Browning deficiency and low mobilization of fatty acids in gonadal white adipose tissue leads to decreased cold-tolerance of transglutaminase 2 knock-out mice

During cold-exposure ‘beige’ adipocytes with increased mitochondrial content are activated in white adipose tissue (WAT). These cells, similarly to brown adipose tissue (BAT), dissipate stored chemical energy in the form of heat with the help of uncoupling protein 1 (UCP1). We investigated the effect of tissue transglutaminase (TG2) ablation on the function of ATs in mice. Although TG2^+/+ and TG2^−/− mice had the same amount of WAT and BAT, we found that TG2^+/+ animals could tolerate acute cold exposure for 4 h, whereas TG2^−/− mice only for 3 h. Both TG2^−/− and TG2^+/+ animals used up half of the triacylglycerol content of subcutaneous WAT (SCAT) after 3 h treatment; however, TG2^−/− mice still possessed markedly whiter and higher amount of gonadal WAT (GONAT) as reflected in the larger size of adipocytes and lower free fatty acid levels in serum. Furthermore, lower expression of ‘beige’ marker genes such as UCP1, TBX1 and TNFRFS9 was observed after cold exposure in GONAT of TG2^−/− mice, paralleled with a lower level of UCP1 protein and a decreased mitochondrial content. The detected changes in gene expression of Resistin and Adiponectin did not provoke glucose intolerance in the investigated TG2^−/− mice, and TG2 deletion did not influence adrenaline, noradrenaline, glucagon and insulin production. Our data suggest that TG2 has a tissue-specific role in GONAT function and browning, which becomes apparent under acute cold exposure.     

Anxiety and increased 5‐HT1A receptor response in NCAM null mutant mice

Mice deficient in the neural cell adhesion molecule (NCAM) show behavioral abnormalities as adults, including altered exploratory behavior, deficits in spatial learning, and increased intermale aggression. Here, we report increased anxiety‐like behavior of homozygous (NCAM^−/−) and heterozygous (NCAM^+/−) mutant mice in a light/dark avoidance test, independent of genetic background and gender. Anxiety‐like behavior was reduced in both NCAM^+/+ and NCAM^−/− mice by systemic administration of the benzodiazepine agonist diazepam and the 5‐HT_1A receptor agonists buspirone and 8‐OH‐DPAT. However, NCAM^−/− mice showed anxiolytic‐like effects at lower doses of buspirone and 8‐OH‐DPAT than NCAM^+/+ mice. Such increased response to 5‐HT_1A receptor stimulation suggests a functional change in the serotonergic system of NCAM^−/− mice, likely involved in the control of anxiety and aggression. However, 5‐HT_1A receptor binding and tissue content of serotonin and its metabolite 5‐hydroxyindolacetic acid were found unaltered in every brain area of NCAM^−/− mice investigated, indicating that expression of 5‐HT_1A receptors as well as synthesis and release of serotonin are largely unchanged in NCAM^−/− mice. We hypothesize a critical involvement of endogenous NCAM in serotonergic transmission via 5‐HT_1A receptors and inwardly rectifying K⁺ channels as the respective effector systems. © 1999 John Wiley & Sons, Inc. J Neurobiol 40: 343–355, 1999     

Secretion of zona pellucida glycoprotein mZP2 by growing oocytes from mZP3+/+ and mZP3−/− mice

The mouse egg extracellular coat, or zona pellucida (ZP), is composed of three glycoproteins, called mZP1–3, which are synthesized and secreted concomitantly by growing oocytes. Disruption of the mZP3 gene by targeted mutagenesis yields mice that are homozygous nulls (mZP3^−/−). Growing oocytes from mZP3^−/− mice do not synthesize mZP3 mRNA or protein and, as a result, do not assemble a ZP. Here, we examined secretion of mZP2 by growing oocytes and eggs from mZP3^−/− mice, as well as incorporation of mZP2 into the ZP of oocytes from mZP3^+/+ mice. Laser scanning confocal microscopy (LSCM) of antibody‐labeled samples showed that, indeed, mZP2 was synthesized and secreted by oocytes isolated from mZP3^−/− mice and cultured in vitro. Nascent mZP2 was found in the culture medium, associated with the surface of the plasma membrane of growing oocytes, and in the oocyte cytoplasm. By contrast, mZP2 was barely detectable at any of these sites when ovulated eggs from mZP3^−/− mice were examined. Examination of oocytes from wild‐type (mZP3^+/+) mice showed that, while a portion of nascent mZP2 was assembled into the ZP (approximately 40%), here too a significant fraction was secreted into the culture medium (approximately 60%). Similar results also were obtained when intact pre‐antral follicles were isolated from mZP3^+/+ mice and cultured in vitro. Several of these observations are consistent with previous results obtained with oocytes from heterozygous null mice (mZP3^+/−). Furthermore, the results suggest that ZP assembly from nascent glycoproteins may be a stochastic process that requires the presence of both mZP2 and mZP3 and occurs completely outside the growing oocyte. Dev. Genet. 25:95–102, 1999. © 1999 Wiley‐Liss, Inc.     

Transferrin receptor 2 mitigates periodontitis-driven alveolar bone loss

Periodontitis is associated with significant alveolar bone loss. Patients with iron overload suffer more frequently from periodontitis, however, the underlying mechanisms remain largely elusive. Here, we investigated the role of transferrin receptor 2 (Tfr2), one of the main regulators of iron homeostasis, in the pathogenesis of periodontitis and the dental phenotype under basal conditions in mice. As Tfr2 suppresses osteoclastogenesis, we hypothesized that deficiency of Tfr2 may exacerbate periodontitis-induced bone loss. Mice lacking Tfr2 (Tfr2^−/−) and wild-type (Tfr2^+/+) littermates were challenged with experimental periodontitis. Mandibles and maxillae were collected for microcomputed tomography and histology analyses. Osteoclast cultures from Tfr2^+/+ and Tfr2^−/− mice were established and analyzed for differentiation efficiency, by performing messenger RNA expression and protein signaling pathways. After 8 days, Tfr2-deficient mice revealed a more severe course of periodontitis paralleled by higher immune cell infiltration and a higher histological inflammation index than Tfr2^+/+ mice. Moreover, Tfr2-deficient mice lost more alveolar bone compared to Tfr2^+/+ littermates, an effect that was only partially iron-dependent. Histological analysis revealed a higher number of osteoclasts in the alveolar bone of Tfr2-deficient mice. In line, Tfr2-deficient osteoclastic differentiation ex vivo was faster and more efficient as reflected by a higher number of osteoclasts, a higher expression of osteoclast markers, and an increased resorptive activity. Mechanistically, Tfr2-deficient osteoclasts showed a higher p38-MAPK signaling and inhibition of p38-MAPK signaling in Tfr2-deficient cells reverted osteoclast formation to Tfr2^+/+ levels. Taken together, our data indicate that Tfr2 modulates the inflammatory response in periodontitis thereby mitigating effects on alveolar bone loss.     

Transcriptional responses of neonatal mouse lung to hyperoxia by Nrf2 status

Hyperoxia exposure can inhibit alveolar growth in the neonatal lung through induction of p21/p53 pathways and is a risk factor for the development of bronchopulmonary dysplasia (BPD) in preterm infants. We previously found that activation of nuclear factor erythroid 2 p45-related factor (Nrf2) improved survival in neonatal mice exposed to hyperoxia likely due to increased expression of anti-oxidant response genes. It is not known however, whether hyperoxic induced Nrf2 activation attenuates the growth impairment caused by hyperoxia in neonatal lung. To determine if Nrf2 activation modulates cell cycle regulatory pathway genes associated with growth arrest we examined the gene expression in the lungs of Nrf2^−/− and Nrf2^+/+ neonatal mice at one and 3 days of hyperoxia exposure.MethodsMicroarray analysis was performed in neonatal Nrf2^+/+ and Nrf2^−/− lungs exposed to one and 3 days of hyperoxia. Sulforaphane, an inducer of Nrf2 was given to timed pregnant mice to determine if in utero exposure attenuated p21 and IL-6 gene expression in wildtype neonatal mice exposed to hyperoxia.ResultsCell cycle regulatory genes were induced in Nrf2^−/− lung at 1 day of hyperoxia. At 3 days of hyperoxia, induction of cell cycle regulatory genes was similar in Nrf2^+/+ and Nrf2^−/− lungs, despite higher inflammatory gene expression in Nrf2^−/− lung.Conclusionp21/p53 pathways gene expression was not attenuated by Nrf2 activation in neonatal lung. In utero SUL did not attenuate p21 expression in wildtype neonatal lung exposed to hyperoxia. These findings suggest that although Nrf2 activation induces expression of anti-oxidant genes, it does not attenuate alveolar growth arrest caused by exposure to hyperoxia.     

CFTR deletion affects mouse osteoblasts in a gender-specific manner

Advancements in research and care have contributed to increase life expectancy of individuals with cystic fibrosis (CF). With increasing age comes a greater likelihood of developing CF bone disease, a comorbidity characterized by a low bone mass and impaired bone quality, which displays gender differences in severity. However, pathophysiological mechanisms underlying this gender difference have never been thoroughly investigated. We used bone marrow-derived osteoblasts and osteoclasts from Cftr^+/+ and Cftr^−/− mice to examine whether the impact of CF transmembrane conductance regulator (CFTR) deletion on cellular differentiation and functions differed between genders. To determine whether in vitro findings translated into in vivo observations, we used imaging techniques and three-point bending testing. In vitro studies revealed no osteoclast-autonomous defect but impairment of osteoblast differentiation and functions and aberrant responses to various stimuli in cells isolated from Cftr^−/− females only. Compared with wild-type controls, knockout mice exhibited a trabecular osteopenic phenotype that was more pronounced in Cftr^−/− males than Cftr^−/− females. Bone strength was reduced to a similar extent in knockout mice of both genders. In conclusion, we find a trabecular bone phenotype in Cftr^−/− mice that was slightly more pronounced in males than females, which is reminiscent of the situation found in patients. However, at the osteoblast level, the pathophysiological mechanisms underlying this phenotype differ between males and females, which may underlie gender differences in the way bone marrow–derived osteoblasts behave in absence of CFTR.     

Gnpat does not play an essential role in systemic iron homeostasis in murine model

The GNPAT variant rs11558492 (p.D519G) was identified as a novel genetic factor that modifies the iron-overload phenotype in homozygous carriers of the HFE p.C282Y variant. However, the reported effects of the GNPAT p.D519G variant vary among study populations. Here, we investigated the role of GNPAT in iron metabolism using Gnpat-knockout (Gnpat^−/−), Gnpat/Hfe double-knockout (Gnpat^−/−Hfe^−/− or DKO) mice and hepatocyte-specific Gnpat-knockout mice (Gnpat^fl/fl;Alb-Cre). Our analysis revealed no significant difference between wild-type (Gnpat^+/+) and Gnpat^−/− mice, between Hfe^−/− and DKO mice, or between Gnpat^fl/fl and Gnpat^fl/fl;Alb-Cre with respect to serum iron and tissue iron. In addition, the expression of hepcidin was not affected by deleting Gnpat expression in the presence or absence of Hfe. Feeding Gnpat^−/− and DKO mice a high-iron diet had no effect on tissue iron levels compared with wild-type and Hfe^−/− mice, respectively. Gnpat knockdown in primary hepatocytes from wild-type or Hfe^−/− mice did not alter hepcidin expression, but it repressed BMP6-induced hepcidin expression. Taken together, these results support the hypothesis that deleting Gnpat expression has no effect on either systemic iron metabolism or the iron-overload phenotype that develops in Hfe^−/− mice, suggesting that GNPAT does not directly mediate iron homeostasis under normal or high-iron dietary conditions.     

IGF‐I deficient mice show reduced peripheral nerve conduction velocities and decreased axonal diameters and respond to exogenous IGF‐I treatment

Although insulin‐like growth factor‐I (IGF‐I) can act as a neurotrophic factor for peripheral neurons in vitro and in vivo following injury, the role IGF‐I plays during normal development and functioning of the peripheral nervous system is unclear. Here, we report that transgenic mice with reduced levels (two genotypes: heterozygous Igf1^+/− or homozygous insertional mutant Igf1^m/m) or totally lacking IGF‐I (homozygous Igf1^−/−) show a decrease in motor and sensory nerve conduction velocities in vivo. In addition, A‐fiber responses in isolated peroneal nerves from Igf1^+/− and Igf1^−/− mice are impaired. The nerve function impairment is most profound in Igf1^−/− mice. Histopathology of the peroneal nerves in Igf1^−/− mice demonstrates a shift to smaller axonal diameters but maintains the same total number of myelinated fibers as Igf1^+/+ mice. Comparisons of myelin thickness with axonal diameter indicate that there is no significant reduction in peripheral nerve myelination in IGF‐I–deficient mice. In addition, in Igf1^m/m mice with very low serum levels of IGF‐I, replacement therapy with exogenous recombinant hIGF‐I restores both motor and sensory nerve conduction velocities. These findings demonstrate not only that IGF‐I serves an important role in the growth and development of the peripheral nervous system, but also that systemic IGF‐I treatment can enhance nerve function in IGF‐I–deficient adult mice. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 142–152, 1999     

Collagen receptors integrin alpha2beta1 and discoidin domain receptor 1 regulate maturation of the glomerular basement membrane and loss of integrin alpha2beta1 delays kidney fibrosis in COL4A3 knockout mice

Maturation of the glomerular basement membrane (GBM) is essential for maintaining the integrity of the renal filtration barrier. Impaired maturation causes proteinuria and renal fibrosis in the type IV collagen disease Alport syndrome. This study evaluates the role of collagen receptors in maturation of the GBM, matrix accumulation and renal fibrosis by using mice deficient for discoidin domain receptor 1 (DDR1), integrin subunit α2 (ITGA2), and type IV collagen α3 (COL4A3). Loss of both collagen receptors DDR1 and integrin α2β1 delays maturation of the GBM: due to a porous GBM filtration barrier high molecular weight proteinuria that more than doubles between day 60 and day 100. Thereafter, maturation of the GBM causes proteinuria to drop down to one tenth until day 200. Proteinuria and the porous GBM cause accumulation of glomerular and tubulointerstitial matrix, which both decrease significantly after GBM-maturation until day 250. In parallel, in a disease with impaired GBM-maturation such as Alport syndrome, loss of integrin α2β1 positively delays renal fibrosis: COL4A3^−/−/ITGA2^−/− double knockouts exhibited reduced proteinuria and urea nitrogen compared to COL4A3^−/−/ITGA2^+/− and COL4A3^−/−/ITGA2^+/+ mice. The double knockouts lived 20% longer and showed less glomerular and tubulointerstitial extracellular matrix deposition than the COL4A3^−/− Alport mice with normal integrin α2β1 expression. Electron microscopy illustrated improvements in the glomerular basement membrane structure. MMP2, MMP9, MMP12 and TIMP1 were expressed at significantly higher levels (compared to wild-type mice) in COL4A3^−/−/ITGA2^+/+ Alport mice, but not in COL4A3^+/+/ITGA2^−/− mice. In conclusion, the collagen receptors DDR1 and integrin α2β1 contribute to regulate GBM-maturation and to control matrix accumulation. As demonstrated in the type IV collagen disease Alport syndrome, glomerular cell–matrix interactions via collagen receptors play an important role in the progression of renal fibrosis.     

Phenotypic consequences of transforming growth factor β1 gene ablation in murine embryonic fibroblasts: Autocrine control of cell proliferation and extracellular matrix biosynthesis

The profound effects of transforming growth factor β1 (TGF-β1) on the immune system, cardiogenesis, in yolk sac hematopoeisis and in differentiation of endothelium have been demonstrated by detailed analyses of TGF-β1 knockout mice during embryogenesis. We have systematically examined the autocrine and paracrine roles of TGF-β1 in cell proliferation and in its ability to modulate the gene expression of selected components of extracellular matrix (ECM) using embryonic fibroblasts from TGF-β1 null mice (TGF-β1^−/−). The rates of cell proliferation of embryonic fibroblasts from normal mice (TGF-β1^+/+) and TGF-β1 null mice were compared by cell counting, by ³H thymidine incorporation, and by measuring the fraction of cells in the G1, S, and G2/M phases of the cell cycle by fluorescent activated cell sorting (FACS). Concurrently, the expression of pro-α1(I) collagen, fibronectin, and plasminogen activator inhibitor-1 (PAI-1) was also quantified by hybridization of total mRNA from TGF-β1^+/+ and TGF-β1^−/− embryonic fibroblasts. We report that TGF-β1^−/− cells proliferated at about twice the rate of TGF-β1^+/+ cells. Further, TGF-β1 null fibroblasts accumulated and synthesized lower constitutive levels of pro-α1(I) collagen, fibronectin, and PAI-1 mRNA. The quantitative differences in the rates of cell proliferation and ECM gene expression between TGF-β1^+/+ and TGF-β1^−/− cells could be eliminated by treatment of TGF-β1^+/+ cells with a neutralizing antibody of TGF-β1. Thus, our results are consistent with the hypothesis that TGF-β1 acts as a negative autocrine regulator of growth and a positive autocrine regulator of ECM biosynthesis in embryonic fibroblasts. 176:67–75, 1998. Published 1998 Wiley-Liss, Inc.

1 This article was prepared by a group of United States government employees and non-United States government employees, and as such is subject to 17 U.S.C. Sec. 105.

     

PITPNC1 promotes the thermogenesis of brown adipose tissue under acute cold exposure

Brown adipose tissue(BAT) plays an essential role in non-shivering thermogenesis. The phosphatidylinositol transfer protein,cytoplasmic 1(PITPNC1) is identified as a lipid transporter that reciprocally transfers phospholipids between intracellular membrane structures. However, the physiological significance of PITPNC1 and its regulatory mechanism remain unclear. Here,we demonstrate that PITPNC1 is a key player in thermogenesis of BAT. While Pitpnc1^-/-mice do not differ with wildtype m...     

Altered Phase-Relationship between Peripheral Oscillators and Environmental Time in Cry1 or Cry2 Deficient Mouse Models for Early and Late Chronotypes

The mammalian circadian system is composed of a light-entrainable central clock in the suprachiasmatic nuclei (SCN) of the brain and peripheral clocks in virtually any other tissue. It allows the organism to optimally adjust metabolic, physiological and behavioral functions to the physiological needs it will have at specific time of the day. According to the resonance theory, such rhythms are only advantageous to an organism when in tune with the environment, which is illustrated by the adverse health effects originating from chronic circadian disruption by jetlag and shift work. Using short-period Cry1 and long-period Cry2 deficient mice as models for morningness and eveningness, respectively, we explored the effect of chronotype on the phase relationship between the central SCN clock and peripheral clocks in other organs. Whereas the behavioral activity patterns and circadian gene expression in the SCN of light-entrained Cry1^-/- and Cry2^-/- mice largely overlapped with that of wild type mice, expression of clock and clock controlled genes in liver, kidney, small intestine, and skin was shown to be markedly phase-advanced or phase-delayed, respectively. Likewise, circadian rhythms in urinary corticosterone were shown to display a significantly altered phase relationship similar to that of gene expression in peripheral tissues. We show that the daily dissonance between peripheral clocks and the environment did not affect the lifespan of Cry1^-/- or Cry2^-/- mice. Nonetheless, the phase-shifted peripheral clocks in light-entrained mice with morningness and eveningness-like phenotypes may have implications for personalized preventive and therapeutic (i.e. chronomodulation-based) health care for people with early and late chronotypes.     

Loss of Nrf2 in bone marrow-derived macrophages impairs antigen-driven CD8+ T cell function by limiting GSH and Cys availability

NF-E2-related factor 2 (Nrf2), known to protect against reactive oxygen species, has recently been reported to resolve acute inflammatory responses in activated macrophages. Consequently, disruption of Nrf2 promotes a proinflammatory macrophage phenotype. In the current study, we addressed the impact of this macrophage phenotype on CD8⁺ T cell activation by using an antigen-driven coculture model consisting of Nrf2^−/− and Nrf2^+/+ bone marrow-derived macrophages (BMDMΦ) and transgenic OT-1 CD8⁺ T cells. OT-1 CD8⁺ T cells encode a T cell receptor that specifically recognizes MHC class I-presented ovalbumin OVA(257–264) peptide, thereby causing a downstream T cell activation. Interestingly, coculture of OVA(257–264)-pulsed Nrf2^−/− BMDMΦ with transgenic OT-1 CD8⁺ T cells attenuated CD8⁺ T cell activation, proliferation, and cytotoxic function. Since the provision of low-molecular-weight thiols such as glutathione (GSH) or cysteine (Cys) by macrophages limits antigen-driven CD8⁺ T cell activation, we quantified the amounts of intracellular and extracellular GSH and Cys in both cocultures. Indeed, GSH levels were strongly decreased in Nrf2^−/− cocultures compared to wild-type counterparts. Supplementation of thiols in Nrf2^−/− cocultures via addition of glutathione ester, N-acetylcysteine, β-mercaptoethanol, or cysteine itself restored T cell proliferation as well as cytotoxicity by increasing intracellular GSH. Mechanistically, we identified two potential Nrf2-regulated genes involved in thiol synthesis in BMDMΦ: the cystine transporter subunit xCT and the modulatory subunit of the GSH-synthesizing enzyme γ-GCS (GCLM). Pharmacological inhibition of γ-GCS-dependent GSH synthesis as well as knockdown of the cystine antiporter xCT in Nrf2^+/+ BMDMΦ mimicked the effect of Nrf2^−/− BMDMΦ on CD8⁺ T cell function. Our findings demonstrate that reduced levels of GCLM as well as xCT in Nrf2^−/− BMDMΦ limit GSH availability, thereby inhibiting antigen-induced CD8⁺ T cell function.     

Protein deglycase DJ-1 deficiency induces phenotypic switching in vascular smooth muscle cells and exacerbates atherosclerotic plaque instability

Protein deglycase DJ-1 (DJ-1) is a multifunctional protein involved in various biological processes. However, it is unclear whether DJ-1 influences atherosclerosis development and plaque stability. Accordingly, we evaluated the influence of DJ-1 deletion on the progression of atherosclerosis and elucidate the underlying mechanisms. We examine the expression of DJ-1 in atherosclerotic plaques of human and mouse models which showed that DJ-1 expression was significantly decreased in human plaques compared with that in healthy vessels. Consistent with this, the DJ-1 levels were persistently reduced in atherosclerotic lesions of ApoE^−/− mice with the increasing time fed by western diet. Furthermore, exposure of vascular smooth muscle cells (VSMCs) to oxidized low-density lipoprotein down-regulated DJ-1 in vitro. The canonical markers of plaque stability and VSMC phenotypes were evaluated in vivo and in vitro. DJ-1 deficiency in Apoe^−/− mice promoted the progression of atherosclerosis and exaggerated plaque instability. Moreover, isolated VSMCs from Apoe^−/−DJ-1^−/− mice showed lower expression of contractile markers (α-smooth muscle actin and calponin) and higher expression of synthetic indicators (osteopontin, vimentin and tropoelastin) and Kruppel-like factor 4 (KLF4) by comparison with Apoe^−/−DJ-1^+/+ mice. Furthermore, genetic inhibition of KLF4 counteracted the adverse effects of DJ-1 deletion. Therefore, our results showed that DJ-1 deletion caused phenotype switching of VSMCs and exacerbated atherosclerotic plaque instability in a KLF4-dependent manner.     

Thymic stromal lymphopoietin is a key cytokine for the immunomodulation of atherogenesis with Freund's adjuvant

Adaptive immune responses regulate the development of atherosclerosis, with a detrimental effect of type 1 but a protective role of type 2 immune responses. Immunization of Apolipoprotein E-deficient (ApoE^−/−) mice with Freund's adjuvant inhibits the development of atherosclerosis. However, the underlying mechanisms are not fully understood. Thymic stromal lymphopoietin (TSLP) is an IL7-like cytokine with essential impact on type 2 immune responses (Th2). Thymic stromal lymphopoietin is strongly expressed in epithelial cells of the skin, but also in various immune cells following appropriate stimulation. In this study, we investigated whether TSLP may be crucial for the anti-atherogenic effect of Freund's adjuvant. Subcutaneous injection of complete Freund's adjuvant (CFA) rapidly led to the expression of TSLP and IL1β at the site of injection. In male mice, CFA-induced TSLP occurred in immigrated monocytes—and not epithelial cells—and was dependent on NLRP3 inflammasome activation and IL1β-signalling. In females, CFA-induced TSLP was independent of IL1β and upon ovariectomy. CFA/OVA led to a more pronounced imbalance of the T cell response in TSLPR^−/− mice, with increased INFγ/IL4 ratio compared with wild-type controls. To test whether TSLP contributes to the anti-atherogenic effects of Freund's adjuvant, we treated ApoE^−/− and ApoE^−/−/TSLPR^−/− mice with either CFA/IFA or PBS. ApoE^−/− mice showed less atherogenesis upon CFA/IFA compared with PBS injections. ApoE^−/−/TSLPR^−/− mice had no attenuation of atherogenesis upon CFA/IFA treatment. Freund's adjuvant executes significant immune-modulating effects via TSLP induction. TSLP-TSLPR signalling is critical for CFA/IFA-mediated attenuation of atherosclerosis.     

Postnatal Constant Light Compensates Cryptochrome1 and 2 Double Deficiency for Disruption of Circadian Behavioral Rhythms in Mice under Constant Dark

Clock genes Cryptochrome (Cry1) and Cry2 are essential for expression of circadian rhythms in mice under constant darkness (DD). However, circadian rhythms in clock gene Per1 expression or clock protein PER2 are detected in the cultured suprachiasmatic nucleus (SCN) of neonatal Cry1 and Cry2 double deficient (Cry1 ^-/-/Cry2 ^-/-) mice. A lack of circadian rhythms in adult Cry1 ^-/-/Cry2 ^-/- mice is most likely due to developmentally disorganized cellular coupling of oscillating neurons in the SCN. On the other hand, neonatal rats exposed to constant light (LL) developed a tenable circadian system under prolonged LL which was known to fragment circadian behavioral rhythms. In the present study, Cry1 ^-/-/Cry2 ^-/- mice were raised under LL from postnatal day 1 for 7 weeks and subsequently exposed to DD for 3 weeks. Spontaneous movement was monitored continuously after weaning and PER2::LUC was measured in the cultured SCN obtained from mice under prolonged DD. Surprisingly, Chi square periodogram analysis revealed significant circadian rhythms of spontaneous movement in the LL-raised Cry1 ^-/-/Cry2 ^-/- mice, but failed to detect the rhythms in Cry1 ^-/-/Cry2 ^-/- mice raised under light-dark cycles (LD). By contrast, prolonged LL in adulthood did not rescue the circadian behavioral rhythms in the LD raised Cry1 ^-/-/Cry2 ^-/- mice. Visual inspection disclosed two distinct activity components with different periods in behavioral rhythms of the LL-raised Cry1^-/-/Cry2^-/- mice under DD: one was shorter and the other was longer than 24 hours. The two components repeatedly merged and separated. The patterns resembled the split behavioral rhythms of wild type mice under prolonged LL. In addition, circadian rhythms in PER2::LUC were detected in some of the LL-raised Cry1^-/-/Cry2^-/- mice under DD. These results indicate that neonatal exposure to LL compensates the CRY double deficiency for the disruption of circadian behavioral rhythms under DD in adulthood.     

Metabolic syndrome exacerbates amyloid pathology in a comorbid Alzheimer's mouse model

Alzheimer's disease (AD) often coexists with other aging-associated diseases including obesity, diabetes, hypertension, and cardiovascular diseases. The early stage of these comorbidities is known as metabolic syndrome (MetS) which is highly prevalent in mid-life. An important cause of MetS is the deficiency of SIRT3, a mitochondrial deacetylase which enhances the functions of critical mitochondrial proteins, including metabolic enzymes, by deacetylation. Deletion of Sirt3 gene has been reported to result in the acceleration of MetS. In a recently published study, we demonstrated in the brain of Sirt3^−/− mice, downregulation of metabolic enzymes, insulin resistance and elevation of inflammatory markers including microglial proliferation. These findings suggested a novel pathway that could link SIRT3 deficiency to neuroinflammation, an important cause of Alzheimer's pathogenesis. Therefore, we hypothesized that MetS and amyloid pathology may interact through converging pathways of insulin resistance and neuroinflammation in comorbid AD. To investigate these interactions, we crossed Sirt3^−/− mice with APP/PS1 mice and successfully generated APP/PS1/Sirt3^−/− mice with amyloid pathology and MetS. In these comorbid AD mice, we observed exacerbation of insulin resistance, glucose intolerance, amyloid plaque deposition, markers of neuroinflammation, including elevated expression of IL-1β, TNF-α and Cox-2 at 8 months of age. There was also increased microglial proliferation and activation. Our observations suggest a novel mechanism by which MetS may interact with amyloid pathology during the cellular phase of AD. Therapeutic targeting of SIRT3 in AD with comorbidities may produce beneficial effects.