Organization and evolution of the class I gene family in the major histocompatibility complex of the C57BL/10 mouse

The major histocompatibility complex (MHC) encodes several classes of protein vital to the regulation of the immune response. We have isolated 26 class I genes that map to this region in the C57BL/10 mouse and linked these into three gene clusters. The number of genes differs from the number found in the BALB/c strain and comparison of the organization of the class I genes in these two strains shows conserved regions and polymorphic regions which probably result from deletions, insertions and translocations within the MHC.

The DNA sequence of the H-2kb gene: evidence for gene conversion as a mechanism for the generation of polymorphism in histocompatibilty antigens

We have determined the DNA sequence of the H-2Kb gene of the C57B1/10 mouse. Comparison of this sequence with that of the allelic H-2Kd shows surprisingly that the exons have accumulated more mutations than their introns. Moreover, many of these changes in the exons are clustered in short regions or hot spots. Additional comparison of these sequences with the H-2Ld and H-2Db sequences shows that, in several cases, the altered sequence generated at the hot spot is identical to the corresponding region of a non-allelic H-2 gene. The clustered changes are responsible for 60% of the amino acid differences between the H-2Kb and H-2Kd genes and suggest that micro-gene conversion events occurring within the exons and involving only tens of nucleotides are an important mechanism for the generation of polymorphic differences between natural H-2 alleles.

Use of menopausal estrogens and medroxyprogesterone in the United States, 1982-1992

OBJECTIVE

To describe trends in the prescription of menopausal estrogens and medroxyprogesterone in the United States.

METHODS

Annual estimates of the number of prescriptions for menopausal estrogens and medroxyprogesterone and descriptive information on patients and providers were obtained from two pharmaceutical marketing research data bases, the National Prescription Audit and the National Disease and Therapeutic Index of IMS America.

RESULTS

An estimated 13.6 million prescriptions were dispensed for oral menopausal estrogens in 1982, and 31.7 million in 1992, a 2.3-fold increase (P = .0001). In 1992, Premarin, the only oral conjugated estrogen currently approved for use, was the most frequently dispensed brand-name pharmaceutical in the United States. Dispensed prescriptions for Estraderm, a transdermal estradiol first marketed in 1986, increased from 1.5 million in 1987 to 4.7 million in 1992. Dispensed prescriptions for oral medroxyprogesterone also increased from 2.3 million prescriptions in 1982 to 11.3 million in 1992, a 4.9-fold increase (P = .0001). An estimated one in six to one in four postmenopausal women were taking menopausal hormones in 1992. These drugs were prescribed mainly by obstetrician-gynecologists.

CONCLUSION

The use of menopausal estrogens and medroxyprogesterone has increased substantially over the past decade. These trends indicate that American women are widely exposed to menopausal hormone replacement.

Accumulation of individual pA+ RNAs during oogenesis of Xenopus laevis

RNA metabolism during amphibian oogenesis has been investigated by the analysis of individual cDNA cloned sequences. Two cDNA clone libraries were constructed from the pA+ RNA of Xenopus ovary and of tadpole. The accumulation of RNAs complementary to individual clones was examined during oogenesis by isolating RNA from oocytes of different stages. There are only two patterns of accumulation during oogenesis. Mitochondrial mRNA sequences accumulate throughout all the stages of oogenesis, whereas all other sequences detected cease accumulation early in oogenesis and remain at a constant steady state level for the remainder of oocyte development. In the earliest stages examined, the individual RNAs are already present at approximately 1/4 their final level, and the subsequent increase of all sequences appears to be coordinant. These basic observations were confirmed by colony screening approximately 500 clones. The pattern of RNA accumulation observed is significant, because it had been determined that the total steady state pA+ RNA levels in the oocyte also ceased to increase at the same stage in oogenesis in which each individual sequenced reached a plateau level. In addition, lampbrush chromosomes, which have traditionally been thought to be the site of oocyte pA+ RNA synthesis, are maximally active after the stage in which all pA+ RNAs seem to have reached their final level of accumulation.

Expression of murine H-2Kb histocompatibility antigen in cells transformed with cloned H-2 genes

Cosmids containing H-2 histocompatibility antigen genes of the H-2b haplotype have been isolated. One of these genes expresses a 45,000 molecular weight protein, indistinguishable from H-2Kb when introduced into mouse L cells. These H-2Kb transformed L cells can be killed by allospecific anti-H-2Kb cytotoxic T cells. Moreover, when infected with influenza virus, they can be killed by an H-2Kb-restricted, influenza virus-specific cytotoxic T cell line. These results show that expression of the H-2Kb gene product on the L-cell surface is sufficient to make it a target for specific T-cell killing.

APOE modulates microglial immunometabolism in response to age, amyloid pathology, and inflammatory challenge

The E4 allele of Apolipoprotein E (APOE) is associated with both metabolic dysfunction and a heightened pro-inflammatory response: two findings that may be intrinsically linked through the concept of immunometabolism. Here, we combined bulk, single-cell, and spatial transcriptomics with cell-specific and spatially resolved metabolic analyses in mice expressing human APOE to systematically address the role of APOE across age, neuroinflammation, and AD pathology. RNA sequencing (RNA-seq) highlighted immunometabolic changes across the APOE4 glial transcriptome, specifically in subsets of metabolically distinct microglia enriched in the E4 brain during aging or following an inflammatory challenge. E4 microglia display increased Hif1α expression and a disrupted tricarboxylic acid (TCA) cycle and are inherently pro-glycolytic, while spatial transcriptomics and mass spectrometry imaging highlight an E4-specific response to amyloid that is characterized by widespread alterations in lipid metabolism. Taken together, our findings emphasize a central role for APOE in regulating microglial immunometabolism and provide valuable, interactive resources for discovery and validation research.

APOΕ4 lowers energy expenditure in females and impairs glucose oxidation by increasing flux through aerobic glycolysis

Background

Cerebral glucose hypometabolism is consistently observed in individuals with Alzheimer’s disease (AD), as well as in young cognitively normal carriers of the Ε4 allele of Apolipoprotein E (APOE), the strongest genetic predictor of late-onset AD. While this clinical feature has been described for over two decades, the mechanism underlying these changes in cerebral glucose metabolism remains a critical knowledge gap in the field.

Methods

Here, we undertook a multi-omic approach by combining single-cell RNA sequencing (scRNAseq) and stable isotope resolved metabolomics (SIRM) to define a metabolic rewiring across astrocytes, brain tissue, mice, and human subjects expressing APOE4.

Results

Single-cell analysis of brain tissue from mice expressing human APOE revealed E4-associated decreases in genes related to oxidative phosphorylation, particularly in astrocytes. This shift was confirmed on a metabolic level with isotopic tracing of ¹³C-glucose in E4 mice and astrocytes, which showed decreased pyruvate entry into the TCA cycle and increased lactate synthesis. Metabolic phenotyping of E4 astrocytes showed elevated glycolytic activity, decreased oxygen consumption, blunted oxidative flexibility, and a lower rate of glucose oxidation in the presence of lactate. Together, these cellular findings suggest an E4-associated increase in aerobic glycolysis (i.e. the Warburg effect). To test whether this phenomenon translated to APOE4 humans, we analyzed the plasma metabolome of young and middle-aged human participants with and without the Ε4 allele, and used indirect calorimetry to measure whole body oxygen consumption and energy expenditure. In line with data from E4-expressing female mice, a subgroup analysis revealed that young female E4 carriers showed a striking decrease in energy expenditure compared to non-carriers. This decrease in energy expenditure was primarily driven by a lower rate of oxygen consumption, and was exaggerated following a dietary glucose challenge. Further, the stunted oxygen consumption was accompanied by markedly increased lactate in the plasma of E4 carriers, and a pathway analysis of the plasma metabolome suggested an increase in aerobic glycolysis.

Conclusions

Together, these results suggest astrocyte, brain and system-level metabolic reprogramming in the presence of APOE4, a ‘Warburg like’ endophenotype that is observable in young females decades prior to clinically manifest AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13024-021-00483-y.

Effect of cimetidine on the pharmacokinetics and pharmacodynamics of quinidine

The influence of cimetidine (1.2 g/day for 7 days) on the disposition and pharmacodynamic effects of a single oral dose of quinidine was studied in 6 normal volunteers. Cimetidine reduced the mean apparent oral clearance of quinidine (+/- standard error of the mean) from 25.5 +/- 2.7 to 16.2 +/- 1.4 liters/h (p less than 0.05). This was reflected in a 55% (range 30 to 109) increase in the mean half-life from 5.8 +/- 0.2 to 9.0 +/- 0.6 hours (p less than 0.05). Peak quinidine plasma concentrations and times to peak were also increased (p less than 0.05). Plasma protein binding and urinary excretion of quinidine were unchanged by cimetidine treatment. Alterations in the pharmacokinetic variables of quinidine were mirrored in simultaneously measured electrocardiographic parameters. Changes in Q-T, rate-corrected Q-T, QRS, and R-R intervals after a single oral dose of quinidine sulfate (400 mg) were significant. Treatment with cimetidine potentiated these pharmacodynamic changes, but failed to achieve significant differences from quinidine alone. Thus, cimetidine impairs the elimination of oral quinidine in normal volunteers. This interaction may lead to quinidine toxicity in patients in whom cimetidine is concomitantly administered.

Superovulation-induced intrauterine growth retardation in mice

Existing animal models for inducing intrauterine growth retardation (IUGR) involve severe maternal compromise or acute fetal insult. We postulated that superovulation would produce IUGR gradually by enhancing fetal competition for nutrients. Mice were superovulated with pregnant mare serum and human chorionic gonadotrophin and killed on day 19 of gestation. Compared to controls, the mean number of fetuses was significantly increased; body, brain, liver, and placental weights were reduced; and brain/liver weight ratios were increased. Additional mice underwent partial unilateral oophorectomy before superovulation. Marked asymmetry in the number of fetuses in the two uterine horns of the same mother was produced, and the fetuses on the more crowded side manifested smaller brains and livers an increased brain/liver ratios. In the mouse, superovulation is a simple, preconceptual method for achieving IUGR and may be combined with partial unilateral oophorectomy to permit comparisons between fetuses with different growth characteristics within the same mother.

Nutritional metabolism and cerebral bioenergetics in Alzheimer's disease and related dementias

Disturbances in the brain's capacity to meet its energy demand increase the risk of synaptic loss, neurodegeneration, and cognitive decline. Nutritional and metabolic interventions that target metabolic pathways combined with diagnostics to identify deficits in cerebral bioenergetics may therefore offer novel therapeutic potential for Alzheimer's disease (AD) prevention and management. Many diet-derived natural bioactive components can govern cellular energy metabolism but their effects on brain aging are not clear. This review examines how nutritional metabolism can regulate brain bioenergetics and mitigate AD risk. We focus on leading mechanisms of cerebral bioenergetic breakdown in the aging brain at the cellular level, as well as the putative causes and consequences of disturbed bioenergetics, particularly at the blood-brain barrier with implications for nutrient brain delivery and nutritional interventions. Novel therapeutic nutrition approaches including diet patterns are provided, integrating studies of the gut microbiome, neuroimaging, and other biomarkers to guide future personalized nutritional interventions.

Dysbiosis of the gut microbiome impairs mouse skeletal muscle adaptation to exercise

There is emerging evidence of a gut microbiome-skeletal muscle axis. The purpose of this study was to determine if an intact gut microbiome was necessary for skeletal muscle adaptation to exercise. Forty-two 4-month-old female C57BL/6J mice were randomly assigned to untreated (U) or antibiotic-treated (T) non-running controls (CU or CT, respectively) or progressive weighted wheel running (PoWeR, P) untreated (PU) or antibiotic-treated (PT) groups. Antibiotic treatment resulted in disruption of the gut microbiome as indicated by a significant depletion of gut microbiome bacterial species in both CT and PT groups. The training stimulus was the same between PU and PT groups as assessed by weekly (12.35 ± 2.06 vs. 11.09 ± 1.76 km/week, respectively) and total (778.9 ± 130.5 vs. 703.8 ± 112.9 km, respectively) running activity. In response to PoWeR, PT showed less hypertrophy of soleus type 1 and 2a fibres and plantaris type 2b/x fibres compared to PU. The higher satellite cell and myonuclei abundance of PU plantaris muscle after PoWeR was not observed in PT. The fibre-type shift of PU plantaris muscle to a more oxidative type 2a fibre composition following PoWeR was blunted in PT. There was no difference in serum cytokine levels among all groups suggesting disruption of the gut microbiome did not induce systemic inflammation. The results of this study provide the first evidence that an intact gut microbiome is necessary for skeletal muscle adaptation to exercise. KEY POINTS: Dysbiosis of the gut microbiome caused by continuous antibiotic treatment did not affect running activity. Continuous treatment with antibiotics did not result in systemic inflammation as indicated by serum cytokine levels. Gut microbiome dysbiosis was associated with blunted fibre type-specific hypertrophy in the soleus and plantaris muscles in response to progressive weighted wheel running (PoWeR). Gut microbiome dysbiosis was associated with impaired PoWeR-induced fibre-type shift in the plantaris muscle. Gut microbiome dysbiosis was associated with a loss of PoWeR-induced myonuclei accretion in the plantaris muscle.

Cochleovestibular toxicity related to dichloromethotrexate

A 69-year-old man receiving monotherapy for lung cancer with dichloromethotrexate (DCM), and without exposure to other chemotherapeutic agents or known ototoxic drugs, developed profound cochleovestibular dysfunction. The initial presentation was vestibular. This resolved, but unilateral hearing loss ensued and continued to progress to a total of 80 db loss in the low frequency range and 40 db in the high range, despite discontinuation of the drug. Because DCM may be used in combination with the known ototoxin cisplatin, the potential of DCM as an ototoxin should also be considered in such patients.

Cyclic AMP, the hyperresponsiveness factor from hog kidney

The isolation and identification of a material present in the plasma of hypertensive dogs and hypertensive human patients has been under study since 1972. The earliest experiments in relation to this work, noted that plasma from hypertensive dogs cause a hyperresponse to norepinephrine when both were administered by way of the vein. Employing a rat assay system that consisted of an anesthetized rat with polyethylene catheters in the vein for giving norepinephrine and the test fractions and a catheter in the artery for blood pressure monitoring, fractions from hog kidney were tested for hyperresponsiveness activity. The active material is very comparable to cyclic AMP in molecular weight, ultraviolet spectrum, paper chromatography, Enzyme hydrolysis and activity in the anesthetized rat system. This evidence indicates that the hyperresponsiveness factor of renal origin is cyclic AMP.

Basic Science and Pathogenesis

BACKGROUND

Compared to the 'neutral' E3, the E4 allele of Apolipoprotein E (APOE) confers up to a 15-fold increase in Alzheimer's Disease (AD) risk. Conversely, the neuroprotective E2 allele decreases AD risk by a similar degree. Here, we aimed to assess the therapeutic potential of cell-type specific allelic 'switching' by investigating the physiological and neuropathological changes associated with an inducible, in vivo APOE4 to APOE2 transition in astrocytes using a novel transgenic mouse model METHOD: The APOE "switch mouse" (APOE4s2) uses the Cre-loxP system to allow for inducible APOE allele switching from E4 to E2. These mice express a floxed human APOE4 coding region followed by the human APOE2 coding region. Allelic discrimination (RT-PCR) and mass spec-based proteomic analyses were employed to validate the E4 to E2 transition. Single-cell RNAseq and Xenium In Situ were used to measure transcriptomic changes following the astrocytic E4 to E2 allele switch. Behavioral measures and neuropathological analyses were applied to assess the effects of an early-life vs. mid-life allelic switch on AD pathology.

RESULT

mRNA and protein analyses confirm that APOE4s2 mice synthesize full-length human APOE4 pre-switch, and that tamoxifen induces an efficient recombination and expression of human APOE2 in target tissues. Single-cell RNAseq and Xenium reveal that, genetic replacement of astrocytic APOE4 with APOE2 results in distinct alterations to glial cell transcriptomes affecting pathways involved with metabolism, inflammation, and amyloid beta. Neuropathological analyses show that an astrocyte-specific E4 to E2 'switch' significantly decreases total amyloid burden, even once severe amyloidosis has already begun (mid-life 'switch'), and that the astrocytic E4 to E2 transition improves cognition. Additionally, amyloid-associated astro- and micro-gliosis are decreased, and mice with E2-expressing astrocytes had less MHCII expressing microglia and a decrease in plaque-associated ApoE.

CONCLUSION

Together, these data suggest that a successful transition from E4 to E2 in astrocytes has broad impact on the cerebral transcriptome and that an astrocyte-specific E4 to E2 'switch' improves multiple AD-associated pathologies at different points across the AD pathophysiological timeline.

Basic Science and Pathogenesis

BACKGROUND

Apolipoprotein E (ApoE) exists in three protein isoforms: E2, E3, and E4, which differ by only one or two amino acids. These slight differences profoundly effect protein structure and function, allowing each isoform to differentially impact Alzheimer's Disease (AD) risk. Relative to the most common E3 isoform, E4 dramatically increases risk, while E2 confers a substantial decrease in risk. The close similarity between protein isoforms makes it difficult to develop isoform-specific antibodies that are reliable and selective. Here, we aim to validate and optimize a number of common, commercially available ApoE antibodies to determine isoform specificity.

METHOD

Control samples included plasma and brain collected from APOE knockout (KO), homozygous E2, E3 and E4 humanized APOE (hAPOE) mice, and human plasma from all 6 possible APOE genotypes. Western blotting was used on plasma and brain homogenates to determine isoform specificity of E2, E3, or E4 antibodies. Commercial antibodies tested included pan-ApoE antibodies from Cell Signaling Technologies (CST) and Abcam, ApoE4 antibodies from Novus and CST, ApoE2 antibodies from CST, and ApoE3 antibodies from Abcam and Novus. Additionally, pan-ApoE antibodies were kindly gifted to us by collaborators (Drs. Lammich and Haass, LMU) and tested. Antibodies were also tested for use in immunohistochemistry (IHC) using hAPOE and APOE KO mouse brain sections (30 uM).

RESULT

Despite the ApoE3 antibodies being marketed as isoform-specific, they did not show efficacy in either application. Commercial pan-ApoE antibodies were outperformed by the LMU antibodies, but still showed efficacy. When used for western blotting, the CST ApoE4 and ApoE2 antibodies showed clear isoform specificity in hAPOE mouse and human samples. While none of the isoform-specific antibodies passed controls for IHC purposes, multiple pan-ApoE antibodies were variably effective for staining of brain tissue.

CONCLUSION

These data identify several isoform-specific ApoE antibodies that are reliable and selective across multiple sample types and applications; albeit some display higher affinity for one application over another. Overall, we hope these results will provide AD researchers with important resources that are crucial for visualizing and quantifying ApoE isoform distribution in heterozygote individuals and across a number of AD models, systems, and studies.

The Effects of Adjuvant Chemoradiotherapy (CRT) on Myeloid-Derived Suppressor Cell (MDSC) Subsets in Glioblastoma (GBM)

PURPOSE/OBJECTIVE(S)

GBM continues to be a diagnosis with an exceedingly low survival rate despite standard therapy of resection followed by concurrent CRT. MDSC, immunosuppressive myeloid cells that aid immune system evasion by the tumor, expand during fractionated RT. To date, little is known about the effects of CRT on MDSC subsets. The goal of our pilot study is to compare peripheral blood MDSC subset frequency in patients (pts) undergoing CRT. We hypothesize that the pro-tumor, monocytic MDSC (M-MDSC) subset increases following CRT.

MATERIALS/METHODS

Pts over the age of 18 yo with a new diagnosis of GBM from a single institution participated in the study between 7/2022 -1/2023. Exclusion criteria included prior history of brain RT. Baseline peripheral blood samples were collected within one week prior to CRT start and post-CRT samples were collected within the last week of CRT. Peripheral blood mononuclear cells (PBMC) were isolated from whole blood and freshly stained for intracellular flow cytometric analyses. Total MDSC (singlet, viable, non-lymphocyte, CD11b+CD33+ HLA-DR- cells) and subsets (M-MDSC, granulocytic (G-MDSC), and early MDSC (eMDSC)) were identified. Percent frequency (%fx) of total and MDSC subsets as well as MDSC activation status (n = 3) (interleukin (IL)-10, transforming growth factor-β (TGF-β), interferon gamma (IFNγ)) was compared before and after CRT.

RESULTS

The average age of pts receiving CRT (n = 4) was 70 yo. Fractionated RT consisted of CF RT (n = 2), 6000 cGy in 30 fractions, and HF RT (n = 2), 4005 cGy in 15 fractions. All pts received concurrent chemotherapy with temozolomide. The %fx of MDSC of non-lymphocytes started at 29.2% prior to CRT and decreased to 9.9% at the end of CRT. The fold change of %fx of total MDSC in CF RT and HF RT was 0.39 and 0.29, respectively. The mean change in %fx of MDSC subsets before and after CRT are shown in Table 1. The mean %fx of TGF-β-expressing MDSC in all GBM pts increased by 3.5% after CRT. The mean IFNγ+ MDSC %fx for all GBM pts decreased after CRT from 24.2% to 16.2% with a corresponding decrease in geometric mean fluorescence intensity (GMFI). The mean %fx of IL-10+ MDSC decreased by 1.5% at the end of CRT with a decrease in GMFI from 5550 to 1806.

CONCLUSION

In this limited dataset of pts with GBM receiving standard of care adjuvant therapy, we identified an expansion in the eMDSC and decrease in the M-MDSC subsets. These early results suggest HF RT may promote immunity that is more supportive of anti-tumor function, with a lesser increase in fold change of total MDSC after CRT. A more detailed understanding of the effect of RT on myeloid subpopulations is essential to addressing immune suppression in pts with GBM.