Protein phosphatase 4 controls circadian clock dynamics by modulating CLOCK/BMAL1 activity.

In all organisms with circadian clocks, post-translational modifications of clock proteins control the dynamics of circadian rhythms, with phosphorylation playing a dominant role. All major clock proteins are highly phosphorylated, and many kinases have been described to be responsible. In contrast, it is largely unclear whether and to what extent their counterparts, the phosphatases, play an equally crucial role.

Reciprocal regulation of carbon monoxide metabolism and the circadian clock.

Circadian clocks are cell-autonomous oscillators regulating daily rhythms in a wide range of physiological, metabolic and behavioral processes. Feedback of metabolic signals, such as redox state, NAD/NADH and AMP/ADP ratios, or heme, modulate circadian rhythms and thereby optimize energy utilization across the 24-h cycle. We show that rhythmic heme degradation, which generates the signaling molecule carbon monoxide (CO), is required for normal circadian rhythms as well as circadian metabolic outputs.

Heme oxygenase-1 suppresses a pro-inflammatory phenotype in monocytes and determines endothelial function and arterial hypertension in mice and humans.

Aims: Heme oxygenase-1 (HO-1) confers protection to the vasculature and suppresses inflammatory properties of monocytes and macrophages. It is unclear how HO-1 determines the extent of vascular dysfunction in mice and humans.

Methods And Results: Decreased HO-1 activity and expression was paralleled by increased aortic expression and activity of the nicotinamide dinucleotide phosphate oxidase Nox2 in HO-1 deficient Hmox1⁻/⁻ and Hmox1(⁺/⁻) compared with Hmox1⁺/⁺ mice.

Interaction of circadian clock proteins CRY1 and PER2 is modulated by zinc binding and disulfide bond formation.

Period (PER) proteins are essential components of the mammalian circadian clock. They form complexes with cryptochromes (CRY), which negatively regulate CLOCK/BMAL1-dependent transactivation of clock and clock-controlled genes. To define the roles of mammalian CRY/PER complexes in the circadian clock, we have determined the crystal structure of a complex comprising the photolyase homology region of mouse CRY1 (mCRY1) and a C-terminal mouse PER2 (mPER2) fragment.

Krüppel-like factor 9 is a circadian transcription factor in human epidermis that controls proliferation of keratinocytes.

Circadian clocks govern a wide range of cellular and physiological functions in various organisms. Recent evidence suggests distinct functions of local clocks in peripheral mammalian tissues such as immune responses and cell cycle control. However, studying circadian action in peripheral tissues has been limited so far to mouse models, leaving the implication for human systems widely elusive.

Ethanol changes gene expression of transcription factors and cytokine production of CD4+ T-cell subsets in PBMCs stimulated with LPS.

Background: Acute ethanol intoxication has the potential to alter immune reactivity by various pathways. The aim of this study was to investigate T-helper cell subsets transcription factors and cytokines in human peripheral blood mononuclear cells (PBMCs) following a single dose of lipopolysaccharide (LPS) with or without ethanol exposure.

Methods: Human PBMCs were cultured in the presence of 100 mM ethanol and/or 100 ng/ml LPS for various time periods (1, 3, 8, and 24 hours) and analyzed for the kinetics of gene expression by quantitative real-time PCR of selected transcription factors (T-bet, GATA3, Foxp3, and RORγt) and cytokines (TNF-α, IL-6, IL-10, and IFN-γ).

Amplifying the fluorescence of bilirubin enables the real-time detection of heme oxygenase activity.

Heme oxygenases (HO) are the rate-limiting enzymes in the degradation of heme to equimolar amounts of antioxidant bile pigments, the signaling molecule carbon monoxide, and ferric iron. The inducible form HO-1 confers protection on cells and tissues that mediates beneficial effects in many diseases. Consequently, measurement of the enzymatic activity is vital in the investigation of the regulatory role of HO.

Inhibition of dendritic cell maturation and function is independent of heme oxygenase 1 but requires the activation of STAT3.

The induction of heme oxygenase 1 (HO-1) by a single treatment with cobalt protoporphyrin (CoPPIX) protects against inflammatory liver failure and ischemia reperfusion injury after allotransplantation. In this context, the HO-1-mediated inhibition of donor-derived dendritic cell maturation and migration is discussed as one of the key events of graft protection. To investigate the poorly understood mechanism of CoPPIX-induced HO-1 activity in more detail, we performed gene expression analysis in murine liver, revealing the up-regulation of STAT3 after CoPPIX treatment.

Heme oxygenase-1 ameliorates ischemia/reperfusion injury by targeting dendritic cell maturation and migration.

Ischemia/reperfusion injury (IRI) has a major impact on short- and long-term renal allograft survival by increasing graft immunogenicity. Donor preconditioning by inducing heme oxygenase 1 (HO-1) has been proven to exert cytoprotective and antiinflammatory effects on the graft, thus resulting in reduced graft immunogenicity. The study analyzed the effects and mechanisms of HO-1-mediated cytoprotection in rat kidney transplants exposed to cold preservation.

Brain death activates donor organs and is associated with a worse I/R injury after liver transplantation.

The majority of transplants are derived from donors who suffered from brain injury. There is evidence that brain death causes inflammatory changes in the donor. To define the impact of brain death, we evaluated the gene expression of cytokines in human brain dead and ideal living donors and compared these data to organ function following transplantation.

Improved long-term graft survival after HO-1 induction in brain-dead donors.

Brain death (BD) of the donor, a risk factor uniquely relevant for organs derived from cadaver donors, influences organ quality by induction of various inflammatory events. Consequently ischemia/reperfusion injury is deteriorated and acute and chronic rejections accelerated. Donor treatment might be an approach to improve the quality of the graft.

Significant reduction of proinflammatory cytokines by treatment of the brain-dead donor.

Introduction: Experimental studies suggest that brain death in the donor has a significant impact on graft quality; however, there are no data correlating organ-specific cytokine expression and the corresponding serum protein levels in human organ donors. Furthermore, it is unknown whether donor treatment can reduce the up-regulation of proinflammatory cytokines and thereby optimize organ quality.

Methods: We investigated the expression pattern of cytokines comparing serum (n = 53) and tissue expression (n = 25) in brain-dead human donors.