nivolumab to the cisplatin–paclitaxel combination reduced cytotoxicity from 73% to 64%. Mechanistic analysis revealed a significant reduction in Rhodamine 123 fluorescence intensity in drug-treated groups versus controls (p < 0.001), indicating loss of mitochondrial membrane potential, a hallmark of intrinsic apoptotic activation, suggesting apoptotic priming. Conclusions: Nivolumab potentiates the cytotoxic effects of cisplatin and paclitaxel in A549 lung adenocarcinoma cells, with a more pronounced effect observed in combination with cisplatin. This enhancement is associated with mitochondrial membrane potential loss, supporting mitochondrial apoptotic priming as a potential underlying mechanism of drug synergy. Full article