Endothelial Drp1 Couples VEGF-induced Redox Signaling with Glycolysis Through Cysteine Oxidation to Drive Angiogenesis.

Angiogenesis plays a vital role for postnatal development and tissue repair following ischemia. Reactive oxygen species (ROS) generated by NADPH oxidases (NOXes) and mitochondria act as signaling molecules that promote angiogenesis in endothelial cells (ECs) which mainly relies on aerobic glycolysis for ATP production. However, the connections linking redox signaling with glycolysis are not well understood. The GTPase Drp1 is a member of the dynamin superfamily that moves from cytosol to mitochondria through posttranslational modifications to induce mitochondrial fission. The role of Drp1 in ROS-dependent VEGF signaling and angiogenesis in ECs has not been previously described. Here, we identify an unexpected function of endothelial Drp1 as a redox sensor, transmitting VEGF-induced H 2 O 2 signals to enhance glycolysis and angiogenesis. Loss of Drp1 expression in ECs inhibited VEGF-induced angiogenic responses. Mechanistically, VEGF rapidly induced the NOX4-dependent sulfenylation (CysOH) of Drp1 on Cys 644 , promoting disulfide bond formation with the metabolic kinase AMPK and subsequent sulfenylation of AMPK at Cys 299 / 304 via the mitochondrial fission-mitoROS axis. This cysteine oxidation of AMPK, in turn, enhanced glycolysis and angiogenesis. In vivo , mice with EC-specific Drp1 deficiency or CRISPR/Cas9-engineered "redox-dead" (Cys to Ala) Drp1 knock-in mutations exhibited impaired retinal angiogenesis and post-ischemic neovascularization. Our findings uncover a novel role for endothelial Drp1 in linking VEGF-induced mitochondrial redox signaling to glycolysis through a cysteine oxidation-mediated Drp1-AMPK redox relay, driving both developmental and reparative angiogenesis.

Protein disulfide isomerase A1 as a novel redox sensor in VEGFR2 signaling and angiogenesis.

VEGFR2 signaling in endothelial cells (ECs) is regulated by reactive oxygen species (ROS) derived from NADPH oxidases (NOXs) and mitochondria, which plays an important role in postnatal angiogenesis. However, it remains unclear how highly diffusible ROS signal enhances VEGFR2 signaling and reparative angiogenesis. Protein disulfide isomerase A1 (PDIA1) functions as an oxidoreductase depending on the redox environment. We hypothesized that PDIA1 functions as a redox sensor to enhance angiogenesis. Here we showed that PDIA1 co-immunoprecipitated with VEGFR2 or colocalized with either VEGFR2 or an early endosome marker Rab5 at the perinuclear region upon stimulation of human ECs with VEGF. PDIA1 silencing significantly reduced VEGF-induced EC migration, proliferation and spheroid sprouting via inhibiting VEGFR2 signaling. Mechanistically, VEGF stimulation rapidly increased Cys-OH formation of PDIA1 via the NOX4-mitochondrial ROS axis. Overexpression of "redox-dead" mutant PDIA1 with replacement of the active four Cys residues with Ser significantly inhibited VEGF-induced PDIA1-CysOH formation and angiogenic responses via reducing VEGFR2 phosphorylation. Pdia1+/- mice showed impaired angiogenesis in developmental retina and Matrigel plug models as well as ex vivo aortic ring sprouting model. Study using hindlimb ischemia model revealed that PDIA1 expression was markedly increased in angiogenic ECs of ischemic muscles, and that ischemia-induced limb perfusion recovery and neovascularization were impaired in EC-specific Pdia1 conditional knockout mice. These results suggest that PDIA1 can sense VEGF-induced H2O2 signal via CysOH formation to promote VEGFR2 signaling and angiogenesis in ECs, thereby enhancing postnatal angiogenesis. The oxidized PDIA1 is a potential therapeutic target for treatment of ischemic vascular diseases.

Exercise improves angiogenic function of circulating exosomes in type 2 diabetes: Role of exosomal SOD3.

Exosomes, key mediators of cell-cell communication, derived from type 2 diabetes mellitus (T2DM) exhibit detrimental effects. Exercise improves endothelial function in part via the secretion of exosomes into circulation. Extracellular superoxide dismutase (SOD3) is a major secretory copper (Cu) antioxidant enzyme that catalyzes the dismutation of O2•- to H2 O2 whose activity requires the Cu transporter ATP7A. However, the role of SOD3 in exercise-induced angiogenic effects of circulating plasma exosomes on endothelial cells (ECs) in T2DM remains unknown. Here, we show that both SOD3 and ATP7A proteins were present in plasma exosomes in mice, which was significantly increased after two weeks of volunteer wheel exercise. A single bout of exercise in humans also showed a significant increase in SOD3 and ATP7A protein expression in plasma exosomes. Plasma exosomes from T2DM mice significantly reduced angiogenic responses in human ECs or mouse skin wound healing models, which was associated with a decrease in ATP7A, but not SOD3 expression in exosomes. Exercise training in T2DM mice restored the angiogenic effects of T2DM exosomes in ECs by increasing ATP7A in exosomes, which was not observed in exercised T2DM/SOD3-/- mice. Furthermore, exosomes overexpressing SOD3 significantly enhanced angiogenesis in ECs by increasing local H2 O2  levels in a heparin-binding domain-dependent manner as well as restored defective wound healing and angiogenesis in T2DM or SOD3-/- mice. In conclusion, exercise improves the angiogenic potential of circulating exosomes in T2DM in a SOD3-dependent manner. Exosomal SOD3 may provide an exercise mimetic therapy that supports neovascularization and wound repair in cardiometabolic disease.

Cysteine oxidation of copper transporter CTR1 drives VEGFR2 signalling and angiogenesis.

Vascular endothelial growth factor receptor type 2 (VEGFR2, also known as KDR and FLK1) signalling in endothelial cells (ECs) is essential for developmental and reparative angiogenesis. Reactive oxygen species and copper (Cu) are also involved in these processes. However, their inter-relationship is poorly understood. Evidence of the role of the endothelial Cu importer CTR1 (also known as SLC31A1) in VEGFR2 signalling and angiogenesis in vivo is lacking. Here, we show that CTR1 functions as a redox sensor to promote angiogenesis in ECs. CTR1-depleted ECs showed reduced VEGF-induced VEGFR2 signalling and angiogenic responses. Mechanistically, CTR1 was rapidly sulfenylated at Cys189 at its cytosolic C terminus after stimulation with VEGF, which induced CTR1-VEGFR2 disulfide bond formation and their co-internalization to early endosomes, driving sustained VEGFR2 signalling. In vivo, EC-specific Ctr1-deficient mice or CRISPR-Cas9-generated redox-dead Ctr1(C187A)-knockin mutant mice had impaired developmental and reparative angiogenesis. Thus, oxidation of CTR1 at Cys189 promotes VEGFR2 internalization and signalling to enhance angiogenesis. Our study uncovers an important mechanism for sensing reactive oxygen species through CTR1 to drive neovascularization.

The P-type ATPase transporter ATP7A promotes angiogenesis by limiting autophagic degradation of VEGFR2.

VEGFR2 (KDR/Flk1) signaling in endothelial cells (ECs) plays a central role in angiogenesis. The P-type ATPase transporter ATP7A regulates copper homeostasis, and its role in VEGFR2 signaling and angiogenesis is entirely unknown. Here, we describe the unexpected crosstalk between the Copper transporter ATP7A, autophagy, and VEGFR2 degradation. The functional significance of this Copper transporter was demonstrated by the finding that inducible EC-specific ATP7A deficient mice or ATP7A-dysfunctional ATP7Amut mice showed impaired post-ischemic neovascularization. In ECs, loss of ATP7A inhibited VEGF-induced VEGFR2 signaling and angiogenic responses, in part by promoting ligand-induced VEGFR2 protein degradation. Mechanistically, VEGF stimulated ATP7A translocation from the trans-Golgi network to the plasma membrane where it bound to VEGFR2, which prevented autophagy-mediated lysosomal VEGFR2 degradation by inhibiting autophagic cargo/adapter p62/SQSTM1 binding to ubiquitinated VEGFR2. Enhanced autophagy flux due to ATP7A dysfunction in vivo was confirmed by autophagy reporter CAG-ATP7Amut -RFP-EGFP-LC3 transgenic mice. In summary, our study uncovers a novel function of ATP7A to limit autophagy-mediated degradation of VEGFR2, thereby promoting VEGFR2 signaling and angiogenesis, which restores perfusion recovery and neovascularization. Thus, endothelial ATP7A is identified as a potential therapeutic target for treatment of ischemic cardiovascular diseases.

Nuclear translocation of Atox1 potentiates activin A-induced cell migration and colony formation in colon cancer.

BACKGROUND: Colorectal cancer remains a deadly cancer due to metastatic disease. To understand the molecular mechanisms of metastasis in colon cancer, we investigated whether the copper chaperone antioxidant-1 (Atox1) protein plays a role in this process. Recent findings indicate that Atox1 protein has transcription factor activities and plays a vital role in cell proliferation in cancer cells. However, the role of Atox1 in metastasis has not been examined. METHODS: Atox1 expression was determined by immunofluorescence in a tissue microarray generated from a spectrum of CRC patients. Subcellular fractionation of colon cancer cell lines SW480 and SW620 cells was used to examine the cellular location of Atox1 in the face of activin A, a cytokine that stimulates colon cancer metastasis. Atox1 expression was genetically manipulated and cellular migration measured through trans-well assay and proliferation measured by colony formation assays. RESULTS: Here we demonstrate that in patients with metastatic colon cancer, there is a significant increase in the expression of nuclear Atox1. Interestingly, the metastatic CRC cell line SW620 has increased nuclear localization of Atox1 compared to its related non-metastatic cell line SW480. Further, inhibition of endogenous Atox1 by siRNA in SW620 decreased colony formation and reactive oxygen species generation via decreased expression of Atox1 targets cyclin D1 and NADPH oxidase subunit p47 phox, respectively. Additionally, overexpression of nuclear-targeted but not copper binding domain-mutated Atox1 in SW480 cells increased colony formation and cell migration that was further augmented by activin A stimulation, a known enhancer of colon cancer metastasis. CONCLUSIONS: Our findings suggest that nuclear Atox1 might be a new therapeutic target as well as a new biomarker for metastatic colorectal cancer.

Copper Transporter ATP7A (Copper-Transporting P-Type ATPase/Menkes ATPase) Limits Vascular Inflammation and Aortic Aneurysm Development: Role of MicroRNA-125b.

OBJECTIVE: Copper (Cu) is essential micronutrient, and its dysregulation is implicated in aortic aneurysm (AA) development. The Cu exporter ATP7A (copper-transporting P-type ATPase/Menkes ATPase) delivers Cu via the Cu chaperone Atox1 (antioxidant 1) to secretory Cu enzymes, such as lysyl oxidase, and excludes excess Cu. Lysyl oxidase is shown to protect against AA formation. However, the role and mechanism of ATP7A in AA pathogenesis remain unknown. Approach and Results: Here, we show that Cu chelator markedly inhibited Ang II (angiotensin II)-induced abdominal AA (AAA) in which ATP7A expression was markedly downregulated. Transgenic ATP7A overexpression prevented Ang II-induced AAA formation. Conversely, Cu transport dysfunctional ATP7Amut/+/ApoE-/- mice exhibited robust AAA formation and dissection, excess aortic Cu accumulation as assessed by X-ray fluorescence microscopy, and reduced lysyl oxidase activity. In contrast, AAA formation was not observed in Atox1-/-/ApoE-/- mice, suggesting that decreased lysyl oxidase activity, which depends on both ATP7A and Atox1, was not sufficient to develop AAA. Bone marrow transplantation suggested importance of ATP7A in vascular cells, not bone marrow cells, in AAA development. MicroRNA (miR) array identified miR-125b as a highly upregulated miR in AAA from ATP7Amut/+/ApoE-/- mice. Furthermore, miR-125b target genes (histone methyltransferase Suv39h1 and the NF-κB negative regulator TNFAIP3 [tumor necrosis factor alpha induced protein 3]) were downregulated, which resulted in increased proinflammatory cytokine expression, aortic macrophage recruitment, MMP (matrix metalloproteinase)-2/9 activity, elastin fragmentation, and vascular smooth muscle cell loss in ATP7Amut/+/ApoE-/- mice and reversed by locked nucleic acid-anti-miR-125b infusion. CONCLUSIONS: ATP7A downregulation/dysfunction promotes AAA formation via upregulating miR-125b, which augments proinflammatory signaling in a Cu-dependent manner. Thus, ATP7A is a potential therapeutic target for inflammatory vascular disease.

Novel interaction of antioxidant-1 with TRAF4: role in inflammatory responses in endothelial cells.

NADPH oxidase (NOX)-derived reactive oxygen species (ROS) and copper (Cu), an essential micronutrient, have been implicated in vascular inflammatory diseases. We reported that in proinflammatory cytokine TNF-α-stimulated endothelial cells (ECs), cytosolic Cu chaperone antioxidant-1 (Atox1) functions as a Cu-dependent transcription factor for the NOX organizer p47phox, thereby increasing ROS-dependent inflammatory gene expression. However, the role and mechanism of Atox1 nuclear translocation in inflamed ECs remain unclear. Using enface staining and nuclear fractionation, here we show that Atox1 was localized in the nucleus in inflamed aortas from ApoE-/- mice with angiotensin II infusion on a high-fat diet, while it was found in cytosol in those from control mice. In cultured human ECs, TNF-α stimulation promoted Atox1 nuclear translocation within 15 min, which was associated with Atox1 binding to TNF-α receptor-associated factor 4 (TRAF4) in a Cu-dependent manner. TRAF4 depletion by siRNA significantly inhibited Atox1 nuclear translocation, p47phox expression, and ROS production as well as its downstream VCAM1/ICAM1 expression and monocyte adhesion to inflamed ECs, which were rescued by overexpression of nuclear targeted Atox1. Furthermore, Atox1 colocalized with TRAF4 at the nucleus in TNF-α-stimulated inflamed ECs and vessels. In summary, Cu-dependent Atox1 binding to TRAF4 plays an important role in Atox1 nuclear translocation and ROS-dependent inflammatory responses in TNF-α-stimulated ECs. Thus the Atox1-TRAF4 axis is a novel therapeutic target for vascular inflammatory disease such as atherosclerosis.

Redox Regulation of Mitochondrial Fission Protein Drp1 by Protein Disulfide Isomerase Limits Endothelial Senescence.

Mitochondrial dynamics are tightly controlled by fusion and fission, and their dysregulation and excess reactive oxygen species (ROS) contribute to endothelial cell (EC) dysfunction. How redox signals regulate coupling between mitochondrial dynamics and endothelial (dys)function remains unknown. Here, we identify protein disulfide isomerase A1 (PDIA1) as a thiol reductase for the mitochondrial fission protein Drp1. A biotin-labeled Cys-OH trapping probe and rescue experiments reveal that PDIA1 depletion in ECs induces sulfenylation of Drp1 at Cys644, promoting mitochondrial fragmentation and ROS elevation without inducing ER stress, which drives EC senescence. Mechanistically, PDIA1 associates with Drp1 to reduce its redox status and activity. Defective wound healing and angiogenesis in diabetic or PDIA1+/- mice are restored by EC-targeted PDIA1 or the Cys oxidation-defective mutant Drp1. Thus, this study uncovers a molecular link between PDIA1 and Drp1 oxidoreduction, which maintains normal mitochondrial dynamics and limits endothelial senescence with potential translational implications for vascular diseases associated with diabetes or aging.

Copper Transport Protein Antioxidant-1 Promotes Inflammatory Neovascularization via Chaperone and Transcription Factor Function.

Copper (Cu), an essential micronutrient, plays a fundamental role in inflammation and angiogenesis; however, its precise mechanism remains undefined. Here we uncover a novel role of Cu transport protein Antioxidant-1 (Atox1), which is originally appreciated as a Cu chaperone and recently discovered as a Cu-dependent transcription factor, in inflammatory neovascularization. Atox1 expression is upregulated in patients and mice with critical limb ischemia. Atox1-deficient mice show impaired limb perfusion recovery with reduced arteriogenesis, angiogenesis, and recruitment of inflammatory cells. In vivo intravital microscopy, bone marrow reconstitution, and Atox1 gene transfer in Atox1(-/-) mice show that Atox1 in endothelial cells (ECs) is essential for neovascularization and recruitment of inflammatory cells which release VEGF and TNFα. Mechanistically, Atox1-depleted ECs demonstrate that Cu chaperone function of Atox1 mediated through Cu transporter ATP7A is required for VEGF-induced angiogenesis via activation of Cu enzyme lysyl oxidase. Moreover, Atox1 functions as a Cu-dependent transcription factor for NADPH oxidase organizer p47phox, thereby increasing ROS-NFκB-VCAM-1/ICAM-1 expression and monocyte adhesion in ECs inflamed with TNFα in an ATP7A-independent manner. These findings demonstrate a novel linkage between Atox1 and NADPH oxidase involved in inflammatory neovascularization and suggest Atox1 as a potential therapeutic target for treatment of ischemic disease.

Causation of cigarette smoke-induced emphysema by p-benzoquinone and its prevention by vitamin C.

Cigarette smoke (CS) is the strongest risk factor for emphysema. However, the mechanism of the disease is not clear. One reason is that each puff of CS is a complex mixture of approximately 4,000 chemicals, and it is yet to be known which of these chemical(s) are directly involved in the pathogenesis of lung injury in emphysema. The purpose of this study was to demonstrate that p-benzoquinone (p-BQ) produced in the lungs of CS-exposed guinea pigs is a causative factor for destruction of alveolar cells resulting in emphysema that is prevented by vitamin C. Vitamin C-restricted guinea pigs were subjected to whole-body CS exposure from five Kentucky research cigarettes (3R4F) per day or intramuscular injection of p-BQ in amounts approximately produced in the lung from CS exposure with and without oral supplementation of vitamin C. Progressive exposure of CS or p-BQ treatment caused progressive accumulation of p-BQ in the lung that was accompanied by destruction of alveolar cells and emphysema. The pathogenesis involved was arylation, oxidative stress, inflammation, and apoptosis. Vitamin C (30 mg/kg body weight/d), a potential antagonist of p-BQ, prevented accumulation of p-BQ in the lung and the pathogenesis of emphysema. Our study provides the first proof that inactivation of p-BQ, a causative factor of emphysema in CS-exposed lung, could constitute a novel and effective approach in the prevention of emphysema. We consider that a moderately high dose of vitamin C may be a simple preventive therapy for emphysema in chronic smokers.

Molecular and cellular mechanisms of cigarette smoke-induced myocardial injury: prevention by vitamin C.

BACKGROUND: Cardiovascular disease (CVD) remains one of the major killers in modern society. One strong risk factor of CVD is cigarette smoking that causes myocardial injury and leads to the genesis of pathological cardiovascular events. However, the exact toxic component(s) of cigarette smoke (CS) and its molecular and cellular mechanisms for causing myocardial injury leading to heart damage and its prevention are largely unknown. METHODOLOGY/PRINCIPAL FINDINGS: Using a guinea pig model, here we show that chronic exposure to CS produces myocardial injury that is prevented by vitamin C. Male guinea pigs were fed either vitamin C-deficient (0.5 mg/day) or vitamin C-sufficient (15 mg/day) diet and subjected to CS exposure from 5 Kentucky Research cigarettes (3R4F)/day (6 days/week) in a smoke chamber up to 8 weeks. Pair-fed sham controls were subjected to air exposure instead of CS exposure under similar conditions. Myocardial injury was produced in CS-exposed marginal vitamin C-deficient guinea pigs as evidenced by release of cardiac Troponin-T and I in the serum, oxidative stress, inflammation, apoptosis, thrombosis and collagen deposition in the myocardium. Treatment of rat cardiomyocyte cells (H9c2) in vitro and guinea pigs in vivo with p-benzoquinone (p-BQ) in amounts derived from CS revealed that p-BQ was a major factor responsible for CS-induced myocardial damage. A moderately large dose of vitamin C (15 mg/day) prevented CS/p-BQ-induced myocardial injury. Population based studies indicated that plasma vitamin C levels of smokers without disease were significantly lower (p = 0,0000) than that of non-smokers. Vitamin C levels of CS-related cardiovascular patients were further lower (p = 0.0000) than that of smokers without disease. CONCLUSIONS/SIGNIFICANCE: The results indicate that dietary supplementation of vitamin C may be a novel and simple therapy for the prevention of pathological cardiovascular events in habitual smokers.

Cigarette smoke induces p-benzoquinone-albumin adduct in blood serum: Implications on structure and ligand binding properties.

Earlier we had reported that irrespective of the source cigarette smoke (CS) contains substantial amounts of p-benzosemiquinone, which is readily converted to p-benzoquinone (p-BQ) by disproportionation and oxidation by transition metal containing proteins. Here we show that after CS-exposure, p-BQ-protein adducts are formed in the lungs as well as serum albumin of guinea pigs. We also show that serum of human smokers contains p-BQ-albumin adduct. It is known that human serum albumin (HSA) plays a very important role in binding and transport of a variety of ligands, including fatty acids and drugs. We show in vitro that p-BQ forms covalent adducts with free amino groups of all twenty amino acids as well as ɛ-amino groups of lysine residues of HSA in a concentration dependent manner. When HSA is incubated with p-BQ in the molar ratio of 1:1, the number of p-BQ incorporated is 1. At the molar ratio of 1:60, the number of p-BQ incorporated is 40. The formation of HSA-p-BQ adduct has been demonstrated by absorption spectroscopy, MALDI-MS and MALDI-TOF-TOF-MS analyses. Upon complexation with p-BQ, the secondary structure and conformation of HSA are altered, as evidenced by steady state and time-resolved fluorescence, circular dichroism, 8-anilino-1-napthalenesulfonic acid binding and differential scanning calorimetry. Alteration of the structure and conformation of HSA results in impairment of its ligand binding properties with respect to myristic acid, quercitin and paracetamol. This might be one of the reasons why transport and distribution of lipids and drugs are impaired in smokers.

NAD(P)H: quinone oxidoreductase 1 deficiency conjoint with marginal vitamin C deficiency causes cigarette smoke induced myelodysplastic syndromes.

BACKGROUND: The etiology of myelodysplastic syndromes (MDS) is largely unknown. Exposure to cigarette smoke (CS) is reported to be associated with MDS risk. There is inconsistent evidence that deficiency of NAD(P)H-quinone: oxidoreductase 1 (NQO1) increases the risk of MDS. Earlier we had shown that CS induces toxicity only in marginal vitamin C-deficient guinea pigs but not in vitamin C-sufficient ones. We therefore considered that NQO1 deficiency along with marginal vitamin C deficiency might produce MDS in CS-exposed guinea pigs. METHODOLOGY AND PRINCIPAL FINDINGS: Here we show that CS exposure for 21 days produces MDS in guinea pigs having deficiency of NQO1 (fed 3 mg dicoumarol/day) conjoint with marginal vitamin C deficiency (fed 0.5 mg vitamin C/day). As evidenced by morphology, histology and cytogenetics, MDS produced in the guinea pigs falls in the category of refractory cytopenia with unilineage dysplasia (RCUD): refractory anemia; refractory thrombocytopenia that is associated with ring sideroblasts, micromegakaryocytes, myeloid hyperplasia and aneuploidy. MDS is accompanied by increased CD34(+) cells and oxidative stress as shown by the formation of protein carbonyls and 8-oxodeoxyguanosine. Apoptosis precedes MDS but disappears later with marked decrease in the p53 protein. MDS produced in the guinea pigs are irreversible. MDS and all the aforesaid pathophysiological events do not occur in vitamin C-sufficient guinea pigs. However, after the onset of MDS vitamin C becomes ineffective. CONCLUSIONS AND SIGNIFICANCE: CS exposure causes MDS in guinea pigs having deficiency of NQO1 conjoint with marginal vitamin C deficiency. The syndromes are not produced in singular deficiency of NQO1 or marginal vitamin C deficiency. Our results suggest that human smokers having NQO1 deficiency combined with marginal vitamin C deficiency are likely to be at high risk for developing MDS and that intake of a moderately large dose of vitamin C would prevent MDS.

Activated charcoal filter effectively reduces p-benzosemiquinone from the mainstream cigarette smoke and prevents emphysema.

In this paper, we have made a comparative evaluation of the cytotoxicity and pathophysiological effects of mainstream smoke from cellulose acetate (CA)-filtered cigarettes with that of charcoal-filtered cigarettes developed in our laboratory. Previously, we had demonstrated that the mainstream smoke from an Indian CA-filtered commercial cigarette contains p-benzosemiquinone (p-BSQ), a major, highly toxic, long-lived water-soluble radical. Here, we have examined 16 brands of different CA-filtered cigarettes including Kentucky research cigarettes, and observed that mainstream smoke from all the cigarettes contains substantial amounts of p-BSQ (100-200 µg/cigarette). We also show that when the CA filter is replaced by a charcoal filter, the amount of p-BSQ in the mainstream smoke is reduced by 73-80%, which is accompanied by a reduction of carbonyl formation in bovine serum albumin to the extent of 70- 90%. The charcoal filter also prevented cytotoxicity in A549 cells as evidenced by MTT assay, apoptosis as evidenced by FACS analysis, TUNEL assay, overexpression of Bax, activation of p53 and caspase 3, as well as emphysematous lung damage in a guinea pig model as seen by histology and morphometric analysis. The results indicate that the charcoal filter developed in our laboratory may protect smokers from cigarette smoke-induced cytotoxity, protein modification, apoptosis and emphysema.