ABSTRACT
PURPOSE: Castration-resistant prostate cancer (CRPC) is the most common cause of death in men. The effectiveness of HDAC inhibitors has been demonstrated by preclinical models, but not in clinical studies, probably due to the ineffectively accumulation of HDACI in prostate cancer cells. The purpose of this work was to evaluate effects of a novel HDACI (CN133) on CRPC xenograft model and 22Rv1 cells, and develops methods, PET/CT imaging, to detect the therapeutic effects of CN133 on this cancer. METHODS: We designed and performed study to compare the effects of CN133 with SAHA on the 22Rv1 xenograft model and 22Rv1 cells. Using PET/CT imaging with [11C] Martinostat and [18F] FDG, we imaged mice bearing 22Rv1 xenografts before and after 21-day treatment with placebo and CN133 (1 mg/kg), and uptake on pre-treatment and post-treatment imaging was measured. The anti-tumor mechanisms of CN133 were investigated by qPCR, western blot, and ChIP-qPCR. RESULTS: Our data showed that the CN133 treatment led to a 50% reduction of tumor volume compared to the placebo that was more efficacious than SAHA treatment in this preclinical model. [11C] Martinostat PET imaging could identify early lesions of prostate cancer and can also be used to monitor the therapeutic effect of CN133 in CRPC. Using pharmacological approaches, we demonstrated that effects of CN133 showed almost 100-fold efficacy than SAHA treatment in the experiment of cell proliferation, invasion, and migration. The anti-tumor mechanisms of CN133 were due to the inhibition of AR signaling pathway activity by decreased HDAC 2 and 3 protein expressions. CONCLUSION: Taken together, these studies provide not only a novel epigenetic approach for prostate cancer therapy but also offering a potential tool, [11C] Martinostat PET/CT imaging, to detect the early phase of prostate cancer and monitor therapeutic effect of CN133. These results will likely lead to human trials in the future.
Subject(s)
Histone Deacetylase Inhibitors , Prostatic Neoplasms, Castration-Resistant , Animals , Cell Line, Tumor , Cell Proliferation , Histone Deacetylase Inhibitors/therapeutic use , Humans , Male , Mice , Positron Emission Tomography Computed Tomography , Prostatic Neoplasms, Castration-Resistant/diagnostic imaging , Prostatic Neoplasms, Castration-Resistant/drug therapy , Xenograft Model Antitumor AssaysABSTRACT
Many nations responded to the corona virus disease-2019 (COVID-19) pandemic by restricting travel and other activities during 2020, resulting in temporarily reduced emissions of CO2, other greenhouse gases and ozone and aerosol precursors. We present the initial results from a coordinated Intercomparison, CovidMIP, of Earth system model simulations which assess the impact on climate of these emissions reductions. 12 models performed multiple initial-condition ensembles to produce over 300 simulations spanning both initial condition and model structural uncertainty. We find model consensus on reduced aerosol amounts (particularly over southern and eastern Asia) and associated increases in surface shortwave radiation levels. However, any impact on near-surface temperature or rainfall during 2020-2024 is extremely small and is not detectable in this initial analysis. Regional analyses on a finer scale, and closer attention to extremes (especially linked to changes in atmospheric composition and air quality) are required to test the impact of COVID-19-related emission reductions on near-term climate.
ABSTRACT
The pandemic in 2020 caused an abrupt change in the emission of anthropogenic aerosols and their precursors. We estimate the associated change in the aerosol radiative forcing at the top of the atmosphere and the surface. To that end, we perform new simulations with the CMIP6 global climate model EC-Earth3. The simulations use the here newly created data for the anthropogenic aerosol optical properties and an associated effect on clouds from the simple plumes parameterization (MACv2-SP), based on revised SO2 and NH3 emission scenarios. Our results highlight the small impact of the pandemic on the global aerosol radiative forcing in 2020 compared to the CMIP6 scenario SSP2-4.5 of the order of +0.04 Wm-2, which is small compared to the natural year-to-year variability in the radiation budget. Natural variability also limits the ability to detect a meaningful regional difference in the anthropogenic aerosol radiative effects. We identify the best chances to find a significant change in radiation at the surface during cloud-free conditions for regions that were strongly polluted in the past years. The post-pandemic recovery scenarios indicate a spread in the aerosol forcing of -0.68 to -0.38 Wm-2 for 2050 relative to the pre-industrial, which translates to a difference of +0.05 to -0.25 Wm-2 compared to the 2050 baseline from SSP2-4.5. This spread falls within the present-day uncertainty in aerosol radiative forcing and the CMIP6 spread in aerosol forcing at the end of the 21st century. We release the new MACv2-SP data for studies on the climate response to the pandemic and the recovery scenarios. Our 2050 forcing estimates suggest that sustained aerosol emission reductions during the post-pandemic recovery cause a stronger climate response than in 2020, i.e., there is a delayed influence of the pandemic on climate.
ABSTRACT
The orexin receptor (OX) is critically involved in motivation and sleep-wake regulation and holds promising therapeutic potential in various mood disorders. To further investigate the role of orexin receptors (OXRs) in the living human brain and to evaluate the treatment potential of orexin-targeting therapeutics, we herein report a novel PET probe ([11C]CW24) for OXRs in the brain. CW24 has moderate binding affinity for OXRs (IC50 = 0.253 µM and 1.406 µM for OX1R and OX2R, respectively) and shows good selectivity to OXRs over 40 other central nervous system (CNS) targets. [11C]CW24 has high brain uptake in rodents and nonhuman primates, suitable metabolic stability, and appropriate distribution and pharmacokinetics for brain positron emission tomography (PET) imaging. [11C]CW24 warrants further evaluation as a PET imaging probe of OXRs in the brain.
Subject(s)
Brain/diagnostic imaging , Neuroimaging , Orexin Receptors/isolation & purification , Positron-Emission Tomography , Brain/physiology , Humans , Orexin Receptors/genetics , Sleep/genetics , Sleep/physiologyABSTRACT
Propolis samples from north-west Argentina (Amaicha del Valle, Tucumán) were evaluated by palynology, FT-IR spectra, and RP-HPTLC. In addition, the volatile fraction was studied by HS-SPME-GC/MS. The botanical species most visited by Apis mellifera L. near the apiaries were collected and their RP-HPTLC extracts profiles were compared with propolis samples. In addition, GC/MS was performed for volatile compounds from Zuccagnia punctata Cav. (Fabaceae). FT-IR spectra and RP-HPTLC fingerprints of propolis samples showed similar profiles. In RP-HPTLC analyses, only Z. punctata presented a similar fingerprint to Amaicha propolis. The major volatile compounds present in both were trans-linalool oxide (furanoid), 6-camphenone, linalool, trans-pinocarveol, p-cymen-8-ol, and 2,3,6-trimethylbenzaldehyde. Potential variations for the Amaicha del Valle propolis volatile fraction as consequence of propolis sample preparation were demonstrated.
Subject(s)
Phytochemicals/chemistry , Propolis/chemistry , Argentina , Chromatography, High Pressure Liquid , Fabaceae/chemistry , Fabaceae/metabolism , Gas Chromatography-Mass Spectrometry , Microscopy , Oils, Volatile/chemistry , Phytochemicals/isolation & purification , Plant Leaves/chemistry , Plant Leaves/metabolism , Principal Component Analysis , Propolis/isolation & purification , Solid Phase Microextraction , Spectroscopy, Fourier Transform Infrared , Volatile Organic Compounds/chemistry , Volatile Organic Compounds/isolation & purificationABSTRACT
Readily exchangeable water molecules are commonly found in the active sites of oxidoreductases, yet the overwhelming majority of studies on small-molecule mimics of these enzymes entirely ignores the contribution of water to the reactivity. Studies of how these enzymes can continue to function in spite of the presence of highly oxidizing species are likewise limited. The mononuclear MnII complex with the potentially hexadentate ligand N-(2-hydroxy-5-methylbenzyl)-N,N',N'-tris(2-pyridinylmethyl)-1,2-ethanediamine (LOH) was previously found to act as both a H2O2-responsive MRI contrast agent and a mimic of superoxide dismutase (SOD). Here, we studied this complex in aqueous solutions at different pH values in order to determine its (i) acid-base equilibria, (ii) coordination equilibria, (iii) substitution lability and operative mechanisms for water exchange, (iv) redox behavior and ability to participate in proton-coupled electron transfer (PCET) reactions, (v) SOD activity and reductive activity toward both oxygen and superoxide, and (vi) mechanism for its transformation into the binuclear MnII complex with (H)OL-LOH and its hydroxylated derivatives. The conclusions drawn from potentiometric titrations, low-temperature mass spectrometry, temperature- and pressure-dependent 17O NMR spectroscopy, electrochemistry, stopped-flow kinetic analyses, and EPR measurements were supported by the structural characterization and quantum chemical analysis of proposed intermediate species. These comprehensive studies enabled us to determine how transiently bound water molecules impact the rate and mechanism of SOD catalysis. Metal-bound water molecules facilitate the PCET necessary for outer-sphere SOD activity. The absence of the water ligand, conversely, enables the inner-sphere reduction of both superoxide and dioxygen. The LOH complex maintains its SOD activity in the presence of â¢OH and MnIV-oxo species by channeling these oxidants toward the synthesis of a functionally equivalent binuclear MnII species.
ABSTRACT
Alcohol use disorder (AUD) is a disorder of clinical and public health significance requiring novel and improved therapeutic solutions. Both environmental and genetic factors play a significant role in its pathophysiology. However, the underlying epigenetic molecular mechanisms that link the gene-environment interaction in AUD remain largely unknown. In this proof-of-concept study, we showed, for the first time, the neuroepigenetic biomarker capability of non-invasive imaging of class I histone deacetylase (HDAC) epigenetic enzymes in the in vivo brain for classifying AUD patients from healthy controls using a machine learning approach in the context of precision diagnosis. Eleven AUD patients and 16 age- and sex-matched healthy controls completed a simultaneous positron emission tomography-magnetic resonance (PET/MR) scan with the HDAC-binding radiotracer [11C]Martinostat. Our results showed lower HDAC expression in the anterior cingulate region in AUD. Furthermore, by applying a genetic algorithm feature selection, we identified five particular brain regions whose combined [11C]Martinostat relative standard uptake value (SUVR) features could reliably classify AUD vs. controls. We validate their promising classification reliability using a support vector machine classifier. These findings inform the potential of in vivo HDAC imaging biomarkers coupled with machine learning tools in the objective diagnosis and molecular translation of AUD that could complement the current diagnostic and statistical manual of mental disorders (DSM)-based intervention to propel precision medicine forward.
ABSTRACT
A trio of Pt-based heterobimetallic lantern complexes of the form [(py)PtM(SAc)4(py)] (M = Co, 1; Ni, 2; Zn, 3) with unusual octahedral coordination of Pt(II) was prepared from a reaction of [PtM(SAc)4] with excess pyridine. These dipyridine lantern complexes could be converted to monopyridine derivatives with gentle heat to give the series [PtM(SAc)4(py)] (M = Co, 4; Ni, 5; Zn, 6). An additional family of the form [PtM(SAc)4(pyNH2)] (M = Co, 7; Ni, 8; Zn, 9) was synthesized from reaction of [PtM(SAc)4(OH2)] or [PtM(SAc)4] with 4-aminopyridine. Dimethylsulfoxide and N,N-dimethylformamide were also determined to react with [PtM(SAc)4] (M = Co, Ni), respectively, to give [PtCo(SAc)4(DMSO)](DMSO), 10, and [PtNi(SAc)4(DMF)](DMF), 11. Structural and magnetic data for these compounds and those for two other previously published families, [PtM(tba)4(OH2)] and [PtM(SAc)4(L)], L = OH2, pyNO2, are used to divide the structures among three distinct categories based on Pt···Pt and Pt···S distances. In general, the weaker donors H2O and pyNO2 seem to favor metallophilicity and antiferromagnetic coupling between 3d metal centers. When Pt···S interactions are favored over Pt···Pt ones, no coupling is observed and the pKa of the pyridine donor correlates with the interlantern S···S distance. UV-vis-NIR electronic and (1)H NMR spectra provide complementary characterization as well.
ABSTRACT
A series of Pt-based heterobimetallic lantern complexes of the form [PtM(SAc)4(OH2)] (M = Co, 1; Ni, 2; Zn, 3) were prepared using a facile, single-step procedure. These hydrated species were reacted with 3-nitropyridine (3-NO2py) to prepare three additional lantern complexes, [PtM(SAc)4(3-NO2py)] (M = Co, 4; Ni, 5; Zn, 6), or alternatively dried in vacuo to the dehydrated species [PtM(SAc)4] (M = Co, 7; Ni, 8; Zn, 9). The Co- and Ni-containing species exhibit Pt-M bonding in solution and the solid state. In the structurally characterized compounds 1-6, the lantern units form dimers in the solid state via a short Pt···Pt metallophilic interaction. Antiferromagnetic coupling between 3d metal ions in the solid state through noncovalent metallophilic interactions was observed for all the paramagnetic lantern complexes prepared, with J-coupling values of -12.7 cm(-1) (1), -50.8 cm(-1) (2), -6.0 cm(-1) (4), and -12.6 cm(-1) (5). The Zn complexes 3 and 6 also form solid-state dimers, indicating that the formation of short Pt···Pt interactions in these complexes is not predicated on the presence of a paramagnetic 3d metal ion. These contacts and the resultant antiferromagnetic coupling are also not unique to heterobimetallic lantern complexes with axially coordinated H2O or the previously reported thiobenzoate supporting ligand.
ABSTRACT
This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgression level has increased for all boundaries earlier identified as overstepped. As primary production drives Earth system biosphere functions, human appropriation of net primary production is proposed as a control variable for functional biosphere integrity. This boundary is also transgressed. Earth system modeling of different levels of the transgression of the climate and land system change boundaries illustrates that these anthropogenic impacts on Earth system must be considered in a systemic context.
ABSTRACT
The chromosome 16p13.11 heterozygous deletion is associated with a diverse array of neuropsychiatric disorders including intellectual disabilities, autism, schizophrenia, epilepsy and attention-deficit hyperactivity disorder. However the clinical significance of its reciprocal duplication is not clearly defined yet. We evaluated 1645 consecutive pediatric patients with various developmental disorders by high-resolution microarray-based comparative genomic hybridization and identified four deletions and eight duplications within the 16p13.11 region, representing â¼0.73% (12/1645) of the patients analyzed. Recurrent clinical features in these patients include mental retardation/intellectual disability, autism, seizure, dysmorphic feature or multiple congenital anomalies. Our data expand the spectrum of the clinical findings in patients with these genomic abnormalities and provide further support for the pathogenic involvement of this duplication in patients who carry them.
Subject(s)
Abnormalities, Multiple/genetics , Autistic Disorder/genetics , Chromosomes, Human, Pair 16/genetics , Developmental Disabilities/genetics , Gene Duplication , Seizures/genetics , Comparative Genomic Hybridization , Humans , Risk Factors , Sequence DeletionABSTRACT
In this paper, we report the design, synthesis, and biological evaluation of the first selective bromodomain and extra-terminal domain (BET) BD1 bromodomains of the PET radiotracer [18F]PB006. The standard compound PB006 showed high affinity and good selectivity toward BRD4 BD1 (K d = 100 nM and 29-fold selectively for BD1 over BD2) in an in vitro binding assay. PET imaging experiments in rodents were performed to evaluate the bioactivity of [18F]PB006 in vivo. A biodistribution study of [18F]PB006 in mice revealed high radiotracer uptake in peripheral tissues, such as liver and kidney, and moderate radiotracer uptake in the brain. Further blocking studies demonstrated the significant radioactivity decreasing (20-30% reduction compared with baseline) by pretreating unlabeled PB006 and JQ1, suggesting the high binding selectivity and specificity of [18F]PB006. Our study indicated that [18F]PB006 is a potent PET probe selectively targeting BET BD1, and further structural optimization of the radiotracer is still required to improve brain uptake to support neuroepigenetic imaging.
ABSTRACT
MicroRNAs (miRNAs) play important roles in many developmental processes, including cell differentiation and apoptosis. Transition of proliferative ovarian granulosa cells to terminally differentiated luteal cells in response to the ovulatory surge of luteinizing hormone (LH) involves rapid and pronounced changes in cellular morphology and function. MicroRNA 21 (miR-21, official symbol Mir21) is one of three highly LH-induced miRNAs in murine granulosa cells, and here we examine the function and temporal expression of Mir21 within granulosa cells as they transition to luteal cells. Granulosa cells were transfected with blocking (2'-O-methyl) and locked nucleic acid (LNA-21) oligonucleotides, and mature Mir21 expression decreased to one ninth and one twenty-seventh of its basal expression, respectively. LNA-21 depletion of Mir21 activity in cultured granulosa cells induced apoptosis. In vivo, follicular granulosa cells exhibit a decrease in cleaved caspase 3, a hallmark of apoptosis, 6 h after the LH/human chorionic gonadotropin surge, coincident with the highest expression of mature Mir21. To examine whether Mir21 is involved in regulation of apoptosis in vivo, mice were treated with a phospho thioate-modified LNA-21 oligonucleotide, and granulosa cell apoptosis was examined. Apoptosis increased in LNA-21-treated ovaries, and ovulation rate decreased in LNA-21-treated ovaries, compared with their contralateral controls. We have examined a number of Mir21 apoptotic target transcripts identified in other systems; currently, none of these appear to play a role in the induction of ovarian granulosa cell apoptosis. This study is the first to implicate the antiapoptotic Mir21 (an oncogenic miRNA) as playing a clear physiologic role in normal tissue function.
Subject(s)
Apoptosis/genetics , Granulosa Cells/physiology , MicroRNAs/physiology , Animals , Caspase 3/analysis , Caspase 3/metabolism , Cells, Cultured , Chorionic Gonadotropin/pharmacology , Female , Follicle Stimulating Hormone/pharmacology , Gene Expression Regulation/drug effects , Gonadotropins, Equine/pharmacology , Granulosa Cells/drug effects , Luteinizing Hormone/pharmacology , Mice , MicroRNAs/antagonists & inhibitors , MicroRNAs/genetics , Oligonucleotides/genetics , Oligonucleotides/pharmacology , Ovulation/drug effects , Ovulation/physiology , Reverse Transcriptase Polymerase Chain Reaction , TransfectionABSTRACT
After prolonged heating in acetonitrile, a highly asymmetric, trinuclear manganous complex self-assembles from MnCl(2) and bis(2-pyridylmethyl)-1,2-ethanediamine (bispicen). The central Mn(II) ion is bridged to the terminal metal ions in the molecule by single chloride anions. The organic ligands each bind to a single Mn(II) ion. The central Mn(II) and only one of the terminal Mn(II) ions are six-coordinate and bound to bispicen ligands. The remaining terminal Mn(II) ion is coordinated by a tetrahedral array of chloride anions, endowing the trinuclear cluster with a high degree of asymmetry. Variable temperature magnetic measurements are consistent with an S = 5/2 system, indicating net antiferromagnetic coupling.
ABSTRACT
Bromodomain and extra-terminal domain (BET) family proteins have become a hot research area because of their close relationship with a variety of human diseases. The non-invasive imaging technique, such as positron emission tomography (PET), provides a powerful tool to visualize and quantify the BET family proteins that accelerating the investigation of this domain. Herein, we describe the development of a promising PET probe, [ 11 C]1, specifically targeting BET family proteins based on the potent BET inhibitor CF53. [ 11 C]1 was successfully radio-synthesized with good yield and high purity after the optimization of radiolabeling conditions. The in vivo bio-activities evaluation of [ 11 C]1 was performed using PET imaging in rodents. The results demonstrated that [ 11 C]1 has favorable uptake in peripheral organs and moderate uptake in the brain. Further blocking studies indicated the high binding specificity and selectivity for BET proteins of this probe. Our findings suggest that [ 11 C]1 is a promising BET PET probe for BET proteins as well as epigenetic imaging.
ABSTRACT
INTRODUCTION: Bromodomain and extra-terminal domain (BET) family proteins play a vital role in the epigenetic regulation process by interacting with acetylated lysine (Ac-K) residues in histones. BET inhibitors have become promising candidates to treat various diseases through the inhibition of the interaction between BET bromodomains and Ac-K of histone tails. With a molecular imaging probe, noninvasive imaging such as positron emission tomography (PET) can visualize the distribution and roles of BET family proteins in vivo and enlighten our understanding of BET protein function in both healthy and diseased tissue. METHODS: We radiolabeled the potent BET inhibitor INCB054329 by N-methylation to make [11C]PB003 as a BET PET radiotracer. The bioactivity evaluation of unlabeled PB003 in vitro was performed to confirm its binding affinity for BRDs, then the PET/CT imaging in rodents was performed to evaluate the bioactivity of [11C]PB003 in vivo. RESULTS: In our in vitro evaluation, PB003 showed a high BET binding affinity for BRDs (Kd = 2 nM, 1.2 nM, and 1.2 nM for BRD2, BRD3, and BRD4, respectively). In vivo PET/CT imaging demonstrated that [11C]PB003 has favorable uptake with appropriate kinetics and distributions in main peripheral organs. Besides, the blockade of [11C]PB003 binding was found in our blocking study which indicated the specificity of [11C]PB003. However, the BBB penetration and brain uptake of [11C]PB003 was limited, with only a maximum 0.2% injected dose/g at ~2 min post-injection. CONCLUSION: The imaging results in rodents in vivo demonstrate that [11C]PB003 binds to BET with high selectivity and specificity and has favorable uptake in peripheral organs. However, the low brain uptake of [11C]PB003 limits the visualization of brain regions indicating the efforts are still needed to discover the new BET imaging probes for brain visualization.
Subject(s)
Nuclear Proteins/chemistry , Nuclear Proteins/metabolism , Positron-Emission Tomography/methods , Brain/diagnostic imaging , Brain/metabolism , Isotope Labeling , Kinetics , Methylation , Protein Domains , Radioactive Tracers , RadiochemistryABSTRACT
The pathogenesis of Alzheimer's disease (AD) is primarily driven by brain accumulation of the amyloid-ß-42 (Aß42) peptide generated from the amyloid-ß precursor protein (APP) via cleavages by ß- and γ-secretase. γ-Secretase is a prime drug target for AD; however, its brain regional expression and distribution remain largely unknown. Here, we are aimed at developing molecular imaging tools for visualizing γ-secretase. We used our recently developed γ-secretase modulators (GSMs) and synthesized our GSM-based imaging agent, [11C]SGSM-15606. We subsequently performed molecular imaging in rodents, including AD transgenic animals, and macaques, which revealed that our probe displayed good brain uptake and selectivity, stable metabolism, and appropriate kinetics and distribution for imaging γ-secretase in the brain. Interestingly, rodents and macaques shared certain brain areas with high γ-secretase expression, suggesting a functional conservation of γ-secretase. Collectively, we have provided the first molecular brain imaging of γ-secretase, which may not only accelerate our drug discovery for AD but also advance our understanding of AD.
Subject(s)
Alzheimer Disease/diagnostic imaging , Alzheimer Disease/enzymology , Amyloid Precursor Protein Secretases/metabolism , Molecular Imaging , Animals , Brain/diagnostic imaging , Brain/metabolism , Brain/pathology , Humans , Macaca mulatta , Magnetic Resonance Imaging , Male , Mice, Transgenic , Positron Emission Tomography Computed Tomography , Presenilin-1/metabolismABSTRACT
The sigma-1 receptor (σ 1R) is a unique intracellular protein. σ 1R plays a major role in various pathological conditions in the central nervous system (CNS), implicated in several neuropsychiatric disorders. Imaging of σ 1R in the brain using positron emission tomography (PET) could serve as a noninvasively tool for enhancing the understanding of the disease's pathophysiology. Moreover, σ 1R PET tracers can be used for target validation and quantification in diagnosis. Herein, we describe the radiosynthesis, in vivo PET/CT imaging of novel σ 1R 11C-labeled radioligands based on 6-hydroxypyridazinone, [11C]HCC0923 and [11C]HCC0929. Two radioligands have high affinities to σ 1R, with good selectivity. In mice PET/CT imaging, both radioligands showed appropriate kinetics and distributions. Additionally, the specific interactions of two radioligands were reduced by compounds 13 and 15 (self-blocking). Of the two, [11C]HCC0929 was further investigated in positive ligands blocking studies, using classic σ 1R agonist SA 4503 and σ 1R antagonist PD 144418. Both σ 1R ligands could extensively decreased the uptake of [11C]HCC0929 in mice brain. Besides, the biodistribution of major brain regions and organs of mice were determined in vivo. These studies demonstrated that two radioligands, especially [11C]HCC0929, possessed ideal imaging properties and might be valuable tools for non-invasive quantification of σ 1R in brain.
ABSTRACT
A new release of the Max Planck Institute for Meteorology Earth System Model version 1.2 (MPI-ESM1.2) is presented. The development focused on correcting errors in and improving the physical processes representation, as well as improving the computational performance, versatility, and overall user friendliness. In addition to new radiation and aerosol parameterizations of the atmosphere, several relatively large, but partly compensating, coding errors in the model's cloud, convection, and turbulence parameterizations were corrected. The representation of land processes was refined by introducing a multilayer soil hydrology scheme, extending the land biogeochemistry to include the nitrogen cycle, replacing the soil and litter decomposition model and improving the representation of wildfires. The ocean biogeochemistry now represents cyanobacteria prognostically in order to capture the response of nitrogen fixation to changing climate conditions and further includes improved detritus settling and numerous other refinements. As something new, in addition to limiting drift and minimizing certain biases, the instrumental record warming was explicitly taken into account during the tuning process. To this end, a very high climate sensitivity of around 7 K caused by low-level clouds in the tropics as found in an intermediate model version was addressed, as it was not deemed possible to match observed warming otherwise. As a result, the model has a climate sensitivity to a doubling of CO2 over preindustrial conditions of 2.77 K, maintaining the previously identified highly nonlinear global mean response to increasing CO2 forcing, which nonetheless can be represented by a simple two-layer model.