Lactate receptor HCAR1 regulates neurogenesis and microglia activation after neonatal hypoxia-ischemia

Neonatal cerebral hypoxia-ischemia (HI) is the leading cause of death and disability in newborns with the only current treatment being hypothermia. An increased understanding of the pathways that facilitate tissue repair after HI may aid the development of better treatments. Here, we study the role of lactate receptor HCAR1 in tissue repair after neonatal HI in mice. We show that HCAR1 knockout mice have reduced tissue regeneration compared with wildtype mice. Furthermore, proliferation of neural progenitor cells and glial cells, as well as microglial activation was impaired. Transcriptome analysis showed a strong transcriptional response to HI in the subventricular zone of wildtype mice involving about 7300 genes. In contrast, the HCAR1 knockout mice showed a modest response, involving about 750 genes. Notably, fundamental processes in tissue repair such as cell cycle and innate immunity were dysregulated in HCAR1 knockout. Our data suggest that HCAR1 is a key transcriptional regulator of pathways that promote tissue regeneration after HI.

ALKBH3 partner ASCC3 mediates P-body formation and selective clearance of MMS-induced 1-methyladenosine and 3-methylcytosine from mRNA

Background

Reversible enzymatic methylation of mammalian mRNA is widespread and serves crucial regulatory functions, but little is known to what degree chemical alkylators mediate overlapping modifications and whether cells distinguish aberrant from canonical methylations.

Methods

Here we use quantitative mass spectrometry to determine the fate of chemically induced methylbases in the mRNA of human cells. Concomitant alteration in the mRNA binding proteome was analyzed by SILAC mass spectrometry.

Results

MMS induced prominent direct mRNA methylations that were chemically identical to endogenous methylbases. Transient loss of 40S ribosomal proteins from isolated mRNA suggests that aberrant methylbases mediate arrested translational initiation and potentially also no-go decay of the affected mRNA. Four proteins (ASCC3, YTHDC2, TRIM25 and GEMIN5) displayed increased mRNA binding after MMS treatment. ASCC3 is a binding partner of the DNA/RNA demethylase ALKBH3 and was recently shown to promote disassembly of collided ribosomes as part of the ribosome quality control (RQC) trigger complex. We find that ASCC3-deficient cells display delayed removal of MMS-induced 1-methyladenosine (m¹A) and 3-methylcytosine (m³C) from mRNA and impaired formation of MMS-induced P-bodies.

Conclusions

Our findings conform to a model in which ASCC3-mediated disassembly of collided ribosomes allows demethylation of aberrant m¹A and m³C by ALKBH3. Our findings constitute first evidence of selective sanitation of aberrant mRNA methylbases over their endogenous counterparts and warrant further studies on RNA-mediated effects of chemical alkylators commonly used in the clinic.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-02948-6.

NEIL3-Dependent Regulation of Cardiac Fibroblast Proliferation Prevents Myocardial Rupture

Myocardial infarction (MI) triggers a reparative response involving fibroblast proliferation and differentiation driving extracellular matrix modulation necessary to form a stabilizing scar. Recently, it was shown that a genetic variant of the base excision repair enzyme NEIL3 was associated with increased risk of MI in humans. Here, we report elevated myocardial NEIL3 expression in heart failure patients and marked myocardial upregulation of Neil3 after MI in mice, especially in a fibroblast-enriched cell fraction. Neil3^-/- mice show increased mortality after MI caused by myocardial rupture. Genome-wide analysis of 5-methylcytosine (5mC) and 5-hydroxymethylcytosine (5hmC) reveals changes in the cardiac epigenome, including in genes related to the post-MI transcriptional response. Differentially methylated genes are enriched in pathways related to proliferation and myofibroblast differentiation. Accordingly, Neil3^-/- ruptured hearts show increased proliferation of fibroblasts and myofibroblasts. We propose that NEIL3-dependent modulation of DNA methylation regulates cardiac fibroblast proliferation and thereby affects extracellular matrix modulation after MI.

Exercise induces cerebral VEGF and angiogenesis via the lactate receptor HCAR1

Physical exercise can improve brain function and delay neurodegeneration; however, the initial signal from muscle to brain is unknown. Here we show that the lactate receptor (HCAR1) is highly enriched in pial fibroblast-like cells that line the vessels supplying blood to the brain, and in pericyte-like cells along intracerebral microvessels. Activation of HCAR1 enhances cerebral vascular endothelial growth factor A (VEGFA) and cerebral angiogenesis. High-intensity interval exercise (5 days weekly for 7 weeks), as well as L-lactate subcutaneous injection that leads to an increase in blood lactate levels similar to exercise, increases brain VEGFA protein and capillary density in wild-type mice, but not in knockout mice lacking HCAR1. In contrast, skeletal muscle shows no vascular HCAR1 expression and no HCAR1-dependent change in vascularization induced by exercise or lactate. Thus, we demonstrate that a substance released by exercising skeletal muscle induces supportive effects in brain through an identified receptor.

Abstract 2479: Nuclear promyelocytic leukemia bodies tether to early endosomes during mitosis

During mitosis, the nuclear envelope breaks down, leading to potential interactions between cytoplasmic and nuclear components. PML bodies are nuclear structures with tumor suppressor functions. However, the protein responsible for generating these bodies, the promyelocytic leukemia protein (PML), has been shown to support both nuclear and cytoplasmic activities. Here we demonstrate that PML bodies form stable interactions with the cytoplasmic transport vesicles early endosomes immediately following entry into mitosis. The two compartments remain stably associated throughout the mitotic phase and dissociate in the cytoplasm of newly divided daughter cells.  We also show that PML promotes ligand-induced endosome-mediated degradation of the epidermal growth factor receptor, and that a minor subset of PML bodies become anchored to the mitotic spindle during cell division. The study demonstrates a stable mitosis-specific interaction between a cytoplasmic and a nuclear compartment. The implications of these findings will be discussed in relation to PMLs role in tumor suppression and as a target for cancer therapy.

Citation Format: Vuk Palibrk, Emma Lång, Anna Lång, Alexander Rowe, Stig Ove Bøe. Nuclear promyelocytic leukemia bodies tether to early endosomes during mitosis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2479. doi:10.1158/1538-7445.AM2014-2479

Promyelocytic leukemia bodies tether to early endosomes during mitosis

During mitosis the nuclear envelope breaks down, leading to potential interactions between cytoplasmic and nuclear components. PML bodies are nuclear structures with tumor suppressor and antiviral functions. Early endosomes, on the other hand, are cytoplasmic vesicles involved in transport and growth factor signaling. Here we demonstrate that PML bodies form stable interactions with early endosomes immediately following entry into mitosis. The 2 compartments remain stably associated throughout mitosis and dissociate in the cytoplasm of newly divided daughter cells. We also show that a minor subset of PML bodies becomes anchored to the mitotic spindle poles during cell division. The study demonstrates a stable mitosis-specific interaction between a cytoplasmic and a nuclear compartment.

Mutational status and gene repertoire of IGHV-IGHD-IGHJ rearrangements in Serbian patients with chronic lymphocytic leukemia

The mutational status and configuration of immunoglobulin heavy variable (IGHV) gene rearrangements was analyzed in 85 Serbian patients with chronic lymphocytic leukemia (CLL). We found that 55.3% of cases belonged to mutated and 44.7% to unmutated CLL, progressive disease predominating in the unmutated subset. IGHV gene use resembled that obtained for Mediterranean countries, except for underrepresentation of the IGHV4 subgroup in our cohort.

BACKGROUND

Chronic lymphocytic leukemia (CLL) results from the clonal expansion of mature B lymphocytes and is characterized by extreme clinical heterogeneity. One of the most reliable prognostic markers in chronic lymphocytic leukemia (CLL) is the mutational status of immunoglobulin heavy variable (IGHV) genes, which defines 2 subsets, mutated CLL (M-CLL) and unmutated CLL (U-CLL), with different clinical courses. Biased IGHV gene use between M-CLL and U-CLL clones, as well as population differences in the IGHV gene repertoire have been reported.

PATIENTS AND METHODS

In this study, mutational status and configuration of IGHV-IGHD-IGHJ rearrangements in 85 Serbian patients were analyzed using reverse transcriptase-polymerase chain reaction (RT-PCR) and sequencing methodology.

RESULTS

We found that 55.3% of cases belonged to M-CLL and 44.7% belonged to U-CLL, with progressive disease predominating in the unmutated subset. Most frequently expressed was the IGHV3 subgroup (55.7%), followed by IGHV1 (27.3%), IGHV4 (12.5%), IGHV5 (2.3%), IGHV2 (1.1%), and IGHV6 (1.1%). The distribution of IGHD subgroups was as follows: IGHD3, 39.1%; IGHD2, 21.8%; IGHD6, 12.6%; IGHD1, 10.3%; IGHD4, 8%; IGHD5, 6.9%; and IGHD7, 1.1%. The most frequent IGHJ gene was IGHJ4 (48.9%), followed by IGHJ6 (28.4%), IGHJ3 (11.4%), and IGHJ5 (11.4%). In 15.3% of cases, heavy complementarity-determining region 3 (VH CDR3) amino acid sequences could be assigned to previously defined stereotyped clusters.

CONCLUSIONS

Our study showed a strong correlation between IGHV gene mutational status and clinical course of CLL. IGHV gene use was comparable to that obtained for Mediterranean countries, with the exception of the IGHV4 subgroup, which was underrepresented in our cohort.

Therapy-related myelodysplastic syndrome and acute myeloid leukemia in patients with chronic lymphocytic leukemia treated with fludarabine and cyclophosphamide

We retrospectively studied four cases of t-MDS/AML among 210 (1.9%) consecutive patients with CLL treated at a single center with fludarabine and cyclophosphamide (FC) either as the first- or second-line therapy. The median follow-up of the whole cohort of patients was 46months (range: 7-60). Two of these patients (2/130, 1.7%) had been treated with FC only, and two more (2/80, 2.3%) with CHOP and CHOP+FND, respectively, prior to FC. The median age was 61.5years (range: 49-71); three were male. They developed t-MDS/AML after a median latency period of 41months (range: 7-56) from the FC completion. Chromosomal aberrations with an adverse prognostic impact were present in the karyotype of all four patients, including abnormalities of chromosome 5 in three of them, and a rare chromosomal translocation in one patient. Median survival after t-MDS/AML diagnosis was 4months (range: 2-8). Although the agents administered prior to FC make it difficult to assess the risk of t-MDS/AML attributable to FC, this report might be a valuable addition to the literature.

FGF-R3 and OPG expression in patient with multiple myeloma following systemic sclerosis: case report and review of the literature

The presence of multiple myeloma (MM) in a patient with systemic sclerosis is a rare and unusual occurrence with unclear significance. We report the case of a 55-year-old woman with a 20-year history of systemic sclerosis, who subsequently presented with clinical stage IIIA IgG-λ MM. The systemic sclerosis was diagnosed and treated in 1988 with D: -penicillamine and methotrexate. Twenty years later, in December 2008, she presented with symptoms of Raynaud's phenomenon and intense facial pruritus. Immunoelectrophoresis confirmed the presence of a IgG-λ paraprotein (71.90 g/l) and Bence Jones proteinuria of the lambda light chains. Bone marrow histology revealed infiltrates of plasmocytes and lymphoplasmocytes which were on immunohistochemistry CD38+, FGF-R3+ and OPG+. An extensive X-ray skeletal survey did not show any osteolytic lesions or fractures. The patient was treated according to the CTD protocol (cyclophosphamide, thalidomide, and dexamethasone) which was effective against the myeloma as well as the systemic sclerosis and patient achieved complete remission.

Mycophenolate mophetil therapy for chronic immune thrombocytopenic purpura resistant to steroids, immunosuppressants, and/or splenectomy in adults

Treatment options are limited in patients with chronic immune thrombocytopenic purpura (ITP) which has been unresponsive to corticosteroids and/or splenectomy. Mycophenolate mophetil (MMF) is effective in many autoimmune disorders including severe and refractory ITP through its targeting of T-cell and B-cell lymphocytes. We report on the efficacy of MMF (1.5-2 g/day) in 16 adults with severe steroid-resistant ITP. MMF was administered for at least 12 weeks (median 37 weeks, range 14-64 weeks). Patients comprised of 10 females and six males, with median pre-treatment platelet counts of 8 × 10(9)/L, median age of 55 years, median ITP duration of 58 months and a median of four prior treatments (range 3-8); nine had been previously splenectomized. Eleven patients (69%) responded after 12 weeks of MMF: 6 (55%) achieving complete remission (CR) and five (45%) achieved partial remission (PR). MMF therapeutic responses were better in those patients who had had fewer prior treatments (p<0.05), and were independent of patient age, sex, disease duration, and splenectomy status (p>0.05). Five of the 11 responders (45%; 3CR/2PR) had sustained remissions; however, six responders (55%; 3CR/3PR) relapsed after median of 14 weeks (range 9-20). Three of the six relapsing patients responded to MMF reinstitution achieving stabile PRs; three were left untreated as none had further bleeding and their platelets remained at "safe" levels (median 30 × 10(9)/L). The MMF treatment was well tolerated; one heavily pretreated patient developed a bronchopneumonia and a second had an episode of diarrhea. MMF used as a second-line agent can produce a sustained response in severe ITP which has been unresponsive to steroid and/or splenectomy without major toxicity.