Research paperProtective effects of inhaled carbon monoxide in endotoxin-induced cholestasis is dependent on its kinetics
Graphical abstract
Introduction
Carbon monoxide (CO) is a ubiquitous air pollutant and toxic gas, but also is an important endogenous signaling molecule, which regulates many biological functions in the body. This product of the heme catabolic pathway, which is catalyzed by the enzyme heme oxygenase (HMOX), plays an important role in inflammation, cell proliferation and cytoprotection [1], [2] and thus has a considerable therapeutic potential. Inhalation of low doses of CO has been shown to have potent cytoprotective properties in animal models of organ injury and disease [3]. According to the National Institutes of Health clinical trial database, the CO inhalation model is currently being used in studies investigating its use in the treatment of lung and cardiac diseases (ClinicalTrials.gov; identifier: NCT00094406, NCT01727167, accessed 12th March 2013). To evaluate the safety and effectiveness of using of CO inhalation as a treatment modality, it is critical to not only closely monitor blood CO-hemoglobin (COHb) levels in order to prevent CO poisoning; but also, to identify the optimal concentration of CO that needs to be delivered to target tissues. However, current knowledge about the kinetics of inhaled CO is still very limited.
Cholestasis is characterized as an impairment of bile formation and/or outflow. Although it is a serious complication of sepsis, the pathogenesis of cholestasis is still not fully known [4]. However, it has been shown that inflammatory cytokines released by endotoxins can down-regulate expression of hepatobiliary transporters and subsequently impair transport function and bile formation [4], [5].
Anti-inflammatory and pro-inflammatory cytokines have been shown to be regulated by the actions of CO via different mechanisms in both in vivo [6], [7] and in vitro studies [6], [7]. Nevertheless, a direct effect of CO on hepatic transporters in vivo has not been described. Yet, CO has been shown to be an important factor in maintaining the balance between liver sinusoidal perfusion and biliary transport [8], [9]. Furthermore, CO is recognized as a regulator of bile canalicular contractility [10]. Taken together, we believe that endogenous CO appears to play an important role in not only inflammation; but also, in the regulation of bile flow and liver integrity.
Therefore, the objective of this study was to first assess the kinetics of inhaled CO administration and then determine its potential use as a treatment for endotoxin-induced liver injury using a rat model.
Section snippets
Reagents
Bovine serum albumin (BSA), hemin, reduced nicotinamide adenine dinucleotide phosphate (NADPH), sulfosalicylic acid (SSA), ethylenediaminetetraacetic acid (EDTA), RNAlater, lipopolysaccharide from Escherichia coli 0111:B4 (LPS) were all purchased from Sigma–Aldrich (St. Louis, MO, USA). The CO (250 ppm) gas mixture and calibration gas (10 ppm) were purchased from Linde Gas (Prague, Czech Republic).
Animals and in vivo animal studies
Female Wistar rats (190–250 g), obtained from Anlab (Prague, Czech Republic), were allowed water
Kinetic profile of gaseous CO in vivo
COHb levels were 12.8 ± 1.9% of total hemoglobin (or 2116 ± 152 pmol CO/mg FW), a concentration considered to be safe in rats [15].
The kinetic profiles of inhaled CO were biphasic (fast and slow phases) in all the tissues. The rate of distribution to all the tissues occurred with no apparent delay. We noted non-zero Tmax values (n ≤ 2) for liver, spleen, and heart, while there were no non-zero Tmax samples in all the other tissues. CO levels in all selected tissues returned to control
Discussion
In this study, we first characterized in detail the kinetic profile of inhaled CO, and then we correlated these findings to observed changes in expressions of hepatic inflammatory and transporter genes. Initial studies investigating CO kinetics date back to the beginning of 20th century when CO was considered only a waste and toxic product from industrial processes. More than 20 years ago, the beneficial effects of CO were identified and since, CO has been intensively studied for its biological
Conflict of interest statement
The authors declare that there are no conflicts of interest.
Author contribution
KV, LM and LV designed the study, KV, JS, TP, DC performed the experiments, HJV, RJW contributed GC-RGD for the study, KV, OS, HJV, RJW, LV, LM analyzed the data and wrote the paper. All authors approved the final article.
Acknowledgments
The work was supported by grants GAUK 251202, IGA MZ NT 11327-4/2010, and RVO-VFN64165/2013 given by the Grant Agency of the Charles University and Czech Ministry of Health, respectively, as well as by the SCIENTIA Foundation. The authors thank Marie Zadinova, Magdalena Kadlecova, Olina Svejdova and Jana Vanikova for excellent technical assistance during animal experiments.
References (29)
- et al.
Effects of proinflammatory cytokines on rat organic anion transporters during toxic liver injury and cholestasis
Hepatology
(2003) - et al.
Suppression of inflammatory cytokine production by carbon monoxide involves the JNK pathway and AP-1
J. Biol. Chem.
(2003) - et al.
Carbon monoxide as an endogenous modulator of hepatic vascular perfusion
Biochem. Biophys. Res. Commun.
(1994) - et al.
Heme oxygenase activity as measured by carbon monoxide production
Anal. Biochem.
(1988) - et al.
Determination of carbon monoxide (CO) in rodent tissue: effect of heme administration and environmental CO exposure
Anal. Biochem.
(2005) - et al.
PKSolver: an add-in program for pharmacokinetic and pharmacodynamic data analysis in Microsoft Excel
Comput. Methods Programs Biomed.
(2010) - et al.
Dose-effects functions for carboxyhemoglobin and behavior
Neurotoxicol. Teratol.
(1990) - et al.
Circulatory effects and kinetics following acute administration of carbon monoxide in a porcine model
Life Sci.
(2004) - et al.
Prediction of the rate of uptake of carbon monoxide from blood by extravascular tissues
Respir. Physiol. Neurobiol.
(2008) - et al.
The rat canalicular conjugate export pump (Mrp2) is down-regulated in intrahepatic and obstructive cholestasis
Gastroenterology
(1997)
Carbon monoxide suppresses arteriosclerotic lesions associated with chronic graft rejection and with balloon injury
Nat. Med.
Heat shock protein-70 mediates the cytoprotective effect of carbon monoxide: involvement of p38 beta MAPK and heat shock factor-1
J. Immunol.
Carbon monoxide and bilirubin: potential therapies for pulmonary/vascular injury and disease
Am. J. Respir. Cell Mol. Biol.
Inflammation-induced cholestasis
J. Gastroenterol. Hepatol.
Cited by (12)
Structure-Photoreactivity Relationship of 3-Hydroxyflavone-Based CO-Releasing Molecules
2022, Journal of Organic ChemistrySystemic vasoprotection by inhaled carbon monoxide is mediated through prolonged alterations in monocyte/macrophage function
2020, Nitric Oxide - Biology and ChemistryCitation Excerpt :Hgb in RBCs can serve as a circulating reservoir for CO for about 2–3 h after CO inhalation. Vanova et al. [28] showed that this may be even shorter at the tissue level. Despite the short half-life of CO in the blood and tissue, the anti-inflammatory effects persisted up to 12hrs in their cholestasis model.
Localized delivery of carbon monoxide
2017, European Journal of Pharmaceutics and BiopharmaceuticsBiological effects of carbon monoxide
2018, Klinicka Biochemie a MetabolismusBiological signaling by carbon monoxide and carbon monoxide-releasing molecules
2017, American Journal of Physiology - Cell Physiology