Jen-nie H. Miller

Sustained hippocampal IL-1β overexpression mediates chronic neuroinflammation and ameliorates Alzheimer plaque pathology

Neuroinflammation is a conspicuous feature of Alzheimer disease (AD) pathology and is thought to contribute to the ultimate neurodegeneration that ensues. IL-1 beta has emerged as a prime candidate underlying this response. Here we describe a transgenic mouse model of sustained IL-1 beta overexpression that was capable of driving robust neuroinflammation lasting months after transgene activation. This response was characterized by astrocytic and microglial activation in addition to induction of proinflammatory cytokines. Surprisingly, when triggered in the hippocampus of the APPswe/PS1dE9 mouse model of AD, 4 weeks of IL-1 beta overexpression led to a reduction in amyloid pathology. Congophilic plaque area fraction and frequency as well as insoluble amyloid beta 40 (A beta 40) and A beta 42 decreased significantly. These results demonstrate a possible adaptive role for IL-1 beta-driven neuroinflammation in AD and may help explain recent failures of antiinflammatory therapeutics for this disease.

Epidermal growth factor and human growth hormone accelerate adaptation after massive enterectomy in an additive, nutrient-dependent, and site-specific fashion

BACKGROUND After massive enterectomy (ME), remnant intestine undergoes compensatory adaptation. Epidermal growth factor (EGF) and human growth hormone (hGH) have each been shown to enhance total length small intestine nutrient transport after ME. This study aims to determine the differential effects of EGF and hGH on proximal and distal small intestinal remnants after ME. METHODS New Zealand white rabbits underwent 70% mid-jejunoileal resection. After 1 week, animals received hGH (0.2 mg/kg/day), EGF (1.5 micrograms/kg/hr), hGH + EGF, or vehicle (equal volume) for 7 days. Sodium-dependent uptake of glucose, glutamine, alanine, leucine, and arginine into brush border membrane vesicles was quantitated. Serum insulin-like growth factor-I concentrations as well as proximal and distal villus and microvillus heights were measured. IGF binding protein-3 and -4 mRNA expression was determined in full-thickness proximal and distal gut remnants. RESULTS Concomitant hGH and EGF treatment up-regulates glucose (100%), glutamine (80%), and leucine (60%) transport in the proximal remnant; alanine (150%) and arginine (400%) transport in the distal remnant; and microvillus height (25% to 35%) both proximally and distally. Serum IGF-I levels and gross villus heights were not different among groups. CONCLUSIONS Co-infusion of hGH and EGF accelerates intestinal adaptation after ME in an additive, nutrient-dependent, and site-specific fashion via enhanced nutrient transport as well as microvillus hypertrophy.

Sequential Down-regulation of E-Cadherin with Squamous Cell Carcinoma Progression: Loss of E-Cadherin via a Prostaglandin E2-EP2–Dependent Posttranslational Mechanism

The incidence of skin cancer is on the rise, with over 1 million new cases yearly. Although it is known that squamous cell cancers (SCC) are caused by UV light, the mechanism(s) involved remains poorly understood. In vitro studies with epithelial cells or reports examining malignant skin lesions suggest that loss of E-cadherin-mediated cell-cell contacts may contribute to SCCs. Other studies show a pivotal role for cyclooxygenase-dependent prostaglandin E2 (PGE2) synthesis in this process. Using chronically UV-irradiated SKH-1 mice, we show a sequential loss of E-cadherin-mediated cell-cell contacts as lesions progress from dysplasia to SCCs. This E-cadherin down-regulation was also evident after acute UV exposure in vivo. In both chronic and acute UV injury, E-cadherin levels declined at a time when epidermal PGE2 synthesis was enhanced. Inhibition of PGE2 synthesis by indomethacin in vitro, targeted deletion of EP2 in primary mouse keratinocyte (PMK) cultures or deletion of the EP2 receptor in vivo abrogated this UV-induced E-cadherin down-regulation. In contrast, addition of PGE2 or the EP2 receptor agonist butaprost to PMK produced a dose- and time-dependent decrease in E-cadherin. We also show that UV irradiation, via the PGE2-EP2 signaling pathway, may initiate tumorigenesis in keratinocytes by down-regulating E-cadherin-mediated cell-cell contacts through its mobilization away from the cell membrane, internalization into the cytoplasm, and shuttling through the lysosome and proteasome degradation pathways. Further understanding of how UV-PGE2-EP2 down-regulates E-cadherin may lead to novel chemopreventative strategies for the treatment of skin and other epithelial cancers.

Osteoarthritis accelerates and exacerbates Alzheimer's disease pathology in mice

BackgroundThe purpose of this study was to investigate whether localized peripheral inflammation, such as osteoarthritis, contributes to neuroinflammation and neurodegenerative disease in vivo.MethodsWe employed the inducible Col1-IL1βXAT mouse model of osteoarthritis, in which induction of osteoarthritis in the knees and temporomandibular joints resulted in astrocyte and microglial activation in the brain, accompanied by upregulation of inflammation-related gene expression. The biological significance of the link between peripheral and brain inflammation was explored in the APP/PS1 mouse model of Alzheimers disease (AD) whereby osteoarthritis resulted in neuroinflammation as well as exacerbation and acceleration of AD pathology.ResultsInduction of osteoarthritis exacerbated and accelerated the development of neuroinflammation, as assessed by glial cell activation and quantification of inflammation-related mRNAs, as well as Aβ pathology, assessed by the number and size of amyloid plaques, in the APP/PS1; Col1-IL1βXAT compound transgenic mouse.ConclusionThis work supports a model by which peripheral inflammation triggers the development of neuroinflammation and subsequently the induction of AD pathology. Better understanding of the link between peripheral localized inflammation, whether in the form of osteoarthritis, atherosclerosis or other conditions, and brain inflammation, may prove critical to our understanding of the pathophysiology of disorders such as Alzheimers, Parkinsons and other neurodegenerative diseases.

Growth Factors Regulation of Rabbit Sodium-Dependent Neutral Amino Acid Transporter ATB0 and Oligopeptide Transporter 1 mRNAs Expression after Enterectomy

BACKGROUND Sucessful intestinal adaptation after massive enterectomy is dependent on increased efficiency of nutrient transport. However, midgut resection (MGR) in rabbits induces an initial decrease in sodium-dependent brush border neutral amino acid transport, whereas parenteral epidermal growth factor (EGF) and growth hormone (GH) reverse this downregulation. We investigated intestinal amino acid transporter B0 (ATB0) and oligopeptide transporter 1 (PEPT 1) mRNA expression after resection and in response to EGF and/or GH. METHODS Rabbits underwent anesthesia alone (control) or proximal, midgut, and distal resections. Full-thickness intestine was harvested from all groups on postoperative day (POD) 7, and on POD 14 from control and MGR rabbits. A second group of MGR rabbits received EGF and/or GH for 7 days, beginning 7 days after resection. ATB0 and PEPT 1 mRNA levels were determined by Northern blot analysis. RESULTS In control animals, ileal ATB0 mRNA abundance was three times higher than jejunal mRNA, whereas PEPT 1 mRNA expression was similar. By 7 and 14 days after MGR, jejunal ATB0 mRNA abundance was decreased by 50% vs control jejunum. A 50% decrease in jejunal PEPT 1 message was delayed until 14 days after MGR. Treatment with EGF plus GH did not alter ATB0 mRNA expression but doubled PEPT 1 mRNA in the jejunum. CONCLUSION The site of resection, time postresection, and growth factors treatment differentially influence ATB0 and PEPT 1 mRNA expression. Enhanced sodium-dependent brush border neutral amino acid transport with GH plus EGF administration is independent of increased ATB0 mRNA expression in rabbit small intestine after enterectomy.

Spinal interleukin-1β in a mouse model of arthritis and joint pain

OBJECTIVE Pain from arthritis has been associated with peripheral sensitization of primary sensory afferents and the development of inflammation at the dorsal horns. This study was undertaken to determine whether the role of spinal interleukin-1beta (IL-1beta) in central processing of pain is important in the development of arthritis. METHODS Col1-IL-1betaXAT mice and GFAP-IL-1betaXAT mice were injected with the feline immunodeficiency virus (FIV) (Cre) vector in the right and left temporomandibular joints (TMJs), or in the cisterna magna, respectively, to induce IL-1beta expression in the dorsal horns of the spinal horn. To inhibit intrathecal IL-1 receptor type I (IL-1RI) signaling, FIV(IL-1Ra) vector was injected into the cisterna magna of Col1-IL-1betaXAT mice. The effects of IL-1RI receptor inhibition in GFAP-IL-1betaXAT mice were studied in the GFAP-IL-1betaXAT-IL-1RI(-/-) compound mouse model. Neuroinflammatory, sensory, and behavioral changes were evaluated in conjunction with arthritic changes in the TMJ, assessed by histopathologic and immunohistochemical analyses. RESULTS Induction of an osteoarthritis-like condition in the TMJ in the Col1-IL-1betaXAT mouse model resulted in up-regulation of murine IL-1beta at the dorsal horns. Moreover, intrathecal inhibition of IL-1RI in Col1-IL-1betaXAT mice with arthritis led to amelioration of joint pathology and attenuation of the attendant joint pain. Overexpression of spinal IL-1beta in the recently developed GFAP-IL-1betaXAT somatic mosaic model of neuroinflammation led to development of arthritis-like pathology accompanied by increased pain-like behavior. CONCLUSION Our results indicate that joint pathology and pain are dependent on spinal IL-1beta, and suggest the presence of a bidirectional central nervous system-peripheral joints crosstalk that may contribute to the development, expansion, and exacerbation of arthritis.

Octreotide diminishes luminal nutrient transport activity, which is reversed by epidermal growth factor

BACKGROUND Octreotide (SMS) is a somatostatin analogue utilized in patients with short bowel syndrome (SBS) to decrease output. It may inhibit small bowel adaptation by blocking the secretion of trophic hormones such as epidermal growth factor (EGF). This study delineates the effects of SMS and EGF on nutrient transport in SBS. METHODS One week after 70% jejunoileal resection, 20 New Zealand White rabbits (2 kg) received subcutaneous infusions of saline or EGF (1.5 micrograms/kg/hr) and injections of saline or SMS s.q.b.i.d. The study groups were EGF/saline, saline/saline, saline/SMS, and EGF/SMS. After 7 days of infusion, intestinal brush border membrane vesicles were prepared and nutrient transport measured. RESULTS SMS reduced active nutrient transport. Kinetics confirmed this was secondary to a reduction in functional carriers in the brush border membrane, without a change in carrier affinity. The coinfusion of EGF ameliorated this effect. On an individual basis, EGF alone did not significantly increase nutrient transport, but when taken as a group, nutrients transport was upregulated 26%. CONCLUSIONS SMS is detrimental to small bowel adaptation. EGF reverses this effect and may benefit patients with SBS who require SMS to control high intestinal output.

Peripheral blood mononuclear cell infiltration and neuroinflammation in the HexB−/− mouse model of neurodegeneration

Myeloid-derived immune cells, including microglia, macrophages and monocytes, have been previously implicated in neurodegeneration. We investigated the role of infiltrating peripheral blood mononuclear cells (PBMC) in neuroinflammation and neurodegeneration in the HexB-/- mouse model of Sandhoff disease. Ablation of the chemokine receptor CCR2 in the HexB-/- mouse resulted in significant inhibition of PBMC infiltration into the brain, decrease in TNFalpha and MHC-II mRNA abundance and retardation in clinical disease development. There was no change in the level of GM2 storage and pro-apoptotic activity or astrocyte activation in HexB-/-; Ccr2-/- double knockout mice, which eventually succumbed secondary to GM2 gangliosidosis.

Glucocorticoids upregulate intestinal nutrient transport in a time-dependent and substrate-specific fashion

Ghicocoracoids mediate skeletal muscle proteolysis during critical illness to provide substrates for hepatic acute-phase protein synthesis and gluconeogenesis The effects of hypercorasolemia on splanchnic substrate uptake are not well defined This study characterizes intestinal nutrient transport in response to acute elevations of plasma glucocorucoid levels New Zealand White rabbits were randomized to receive either dexamethasone (2 mg/kg intramuscularly) or vehicle and were killed 8, 16, or 24 hours after steroid treatment Brush-border membrane vesicles were prepared from pooled small intestinal mucosa and the uptake of tritiated substrates was quantified. Serum insuhn-like growth factor 1 (IGF-1) levels, mucosal DNA content, and mucosal morphology were determined Glucocorticoids increased glucose and leucme uptake at 8 hours (80% and 24%, respectively) and 24 hours (147% and 50%, respectively) Glutamine, alanine, and arginine transport increased by 42%, 96%, and 236%, respectively, at 24 hours Sodium-m-dependent transport (diffusion) of all substrates was increased by 240% by dexamethasone treatment at 24 hours Mucosal DNA content increased by 32%, whereas microvillus heights decreased by 27% at 24 hours No effects were noted on IGF-1 levels or gross villus heights Glucocorticoids acutely accelerate intestinal nutrient transport m a time-related and substrate-specific fashion Although the mechanism of glucocorticoid action remains unclear, both genomic and plasma membrane effects are implicated

Sequential alterations in gut mucosal amino acid and glucose transport after 70% small bowel resection

BACKGROUND Studies in animals with short bowel syndrome (SBS) suggest that up-regulation of nutrient transporter activity occurs as an adaptive response to the loss of absorptive area. It is unclear, however, whether nutrient transport is altered at the cell membrane in SBS. The purpose of this study is to clarify amino acid and glucose transport in small intestinal luminal mucosa after 70% small bowel resection in rabbits. METHODS New Zealand white rabbits underwent 70% jejunoileal resection (n = 27) or a sham operation (n = 19). Brush border membrane vesicles were prepared from small intestinal mucosa at 1 week, 1 month, and 3 months by magnesium aggregation-differential centrifugation. Transport of L-glutamine, L-alanine, L-leucine, L-arginine, and D-glucose was assayed by a rapid mixing-filtration technique. RESULTS We observed no difference in uptake of all amino acids and glucose at 1 week. The uptake of amino acids and glucose was decreased by 20% to 80% in animals with SBS at 1 month. By 3 months all uptake values except that of glucose returned to normal. Kinetic studies of the system B transporter for glutamine indicate that the decrease in uptake at 1 month was caused by a reduction in the Vmax (1575 +/- 146 versus 2366 +/- 235, p < 0.05) consistent with a decrease in the number of functional carriers on the brush border membrane. CONCLUSIONS In addition to the anatomic loss of absorptive area after massive bowel resection, alterations in enterocyte transport function may be responsible for malabsorption in patients with SBS.