Increased fatty acid synthesis and disturbed lipid metabolism in Neuro2a cells after repeated cocaine exposure: A preliminary study.

Chronic use of cocaine prompts neurodegeneration and neuroinflammation. Lipids play pivotal roles in neuronal function and pathology. Although evidence correlates cocaine use with the alteration of lipid metabolism in blood and brain, the precise mechanism remains to be elucidated. In this study, we explore the effect of cocaine on neuronal fatty acid profiles in vitro. Neuro2a cells following seven days of repeated exposure to cocaine (0, 600, 800, 1000 µM) showed apoptosis-irrelevant cell death, dysregulated autophagy, activation of atypical endoplasmic reticulum stress response, increased saturated and unsaturated fatty acid synthesis, and disrupted lipid metabolism. These preliminary findings indicated the association between lipid metabolism and cocaine-induced neurotoxicity, which should be beneficial for understanding the neurotoxicity of cocaine.

Effects of microsampling on toxicity evaluation of 1-naphthylisothiocyanate (ANIT), a hepatotoxic substance, in a mouse toxicity study.

ICH S3A Q&A focused on microsampling (MS) was published to help accelerate the use of MS and states that MS is useful because toxicokinetic (TK) evaluation with conventional blood sampling volume requires many animals for TK satellite groups; however, there are few reports of MS application in mice. We investigated the influence of MS on toxicity evaluation in mice by comparing the toxicity parameters with and without MS after a single oral administration of 1-naphthylisothiocyanate (ANIT), a hepatotoxic substance. Blood samples (50 µL/point) were collected from the tail vein of 3 mice per group at 2 or 3 time points during a 24-hr period, and toxicity was evaluated 2 days after administration. ANIT-related changes suggesting liver or gallbladder injury were noted in blood chemistry and histopathology. Some of these changes such as increases in focal hepatocyte necrosis and inflammatory cell infiltration in the liver as well as mucosal epithelium necrosis in the gallbladder were apparently influenced by MS. A tendency to anemia was noted in animals with MS but not without MS, which was also noted in the vehicle-treated controls, suggesting influence of blood loss. The current results indicate that ANIT hepatotoxicity could be evaluated in mice in which blood samples were collected by MS for most parameters; however, parameters in anemia and pathology in the liver and gallbladder were influenced by MS in this study condition with ANIT. Therefore, MS application in mice should be carefully considered.

Cocaine induces vascular smooth muscle cells proliferation via DRP1-mediated mitochondrial fission and PI3K/HIF-1α signaling.

Long-term cocaine abuse is associated with cardiovascular and pulmonary vascular complications. The vascular toxicity of cocaine can lead to vascular remodeling characterized by excessive proliferation of vascular smooth muscle cells. Though hypoxia-inducible factor (HIF) signaling and mitochondrial fission have been suggested to play essential roles in the pathogenesis of hypoxia-induced vascular remodeling, pathogenetic mechanism for cocaine-related vascular remodeling remains to be elucidated. In this study, we explore the effect of cocaine on the proliferation of vascular smooth muscle cells by in vitro experiments. The findings indicated that the cocaine-induced vascular smooth muscle cell hyperproliferation is achieved by enhancing DRP1-mediated mitochondrial fission and activating PI3K/HIF-1α signaling. Current findings suggested that mitochondrial fission would play a pivotal role in cocaine-related vascular remodeling and would be helpful in understanding the vascular toxicity of cocaine.

Excessive N-acetylcysteine exaggerates glutathione redox homeostasis and apoptosis during acetaminophen exposure in Huh-7 human hepatoma cells.

Acetaminophen (APAP) hepatotoxicity is one of the biggest drawbacks of this relatively safe and widely used drug. In addition to its hepatotoxicity, APAP also cause comparable levels of toxicity on human hepatoma cells. Here we show activation of the intrinsic caspase-9/3 pathway of apoptosis followed by gasdermin E (GSDME) cleavage and subsequent ballooning in APAP (10 mM, 72 h)-treated Huh-7 human hepatocarcinoma cells. N-acetylcysteine (NAC), an antioxidant currently used as an antidote for APAP overdose, does not alleviate APAP toxicity in Huh-7 cells; NAC overdose (10 mM) rather aggravates APAP toxicity. NAC overdose not only aggravates cell death, but also decreases the cellular GSH/GSSG ratio, an indicator of redox homeostasis of glutathione. These results show for the first time that APAP-induced apoptosis in hepatoma cells is followed by secondary necrosis via the caspase-3/GSDME pathway. NAC overdose (10 mM) not only worsens the glutathione redox status, but also accelerates this pathway.

Aristolochic acid induces an inflammatory response with prostaglandin E2 production and apoptosis in NRK-52E proximal tubular cells.

Aristolochic acid nephropathy (AAN) is a type of drug-induced nephropathy in which ingestion of aristolochic acid (AA) causes acute kidney injury, with progressive renal fibrosis and upper urothelial carcinoma. Although the pathological features of AAN have been reported to involve significant cell degeneration and loss in the proximal tubules, the details of the toxic mechanism in the acute phase of the disease remain unclear. This study investigates the cell death pathway and intracellular metabolic kinetics of AA exposure in rat NRK-52E proximal tubular cells. AA exposure induces dose- and time-dependent apoptotic cell death in NRK-52E cells. We examined the inflammatory response to further investigate the mechanism of AA-induced toxicity. AA exposure increased the gene expression of inflammatory cytokines IL-6 and TNF-α, suggesting that AA exposure induces inflammation. Furthermore, analysis of lipid mediators by LC-MS revealed increases in intra- and extra-cellular arachidonic acid and prostaglandin E2 (PGE2). To investigate the relationship between the AA-induced increase in PGE2 production and cell death, celecoxib, an inhibitor of cyclooxygenase-2 (COX-2), which is involved in the production of PGE2, was administered, and a marked inhibition of AA-induced cell death was observed. These results suggest that exposure to AA induces concentration- and time-dependent apoptosis in NRK-52E cells, which is attributed to inflammatory responses mediated by COX-2 and PGE2.

Induction of filamin-C and its involvement in the regulation of cellular senescence and apoptosis in Huh-7 hepatoma cells during arsenic trioxide exposure.

Arsenic trioxide (ATO) is one of the most toxic inorganic arsenic compounds. In this study, we examined the effects of long-term (7 days) exposure to low dose (5 µM) ATO on a human hepatocellular carcinoma cell line, Huh-7. Along with apoptosis accompanied by secondary necrosis though GSDME cleavage, we observed enlarged and flattened cells adhering to the culture dish and surviving even after exposure to ATO. An increase in cyclin-dependent kinase inhibitor p21 levels as well as positive staining for senescence-associated ß-galactosidase activity were observed in ATO-treated cells, indicating cellular senescence. Screening for both ATO-inducible proteins by MALDI-TOF-MS analysis and ATO-inducible genes by DNA microarray analysis showed a marked increase in filamin-C (FLNC), an actin cross-linking protein. Interestingly, the increase in FLNC was observed in both dead and surviving cells, suggesting that the upregulation of FLNC by ATO occurs in both apoptotic and senescent cells. Small interference RNA-mediated knock down of FLNC resulted in not only a reduction of senescence-associated enlarged morphology of the cells, but also an exacerbation of cell death. Taken together, these results suggest a regulatory role of FLNC in the execution of senescence as well as apoptosis during ATO exposure.

Aggregation-prone A53T mutant of α-synuclein exaggerates methamphetamine neurotoxicity in SH-SY5Y cells: Protective role of cellular cholesterol.

The aim of this study is to examine the effects of wild type as well as a mutant (A53T) form of α-synuclein (α-syn) on neuronal cells exposed to methamphetamine (METH). SH-SY5Y human dopaminergic neuronal cells stably expressing exogenously added wild type (WT) or A53T α-syn were established for this purpose. Among the three types of cells, parental, WT α-syn-overexpressing, and A53T α-syn overexpressing SH-SY5Y cells (hereafter referred to as SH-SY5Y, WT SH-SY5Y, and A53T SH-SY5Y, respectively), only A53T SH-SY5Y cells showed significant loss of cell viability after exposure to 2 mM METH for 24 h. Transcriptome analysis using DNA microarray showed that METH induced genes for cholesterol biosynthesis in all of these three cell lines, suggesting that METH upregulates cellular cholesterol biosynthesis independently from cellular α-syn levels. Visualization of the cellular localization of free cholesterol showed that METH induces an aberrant intracellular accumulation of free cholesterol in all three cell lines. In addition, we observed the aggregation of α-syn into cytoplasmic granules, which was more apparent with A53T α-syn than WT α-syn, in cells exposed to METH. Furthermore, the cell death observed in METH-treated A53T SH-SY5Y cells was exaggerated by the addition of 2-hydroxypropyl-ß-cyclodextrin (CD), a substance used to extract cholesterol from cells. These results suggest that the aggregation of A53T α-syn in METH-treated cells should be involved in cell death. The upregulation of cellular biosynthesis and cholesterol accumulation by METH should play a protective role against A53T α-syn neurotoxicity in METH-treated SH-SY5Y cells.

Thymic involution caused by repeated cocaine administration includes apoptotic cell loss followed by ectopic adipogenesis.

Cocaine abuse has a negative impact on the immune system. To investigate the adverse effects of binge cocaine administration on lymphoid organs such as thymus and spleen, we examined the effects of repeated intravenous (i.v.) administration of cocaine on rats. Sprague Dawley rats (male, 8 weeks old) received 20 mg/kg body weight of cocaine hydrochloride per day for 7 or 14 days. In addition to a significant loss in the weight of the spleen, consistent with our previous intraperitoneal (i.p.) injection model of binge cocaine abuse (50 mg/kg cocaine for 7 days), we also found a significant loss of weight as well as apparent shrinkage of the thymus in the cocaine group. Transcriptome analysis of the thymus revealed increased expressions of genes involved in apoptosis, such as Ifi27 and Traf2, as well as decreased expressions of several genes related to lipid metabolism, such as Cd36, Adipoq, Scd1, and Fabp4, in the thymus of the cocaine group (7 days), suggesting an apoptotic loss of thymic cells as well as alterations in lipid metabolism. Paradoxically, cocaine activates PPARγ, a key transcriptional factor activating lipid metabolism, although ectopic adipogenesis was scarcely observed in the thymus. Further analysis of rats administered 20 mg/kg cocaine for 14 days revealed ectopic adipogenesis, which was accompanied with the activation of PPARγ as well as increased expression of Adipoq and Fabp4, in the thymus. Taken together, these results indicate that repeated cocaine administration induces thymic involution, which is initiated by the loss of thymic cells through apoptosis and subsequent ectopic adipocyte development.

Contraction Band Necrosis with Dephosphorylated Connexin 43 in Rat Myocardium after Daily Cocaine Administration.

Contraction band necrosis (CBN) is a common abnormality found in the myocardium of cocaine abusers, but is rarely reported in experimental models of cocaine abuse. Connexin 43 (Cx43) is essential for cardiac intercellular communication and the propagation of CBN. Under stress or injury, cardiac Cx43 is dephosphorylated, which is related to cardiomyocyte dysfunction and pathogenesis, whereas adiponectin exerts beneficial effects in the myocardium. In this study, we explore the effects of cocaine on cardiac Cx43 in vivo. Rats were administered cocaine via the tail vein at 20 mg/kg/day for 14 days, and showed widespread CBN, microfocal myocarditis and myocardial fibrosis, corresponding to a dysfunction of cardiac mitochondria under increased oxidative stress. The increase in dephosphorylated cardiac Cx43 and its negative correlation with the myocardial distribution of CBN after cocaine administration were determined. In addition, apoptosis and necroptosis, as well as increased adiponectin levels, were observed in the myocardium after cocaine exposure. Accordingly, we found altered profiles of cardiac Cx43, CBN and its negative correlation with dephosphorylated cardiac Cx43, and the possible involvement of adiponectin in the myocardium after 14 days of cocaine administration. The latter might play a protective role in the cardiotoxicity of cocaine. The current findings would be beneficial for establishing novel therapeutic strategies in cocaine-induced cardiac consequences.

Role of Mitochondrial Dynamics in Cocaine's Neurotoxicity.

The dynamic balance of mitochondrial fission and fusion maintains mitochondrial homeostasis and optimal function. It is indispensable for cells such as neurons, which rely on the finely tuned mitochondria to carry out their normal physiological activities. The potent psychostimulant cocaine impairs mitochondria as one way it exerts its neurotoxicity, wherein the disturbances in mitochondrial dynamics have been suggested to play an essential role. In this review, we summarize the neurotoxicity of cocaine and the role of mitochondrial dynamics in cellular physiology. Subsequently, we introduce current findings that link disturbed neuronal mitochondrial dynamics with cocaine exposure. Finally, the possible role and potential therapeutic value of mitochondrial dynamics in cocaine neurotoxicity are discussed.

Inverse regulation of GSDMD and GSDME gene expression during LPS-induced pyroptosis in RAW264.7 macrophage cells.

GSDMD and GSDME, members of the gasdermin protein family, are involved in the formation of plasma membrane channels contributing to cell rupture during a certain type of necrosis called pyroptosis. GSDMD is activated in response to immunological stimulation such as lipopolysaccharides (LPS) treatment while GSDME is mainly involved in drug-induced tumor cell death. Here we show that the expression of the GSDMD gene increases significantly during LPS-induced pyroptosis in RAW264.7 murine macrophage cells. In contrast, GSDME expression is decreased in the same cells. The increasing effect of LPS on GSDMD expression was observed only when the cells were cultured in high glucose (4.5 g/l) medium, suggesting that glucose availability is important for this effect. The effect of LPS on GSDMD expression is abolished by 2-deoxyglucose (2DG), confirming that glycolysis plays crucial roles in the increasing effect of LPS. Small interference RNA-mediated knock down of GSDMD or overexpression of GSDME causes LPS-induced pyroptosis to take place through GSDME rather than through GSDMD. Taken together, LPS regulates GSDMD and GSDME expression in opposite directions through, at least in part, its effect on glycolysis. This transcriptional regulation may contribute to the execution of pyroptosis in a GSDMD-dependent manner.

Altered cardiac mitochondrial dynamics and biogenesis in rat after short-term cocaine administration.

Abuse of the potent psychostimulant cocaine is widely established to have cardiovascular consequences. The cardiotoxicity of cocaine is mainly associated with oxidative stress and mitochondrial dysfunction. Mitochondrial dynamics and biogenesis, as well as the mitochondrial unfolded protein response (UPRmt), guarantee cardiac mitochondrial homeostasis. Collectively, these mechanisms act to protect against stress, injury, and the detrimental effects of chemicals on mitochondria. In this study, we examined the effects of cocaine on cardiac mitochondrial dynamics, biogenesis, and UPRmt in vivo. Rats administered cocaine via the tail vein at a dose of 20 mg/kg/day for 7 days showed no structural changes in the myocardium, but electron microscopy revealed a significant increase in the number of cardiac mitochondria. Correspondingly, the expressions of the mitochondrial fission gene and mitochondrial biogenesis were increased after cocaine administration. Significant increase in the expression and nuclear translocation of activating transcription factor 5, the major active regulator of UPRmt, were observed after cocaine administration. Accordingly, our findings show that before any structural changes are observable in the myocardium, cocaine alters mitochondrial dynamics, elevates mitochondrial biogenesis, and induces the activation of UPRmt. These alterations might reflect cardiac mitochondrial compensation to protect against the cardiotoxicity of cocaine.

Oxcarbazepine induces mitotic catastrophe and apoptosis in NRK-52E proximal tubular cells.

Certain medicines including anticancer drugs, NSAIDs and antiepileptic drugs are known to cause drug-induced nephropathy. For example, antiepileptic drugs such as carbamazepine (CBZ) and valproic acid have been reported to cause damage to the proximal tubular cells. Although there has been a great deal of research concerning the nephrotoxicity of CBZ, little is known about that of oxcarbazepine (OXC), a derivative of CBZ. To investigate the molecular mechanism underlying renal proximal tubular cell death caused by OXC, we examined alterations in the gene expression profile of NRK-52E proximal tubular cells during OXC exposure. DNA microarray analysis revealed that the levels of genes related to mitotic processes including chromosomal and cytoplasmic segregation, progression to G2/M phase, and formation of the mitotic spindle are increased after exposure to 50 µM OXC for 6 h. Cell cycle analysis by flow cytometry showed that OXC at concentrations between 25 and 100 µM induces G2/M arrest. We also found that OXC significantly increases histone H3 phosphorylation, indicative of mitotic cells. These results imply that OXC induces cell cycle arrest at the mitotic phase. Immunofluorescence analysis showed monopolar spindles, which are formed in response to centrosome separation defects, in OXC-treated cells. We also show that OXC suppresses the phosphorylation of PLK1, which is involved not only in the activation of the kinesin family of motor proteins for centrosome separation and bipolar spindle assembly, but also in the cleavage of centrosomal proteins. Thus, our results indicate that OXC inhibits centrosome separation by reducing the activation of PLK1, which leads to the formation of an abnormal spindle and induces mitotic catastrophe and apoptosis in NRK-52E cells.

Evaluation of Parameters for Estimating the Postmortem Interval of Skeletal Remains Using Bovine Femurs: A Pilot Study.

The postmortem interval (PMI) of victims is a key parameter in criminal investigations. However, effective methods for estimating the PMI of skeletal remains have not been established because it is determined by various factors, including environmental conditions. To identify effective parameters for estimating the PMI of skeletal remains, we investigated the change in bone focusing on the amount of DNA, element concentrations, and bone density that occurred in the bone samples of bovine femurs, each maintained under one of five simulated environmental conditions (seawater, freshwater, underground, outdoors, and indoors) for 1 year. The amount of extracted mitochondrial DNA (mtDNA; 404 bp fragment) decreased over time, and significant DNA degradation (p < 0.01), as estimated by a comparison with amplification results for a shorter fragment (128 bp), was detected between 1 month and 3 months. Eleven of 30 elements were detected in samples by inductively coupled plasma optical emission spectrometry, and Na and Ba showed significant quantitative differences in terms of environmental conditions and time (p < 0.01). This preliminary study suggests that the level of DNA degradation determined by real-time polymerase chain reaction and element concentrations determined by inductively coupled plasma optical emission may be useful indices for estimating the PMI of victims under a wide range of environmental conditions. However, this study is a limited experimental research and not applicable to forensic cases as it is. Further studies of human bone with longer observation periods are required to verify these findings and to establish effective methods for PMI estimation.

Extracellular glucose is crucially involved in the fate decision of LPS-stimulated RAW264.7 murine macrophage cells.

Pyroptosis, a type of inflammatory cell death, is dependent on the inflammatory caspase-mediated cleavage of gasdermin D (GSDMD), and the subsequent pore formation on plasma membranes through which interleukin (IL)-1ß and IL-18 are released from cells. During proinflammatory activation, macrophages shift their metabolism from aerobic oxidative phosphorylation to anaerobic glycolysis. Hypoxia-inducible factor (HIF)1α is involved in the induction of IL-1ß gene expression as well as the metabolic shift towards glycolysis. However, the relationships between pyroptosis and glycolysis, as well as between pyroptosis and HIF1α are poorly investigated. Here we show that lipopolysaccharide (LPS) stimulation of RAW264.7 murine macrophage cells results in pyroptosis when cells are cultured in high glucose medium. During pyroptosis, HIF1α activation occurs transiently followed by downregulation to sub-basal levels. HIF1α downregulation and pyroptosis are observed when cells are stimulated with LPS under high glucose conditions. We also found that intracellular levels of methylglyoxal (MGO), a side product of glycolysis, increase when cells are stimulated with LPS under high glucose conditions. The addition of glycolysis inhibitor and rapamycin suppresses HIF1α downregulation and pyroptosis. These results show that glycolysis plays a crucial role not only in pro-inflammatory activation, but also in pyroptosis in LPS-stimulated RAW264.7 macrophages.

Repeated exposure of cocaine alters mitochondrial dynamics in mouse neuroblastoma Neuro2a.

Chronic abuse of psychoactive drugs including cocaine causes addiction, dependence, and brain disorders through the alteration of neuronal plasticity. Mitochondrial fission and fusion, collectively called as mitochondrial dynamics, participates in not only the maintenance of neuronal homeostasis but also reorganization of neuronal circuits. The purpose of this study is to examine effects of direct and repeated exposure of cocaine on mitochondrial dynamics in neuronal cells in vitro. Repeated exposure to 600 µM cocaine (2∼3 times per week) of Neuro2a mouse neuroblastoma cells for 3 weeks resulted in decrease of mitochondrial transmembrane potential, activation of autophagy, and upregulation of Parkin, a protein involved in mitochondrial autophagy. Increased expression of mitochondrial fission genes and significant increase in the ser-616 phosphorylated-DRP1, the key regulator of mitochondrial fission, were observed in the cells exposed repeatedly to 600 µM cocaine. Electron microscopy showed significant increase in the number of mitochondria in cocaine-treated cells compared with control cells. Thus, our results show that repeated cocaine exposure not only causes mitochondrial dysfunction but also alters mitochondrial dynamics in Neuro2a cells. Changes in the mitochondrial dynamics might be involved in neural adaptation during repeated cocaine exposure.

Preparation of dentin standard samples for age estimation based on increased aspartic acid racemization rate by heating.

Age estimation in adults based on aspartic acid racemization (AAR) provides fewer errors and higher precision than that based on bone morphology for the identification of cadavers. The technique has been established in some labs as a routine method. However, as the essential requisites for the technique, a wide age range of teeth of the same type as the target tooth must be collected for calibration for each examination. We investigated whether dentin standard samples could be prepared by increasing the AAR rate via heat. Powdered dentin was prepared from a maxillary first premolar (13 years) and heated for 0-72 h at 110 °C. The extent of AAR increased significantly with heating time and the correlation was strong (r = 0.913; p < 0.01). Similar results were found for a mandibular canine (24 years, r = 0.948; p < 0.01) and a maxillary third molar (20 years, r = 0.944; p < 0.01). We attempted to estimate the age of four maxillary first premolars of persons aged 25-58 years by using the heated samples (18 years, 12 h to 7 days). The differences between the actual and estimated ages were within ±5 years. The stability of the AAR rates in the powdered dentin during storage at 22-25 °C, 4 °C, and -30 °C was examined after 1 year and no significant changes had occurred. We were able to prepare dentin standard samples and created a calibration curve. This is a pilot study that needs to be validated before it can be used in forensic practice.

Formation of high molecular weight p62 by CORM-3.

CORM-3 is a water-soluble carbon monoxide (CO)-releasing molecule developed for possible therapeutic use of CO. CORM-3 belongs to a group of metal carbonyl compounds that contain transition metals and carbonyls as the central scaffold and coordinated ligands, respectively. CORM-3 has been reported to be reactive with many proteins in eukaryotes including mammals. Among them, several extracellular proteins, such as lysozyme, as well as plasma albumin and fibronectin, have been shown to interact directly with CORM-3. p62 is an intracellular adaptor protein required for targeting ubiquitinated (Ub) proteins to lysosomal degradation through autophagy. p62 has been shown to undergo self-oligomerization via covalent crosslinking in response to treatment with verteporfin, a benzoporphyrin derivative used for photodynamic therapy. Here we show that CORM-3 also interacts directly with p62. When applied to mouse embryonic fibroblasts (MEFs) at a high concentration (1 mM), CORM-3 causes the formation of reduction- and detergent-resistant high molecular weight (HMW)-p62. HMW-p62 accumulates more in atg5-/- MEFs than in wild type (WT) MEFs, showing the elimination of HMW-p62 through autophagy. HMW-p62 is also generated in H9c2 rat cardiomyoblastoma as well as A549 human alveolar epithelial cells, suggesting that HMW-p62 formation is not specific to MEFs, but, rather, is a general event in mammalian cells. HMW-p62 formation by CORM-3 can be reproduced using purified p62 in vitro, demonstrating the direct interaction between CORM-3 and p62. These results show that p62 is a CORM-3-interactive intracellular protein.

Necrosis in human neuronal cells exposed to paraquat.

Paraquat (PQ) is an herbicide that was once used worldwide, but is now prohibited in many nations due to its high toxicity to humans. However, there are still rare cases of the fetal intoxication of PQ, which was purchased prior to the prohibition in Japan. In this study, several cell death pathways, the mitochondrial stress response, and autophagy were examined in SH-SY5Y cells exposed to PQ. The results reveal the decrease of a mitochondrial stress sensitive-BNIP3 (Bcl-2/adenovirus E1B 19-kDa-interacting protein 3) protein, the suppression of autophagic flux, and the lack of apoptosis as well as other regulated forms of necrosis, such as necroptosis and ferroptosis. Taken together, our preliminary survey of cellular responses against PQ shows that, although responses of mitochondria and autophagy are observed, subsequent cell death is necrosis. Mechanism of PQ-induced SH-SY5Y cell death should be complicated and cannot be explained thoroughly by already-known mechanisms.

Interaction of carbon monoxide-releasing ruthenium carbonyl CORM-3 with plasma fibronectin.

Inhaled carbon monoxide (CO) gas is highly toxic, but the human body produces low levels of CO for vasoregulation and other purposes. Given the established protective roles of low concentrations of CO gas against a panel of pathological insults, CO-releasing molecules (CORMs) have been developed and examined in disease models both in vitro and in vivo. Among CORMs, CORM-3 [Ru(CO)3Cl(glycinate)], a ruthenium carbonyl compound, has been extensively studied since it is water-soluble and is suitable for in vivo application. As one of the most prominent features of CO gas is its anti-fibrotic effect, we examined the effects of CORM-3 on mouse embryonic fibroblasts (MEFs). The application of 1 mM CORM-3 to MEFs resulted in the decreased syntheses of collagens I and III within 24 h, confirming an anti-fibrotic effect. To our surprise, CORM-3 caused a rapid (within 1 h) dissociation of cell-associated plasma fibronectin (FN) from the cells, which is associated with formation of a reduction-resistant oligomer of plasma FN. This aberrant oligomerization of plasma FN was reproduced using purified FN in vitro. Furthermore, we showed that RuCl3, but not another water-soluble CORM, CORM-A1 [Na2H3BCO2], also oligomerized plasma FN in vitro. FN depletion from the serum substantially ameliorates cell death by prolonged (72 h) exposure to CORM-3, suggesting a detrimental role of FN oligomerization on cell death. Taken together, we reveal for the first time that FN is a CORM-3-interactive plasma protein, and that the CORM-3-FN interaction is involved in the death of fibroblasts.