In vitro and in vivo effects of the carbon monoxide-releasing molecule, CORM-3, in the xenogeneic pig-to-primate context

Metal-based carbon monoxide releasing molecules with promising cytotoxic properties

Carbon monoxide, the "silent killer" gas, is increasingly recognised as an important signalling molecule in human physiology, which has beneficial biological properties. A particular way of achieving controlled CO administration is based on the use of biocompatible molecules that only release CO when triggered by internal or external factors. These approaches include the development of pharmacologically effective prodrugs known as CO releasing molecules (CORMs), which can supply biological systems with CO in well-regulated doses. An overview of transition metal-based CORMs with cytotoxic properties is here reported. The mechanisms at the basis of the biological activities of these molecules and their potential therapeutical applications with respect to their stability and CO releasing properties have been discussed. The activation of metal-based CORMs is determined by the type of metal and by the nature and features of the auxiliary ligands, which affect the metal core electronic density and therefore the prodrug resistance towards oxidation and CO release ability. A major role in regulating the cytotoxic properties of these CORMs is played by CO and/or CO-depleted species. However, several mysteries concerning the cytotoxicity of CORMs remain as intriguing questions for scientists.

Fluorescent detection mechanism of CO-releasing molecule-3: Competition of inter-/intra-molecular hydrogen bonds

The fluorescent detection mechanism of 2-(4-nitro-1,3-dioxoisoindolin-2-yl) acetic acid (CORM3-green) on CO-Releasing Molecule-3 (CORM-3) is theoretically studied. Upon reaction with CORM-3, the non-fluorescent CORM3-green is transferred to the keto form of 2-(4-amino-1,3-dioxoisoindolin-2-yl)acetic acid (PTI) to produce strong fluorescence peak located at 423 nm. This peak red-shifts to 489 nm, which is induced by the strengthening of intermolecular hydrogen bond (HB) between PTI and water molecules and attributed to the experimentally observed fluorescence emission at 503 nm. This result is dramatically different from previous reports that the experimental fluorescence corresponds to the proton transferred enol form of PTI. To illustrate this confusion, the calculated fluorescence peak of PTI-Enol is located at 689 nm, which is much larger than that of experimental result. This result excludes the occurrence of excited state intramolecular proton transfer (ESIPT). It is concluded that intermolecular HBs hinders the formation of intramolecular HB and the ESIPT of the keto form of PTI. This conclusion confirms that experimental Stokes shift of 113 nm is mainly caused by the intermolecular hydrogen bonding rather than by ESIPT process. This work proposes a reasonable explanation for the detection mechanism of CORM3-green and experimental fluorescence phenomenon.

Carbon Monoxide Therapy Using Hybrid Carbon Monoxide-Releasing/Nrf2-Inducing Molecules through a Neuroprotective Lens

Carbon monoxide (CO) has long been known for its toxicity. However, in recent decades, new applications for CO as a therapeutic compound have been proposed, and multiple forms of CO therapy have since been developed and studied. Previous research has found that CO has a role as a gasotransmitter and promotes anti-inflammatory and antioxidant effects, making it an avenue of interest for medicine. Such effects are possible because of the Nrf2/HO1 pathway, which has become a target for therapy development because its activation also leads to CO release. Currently, different forms of treatment involving CO include inhaled CO (iCO), carbon monoxide-releasing molecules (CORMs), and hybrid carbon monoxide-releasing molecules (HYCOs). In this article, we review the progression of CO studies to develop possible therapies, the possible mechanisms involved in the effects of CO, and the current forms of therapy using CO.

CO as a therapeutic agent: discovery and delivery forms

Carbon monoxide (CO) as one of the three important endogenously produced signaling molecules, termed as "gasotransmitter," has emerged as a promising therapeutic agent for treating various inflammation and cellular-stress related diseases. In this review, we discussed CO's evolution from a well-recognized toxic gas to a signaling molecule, and the effort to develop different approaches to deliver it for therapeutic application. We also summarize recently reported chemistry towards different CO delivery forms.

Carbon Monoxide-Releasing Molecule-3 Suppresses Tumor Necrosis Factor-α- and Interleukin-1β-Induced Expression of Junctional Molecules on Human Gingival Fibroblasts via the Heme Oxygenase-1 Pathway

Human gingival fibroblast barrier dysfunction caused by inflammation contributes to gingivitis and can lead to inflammatory periodontal disease. The disease features include upregulated epithelial permeability, increased inflammatory mediators, and downregulated junctional complex molecules. Carbon monoxide- (CO-) releasing molecule-3 (CORM-3) is a water-soluble compound that has demonstrated anti-inflammatory effects in in vitro and in vivo studies. In this study, we aimed to investigate the effects of CORM-3 on the expression of tight and adherens junction molecules on human gingival fibroblasts (HGFs) stimulated with tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). HGFs were cultured from the explants of normal human gingival tissues, which were stimulated in the presence or absence of CORM-3. Epithelial barrier function was evaluated by paracellular permeability and junctional complex molecule expression analyses. The protein and mRNA expression levels of adherens junction molecules (VE-cadherin and β-catenin) and tight junction molecules (zona occludens-1, ZO-1) were studied using western blot analysis and reverse transcription-quantitative polymerase chain reaction (RT-PCR). The mRNA and protein expression levels of these cytokines were also analyzed in HGFs transiently transfected with HO-1 small interfering RNA (siRNA) in response to TNF-α and IL-1β stimulation. CORM-3 reduced permeability and enhanced the expression of junctional complex molecules (ZO-1, VE-cadherin, and β-catenin) in TNF-α- and IL-1β-induced HGFs. However, these effects of CORM-3 were attenuated when HO-1 siRNA was transiently transfected in HGFs. These findings indicate that CORM-3 exerts anti-inflammatory effects on TNF-α- and IL-1β-stimulated HGFs via the HO-1 pathway, which suggests the promising potential of CORM-3 in the treatment of inflammatory periodontal disease.

Systemic Administration of Carbon Monoxide-Releasing Molecule-3 Protects the Skeletal Muscle in Porcine Model of Compartment Syndrome

OBJECTIVES

Acute limb compartment syndrome, a complication of musculoskeletal trauma, results in muscle necrosis and cell death. Carbon monoxide, liberated from the carbon monoxide-releasing molecule-3, has been shown protective in a rat model of compartment syndrome. The purpose of this study was to test the effect of carbon monoxide-releasing molecule-3 in a preclinical large animal model of compartment syndrome, with the ultimate goal of developing a pharmacologic adjunct treatment for compartment syndrome.

DESIGN

Animal research study.

SETTING

Basic research laboratory in a hospital setting.

SUBJECTS

Male Yorkshire-Landrace pigs (50-60 kg).

INTERVENTIONS

Pigs underwent 6 hours of intracompartmental pressure elevation by infusing fluid into the anterior compartment of the right hind limb. Carbon monoxide-releasing molecule-3 was administered systemically (2 mg/kg, IV) at fasciotomy, followed by 3-hour reperfusion.

MEASUREMENTS AND MAIN RESULTS

Muscle perfusion, inflammation, injury, and apoptosis were assessed in the skeletal muscle. Systemic leukocyte activation was assessed during compartment syndrome and reperfusion. Elevation of hind limb intracompartmental pressure resulted in significant microvascular perfusion deficits (44% ± 1% continuously perfused capillaries in compartment syndrome vs 76% ± 4% in sham; p < 0.001), increased tissue injury (ethidium bromide/bisbenzimide of 0.31 ± 0.07 in compartment syndrome vs 0.17 ± 0.03 in sham; p < 0.05), apoptosis (fluorescence in vivo/bisbenzimide of 0.26 ± 0.06 in compartment syndrome vs 0.13 ± 0.03 in sham; p < 0.05), and systemic leukocyte activation (14.7 relative luminescence units/10 polymorphonuclear leukocytes in compartment syndrome vs 1.0 ± 0.1 in baseline; p < 0.001). Systemic application of carbon monoxide-releasing molecule-3 at fasciotomy increased the number of continuously perfused capillaries (68% ± 3%; p < 0.001), diminished tissue injury (ethidium bromide/bisbenzimide of 0.13 ± 0.04; p < 0.05), apoptosis (fluorescence in vivo/bisbenzimide of 0.12 ± 0.03; p < 0.05), and blocked systemic leukocyte activation (3.9 ± 0.3 relative luminescence unit/10 polymorphonuclear leukocytes; p < 0.001).

CONCLUSIONS

Administration of carbon monoxide-releasing molecule-3 at fasciotomy offered protection against compartment syndrome-induced microvascular perfusion deficit, tissue injury, and systemic leukocyte activation. The data suggest the potential therapeutic application of carbon monoxide-releasing molecule-3 to patients at risk of developing compartment syndrome.

Investigating in Vitro Amyloid Peptide 1-42 Aggregation: Impact of Higher Molecular Weight Stable Adducts

The self-assembly of amyloid peptides (Aβ), in particular Aβ_1-42, into oligomers and fibrils is one of the main pathological events related to Alzheimer's disease. Recent studies have demonstrated the ability of carbon monoxide-releasing molecules (CORMs) to protect neurons and astrocytes from Aβ_1-42 toxicity. In fact, CORMs are able to carry and release controlled levels of CO and are known to exert a wide range of anti-inflammatory and anti-apoptotic activities at physiologically relevant concentrations. In order to investigate the direct effects of CORMs on Aβ_1-42, we studied the reactivity of CORM-2 and CORM-3 with Aβ_1-42 in vitro and the potential inhibition of its aggregation by mass spectrometry (MS), as well as fluorescence and circular dichroism spectroscopies. The application of an electrospray ionization-MS (ESI-MS) method allowed the detection of stable Aβ_1-42/CORMs adducts, involving the addition of the Ru(CO)₂ portion of CORMs at histidine residues on the Aβ_1-42 skeleton. Moreover, CORMs showed anti-aggregating properties through formation of stable adducts with Aβ_1-42 as demonstrated by a thioflavin T fluorescence assay and MS analysis. As further proof, comparison of the CD spectra of Aβ_1-42 recorded in the absence and in the presence of CORM-3 at a 1:1 molar ratio showed the ability of CORM-3 to stabilize the peptide in its soluble, unordered conformation, thereby preventing its misfolding and aggregation. This multi-methodological investigation revealed novel interactions between Aβ_1-42 and CORMs, contributing new insights into the proposed neuroprotective mechanisms mediated by CORMs and disclosing a new strategy to divert amyloid aggregation and toxicity.

Carbon monoxide-releasing molecule-3 (CORM-3) offers protection in an in vitro model of compartment syndrome

OBJECTIVE

Limb compartment syndrome (CS), a complication of trauma, results in muscle necrosis and cell death; ischemia and inflammation contribute to microvascular dysfunction and parenchymal injury. Carbon monoxide-releasing molecule-3 (CORM-3) has been shown to protect microvascular perfusion and reduce inflammation in animal models of CS. The purpose of the study was to test the effect of CORM-3 in human in vitro CS model, allowing exploration of the mechanism(s) of CO protection and potential development of pharmacologic treatment.

METHODS

Confluent human vascular endothelial cells (HUVECs) were stimulated for 6 h with serum isolated from patients with CS. Intracellular oxidative stress (production of reactive oxygen species (ROS)) apoptosis, transendothelial resistance (TEER), polymorphonuclear leukocyte (PMN) activation and transmigration across the monolayer in response to the CS stimulus were assessed. All experiments were performed in the presence of CORM-3 (100 μM) or its inactive form, iCORM-3.

RESULTS

CS serum induced a significant increase in ROS, apoptosis and endothelial monolayer breakdown; it also increased PMN superoxide production, leukocyte rolling and adhesion/transmigration. CORM-3 completely prevented CS-induced ROS production, apoptosis, PMN adhesion, rolling and transmigration, while improving monolayer integrity.

CONCLUSION

CORM-3 offers potent anti-oxidant and anti-inflammatory effects, and may have a potential application to patients at risk of developing CS.

A thiol-reactive Ru(II) ion, not CO release, underlies the potent antimicrobial and cytotoxic properties of CO-releasing molecule-3

Carbon monoxide (CO)-releasing molecules (CORMs), mostly metal carbonyl compounds, are extensively used as experimental tools to deliver CO, a biological ‘gasotransmitter’, in mammalian systems. CORMs are also explored as potential novel antimicrobial drugs, effectively and rapidly killing bacteria in vitro and in animal models, but are reportedly benign towards mammalian cells. Ru-carbonyl CORMs, exemplified by CORM-3 (Ru(CO)₃Cl(glycinate)), exhibit the most potent antimicrobial effects against Escherichia coli. We demonstrate that CORM-3 releases little CO in buffers and cell culture media and that the active antimicrobial agent is Ru(II), which binds tightly to thiols. Thus, thiols and amino acids in complex growth media – such as histidine, methionine and oxidised glutathione, but most pertinently cysteine and reduced glutathione (GSH) – protect both bacterial and mammalian cells against CORM-3 by binding and sequestering Ru(II). No other amino acids exert significant protective effects. NMR reveals that CORM-3 binds cysteine and GSH in a 1:1 stoichiometry with dissociation constants, K_d, of about 5 μM, while histidine, GSSG and methionine are bound less tightly, with K_d values ranging between 800 and 9000 μM. There is a direct positive correlation between protection and amino acid affinity for CORM-3. Intracellular targets of CORM-3 in both bacterial and mammalian cells are therefore expected to include GSH, free Cys, His and Met residues and any molecules that contain these surface-exposed amino acids. These results necessitate a major reappraisal of the biological effects of CORM-3 and related CORMs.

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Carbon monoxide-releasing molecules (CORMs) are used for experimental CO delivery.

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CORM-3 is a potent antimicrobial, but is reportedly beneficial to mammalian cells.

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We demonstrate CORM-3 releases little CO in buffers and cell culture media.

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Redox-active Ru²⁺ is the biological agent, binding tightly to metabolites e.g. thiol.

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These results necessitate a major reappraisal of the biological effects of CORMs.

Norborn-2-en-7-ones as physiologically-triggered carbon monoxide-releasing prodrugs

A prodrug strategy for the release of the gasotransmitter carbon monoxide (CO) at physiological pH, based upon 3a-bromo-norborn-2-en-7-one Diels–Alder cycloadducts has been developed.

A prodrug strategy for the release of the gasotransmitter CO at physiological pH, based upon 3a-bromo-norborn-2-en-7-one Diels–Alder cycloadducts of 2-bromomaleimides and 2,5-dimethyl-3,4-diphenylcyclopentadienone has been developed. Examples possessing protonated amine and diamine groups showed good water solubility and thermal stability. Half-lives for CO-release in TRIS-sucrose buffer at pH 7.4 ranged from 19 to 75 min at 37 °C and 31 to 32 h at 4 °C. Bioavailability in rats was demonstrated by oral gavage and oCOm-21 showed a dose dependent vasorelaxant effect in pre-contracted rat aortic rings with an EC₅₀ of 1.6 ± 0.9 μM. Increased intracellular CO levels following oCOm-21 exposure were confirmed using a CO specific fluorescent probe.

The severity of microvascular dysfunction due to compartment syndrome is diminished by the systemic application of CO-releasing molecule-3

OBJECTIVES

To examine the protective effects of carbon monoxide (CO), liberated from a novel CO-releasing molecule (CORM-3), on the function of compartment syndrome (CS)-challenged muscle in a rodent model, thus providing for a potential development of a pharmacologic adjunctive treatment for CS.

METHODS

Wistar rats were randomized into 4 groups: sham (no CS), CS, CS with inactive CORM-3 (iCORM-3), and CS + CORM-3 (10 mg/kg intraperitoneally). CS was induced by elevation of intracompartmental pressure to 30 mm Hg through an infusion of isotonic saline into the anterior compartment of the hind limb for 2 hours. Both CORM-3 and iCORM-3 were injected immediately after fasciotomy. Microvascular perfusion, cellular tissue injury, and inflammatory response within the extensor digitorum longus muscle were assessed using intravital video microscopy 45 minutes after fasciotomy. Systemic levels of tumor necrosis factor alpha (TNF-α) were also measured.

RESULTS

Elevation of intracompartmental pressure resulted in significant microvascular perfusion deficits (23% ± 2% continuously perfused capillaries in CS vs. 76% ± 4% in sham, P < 0.0001; 55% ± 2% nonperfused capillaries in CS vs. 13% ± 2% in sham, P < 0.0001), significant increase in tissue injury (ethidium bromide/bisbenzimide of 0.31 ± 0.05 in CS vs. 0.05 ± 0.03 in sham, P < 0.0001) and adherent leukocytes (13.7 ± 0.9 in CS vs. 1.8 ± 0.5 in sham, P < 0.0001), and a progressive rise in systemic TNF-α. CORM-3 (but not iCORM-3) treatment restored the number of continuously perfused capillaries (57% ± 5%, P < 0.001), diminished tissue injury (ethidium bromide/bisbenzimide of 0.07 ± 0.01, P < 0.001), reversed the CS-associated rise in TNF-α, and decreased leukocyte adherence (0.6 ± 0.3, P < 0.001).

CONCLUSIONS

CORM-3 displays a potent protective/anti-inflammatory action in an experimental model of CS, suggesting a potential therapeutic application to patients at risk of developing CS.

Does carbon monoxide inhibit proinflammatory cytokine production by fetal membranes?

AIM

Infection-induced inflammation is a common cause of preterm birth. Pharmacologic inhibition of proinflammatory cytokines improves pregnancy outcome in animal models but there are no universally effective therapies for preterm birth in women. Carbon monoxide (CO) has anti-inflammatory properties at low concentrations but its effects on reproductive tissues is unclear. Therefore, we studied the effect of supplemental CO on the production of cytokines associated with preterm birth by fetal membranes.

METHODS

Cross-sections of whole fetal membranes, isolated choriodecidua, and isolated amnion were prepared using tissues collected from women who had normal vaginal deliveries at term. Tissues were placed in an organ explant culture system and stimulated with up to 10(8) CFU/mL Escherichia coli. Cultures were incubated under room air or room air+250 ppm CO for 18 h and cytokine concentrations in conditioned medium were quantified by ELISA.

RESULTS

CO inhibited IL-1β and TNF-α (P≤0.001) production by cultures stimulated with 10(7) CFU/mL bacteria but had no detectable effect on IL-10 by full-thickness membranes. Although CO also tended to reduce TNF-α production (P=0.053), no effect of CO was detected for IL-10 or IL-1β for membranes stimulated with 10(8) CFU/mL E. coli. TNF-α, but not IL-1β or IL-10 production, was inhibited by CO for choriodecidual cultures stimulated with 10(7) or 10(8) CFU/mL E. coli (P<0.001). IL-1β production was significantly inhibited by CO for amnion cultures stimulated with 10(7) (P=0.002) and 10(8) (P=0.017) CFU/mL E. coli. Exposure to bacteria had no effect on TNF-α or IL-10 production but CO tended to increase IL-10 production by amnion cultures stimulated with 10(8) CFU/mL E. coli (P=0.037).

CONCLUSIONS

These results suggest that CO may help promote an anti-inflammatory environment during intrauterine infections by inhibiting TNF-α and IL-1β production.

Carbon monoxide abrogates ischemic insult to neuronal cells via the soluble guanylate cyclase-cGMP pathway

Purpose

Carbon monoxide (CO) is an accepted cytoprotective molecule. The extent and mechanisms of protection in neuronal systems have not been well studied. We hypothesized that delivery of CO via a novel releasing molecule (CORM) would impart neuroprotection in vivo against ischemia-reperfusion injury (IRI)-induced apoptosis of retinal ganglion cells (RGC) and in vitro of neuronal SH-SY5Y-cells via activation of soluble guanylate-cyclase (sGC).

Methods

To mimic ischemic respiratory arrest, SH-SY5Y-cells were incubated with rotenone (100 nmol/L, 4 h) ± CORM ALF186 (10–100 µmol/L) or inactivated ALF186 lacking the potential of releasing CO. Apoptosis and reactive oxygen species (ROS) production were analyzed using flow-cytometry (Annexin V, mitochondrial membrane potential, CM-H₂DCFDA) and Western blot (Caspase-3). The impact of ALF186± respiratory arrest on cell signaling was assessed by measuring expression of nitric oxide synthase (NOS) and soluble guanylate-cyclase (sGC) and by analyzing cellular cGMP levels. The effect of ALF186 (10 mg/kg iv) on retinal IRI in Sprague-Dawley rats was assessed by measuring densities of fluorogold-labeled RGC after IRI and by analysis of apoptosis-related genes in retinal tissue.

Results

ALF186 but not inactivated ALF186 inhibited rotenone-induced apoptosis (Annexin V positive cells: 25±2% rotenone vs. 14±1% ALF186+rotenone, p<0.001; relative mitochondrial membrane potential: 17±4% rotenone vs. 55±3% ALF186+rotenone, p<0.05). ALF186 increased cellular cGMP levels (33±5 nmol/L vs. 23±3 nmol/L; p<0.05) and sGC expression. sGC-inhibition attenuated ALF186-mediated protection (relative mitochondrial membrane potential: 55±3% ALF186+rotenone vs. 20±1% ODQ+ALF186+rotenone, p<0.05). ALF186 protected RGC in vivo (IRI 1255±327 RGC/mm² vs. ALF186+IRI 2036±83; p<0.05) while sGC inhibition abolished the protective effects of ALF186 (ALF186+IRI 2036±83 RGC/mm² vs. NS-2028+ALF186+IRI 1263±170, p<0.05).

Conclusions

The CORM ALF186 inhibits IRI-induced neuronal cell death via activation of sGC and may be a useful treatment option for acute ischemic insults to the retina and the brain.

Cell damage following carbon monoxide releasing molecule exposure: implications for therapeutic applications

The cytoprotective properties of carbon monoxide (CO) gas and CO-releasing molecules (CORMs) are well established. Despite promising pre-clinical results, little attention has been paid to the toxicological profile of CORMs. The effects of CORM-2 and its CO-depleted molecule (iCORM-2) (20-400 μM) were compared in primary rat cardiomyocytes and two cell lines [human embryonic kidney (HeK) and Madine-Darby canine kidney Cells (MDCK)]. Cells were assessed for cell viability, apoptosis, necrosis, cytology, mitochondrial energetics, oxidative stress and cell cycle arrest markers. In separate experiments, the anti-apoptotic effects of CORM-2 and i-CORM-2 treatment were compared against CO gas treatment in HeK and MDCK lines. H(2)O(2) -induced cellular damage, measured by lactate dehydrogenase (LDH) release from primary cardiomyocytes, was reduced by 20 μM CORM-2; LDH activity, however, was directly inhibited by 400 μM CORM-2. Both CORM-2/iCORM-2 and CO gas decreased cisplatin-induced caspase-3 activity in MDCK and HeK cells suggesting an anti-apoptotic effect. Conversely, both CORM-2 and iCORM-2 induced significant cellular toxicity in the form of decreased cell viability, abnormal cell cytology, increased apoptosis and necrosis, cell cycle arrest and reduced mitochondrial enzyme activity. Comparison of these markers after CO gas administration to MDCK cells found significantly less cellular toxicity than in 100 μM CORM-2/iCORM-2-treated cells. CO gas did not have an adverse effect on mitochondrial energetics and integrity. Release of CO by low concentrations of intact CORM-2 molecules provides cytoprotective effects. These results show, however, that the ruthenium-based CORM by-product, iCORM-2, is cytotoxic and suggest that the accumulation of iCORM-2 would seriously limit any clinical application of the ruthenium-based CORMs.

A Peptide-Based Material for Therapeutic Carbon Monoxide Delivery

We report on the preparation of the first material for therapeutic delivery of CO. A peptide amphiphile was synthesized with a covalently attached ruthenium tricarbonyl. Self-assembled nanofiber gels containing this peptide spontaneously released CO with prolonged release kinetics compared to soluble CO donors. Oxidatively stressed cardiomyocytes had improved viability when treated with this peptide, demonstrating its potential as a biodegradable gel for localized therapeutic CO delivery.

p38β-regulated induction of the heat shock response by carbon monoxide releasing molecule CORM-2 mediates cytoprotection in lung cells in vitro

The carbon monoxide releasing molecule tricarbonyldichlororuthenium (CORM-2) displays protective actions like carbon monoxide. The molecular mechanism underlying this effect remains controversial. We hypothesized that CORM-2 mediates cytoprotection via induction of heat shock proteins through activation of p38 mitogen-activated kinase. Embryonic bovine lung cells were incubated with CORM-2. Apoptosis was induced by staurosporine and analyzed by flow cytometry following annexin-V staining, caspase-3 activity assay, and by Western Blot for caspase-3 cleavage. Heat shock response was assessed by DNA-binding activity of heat shock factor 1 and by reporter gene activity. Cells were transfected with siRNA targeting p38 isoforms. Data were analyzed with ANOVA and post-hoc Holm-Sidak test. CORM-2 inhibited staurosporine-induced apoptosis (% annexin-V positive cells: staurosporine = 60 ± 4% vs. CORM-2 10 μM = 48 ± 4%, CORM-2 25 μM=42 ± 5%, CORM-2 50 μM = 40 ± 4% and CORM-2 100 μM = 38 ± 2%, mean ± S.D., P<0.001; caspase-3 activity: staurosporine=92 ± 15 RFUs vs. CORM-2 50 μM=60 ± 14 RFUs, mean ± S.D. P<0.001). CORM-2 induced phosphorylation of p38 MAPK, but not of JNK and ERK1/2. CORM-2 induced DNA-binding of heat shock factor 1 and elicited a 4-fold induction of gene activity (P<0.05). Incubation with the Hsp inhibitors KNK437 attenuated and 17-AAG abolished the anti-apoptotic effect of CORM-2 (P<0.001). p38 inhibition and silencing of p38β attenuated the anti-apoptotic effect of CORM-2 (P<0.05), most likely by abolishing CORM-2-induced HSF-1 binding activity. These findings suggest that CORM-2-mediated cytoprotection is caused by induction of the heat shock response and by p38 activation. Furthermore, the p38β isoform activation may represent an upstream mechanism of heat shock response induction.

CORM-3 reactivity toward proteins: the crystal structure of a Ru(II) dicarbonyl-lysozyme complex

CORM-3, [fac-Ru(CO)(3)Cl(κ(2)-H(2)NCH(2)CO(2))], is a well-known carbon monoxide releasing molecule (CORM) capable of delivering CO in vivo. Herein we show for the first time that the interactions of CORM-3 with proteins result in the loss of a chloride ion, glycinate, and one CO ligand. The rapid formation of stable adducts between the protein and the remaining cis-Ru(II)(CO)(2) fragments was confirmed by Inductively Coupled Plasma-Atomic Emission Spectroscopy (ICP-AES), Liquid-Chromatography Mass Spectrometry (LC-MS), Infrared Spectroscopy (IR), and X-ray crystallography. Three Ru coordination sites are observed in the structure of hen egg white lysozyme crystals soaked with CORM-3. The site with highest Ru occupancy (80%) shows a fac-[(His15)Ru(CO)(2)(H(2)O)(3)] structure.

Role of carbon monoxide and nitric oxide in adult rat hepatocytes proliferating in vitro: Effects of CAS 1609

During liver regeneration in vivo carbon monoxide (CO) and nitric oxide (NO) are supposed to play a significant role. We raise the question whether CO and NO are involved in the growth process of cultured hepatocytes. Rat hepatocytes were stimulated into proliferation, growth being estimated by DNA content, mRNA by quantitative RT-PCR, and inducible NO synthase (iNOS) activity by GC-MS. Dexamethasone proved obligatory for fast proliferation. It suppressed the spontaneous rise of iNOS-mRNA in cultures devoid of glucocorticoids, but did not counteract the rise in mRNA in actively dividing cultures. Expression of iNOS-mRNA and cell growth were further enhanced by LiCl (10 mM). NOS activity was completely suppressed by the iNOS-specific inhibitors N-(3-(aminomethyl)benzyl) acetamidine (1400 W,100 microM) and L-N(6)-(1-iminoethyl)lysine (L-NIL, 500 microM), however, without a decrease in hepatocyte growth. Proliferation was attenuated only by very high concentrations (>0.5 mM) of N-nitro-L-arginine methyl ester (L-NAME) and asymmetric dimethylarginine (ADMA). Various NO donors (at 100 microM) did not stimulate cell growth. The furoxan CAS 1609 stimulated growth, decreased iNOS-mRNA expression and transiently increased haem oxygenase-1 (HO-1)-mRNA without releasing considerable amounts of NO. 1H-[1,2,4]Oxadiazolo[4,3,-alpha]quinoxalin-1-one (ODQ) attenuated the action of CAS 1609. Proliferation was stimulated by Co-protoporphyrin and tricarbonyldichlororuthenium(II) dimer (CORM-2). We conclude that CAS 1609 triggers hepatocyte mitosis most likely via direct, NO-independent induction of HO-1 expression, pointing to CO as a growth-promoting signal in the proliferation cascade in cultured hepatocytes.

Ki-67 staining for determination of rhesus macaque T cell proliferative responses ex vivo

The capacity for robust proliferation upon re-infection is a hallmark of adaptive immunity and the basis of vaccination. A widely used animal model for the study of human disease is the rhesus macaque (RM), where capacity for proliferation can be assessed ex vivo using carboxyfluorescein succinimidyl ester (CFSE)-based dilution assays. However, we show over the course of the standard ex vivo proliferation assay that CFSE-labeling at commonly used dye concentrations induces significant cell death, but that this phenomenon is dose-dependent. Here, we describe an alternative semiquantitative method for estimating T cell proliferative responses that avoids the putative biases associated with chemical modification. RM peripheral blood mononuclear cells were stimulated ex vivo with cognate peptides for 5 days, immunostained for intracellular Ki-67, and then analyzed by flow cytometry. We describe a gating strategy using Ki-67 and side light scatter, also a marker of blastogenesis, which correlates strongly with data from CFSE dilution. We show that this method is a valid tool for measuring RM antigen-specific cellular proliferation ex vivo and can be used as an alternative to CFSE dilution assays.