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MBio Jun 2024The purine nucleotides ATP and GTP are made from the common precursor inosine monophosphate (IMP). Maintaining the correct balance of these nucleotides for optimal cell...
UNLABELLED
The purine nucleotides ATP and GTP are made from the common precursor inosine monophosphate (IMP). Maintaining the correct balance of these nucleotides for optimal cell growth is controlled in part by the enzyme IMP dehydrogenase (IMPDH), which catalyzes the first dedicated step of GTP biosynthesis. The regulation of IMPDH mRNA and protein levels in the yeast grown in liquid culture has been studied in some detail, but regulation of IMPDH protein under conditions of cellular crowding on a solid substrate has not been examined. Here, we report real-time, live-cell analysis of the accumulation of the Imd2 isoform of IMPDH in yeast cells forming a monolayer colony in a microfluidic device over a 50-hour time course. We observe two distinct phases of increased Imd2 accumulation: a guanine-insensitive phase early in outgrowth and a guanine-sensitive phase later, when cells become crowded. We show that the IMPDH inhibitor mycophenolic acid enhances both phases of increase. Deletion of a transcription attenuator upstream of the mRNA start site that decreases Imd2 mRNA synthesis in the presence of high GTP increases the baseline level of Imd2 protein 10-fold and abolishes guanine-sensitive but not guanine-insensitive induction. Our results suggest that at least two mechanisms of yeast Imd2 regulation exist, the known GTP-dependent attenuation of RNA polymerase II elongation and a GTP concentration-independent pathway that may be controlled by cell growth state. Live-cell analysis of IMPDH protein levels in a growing yeast colony confirms a known mechanism of regulation and provides evidence for an additional mode of regulation.
IMPORTANCE
This study used live-cell microscopy to track changes in the level of a key enzyme in GTP nucleotide biosynthesis, inosine monophosphate dehydrogenase (IMPDH), during growth of a brewers yeast colony over 2 days in a microfluidic device. The results show that feedback regulation via transcription attenuation allows cells to adapt to nutrient limitation in the crowded environs of a yeast colony. They also identify a novel mode of regulation of IMPDH level that is not driven by guanine nucleotide availability.
PubMed: 38940616
DOI: 10.1128/mbio.01021-24 -
Chemistry (Weinheim An Der Bergstrasse,... Jun 2024In several biological processes, H2S is known to function as an endogenous gaseous agent. It is very necessary to monitor H2S and relevant physiological processes in...
In several biological processes, H2S is known to function as an endogenous gaseous agent. It is very necessary to monitor H2S and relevant physiological processes in vivo. Herein, a new type of fluorophore with a reliable leaving group allows for excited-state intramolecular transfer characteristics (ESIPT), inspired by mycophenolic acid. A morpholine ring was connected at the maleimide position to target the lysosome. Subsequently, the dinitrophenyl group known for a photoinduced electron transfer (PET) effect, was connected to allow for an effective "turn-on" probe Lyso-H2S. Lyso-H2S demonstrated strong selectivity towards H2S, large Stokes shift (111 nm), and an incredibly low detection limit (41.8 nM). The imaging of endogenous and exogenous H2S in living cells (A549 cell line) was successfully achieved because of the specificity and ultra-low toxicity (100 % cell viability at 50 µM concentration of Lyso-H2S.) Additionally, Lyso-H2S was also employed to visualize the activity of H2S in the gallbladder and intestine in a living zebrafish model. This is the first report of a fluorescent probe to track H2S sensing in specific organ systems to our knowledge.
PubMed: 38934891
DOI: 10.1002/chem.202401733 -
International Journal of Molecular... Jun 2024C3 glomerulopathy is a rare disease, characterized by an abnormal activation of the complement's alternative pathway that leads to the accumulation of the C3 component... (Review)
Review
C3 glomerulopathy is a rare disease, characterized by an abnormal activation of the complement's alternative pathway that leads to the accumulation of the C3 component in the kidney. The disease recurs in more than half of kidney transplant recipients, with a significant impact on graft survival. Recurrence of the primary disease represents the second cause of graft loss after organ rejection. In C3 glomerulopathy, there are several risk factors which can promote a recurrence during transplantation, such as delayed graft function, infection and monoclonal gammopathy. All these events can trigger the alternative complement pathway. In this review, we summarize the impact of C3 glomerulopathy on kidney grafts and present the latest treatment options. The most widely used treatments for the disease include corticosteroids and mycophenolate mofetil, which are already used chronically by kidney transplant recipients; thus, additional treatments for C3 glomerulopathy are required. Currently, several studies using anti-complement drugs (i.e., eculizumab, Ravalizumab, avacopan) for C3 glomerulopathy in kidney transplant patients are ongoing with encouraging results.
Topics: Humans; Kidney Transplantation; Complement C3; Graft Rejection; Glomerulonephritis; Mycophenolic Acid
PubMed: 38928213
DOI: 10.3390/ijms25126508 -
Clinical and Translational Science Jun 2024The recommended immunosuppressive treatment after kidney transplantation consists of tacrolimus, mycophenolate mofetil, and low-dose corticosteroids. Drug concentrations...
Immune responsiveness in stable kidney transplantation patients: Complete inhibition of T-cell proliferation but residual T-cell activity during maintenance immunosuppressive treatment.
The recommended immunosuppressive treatment after kidney transplantation consists of tacrolimus, mycophenolate mofetil, and low-dose corticosteroids. Drug concentrations are monitored using therapeutic drug monitoring (TDM), which does not necessarily correlate with pharmacodynamic activity. To find the balance between optimal efficacy and minimal toxicity, it might be more informative to monitor patients' immunological status rather than drug concentrations. We selected a panel of T-cell-based immune assays, which were used for immunomonitoring of 14 stable kidney transplantation patients. Whole blood was incubated with a T-cell stimulus, after which T-cell proliferation, T-cell activation marker expression and cytokine production were measured to study residual immune activity in vitro (before drug intake; drug added to the incubation) and ex vivo (after drug intake). T-cell proliferation was completely suppressed in all patients over the full day, while IL-2, IFN-γ, CD71, and CD154 showed fluctuations over the day with a strong inhibition (75%-25%) at 2 h post-dose. The level of inhibition was variable between patients and could not be related to pharmacokinetic parameters or the presence of regulatory or senescence immune cells. Moreover, the level of inhibition did not correlate with the in vitro tacrolimus drug effect as studied by incubating pre-dose blood samples with additional tacrolimus. Overall, IL-2, IFN-γ, CD71, and CD154 seem to be good markers to monitor residual immune activity of transplantation patients. To evaluate the correlation between these pharmacodynamic biomarkers and clinical outcome, prospective observational studies are needed.
Topics: Humans; Kidney Transplantation; Male; Immunosuppressive Agents; Middle Aged; Female; T-Lymphocytes; Cell Proliferation; Adult; Tacrolimus; Lymphocyte Activation; Drug Monitoring; Aged; Mycophenolic Acid; Interferon-gamma
PubMed: 38923308
DOI: 10.1111/cts.13860 -
Pharmacological Reports : PR Jun 2024
Correction: Liquid chromatography-tandem mass spectrometry method for mycophenolic acid and its glucuronide determination in saliva samples from children with nephrotic syndrome.
PubMed: 38916851
DOI: 10.1007/s43440-024-00617-1 -
Transplantation Direct Jul 2024The mammalian target of rapamycin inhibitor (mTORi) therapy after kidney transplantation is solely monitored pharmacokinetically, not necessarily reflecting...
BACKGROUND
The mammalian target of rapamycin inhibitor (mTORi) therapy after kidney transplantation is solely monitored pharmacokinetically, not necessarily reflecting PI3K-Akt-mTOR pathway blockade efficacy leading to potential under-or overimmunosuppression.
METHODS
In this cross-sectional study, phosphoflow cytometry was used to determine the efficacy of mTOR inhibition in peripheral T- and B-lymphocyte subsets by assessing p70S6 kinase (p70S6K) phosphorylation in renal transplant recipients upon treatment with a combination of either mTORi and calcineurin inhibitors (n = 18), or mTORi with mycophenolic acid (n = 9). Nine dialysis patients with end-stage renal disease and 17 healthy age-matched volunteers served as controls.
RESULTS
mTORi treatment reduced p70S6K phosphorylation in CD4, CD8 T, and CD19 B cells compared with healthy controls (HCs). Subpopulation analysis of CD4 T cells and CD19 B cells revealed a significant reduction of p70S6K phosphorylation in CD4CD45RACD25 Th cells ( < 0.05), CD24CD38 transitional B cells ( < 0.001), CD24CD38 memory B cells ( < 0.001), and CD24CD38-naive B cells ( < 0.05) upon mTORi treatment, whereas CD4CD45RACD25CD127 regulatory T cells and CD24CD38 plasmablasts were not affected. Compared with mTORi + mycophenolic acid therapy, mTORi + calcineurin inhibitor treatment exhibited an even stronger inhibition of p70S6K phosphorylation in CD4CD45RACD25 Th cells and CD8 T cells. However, trough levels of mTORi did not correlate with p70S6K phosphorylation.
CONCLUSIONS
mTORi selectively inhibited p70S6K phosphorylation in select lymphocyte subtypes. Assessing p70S6K phosphorylation by phosphoflow cytometry may serve as an approach to understand cell subset specific effects of mTORi providing detailed pharmacodynamic information for individualizing immunosuppression.
PubMed: 38911271
DOI: 10.1097/TXD.0000000000001666 -
Transplantation Proceedings Jun 2024Kidney transplant recipients are vulnerable to infections, especially cytomegalovirus (CMV) disease. It is recommended that clinicians plan their prophylaxis and...
BACKGROUND
Kidney transplant recipients are vulnerable to infections, especially cytomegalovirus (CMV) disease. It is recommended that clinicians plan their prophylaxis and therapeutic regimens based on viral load testing.
OBJECTIVE
CMV viral load monitoring testing provides useful information for identifying virologic response and possible antiviral resistance. Due to the paucity of medical literature on guiding viral therapy in cases of CMV tissue disease with nondetectable serum viral load, we intend to provide physicians with evidence on how to guide medical therapy in these cases.
CASE REPORT
A 49-year-old Hispanic male recipient of a kidney transplant from a cadaver donor presented to the emergency department with anorexia, asthenia, diarrhea, weight loss, and supraclavicular and mediastinal adenomegalies at 2 months post-transplantation. Both patients were serum IgG- and IgM-positive for CMV, which classified them as intermediate risk for developing CMV disease or tissue-invasive disease (donor-positive/recipient-positive [D+/R+]). The patient was induced with basiliximab and methylprednisolone and received maintenance therapy with tacrolimus, mycophenolic acid, and prednisone. Real-time polymerase chain reaction analyses were performed due to suspicion for BK virus, B19 parvovirus, Epstein-Barr virus, and CMV, with an undetectable viral load for all. A biopsy specimen taken from the gastrointestinal tract confirmed CMV infection, which was corroborated through immunocytochemistry.
CONCLUSIONS
Histopathologic testing is a possible option for patients with CMV tissue disease symptoms but no detectable serum viral load. Clinical observation is fundamental when viral monitoring is difficult.
PubMed: 38908954
DOI: 10.1016/j.transproceed.2024.05.005 -
Transplantation Jun 2024Insight into cellular immune responses to COVID-19 vaccinations is crucial for optimizing booster programs in kidney transplant recipients (KTRs).
BACKGROUND
Insight into cellular immune responses to COVID-19 vaccinations is crucial for optimizing booster programs in kidney transplant recipients (KTRs).
METHODS
In an immunologic substudy of a multicenter randomized controlled trial (NCT05030974) investigating different repeated vaccination strategies in KTR who showed poor serological responses after 2 or 3 doses of an messenger RNA (mRNA)-based vaccine, we compared SARS-CoV-2-specific interleukin-21 memory T-cell and B-cell responses by enzyme-linked immunosorbent spot (ELISpot) assays and serum IgG antibody levels. Patients were randomized to receive: a single dose of mRNA-1273 (100 μg, n = 25), a double dose of mRNA-1273 (2 × 100 μg, n = 25), or a single dose of adenovirus type 26 encoding the SARS-CoV-2 spike glycoprotein (Ad26.COV2.S) (n = 25). In parallel, we also examined responses in 50 KTR receiving 100 μg mRNA-1273, randomized to continue (n = 25) or discontinue (n = 25) mycophenolate mofetil/mycophenolic acid. As a reference, the data were compared with KTR who received 2 primary mRNA-1273 vaccinations.
RESULTS
Repeated vaccination increased the seroconversion rate from 21% to 66% in all patients, which was strongly associated with enhanced levels of SARS-CoV-2-specific interleukin-21 memory T cells (odd ratio, 3.84 [1.89-7.78]; P < 0.001) and B cells (odd ratio, 35.93 [6.94-186.04]; P < 0.001). There were no significant differences observed in these responses among various vaccination strategies. In contrast to KTR vaccinated with 2 primary vaccinations, the number of antigen-specific memory B cells demonstrated potential for classifying seroconversion after repeated vaccination (area under the curve, 0.64; 95% confidence interval, 0.37-0.90; P = 0.26 and area under the curve, 0.95; confidence interval, 0.87-0.97; P < 0.0001, respectively).
CONCLUSIONS
Our study emphasizes the importance of virus-specific memory T- and B-cell responses for comprehensive understanding of COVID-19 vaccine efficacy among KTR.
PubMed: 38902860
DOI: 10.1097/TP.0000000000005119 -
Kidney International Reports Jun 2024
The Conversion From Mycophenolic Acid to Mammalian Target of Rapamycin Inhibitor Reduces the Incidence of Cytomegalovirus Replication in Belatacept-Treated Kidney-Transplant Recipients.
PubMed: 38899171
DOI: 10.1016/j.ekir.2024.02.1433 -
International Journal of Molecular... May 2024IMP dehydrogenase (IMPDH) inhibition has emerged as a new target therapy for glioblastoma multiforme (GBM), which remains one of the most refractory tumors to date. TCGA...
IMP dehydrogenase (IMPDH) inhibition has emerged as a new target therapy for glioblastoma multiforme (GBM), which remains one of the most refractory tumors to date. TCGA analyses revealed distinct expression profiles of IMPDH isoenzymes in various subtypes of GBM and low-grade glioma (LGG). To dissect the mechanism(s) underlying the anti-tumor effect of IMPDH inhibition in adult GBM, we investigated how mycophenolic acid (MPA, an IMPDH inhibitor) treatment affected key oncogenic drivers in glioblastoma cells. Our results showed that MPA decreased the expression of telomerase reverse transcriptase (TERT) in both U87 and U251 cells, and the expression of O-methylguanine-DNA methyltransferase (MGMT) in U251 cells. In support, MPA treatment reduced the amount of telomere repeats in U87 and U251 cells. TERT downregulation by MPA was associated with a significant decrease in c-Myc (a TERT transcription activator) in U87 but not U251 cells, and a dose-dependent increase in p53 and CCCTC-binding factor (CTCF) (TERT repressors) in both U87 and U251 cells. In U251 cells, MPA displayed strong cytotoxic synergy with BCNU and moderate synergy with irinotecan, oxaliplatin, paclitaxel, or temozolomide (TMZ). In U87 cells, MPA displayed strong cytotoxic synergy with all except TMZ, acting primarily through the apoptotic pathway. Our work expands the mechanistic potential of IMPDH inhibition to TERT/telomere regulation and reveals a synthetic lethality between MPA and anti-GBM drugs.
Topics: Humans; Telomerase; Glioblastoma; Cell Line, Tumor; IMP Dehydrogenase; Drug Synergism; Gene Expression Regulation, Neoplastic; Antineoplastic Agents; Brain Neoplasms; Apoptosis
PubMed: 38892179
DOI: 10.3390/ijms25115992