Inappropriate quetiapine use at a large academic medical center: frequency of misuse and associated costs of adverse effects.

Background: Quetiapine is an antipsychotic with dose-related receptor affinity, which is commonly prescribed by specialties outside of psychiatry. Quetiapine can have adverse effects including weight gain, hyperglycemia, and falls. Therefore, quetiapine is a good focus medication to assess the need for an antipsychotic stewardship protocol. Objective: To assess the need for an antipsychotic stewardship protocol at a large, urban academic medical center by evaluating quetiapine usage. Design: A retrospective review of quetiapine dispensing history for all strengths (immediate release: 25, 50, 100, 200, 300 mg; extended release: 50, 150, 200, 300 mg) over 1 year (1 December 2021 to 30 November 2022) in patients aged 18 and older was conducted at a large, urban academic medical center. Methods: An antipsychotic protocol for safe and effective quetiapine use was developed utilizing its package insert, clinical guidelines, and primary peer-reviewed literature. Once identified by prescription fill, a retrospective chart review was completed for quetiapine indication, dose, and frequency. Each prescription was reviewed for appropriateness using the antipsychotic stewardship protocol. Results: Out of 521 quetiapine prescriptions for 181 unique patients, 67% of scripts were inappropriate. The costs associated with this inappropriate use were extrapolated to be over $350,000 per year when accounting for long-term harms associated with the development of type 2 diabetes mellitus and falls in older adults. Conclusion: Promoting the safe and effective use of antipsychotics through developing and implementing an antipsychotic stewardship protocol may reduce patient harm and associated costs from inappropriate use.

Inappropriate quetiapine use at a large academic medical center Psychotropic stewardship aims to improve patient outcomes and minimize side effects associated with psychotropic use ­ including antipsychotics. Studies have investigated psychotropic stewardship in elderly patients but have not reviewed its utility in the general adult population. Quetiapine is an antipsychotic with dose-related receptor affinity, meaning that at different doses of the medication, it acts on different receptors and exerts different clinical effects as a sedative, antidepressant, or antipsychotic. Quetiapine is commonly prescribed across medical specialties and can have significant adverse effects, including weight gain, hyperglycemia, and falls. Therefore, quetiapine is a suitable focus medication to assess the need for an antipsychotic stewardship protocol. We developed a protocol for safe and effective quetiapine use utilizing its package insert, clinical guidelines, and primary peer-reviewed literature. We reviewed the dispensing history of quetiapine over one year at two pharmacies at a large, urban academic medical center. Once identified by prescription fill, we completed a retrospective chart review for quetiapine indication, dose, and frequency. We reviewed each prescription for appropriateness using our antipsychotic stewardship protocol. Of 521 quetiapine prescriptions for 181 unique patients filled over one year, 67% of scripts were inappropriate. We extrapolated the costs associated with this inappropriate use to be over $350,000 per year when accounting for long-term harms associated with quetiapine use, including the development of type 2 diabetes mellitus and falls in older adults. Our findings illustrate that promoting the safe and effective use of antipsychotics through developing and implementing an antipsychotic stewardship protocol may reduce patient harm and associated costs from inappropriate use. Psychiatric pharmacists are well-positioned to manage these stewardship program's development, implementation, and dissemination.

Interleukin-9 promotes mast cell progenitor proliferation and CCR2-dependent mast cell migration in allergic airway inflammation.

Allergic asthma is a chronic lung disease characterized by airway hyperresponsiveness and cellular infiltration that is exacerbated by immunoglobulin E-dependent mast cell (MC) activation. Interleukin-9 (IL-9) promotes MC expansion during allergic inflammation but precisely how IL-9 expands tissue MCs and promotes MC function is unclear. In this report, using multiple models of allergic airway inflammation, we show that both mature MCs (mMCs) and MC progenitors (MCp) express IL-9R and respond to IL-9 during allergic inflammation. IL-9 acts on MCp in the bone marrow and lungs to enhance proliferative capacity. Furthermore, IL-9 in the lung stimulates the mobilization of CCR2+ mMC from the bone marrow and recruitment to the allergic lung. Mixed bone marrow chimeras demonstrate that these are intrinsic effects in the MCp and mMC populations. IL-9-producing T cells are both necessary and sufficient to increase MC numbers in the lung in the context of allergic inflammation. Importantly, T cell IL-9-mediated MC expansion is required for the development of antigen-induced and MC-dependent airway hyperreactivity. Collectively, these data demonstrate that T cell IL-9 induces lung MC expansion and migration by direct effects on the proliferation of MCp and the migration of mMC to mediate airway hyperreactivity.

Chronic developmental hypoxia alters rat lung immune cell transcriptomes during allergic airway inflammation.

Populations that are born and raised at high altitude develop under conditions of chronic developmental hypoxia (CDH), which results in pulmonary adaptations of increased lung volume and diffusion capacity to increase gas exchange. It is not clear how CDH may alter allergic inflammation in the lung. In this study, we sought to characterize the impact of CDH on immune cell populations in the rat lung during a murine model of asthma. Rats were bred and raised in either hypoxic (15% oxygen, CDH) or normobaric room air (20% oxygen). At 3-weeks of age, animals were sensitized to ovalbumin (OVA) or physiologic saline (phosphate-buffered saline [PBS]) as a control, followed by three consecutive days of intra-nasal OVA or PBS at 6-weeks of age. We then assessed airway reactivity and allergic-associated cytokine levels. This was followed by single-cell transcriptomic profiling of lung cell populations. In scRNA-seq analysis, we assessed differentially expressed genes, differentially enriched functional pathways, immune cell exhaustion/activation markers, and immune cell secretory products. Our results show that while OVA heightened airway reactivity, CDH suppressed airway reactivity in OVA-challenged and control animals. Through scRNA-seq analysis, we further demonstrate that CDH alters the transcriptional landscape in the lung and alters transcriptional programs in immune cells. These data define CDH-dependent changes in the lung that impact airway reactivity.

ERG Functionally Overlaps with Other Ets Proteins in Promoting TH9 Cell Expression of Il9 during Allergic Lung Inflammation.

CD4+ TH cells develop into subsets that are specialized in the secretion of particular cytokines to mediate restricted types of inflammation and immune responses. Among the subsets that promote development of allergic inflammatory responses, IL-9-producing TH9 cells are regulated by a number of transcription factors. We have previously shown that the E26 transformation-specific (Ets) family members PU.1 and Ets translocation variant 5 (ETV5) function in parallel to regulate IL-9. In this study we identified a third member of the Ets family of transcription factors, Ets-related gene (ERG), that mediates IL-9 production in TH9 cells in the absence of PU.1 and ETV5. Chromatin immunoprecipitation assays revealed that ERG interaction at the Il9 promoter region is restricted to the TH9 lineage and is sustained during murine TH9 polarization. Knockdown or knockout of ERG during murine or human TH9 polarization in vitro led to a decrease in IL-9 production in TH9 cells. Deletion of ERG in vivo had modest effects on IL-9 production in vitro or in vivo. However, in the absence of PU.1 and ETV5, ERG was required for residual IL-9 production in vitro and for IL-9 production by lung-derived CD4 T cells in a mouse model of chronic allergic airway disease. Thus, ERG contributes to IL-9 regulation in TH9 cells.

Allergic airway recall responses require IL-9 from resident memory CD4+ T cells.

Asthma is a chronic inflammatory lung disease with intermittent flares predominately mediated through memory T cells. Yet, the identity of long-term memory cells that mediate allergic recall responses is not well defined. In this report, using a mouse model of chronic allergen exposure followed by an allergen-free rest period, we characterized a subpopulation of CD4+ T cells that secreted IL-9 as an obligate effector cytokine. IL-9-secreting cells had a resident memory T cell phenotype, and blocking IL-9 during a recall challenge or deleting IL-9 from T cells significantly diminished airway inflammation and airway hyperreactivity. T cells secreted IL-9 in an allergen recall-specific manner, and secretion was amplified by IL-33. Using scRNA-seq and scATAC-seq, we defined the cellular identity of a distinct population of T cells with a proallergic cytokine pattern. Thus, in a recall model of allergic airway inflammation, IL-9 secretion from a multicytokine-producing CD4+ T cell population was required for an allergen recall response.

Secondary Prevention Using Cholesterol-Lowering Medications in Patients with Prior Atherosclerotic Cardiovascular Disease Events: A Retrospective Cohort Analysis.

Background: Secondary prevention with lipid-lowering medications in patients with atherosclerotic cardiovascular disease (ASCVD) is known to reduce the risk of clinical events and death. Current guidelines codify recommendations for implementing secondary prevention in appropriate patients. However, in real-world practice, secondary prevention is frequently initiated only after the patient experiences a cardiovascular-related hospitalization. The impact of these delays is not well known. Objectives: To estimate the effects of delaying treatment on the risk of cardiovascular-related hospitalization and on costs for patients who meet the criteria for secondary prevention as specified in the 2013 American College of Cardiology/American Heart Association (ACC/AHA) Guidelines for Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults. Methods: This is a retrospective cohort analysis using Humana data. Eligible patients were categorized by treatment group: (1) patients who initiated treatment before an ASCVD-related hospitalization and (2) patients who either did not initiate treatment until after an ASCVD hospitalization or never initiated treatment. The associations between the timely initiation of cholesterol-lowering medications for secondary prevention and (1) the risk for an ASCVD hospitalization and (2) health-care costs over one year, were estimated using multivariate regressions. Results: A total of 272 899 secondary prevention patients were identified who met study selection criteria. Early treatment was associated with significant reductions in the risk of an ASCVD hospitalization at any time following the identification of the patient's eligibility for secondary prevention (by 33% compared to those treated late or never, P<.0001), but was significantly associated with higher total cost over the first post-index year (by US $509, P<.001). Patients whose low-density lipoprotein cholesterol (LDL-C) levels were >130 mg/dL experienced higher ASCVD hospitalization risks, and also larger risk reductions if treated before an ASCVD hospitalization compared to patients with lower LDL-C levels who were treated late or never treated. Conclusions: More widespread implementation of the treatment policies specified in the 2013 ACC/AHA Guidelines for secondary prevention should significantly reduce cardiovascular disease hospitalizations and reduce costs.

DnaJ and ClpX Are Required for HitRS and HssRS Two-Component System Signaling in Bacillus anthracis.

Bacillus anthracis is the causative agent of anthrax. This Gram-positive bacterium poses a substantial risk to human health due to high mortality rates and the potential for malicious use as a bioterror weapon. To survive within the vertebrate host, B. anthracis relies on two-component system (TCS) signaling to sense host-induced stresses and respond to alterations in the environment through changes in target gene expression. HitRS and HssRS are cross-regulating TCSs in B. anthracis that respond to cell envelope disruptions and high heme levels, respectively. In this study, an unbiased and targeted genetic selection was designed to identify gene products that are involved in HitRS and HssRS signaling. This selection led to the identification of inactivating mutations within dnaJ and clpX that disrupt HitRS- and HssRS-dependent gene expression. DnaJ and ClpX are the substrate-binding subunits of the DnaJK protein chaperone and ClpXP protease, respectively. DnaJ regulates the levels of HitR and HitS to facilitate signal transduction, while ClpX specifically regulates HitS levels. Together, these results reveal that the protein homeostasis regulators, DnaJ and ClpX, function to maintain B. anthracis signal transduction activities through TCS regulation.

Directed evolution reveals the mechanism of HitRS signaling transduction in Bacillus anthracis.

Two component systems (TCSs) are a primary mechanism of signal sensing and response in bacteria. Systematic characterization of an entire TCS could provide a mechanistic understanding of these important signal transduction systems. Here, genetic selections were employed to dissect the molecular basis of signal transduction by the HitRS system that detects cell envelope stress in the pathogen Bacillus anthracis. Numerous point mutations were isolated within HitRS, 17 of which were in a 50-residue HAMP domain. Mutational analysis revealed the importance of hydrophobic interactions within the HAMP domain and highlighted its essentiality in TCS signaling. In addition, these data defined residues critical for activities intrinsic to HitRS, uncovered specific interactions among individual domains and between the two signaling proteins, and revealed that phosphotransfer is the rate-limiting step for signal transduction. Furthermore, this study establishes the use of unbiased genetic selections to study TCS signaling and provides a comprehensive mechanistic understanding of an entire TCS.

Impact of early initiation of antihypertensive medications for patients with hypertension or elevated blood pressure.

OBJECTIVES: The 2017 American College of Cardiology/American Heart Association High Blood Pressure Guidelines lowered high blood pressure (BP) threshold, recommending earlier treatment to prevent cardiovascular disease. This study estimated the impact of initiating early antihypertensive medications on the risk of acute myocardial infarction (AMI), stroke, death, and on healthcare costs in patients potentially qualifying for antihypertensive treatment under the 2017 guidelines. METHODS: High-risk patients qualifying for antihypertensive medications under the 2017 guidelines were identified using Optum data. Patients with a diagnosis of elevated BP were also assumed eligible for hypertension treatment under the new guidelines. Patients were defined to have initiated early treatment if they initiated treatment before experiencing a cardiovascular event postdiagnosis. RESULTS: A total of 916 633 patients met eligibility requirements and all other study inclusion criteria. Of those, 66% initiated treatment during 2007-2016. Initiating early antihypertensive treatment decreased the likelihood of having AMI by 59%, stroke by 60% and death by 9%. Patients with only an 'elevated BP' diagnosis experienced reduced risk of stroke once they initiated medications. Treatment reduced the risk of AMI or stroke for patients with diabetes, chronic renal disease and obesity and also significantly lowered all-cause healthcare costs in the first postindex year. CONCLUSION: Initiating antihypertensive medications before experiencing a cardiovascular disease-related clinical event was associated with reduced risk of AMI, stroke and death for all hypertensive patients identified in the new guidelines. However, early treatment had a significantly smaller effect for patients with only 'elevated' BP, who experienced just a lower risk of stroke once treated.

Pretreatment Inflammation-Based Markers Predict Survival Outcomes in Patients with Early Stage Hepatocellular Carcinoma After Radiofrequency Ablation.

The prognostic significance of various systemic inflammation-based markers has been explored in different cancers after surgery. This study aimed to investigate whether these markers could predict outcomes in patients with early-stage hepatocellular carcinoma (HCC) undergoing radiofrequency ablation (RFA). One hundred eighteen patients with newly diagnosed HCC within the Milan criteria receiving RFA as initial therapy were retrospectively enrolled. Pretreatment inflammation-based markers including the neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR) and prognostic nutritional index (PNI), together with other clinicopathologic parameters were collected. Cumulative overall survival (OS) and recurrence-free survival (RFS) were estimated by the Kaplan-Meier method and by multivariate analysis using Cox proportional hazard model. The 1-, 3-, and 5-year OS rates of patients were 90%, 67%, and 52%, respectively. Kaplan-Meier curves showed that baseline high NLR ≥ 2.5 (p = 0.006), low PNI < 40 (p = 0.005), history of end-stage renal disease (ESRD) (p = 0.005), non-Child-Pugh class A (p = 0.001) and elevated alpha-fetoprotein (AFP) ≥ 200 ng/mL (p = 0.005) significantly associated with the poor OS, whereas high PLR ≥ 100 did not. By multivariate analysis, high NLR ≥ 2.5 (hazard ratio (HR) 1.94; 95% confidence interval (CI), 1.05-3.59; p = 0.034), low PNI < 40 (HR 0.38; 95% CI, 0.20-0.72; p = 0.003), ESRD history (HR 3.60; 95% CI, 1.48-8.76; p = 0.005) and elevated AFP ≥ 200 ng/mL (HR 4.61; 95% CI, 1.75-12.13; p = 0.002) were independent factors. An elevated AFP level of ≥200 ng/mL was the significant factor associated with intrahepatic new RFS by univariate and multivariate analyses. In conclusion, pretreatment NLR and PNI are simple and useful predictors for OS in patients with early-stage HCC after RFA.

Primary Prevention Using Cholesterol-Lowering Medications in Patients Meeting New Treatment Guidelines: A Retrospective Cohort Analysis.

BACKGROUND: The American College of Cardiology and American Heart Association (ACC/AHA) issued new cholesterol treatment guidelines in 2013. Two of the groups designated for primary prevention were analyzed: patients with a low-density lipoprotein cholesterol (LDL-C) level ≥ 190 mg per dL and diabetic patients aged 40-75 years. OBJECTIVE: To estimate the effects of primary prevention as specified in the 2013 guidelines on cardiovascular event risk and cost. METHODS: Primary prevention patients were identified using laboratory and diagnostic data for Humana members from 2007 to 2013. Potential study patients were classified into 3 risk groups: elevated LDL-C, diabetes, and elevated LDL-C and diabetes. Patients receiving cholesterol-lowering medications before their index date were excluded. Eligible patients were divided into 2 treatment groups: (1) primary prevention patients who initiated treatment before experiencing any cardiovascular disease (CVD)-related event, and (2) patients who either did not initiate treatment until after experiencing a CVD event or never initiated treatment. The associations between initiating cholesterol-lowering medications for primary prevention and the risk for acute myocardial infarction, stroke, coronary angioplasty, or coronary artery bypass graft surgery were estimated using Cox proportional hazards models. The effect of primary prevention on health care costs was estimated using generalized linear models. RESULTS: 91,066 patients met study selection criteria. Primary prevention rates were the lowest in diabetic patients (35%), who were newly designated for treatment in the 2013 guidelines. Primary prevention rates were higher for patients designated for treatment under earlier guidelines: 65% for patients with elevated LDL-C and 78% for the combined LDL-C and diabetes group. Primary prevention treatment was associated with significant reductions in cardiovascular event risk (up to 37%) and lower total all-cause costs (by $673) in the first post-index year. CONCLUSIONS: Initiating cholesterol-lowering medications for primary prevention, as specified in the ACC/AHA 2013 guidelines, for patients with high LDL-C and diabetes is associated with reduced CVD event risks and lower health care costs. DISCLOSURES: No outside funding supported this study. Han received fellowship support from the Pharmaceutical Research and Manufacturers Association Foundation (PhRMA) during the conduct of this study. Dougherty is employed by PhRMA. The authors have nothing to disclose.

Calcitonin receptors are ancient modulators for rhythms of preferential temperature in insects and body temperature in mammals.

Daily body temperature rhythm (BTR) is essential for maintaining homeostasis. BTR is regulated separately from locomotor activity rhythms, but its molecular basis is largely unknown. While mammals internally regulate BTR, ectotherms, including Drosophila, exhibit temperature preference rhythm (TPR) behavior to regulate BTR. Here, we demonstrate that the diuretic hormone 31 receptor (DH31R) mediates TPR during the active phase in Drosophila DH31R is expressed in clock cells, and its ligand, DH31, acts on clock cells to regulate TPR during the active phase. Surprisingly, the mouse homolog of DH31R, calcitonin receptor (Calcr), is expressed in the suprachiasmatic nucleus (SCN) and mediates body temperature fluctuations during the active phase in mice. Importantly, DH31R and Calcr are not required for coordinating locomotor activity rhythms. Our results represent the first molecular evidence that BTR is regulated distinctly from locomotor activity rhythms and show that DH31R/Calcr is an ancient specific mediator of BTR during the active phase in organisms ranging from ectotherms to endotherms.

Feeding-State-Dependent Modulation of Temperature Preference Requires Insulin Signaling in Drosophila Warm-Sensing Neurons.

Starvation is life-threatening and therefore strongly modulates many aspects of animal behavior and physiology [1]. In mammals, hunger causes a reduction in body temperature and metabolism [2], resulting in conservation of energy for survival. However, the molecular basis of the modulation of thermoregulation by starvation remains largely unclear. Whereas mammals control their body temperature internally, small ectotherms, such as Drosophila, set their body temperature by selecting an ideal environmental temperature through temperature preference behaviors [3, 4]. Here, we demonstrate in Drosophila that starvation results in a lower preferred temperature, which parallels the reduction in body temperature in mammals. The insulin/insulin-like growth factor (IGF) signaling (IIS) pathway is involved in starvation-induced behaviors and physiology and is well conserved in vertebrates and invertebrates [5-7]. We show that insulin-like peptide 6 (Ilp6) in the fat body (fly liver and adipose tissues) is responsible for the starvation-induced reduction in preferred temperature (Tp). Temperature preference behavior is controlled by the anterior cells (ACs), which respond to warm temperatures via transient receptor potential A1 (TrpA1) [4]. We demonstrate that starvation decreases the responding temperature of ACs via insulin signaling, resulting in a lower Tp than in nutrient-rich conditions. Thus, we show that hunger information is conveyed from fat tissues via Ilp6 and influences the sensitivity of warm-sensing neurons in the brain, resulting in a lower temperature set point. Because starvation commonly results in a lower body temperature in both flies and mammals, we propose that insulin signaling is an ancient mediator of starvation-induced thermoregulation.

The role of PDF neurons in setting the preferred temperature before dawn in Drosophila.

Animals have sophisticated homeostatic controls. While mammalian body temperature fluctuates throughout the day, small ectotherms, such as Drosophila achieve a body temperature rhythm (BTR) through their preference of environmental temperature. Here, we demonstrate that pigment dispersing factor (PDF) neurons play an important role in setting preferred temperature before dawn. We show that small lateral ventral neurons (sLNvs), a subset of PDF neurons, activate the dorsal neurons 2 (DN2s), the main circadian clock cells that regulate temperature preference rhythm (TPR). The number of temporal contacts between sLNvs and DN2s peak before dawn. Our data suggest that the thermosensory anterior cells (ACs) likely contact sLNvs via serotonin signaling. Together, the ACs-sLNs-DN2s neural circuit regulates the proper setting of temperature preference before dawn. Given that sLNvs are important for sleep and that BTR and sleep have a close temporal relationship, our data highlight a possible neuronal interaction between body temperature and sleep regulation.

Drosophila DH31 Neuropeptide and PDF Receptor Regulate Night-Onset Temperature Preference.

Body temperature exhibits rhythmic fluctuations over a 24 h period (Refinetti and Menaker, 1992) and decreases during the night, which is associated with sleep initiation (Gilbert et al., 2004; Kräuchi, 2007a,b). However, the underlying mechanism of this temperature decrease is largely unknown. We have previously shown that Drosophila exhibit a daily temperature preference rhythm (TPR), in which their preferred temperatures increase during the daytime and then decrease at the transition from day to night (night-onset) (Kaneko et al., 2012). Because Drosophila are small ectotherms, their body temperature is very close to that of the ambient temperature (Stevenson, 1985), suggesting that their TPR generates their body temperature rhythm. Here, we demonstrate that the neuropeptide diuretic hormone 31 (DH31) and pigment-dispersing factor receptor (PDFR) contribute to regulate the preferred temperature decrease at night-onset. We show that PDFR and tethered-DH31 expression in dorsal neurons 2 (DN2s) restore the preferred temperature decrease at night-onset, suggesting that DH31 acts on PDFR in DN2s. Notably, we previously showed that the molecular clock in DN2s is important for TPR. Although PDF (another ligand of PDFR) is a critical factor for locomotor activity rhythms, Pdf mutants exhibit normal preferred temperature decreases at night-onset. This suggests that DH31-PDFR signaling specifically regulates a preferred temperature decrease at night-onset. Thus, we propose that night-onset TPR and locomotor activity rhythms are differentially controlled not only by clock neurons but also by neuropeptide signaling in the brain. SIGNIFICANCE STATEMENT: Body temperature rhythm (BTR) is fundamental for the maintenance of functions essential for homeostasis, such as generating metabolic energy and sleep. One major unsolved question is how body temperature decreases dramatically during the night. Previously, we demonstrated that a BTR-like mechanism, referred to as temperature preference rhythm (TPR), exists in Drosophila Here, we demonstrate that the diuretic hormone 31 (DH31) neuropeptide and pigment-dispersing factor receptor (PDFR) regulate preferred temperature decreases at night-onset via dorsal neurons 2. This is the first in vivo evidence that DH31 could function as a ligand of PDFR. Although both DH31 and PDF are ligands of PDFR, we show that DH31 regulates night-onset TPR, but PDF does not, suggesting that night-onset TPR and locomotor activity rhythms are controlled by different neuropeptides via different clock cells.

Heme sensing in Bacillus thuringiensis: a supplementary HssRS-regulated heme resistance system.

Several Gram-positive pathogens scavenge host-derived heme to satisfy their nutritional iron requirement. However, heme is a toxic molecule capable of damaging the bacterial cell. Gram-positive pathogens within the phylum Firmicutes overcome heme toxicity by sensing heme through HssRS, a two-component system that regulates the heme detoxification transporter HrtAB. Here we show that heme sensing by HssRS and heme detoxification by HrtAB occur in the insect pathogen Bacillus thuringiensis We find that in B. thuringiensis, HssRS directly regulates an operon, hrmXY, encoding hypothetical membrane proteins that are not found in other Firmicutes with characterized HssRS and HrtAB systems. This novel HssRS-regulated operon or its orthologs BMB171_c3178 and BMB171_c3330 are required for maximal heme resistance. Furthermore, the activity of HrmXY is not dependent on expression of HrtAB. These results suggest that B. thuringiensis senses heme through HssRS and induces expression of separate membrane-localized systems capable of overcoming different aspects of heme toxicity.

Inferring relative numbers of human leucocyte genome replications.

Genome duplication inevitably results in replication errors. A priori, the more times a genome is copied, the greater the average number of replication errors. This principle could be used to 'count' mitotic divisions. Although somatic mutations are rare, cytosine methylation is also copied after DNA replication, but measurably increases with aging at certain CpG rich sequences in mitotic tissues, such as the colon. To further test whether such age-related methylation represents replication errors, these CpG rich 'clock' sequences were measured in leucocytes. Leucocytes within an individual have identical chronological ages (time since birth) but their mitotic ages (numbers of divisions since the zygote) may differ. Neutrophils, B-lymphocytes, and red cell progenitors are produced from relatively quiescent stem cells throughout life, but T-lymphocyte production largely ceases after puberty when the thymus disappears. However, T-lymphocyte genomes may continue to replicate throughout life in response to immunological stimulation. Consistent with this biology, clock methylation significantly increased with aging for T-lymphocyte genomes, but no significant increase was measured in other cell populations. Moreover, this methylation was greater in genomes isolated from their corresponding neoplastic populations. These studies tentatively support the hypothesis that methylation at certain CpG rich sequences in leucocytes could record their mitotic ages.

Lack of increases in methylation at three CpG-rich genomic loci in non-mitotic adult tissues during aging.

BACKGROUND: Cell division occurs during normal human development and aging. Despite the likely importance of cell division to human pathology, it has been difficult to infer somatic cell mitotic ages (total numbers of divisions since the zygote) because direct counting of lifetime numbers of divisions is currently impractical. Here we attempt to infer relative mitotic ages with a molecular clock hypothesis. Somatic genomes may record their mitotic ages because greater numbers of replication errors should accumulate after greater numbers of divisions. Mitotic ages will vary between cell types if they divide at different times and rates. METHODS: Age-related increases in DNA methylation at specific CpG sites (termed "epigenetic molecular clocks") have been previously observed in mitotic human epithelium like the intestines and endometrium. These CpG rich sequences or "tags" start unmethylated and potentially changes in methylation during development and aging represent replication errors. To help distinguish between mitotic versus time-associated changes, DNA methylation tag patterns at 8-20 CpGs within three different genes, two on autosomes and one on the X-chromosome were measured by bisulfite sequencing from heart, brain, kidney and liver of autopsies from 21 individuals of different ages. RESULTS: Levels of DNA methylation were significantly greater in adult compared to fetal or newborn tissues for two of the three examined tags. Consistent with the relative absence of cell division in these adult tissues, there were no significant increases in tag methylation after infancy. CONCLUSION: Many somatic methylation changes at certain CpG rich regions or tags appear to represent replication errors because this methylation increases with chronological age in mitotic epithelium but not in non-mitotic organs. Tag methylation accumulates differently in different tissues, consistent with their expected genealogies and mitotic ages. Although further studies are necessary, these results suggest numbers of divisions and ancestry are at least partially recorded by epigenetic replication errors within somatic cell genomes.

Persistent nicotine treatment potentiates amplification of the dihydrofolate reductase gene in rat lung epithelial cells as a consequence of Ras activation.

Although nicotine has been suggested to promote lung carcinogenesis, the mechanism of its action in this process remains unknown. The present investigation demonstrates that the treatment of rat lung epithelial cells with nicotine for various periods differentially mobilizes multiple intracellular pathways. Protein kinase C and phosphoinositide 3-OH-kinase are transiently activated after the treatment. Also, Ras and its downstream effector ERK1/2 are activated after long term exposure to nicotine. The activation of Ras by nicotine treatment is responsible for the subsequent perturbation of the methotrexate (MTX)-mediated G1 cell cycle restriction as well as an increase in production of reactive oxygen species. When p53 expression is suppressed by introducing E6, persistent exposure to nicotine enables dihydrofolate reductase gene amplification in the presence of methotrexate (MTX) and the formation of the MTX-resistant colonies. Altering the activity of phosphoinositide 3-OH-kinase has no effect on dihydrofolate reductase amplification. However, the suppression of protein kinase C dramatically affects the colony formation in soft agar. Thus, our data suggest that persistent exposure to nicotine perturbs the G1 checkpoint and causes DNA damage through the increase of the production of reactive oxygen species. However, a third element rendered by loss of p53 is required for the initiation of the process of gene amplification. Under p53-deficient conditions, the establishment of a full oncogenic transformation, in response to long term nicotine exposure, is achieved through the cooperation of multiple signaling pathways.