The Effect of Diet Composition on the Post-operative Outcomes of Roux-en-Y Gastric Bypass in Mice

PURPOSE

Roux-en-Y gastric bypass (RYGB) leads to the improvement of many obesity-associated conditions. The degree to which post-operative macronutrient composition contributes to metabolic improvement after RYGB is understudied.

METHODS

A mouse model of RYGB was used to examine the effects of diet on the post-operative outcomes of RYGB. Obese mice underwent either Sham or RYGB surgery and were administered either chow or HFD and then monitored for an additional 8 weeks.

RESULTS

After RYGB, reductions to body weight, fat mass, and lean mass were similar regardless of diet. RYGB and HFD were independently detrimental to bone mineral density and plasma vitamin D levels. Independent of surgery, HFD accelerated hematopoietic stem and progenitor cell proliferation and differentiation and exhibited greater myeloid lineage commitment. Independent of diet, systemic iron deficiency was present after RYGB. In both Sham and RYGB groups, HFD increased energy expenditure. RYGB increased fecal energy loss, and HFD after RYGB increased fecal lipid content. RYGB lowered fasting glucose and liver glycogen levels but HFD had an opposing effect. Indices of insulin sensitivity improved independent of diet. HFD impaired improvements to dyslipidemia, NAFLD, and fibrosis.

CONCLUSION

Post-operative diet plays a significant role in determining the degree to which RYGB reverses obesity-induced metabolic abnormalities such as hyperglycemia, dyslipidemia, and NAFLD. Diet composition may be targeted in order to assist in the treatment of post-RYGB bone mineral density loss and vitamin D deficiency as well as to reverse myeloid lineage commitment. HFD after RYGB continues to pose a significant multidimensional health risk.

Therapeutic Potential of P110 Peptide: New Insights into Treatment of Alzheimer's Disease

Mitochondrial degeneration in various neurodegenerative diseases, specifically in Alzheimer's disease, involves excessive mitochondrial fission and reduced fusion, leading to cell damage. P110 is a seven-amino acid peptide that restores mitochondrial dynamics by acting as an inhibitor of mitochondrial fission. However, the role of P110 as a neuroprotective agent in AD remains unclear. Therefore, we performed cell culture studies to evaluate the neuroprotective effect of P110 on amyloid-β accumulation and mitochondrial functioning. Human SH-SY5Y neuronal cells were incubated with 1 µM and 10 µM of P110, and Real-Time PCR and Western blot analysis were done to quantify the expression of genes pertaining to AD and neuronal health. Exposure of SH-SY5Y cells to P110 significantly increased APP mRNA levels at 1 µM, while BACE1 mRNA levels were increased at both 1 µM and 10 µM. However, protein levels of both APP and BACE1 were significantly reduced at 10 µM of P110. Further, P110 treatment significantly increased ADAM10 and Klotho protein levels at 10 µM. In addition, P110 exposure significantly increased active mitochondria and reduced ROS in live SH-SY5Y cells at both 1 µM and 10 µM concentrations. Taken together, our results indicate that P110 might be useful in attenuating amyloid-β generation and improving neuronal health by maintaining mitochondrial function in neurons.

NOGOB receptor deficiency increases cerebrovascular permeability and hemorrhage via impairing histone acetylation-mediated CCM1/2 expression

The loss function of cerebral cavernous malformation (CCM) genes leads to most CCM lesions characterized by enlarged leaking vascular lesions in the brain. Although we previously showed that NOGOB receptor (NGBR) knockout in endothelial cells (ECs) results in cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NGBR regulates CCM1/2 expression has not been elucidated. Here, we show that genetic depletion of Ngbr in ECs at both postnatal and adult stages results in CCM1/2 expression deficiency and cerebrovascular lesions such as enlarged vessels, blood-brain-barrier hyperpermeability, and cerebral hemorrhage. To reveal the molecular mechanism, we used RNA-sequencing analysis to examine changes in the transcriptome. Surprisingly, we found that the acetyltransferase HBO1 and histone acetylation were downregulated in NGBR-deficient ECs. The mechanistic studies elucidated that NGBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NGBR impairs the binding of HBO1 and acetylated histone H4K5 and H4K12 on the promotor of the CCM1 and CCM2 genes. Our findings on epigenetic regulation of CCM1 and CCM2 that is modulated by NGBR and HBO1-mediated histone H4 acetylation provide a perspective on the pathogenesis of sporadic CCMs.

Abstract WMP76: Nogo-B Receptor Is Essential For Preserving HBO1-mediated Histone Acetylation In Brain Endothelial Cells And Preventing Cerebrovascular Hemorrhage

Cerebral cavernous malformations (CCMs) are enlarged leaking vascular lesions in the brain caused by loss-of-function mutations in CCM1/2/3 genes or loss of expression. Although we previously showed that Nogo-B receptor (NgBR) knockout in endothelial cells (ECs) results in CCMs-like cerebrovascular lesions in the mouse embryo, the molecular mechanism by which NgBR regulates CCM1/2 expression has not been elucidated. Here, we show that temporal genetic depletion of NgBR in ECs at both the postnatal and adult stages results in CCM1/2 expression deficiency and consequently CCMs-like lesions such as enlarged vessels, blood-brain barrier (BBB) hyperpermeability, and intracerebral hemorrhage. These cerebrovascular defects in the brain of NgBR endothelial-specific knockout (ecKO) mice can be rescued by adeno-associated virus (AAV)-mediated overexpression of CCM1 and CCM2 genes. To reveal the molecular mechanism, we used RNA-seq analysis to examine changes in the transcriptome. Surprisingly, we found that acetyltransferase HBO1 was downregulated in NgBR deficient ECs. The mechanistic study elucidated that NgBR is required for maintaining the expression of CCM1/2 in ECs via HBO1-mediated histone acetylation. ChIP-qPCR data further demonstrated that loss of NgBR impairs the binding of both the HBO1 and acetylated H4K5/K12 at the promoter of CCM1 and CCM2 genes. Similarly, AAV-mediated overexpression of HBO1 restores the acetylation of H4K5/K12 and rescues the CCMs-like cerebrovascular defects in the brain of NgBR ecKO mice. Our findings on epigenetic regulation of CCM1 and CCM2 provide a perspective that NgBR and HBO1-mediated histone H4 acetylation may be targeted for preventing the onset of CCMs-like cerebrovascular disease.

A simple, rapid, and sensitive fluorescence-based method to assess triacylglycerol hydrolase activity

Lipases constitute an important class of water-soluble enzymes that catalyze the hydrolysis of hydrophobic triacylglycerol (TAG). Their enzymatic activity is typically measured using multistep procedures involving isolation and quantification of the hydrolyzed products. We report here a new fluorescence method to measure lipase activity in real time that does not require the separation of substrates from products. We developed this method using adipose triglyceride lipase (ATGL) and lipoprotein lipase (LpL) as model lipases. We first incubated a source of ATGL or LpL with substrate vesicles containing nitrobenzoxadiazole (NBD)-labeled TAG, then measured increases in NBD fluorescence, and calculated enzyme activities. Incorporation of NBD-TAG into phosphatidylcholine (PC) vesicles resulted in some hydrolysis; however, incorporation of phosphatidylinositol into these NBD-TAG/PC vesicles and increasing the ratio of NBD-TAG to PC greatly enhanced substrate hydrolysis. This assay was also useful in measuring the activity of pancreatic lipase and hormone-sensitive lipase. Next, we tested several small-molecule lipase inhibitors and found that orlistat inhibits all lipases, indicating that it is a pan-lipase inhibitor. In short, we describe a simple, rapid, fluorescence-based triacylglycerol hydrolysis assay to assess four major TAG hydrolases: intracellular ATGL and hormone-sensitive lipase, LpL localized at the extracellular endothelium, and pancreatic lipase present in the intestinal lumen. The major advantages of this method are its speed, simplicity, and elimination of product isolation. This assay is potentially applicable to a wide range of lipases, is amenable to high-throughput screening to discover novel modulators of triacylglycerol hydrolases, and can be used for diagnostic purposes.

Abstract P112: A Simple, Rapid, And Sensitive Fluorescence-based Method To Assess Triacylglycerol Hydrolase Activities

Introduction: Lipases constitute an important class of water-soluble enzymes that catalyze the hydrolysis of hydrophobic triacylglycerol (TAG). Their activity is usually measured after isolation and quantification of the hydrolyzed free fatty acids. We have used NBD-labeled lipids previously to develop TAG, cholesteryl ester, and phospholipid transfer assays for microsomal triglyceride transfer protein. To date, however, NBD-labeled TAG (NBD-TAG) has not been used to assess the enzymatic activities of different lipases.

Methods: We developed methods to measure lipase activities using adipose triglyceride lipase (ATGL), lipoprotein lipase (LpL), and pancreatic triglyceride lipase (PNLIP) as model lipases. In these assays, we incubated a source of ATGL, LpL, or PNLIP with substrate emulsions containing nitrobenzoxadiazole (NBD)-labeled TAG in phosphatidylcholine (PC) and phosphatidylinositol (PI), measured increases in NBD fluorescence with time, and calculated enzyme activities.

Results: Incorporation of NBD-TAG into PC vesicles resulted in some hydrolysis; but required product isolation step to measure NBD fluorescence. However, incorporation of PI into these NBD-TAG/PC vesicles significantly increased substrate hydrolysis in time, protein, and substrate concentration dependent manner negating the need to isolate products to measure lipase activities. Further, increasing the ratio of NBD-TAG to PC enhanced substrate hydrolysis. Next, we tested specific lipase inhibitors and found that orlistat inhibits all three enzymes indicating that it is a pan-lipase inhibitor.

Conclusions: We describe a simple, rapid fluorescence-based TAG hydrolysis assay to assess three major TAG hydrolases: ATGL localized intracellularly, LpL localized at the extracellular endothelium, and PNLIP produced and secreted from the pancreas into the intestinal lumen. The major advantages of this method are its speed, simplicity, and avoidance of a product isolation step. This assay is potentially applicable to a wide range of lipases and is amenable to high-throughput screening to discover novel modulators of triacylglycerol hydrolases, and in the diagnosis of diseases associated with increases in plasma lipase activities.

Lipocalin-type Prostaglandin D2 Synthase appears to function as a Novel Adipokine Preventing Adipose Dysfunction in response to a High Fat Diet

Adipose dysfunction is the primary defect in obesity that contributes to the development of dyslipidemia, insulin resistance, cardiovascular diseases, type 2 diabetes, non-alcoholic fatty liver disease (NAFLD) and some cancers. Previously, we demonstrated the development of NAFLD in lipocalin-type prostaglandin D₂ synthase (L-PGDS) knockout mice regardless of diet. In the present study, we examined the role of L-PGDS in adipose in response to a high fat diet. We observed decreased expression of L-PGDS in adipose tissue and concomitant lower plasma levels in a dietary model of obesity as well as in insulin resistant 3T3-L1 adipocytes. We show reduced adiponectin expression and phosphorylation of AMPK in white adipose tissue of L-PGDS KO mice after 14 weeks on a high fat diet as compared to control C57BL/6 mice. We also observe an increased fat content in L-PGDS KO mice as demonstrated by adipocyte hypertrophy and increased expression of lipogenenic genes. We confirmed our in vivo findings in in vitro 3T3-L1 adipocytes, using an enzymatic inhibitor of L-PGDS (AT56). Rosiglitazone treatment drastically increased L-PGDS expression in insulin resistant 3T3-L1 adipocytes and increased adiponectin expression and AMPK phosphorylation in AT56 treated 3T3-L1 adipocytes. We conclude that the absence of L-PGDS has a deleterious effect on adipose tissue functioning, which further reduces insulin sensitivity in adipose tissue. Consequently, we propose L-PGDS appears to function as a potential member of the adipokine secretome involved in the regulation of the obesity-associated metabolic syndrome.

Pathological findings in the postmortem liver of patients with coronavirus disease 2019 (COVID-19)

Although coronavirus disease 2019 (COVID-19) is transmitted via respiratory droplets, there are multiple gastrointestinal and hepatic manifestations of the disease, including abnormal liver-associated enzymes. However, there are not many published articles on the pathological findings in the liver of patients with COVID-19. We collected the clinical data from 17 autopsy cases of patients with COVID-19 including age, sex, Body mass index (BMI), liver function test (alanine aminotransaminase (ALT), aspartate aminotransaminase (AST), alkaline phosphatase (ALP), direct bilirubin, and total bilirubin), D-dimer, and anticoagulation treatment. We examined histopathologic findings in postmortem hepatic tissue, immunohistochemical (IHC) staining with antibody against COVID-19 spike protein, CD68 and CD61, and electron microscopy. We counted the number of megakaryocytes in liver sections from these COVID-19-positive cases. Abnormal liver-associated enzymes were observed in 12 of 17 cases of COVID-19 infection. With the exception of three cases that had not been tested for D-dimer, all 14 patients' D-dimer levels were increased, including the cases that received varied doses of anticoagulation treatment. Microscopically, the major findings were widespread platelet-fibrin microthrombi, steatosis, histiocytic hyperplasia in the portal tract, mild lobular inflammation, ischemic-type hepatic necrosis, and zone 3 hemorrhage. Rare megakaryocytes were found in sinusoids. COVID-19 IHC demonstrates positive staining of the histiocytes in the portal tract. Under electron microscopy, histiocyte proliferation is present in the portal tract containing lipid droplets, lysosomes, dilated ribosomal endoplasmic reticulum, microvesicular bodies, and coronavirus. The characteristic findings in the liver of patients with COVID-19 include numerous amounts of platelet-fibrin microthrombi, as well as various degrees of steatosis and histiocytic hyperplasia in the portal tract. Possible mechanisms are also discussed.

Field demonstration of polymer-amended in situ chemical oxidation (PA-ISCO)

The methods and results of the first field-scale demonstration of polymer-amended in situ chemical oxidation (PA-ISCO) are presented. The demonstration took place at MCB CAMLEJ (Marine Corps Base, Camp Lejeune) Operable Unit (OU) 15, Site 88, in Camp Lejeune, North Carolina between October and December 2010. PA-ISCO was developed as an alternative treatment approach that utilizes viscosity-modified fluids to improve the in situ delivery and distribution (i.e. sweep-efficiency) of chemical oxidants within texturally heterogeneous contaminated aquifers. The enhanced viscosity of the fluid mitigates the effects of preferential flows, improving sweep-efficiency and enhancing the subsurface contact between the injected oxidant and the target contamination within the treatment zone. The PA-ISCO fluid formulation used in this demonstration included sodium permanganate as oxidant, xanthan gum biopolymer as a shear-thinning viscosifier, and sodium hexametaphosphate (SHMP) as an anti-coagulant. It was the goal of this demonstration to validate the utility of PA-ISCO within a heterogeneous aquifer. An approximate 100% improvement in sweep-efficiency was achieved for the PA-ISCO fluid, as compared to a permanganate-only injection within an adjacent control plot.

Lipocalin-type prostaglandin D2 synthase reduces glucagon secretion in alpha TC-1 clone 6 cells via the DP1 receptor

Diabetes is associated with disturbances in the normal levels of both insulin and glucagon, both of which play critical roles in the regulation of glycemia. Recent studies have found lipocalin-type prostaglandin D₂ synthase (l-PGDS) to be an emerging target involved in the pathogenesis of type-2 diabetes. This study focused on the effect of l-PGDS on glucagon secretion from cultured pancreatic Alpha TC-1 Clone 6 cells. When cells were treated with various concentrations of l-PGDS (0, 10, 50, and 100 ug/ml) for 2 h in 1 mM glucose; glucagon secretion decreased to 670±45, 838±38, 479±11, and 437±45 pg/ml, respectively. In addition, pancreatic islets were isolated from C57BL/6 mice and stained for prostaglandin D₂ receptors, DP1 and DP2, using immunohistochemistry. Our results showed that these islets express only the DP1 receptor. Pancreatic islets were then stained for alpha and beta cells, as well as DP1, to find the primary location of the receptor within the islets using immunofluorescence. Interestingly, DP1 receptor density was found primarily in alpha cells rather than in beta cells. Our study is the first to report a correlation between l-PGDS and glucagon secretion in alpha cells. Based on our obtained results, it can be concluded that higher concentrations of l-PGDS significantly reduced the secretion of glucagon in alpha cells, which may contribute to the pathogenesis of diabetes as well as offer a novel therapeutic site for the treatment of diabetes.

Acute anoxic changes in peripheral nerve: anatomic and physiologic correlations

INTRODUCTION

The response of the peripheral nerve to anoxia is modulated by many factors including glucose and temperature. The purposes of this article are to demonstrate the effects of these factors on the pathological changes induced by anoxia and to compare the electrophysiologic changes and pathological changes in the same nerves.

METHODS

Sciatic nerves were harvested from rats and placed in a perfusion apparatus where neurophysiologic responses could be recorded continuously during a 16 h experiment. After the experiment, light microscopy and electron microscopy were performed.

RESULTS

Light microscopic images showed mild changes from anoxia at normoglycemia. Hypoglycemic anoxia produced massive axonal swelling while hyperglycemic anoxia produced apparent changes in the myelin. Anoxic changes were not uniform in all axons. Electron microscopy showed only minor disruptions of the cytoskeleton with anoxia during normoglycemia. At the extremes of glucose concentration especially with hyperglycemia, there was a more severe disruption of intermediate filaments and loss of axonal structure with anoxia. Hypothermia protected axons from the effect of anoxia and produced peak axonal swelling in the 17-30°C range.

CONCLUSIONS

The combination of hyperglycemia or hypoglycemia and anoxia produces extremely severe axonal disruption. Changes in axonal diameter are complex and are influenced by many factors.

Inflaming the diseased brain: a role for tainted melanins

Inflammation plays a crucial role in neurodegenerative diseases, but the irritants responsible for this response remain largely unknown. This report addressed the hypothesis that hypochlorous acid reacts with dopamine to produce melanic precipitates that promote cerebral inflammation. Spectrophotometric studies demonstrated that nM amounts of HOCl and dopamine react within seconds. A second-order rate constant for the reaction of HOCl and dopamine of 2.5 × 10(4)M(-1)s(-1) was obtained by measuring loss of dopaminergic fluorescence due to HOCl. Gravimetric measurements, electron microscopy, elemental analysis, and a novel use of flow cytometry confirmed that the major product of this reaction is a precipitate with an average diameter of 1.5 μm. Flow cytometry was also used to demonstrate the preferential reaction of HOCl with dopamine rather than albumin. Engulfment of the chlorodopamine particulates by phagocytes in vitro caused these cells to release TNFα and die. Intrastriatal administration of 10(6) particles also increased the content of TNFα in the brain and led to a 50% loss of the dopaminergic neurons in the nigra. These studies indicate that HOCl and dopamine react quickly and preferentially with each other to produce particles that promote inflammation and neuronal death in the brain.

Prostaglandin D2 synthase: Apoptotic factor in alzheimer plasma, inducer of reactive oxygen species, inflammatory cytokines and dialysis dementia

BACKGROUND

Apoptosis, reactive oxygen species (ROS) and inflammatory cytokines have all been implicated in the development of Alzheimer's disease (AD).

OBJECTIVES

The present study identifies the apoptotic factor that was responsible for the fourfold increase in apoptotic rates that we previously noted when pig proximal tubule, LLC-PK1, cells were exposed to AD plasma as compared to plasma from normal controls and multi-infarct dementia.

PATIENTS AND METHODS

The apoptotic factor was isolated from AD urine and identified as lipocalin-type prostaglandin D2 synthase (L-PGDS). L-PGDS was found to be the major apoptotic factor in AD plasma as determined by inhibition of apoptosis approximating control levels by the cyclo-oxygenase (COX) 2 inhibitor, NS398, and the antibody to L-PGDS. Blood levels of L-PGDS, however, were not elevated in AD. We now demonstrate a receptor-mediated uptake of L-PGDS in PC12 neuronal cells that was time, dose and temperature-dependent and was saturable by competition with cold L-PGDS and albumin. Further proof of this endocytosis was provided by an electron microscopic study of gold labeled L-PGDS and immunofluorescence with Alexa-labeled L-PGDS.

RESULTS

The recombinant L-PGDS and wild type (WT) L-PGDS increased ROS but only the WTL-PGDS increased IL6 and TNFα, suggesting that differences in glycosylation of L-PGDS in AD was responsible for this discrepancy.

CONCLUSIONS

These data collectively suggest that L-PGDS might play an important role in the development of dementia in patients on dialysis and of AD.

Endometrial cancer recurrence: Adjuvant high-dose rate vaginal brachytherapy (HDR) versus HDR with whole pelvic radiation

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Background: Investigators hypothesize that patients with endometrioid carcinoma of the endometrium treated with adjuvant high-dose-rate vaginal brachytherapy (HDR) alone vs. HDR with whole pelvic radiation (WPXRT) have similar recurrence patterns. Methods: Patients reated with any adjuvant HDR between March 2005 and January 2011 were included retrospectively. Demographic, pathologic and treatment data was extracted from the medical record. These clinical data were compared among subjects receiving HDR only vs. HDR with 4500 cGy whole pelvic radiation using t-tests, Mann-Whitney tests, and chi-square analyses as appropriate. Results: One hundred eighty-six patients received adjuvant HDR. Fifty eight were excluded from analyses (46 based on non-endometrioid histology; 12 lost to follow-up). Among the sample of 128 subjects, 56 were treated with HDR only vs. 72 with HDR and WPXRT (43.8% vs. 56.2%, respectively). Subjects were similar in age, body mass index, and the existence of medical co morbidities. Of the 72 patients receiving HDR and WPXRT, 28 (38.9) were staged IA-IC, 28 (38.9) were staged as IIA-IIB, 11 (15.4%) were staged as IIIA-IIIC, 1 was staged as IVA-IVB (1.4%) and 4 (5.5%) was unstaged at diagnosis. Complications were similar between the groups. A total of 5 subjects experienced a recurrence, 1 who received HDR only vs. 4 who received HDR and WPXRT (1.8% vs. 5.6%, respectively, p=0.27). The subject treated with HDR was diagnosed with a grade 1 endometrioid carcinoma and had recurrence in the lung. Of the 4 subjects treated with HDR and WPXRT, 3 had recurrence in the vaginal cuff and 1 had recurrence in the peri-aortic lymph nodes. Conclusions: Recurrence was low among all subjects and did not differ among those who received HDR therapy only compared to HDR therapy with whole pelvic radiation. Investigators plan to conduct additional studies with a larger sample size to determine whether a difference in recurrence exists while adjusting for disease stage and total treatment dosage. If such confirmatory evidence is found, HDR brachytherapy alone may be a viable alternative to the additional radiation exposure of WPXRT in treating patients with endometrioid carcinoma of the endometrium.

Impaired insulin-stimulated myosin phosphatase Rho-interacting protein signaling in diabetic Goto-Kakizaki vascular smooth muscle cells

Insulin resistance associated with Type 2 diabetes contributes to impaired vasorelaxation and therefore contributes to the enhanced incidence of hypertension observed in diabetes. In this study, we examined the role of insulin on the association of the myosin-binding subunit of myosin phosphatase (MYPT1) to myosin phosphatase Rho-interacting protein (MRIP), a relatively novel member of the myosin phosphatase complex that directly binds RhoA in vascular smooth muscle cells (VSMCs). Through a series of molecular and cellular studies, we investigated whether insulin stimulates the binding of MRIP to MYPT1 and compared the results generated from VSMCs isolated from both Wistar-Kyoto (WKY) control and Goto-Kakizaki (GK) diabetic rats. We demonstrate for the first time that insulin stimulates the binding of MRIP to MYPT1 in a dose- and time-dependent manner, as determined by immunoprecipitation, implying a regulatory role for MRIP in insulin-induced vasodilation signaling via MYPT1 interaction. VSMCs from GK model of Type 2 diabetes had impaired insulin-induced MRIP/MYPT1 binding as well as reduced MRIP expression. Adenovirus-mediated overexpression of MRIP in GK VSMCs led to significantly improved insulin-stimulated MRIP/MYPT1 binding. Finally, insulin-stimulated MRIP translocation out of stress fibers, which was observed in control VSMCs, was impaired in GK VSMCs. We believe the impaired expression of MRIP, and therefore decreased insulin-stimulated MRIP/MYPT1 association, in the GK diabetic model may contribute to the impaired insulin-mediated vasodilation observed in the diabetic vasculature and provides a novel therapeutic strategy for the treatment of Type 2 diabetes.

Retrospective review of colorectal cancer specimens in individuals younger than age 50 for microsatellite instability testing and DNA mismatch repair enzyme expression

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Background: Data from studies performed at tertiary referral centers suggest that the yield of patients with the underlying defect in hereditary non-polyposis colon cancer (HNPCC) could be improved by screening every colon cancer for the phenotypic expression of the MMR defect by immunohistochemistry (IHC) and/or an assay for microsatellite instability (MSI). We propose to determine the incidence of microsatellite unstable colon cancers and the incidence of absence of expression of DNA MMR enzymes in de-identified colorectal cancer specimens from patients under the age of 50 who have presented to Winthrop University Hospital over the past ten years. This incidence will be compared with those suggested by recent large retrospective studies in tertiary care centers.

Methods: Immunoperoxidase staining for MLH1, MSH2, MSH6 and PMS2 were performed on formalin-fixed tissue. MSI assays were performed on microdissected DNA from paraffin-embedded tissue blocks. All cases were tested with five mononucleotide repeat markers (BAT-25, BAT-26, NR-21, NR-24 and MONO-27) and two pentanucleotide repeat markers (Penta C and Penta D). Tumor samples in which two or more altered monoclonal repeat markers were found out of five were classified as MSI-H.

Results: Screening for expression of DNA mismatch repair enzymes and MSI in an enriched selected (by age <50) population of colorectal cancer patients resulted in detection of 7/51 (14%) specimens that were MSI-H and 7/61 (12%) that were “positive” for lack of expression of at least one DNA mismatch repair enzyme.

Conclusions: Our results are similar to those reported in the literature in unselected series of patients with colorectal cancer. IHC staining or MSI analysis alone may be insufficient in selecting those colorectal cancer patients that should be referred for genetic testing for HNPCC. However, screening of an unselected population with both these modalities should have a low but clinically significant yield. Since other research have shown that traditional criteria such as the Bethesda guidelines are inadequate, we support the use of both measures prospectively in all colorectal cancer patients.

No significant financial relationships to disclose.

Impaired insulin-mediated vasorelaxation in diabetic Goto-Kakizaki rats is caused by impaired Akt phosphorylation

Insulin resistance associated with Type 2 diabetes contributes to impaired vasorelaxation. Previously, we showed the phosphorylation of myosin-bound phosphatase substrate MYPT1, a marker of the vascular smooth muscle cell (VSMC) contraction, was negatively regulated by Akt (protein kinase B) phosphorylation in response to insulin stimulation. In this study we examined the role of Akt phosphorylation on impaired insulin-induced vasodilation in the Goto-Kakizaki (GK) rat model of Type 2 diabetes. GK VSMCs had impaired basal and insulin-induced Akt phosphorylation as well as increases in basal MYPT1 phosphorylation, inducible nitric oxide synthase (iNOS) expression, and nitrite/nitrate production compared with Wistar-Kyoto controls. Both iNOS expression and the inhibition of angiotensin (ANG) II-induced MYPT1 phosphorylation were resistant to the effects of insulin in diabetic GK VSMC. We also measured the isometric tension of intact and denuded GK aorta using a myograph and observed significantly impaired insulin-induced vasodilation. Adenovirus-mediated overexpression of constitutively active Akt in GK VSMC led to significantly improved insulin sensitivity in terms of counteracting ANG II-induced contractile signaling via MYPT1, myosin light chain dephosphorylation, and reduced iNOS expression, S-nitrosylation and survivin expression. We demonstrated for the first time the presence of Akt-independent iNOS expression in the GK diabetic model and that the defective insulin-induced vasodilation observed in the diabetic vasculature can be restored by the overexpression of active Akt, which advocates a novel therapeutic strategy for treating diabetes.

Effect of cyclooxygenase inhibition on cholesterol efflux proteins and atheromatous foam cell transformation in THP-1 human macrophages: a possible mechanism for increased cardiovascular risk

Both selective cyclooxygenase (COX)-2 inhibitors and non-steroidal anti-inflammatory drugs (NSAIDs) have been beneficial pharmacological agents for many patients suffering from arthritis pain and inflammation. However, selective COX-2 inhibitors and traditional NSAIDs are both associated with heightened risk of myocardial infarction. Possible pro-atherogenic mechanisms of these inhibitors have been suggested, including an imbalance in prostanoid production leaving the pro-aggregatory prostaglandins unopposed, but the precise mechanisms involved have not been elucidated. We explored the possibility that downregulation of proteins involved in reverse cholesterol transport away from atheromatous plaques contributes to increased atherogenesis associated with COX inhibition. The reverse cholesterol transport proteins cholesterol 27-hydroxylase and ATP-binding cassette transporter A1 (ABCA1) export cholesterol from macrophages. When mechanisms to process lipid load are inadequate, uncontrolled cholesterol deposition in macrophages transforms them into foam cells, a key element of atheromatous plaques. We showed that in cultured THP-1 human monocytes/macrophages, inhibition of COX-1, COX-2, or both reduced expression of 27-hydroxylase and ABCA1 message (real-time reverse transcription-polymerase chain reaction) and protein (immunoblot). The selective COX-2 inhibitor N-(2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide (NS398) significantly reduced 27-hydroxylase and ABCA1 message (to 62.4% +/- 2.2% and 71.1% +/- 3.9% of control, respectively). Incubation with prostaglandin (PG) E2 or PGD2 reversed reductions in both of these cholesterol transport proteins induced by NS398. Cholesterol-loaded THP-1 macrophages showed significantly increased foam cell transformation in the presence of NS398 versus control (42.7% +/- 6.6% versus 20.1% +/- 3.4%, p = 0.04) as determined by oil red O staining. Pharmacological inhibition of COX in monocytes is involved in downregulation of two proteins that mediate cholesterol efflux: cholesterol 27-hydroxylase and ABCA1. Because these proteins are anti-atherogenic, their downregulation may contribute to increased incidence of cardiac events in patients treated with COX inhibitors. Reversal of inhibitory effects on 27-hydroxylase and ABCA1 expression by PGD2 and PGE2 suggests involvement of their respective signaling pathways. NS398-treated THP-1 macrophages show greater vulnerability to form foam cells. Increased cardiovascular risk with COX inhibition may be ascribed at least in part to altered cholesterol metabolism.

Post-translational modification regulates prostaglandin D2 synthase apoptotic activity: characterization by site-directed mutagenesis

Lipocalin-type prostaglandin D(2) synthase (L-PGDS) is a highly glycosylated protein found in several body fluids. Elevated L-PGDS levels have been observed in the serum of patients with renal impairment, diabetes mellitus, and hypertension. Recently, we demonstrated the ability of L-PGDS to induce apoptosis in a variety of cell types including epithelial cells, neuronal cells, and vascular smooth muscle cells (VSMCs). The aim of this study was to investigate the effect several site-directed mutations had on L-PGDS-induced apoptosis in order to identify potential sites of regulation. Point mutations created in a glycosylation site (Asn51), a protein kinase C phosphorylation site (Ser106), and the enzymatic active site (Cys65) all inhibited L-PGDS-induced apoptosis as determined by both terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) and caspase3 activity. We also compared the L-PGDS isoforms present in GK rat serum to WKY control serum using two-dimensional gel electrophoresis and observed distinct differences which vanished after PNGase F glycolytic digestion. We conclude that post-translational modification of L-PGDS, by either glycosylation or phosphorylation, enhances its apoptotic activity and inhibits VSMC hyperproliferation and postulate that this process is altered in type 2 diabetes.

Accelerated glucose intolerance, nephropathy, and atherosclerosis in prostaglandin D2 synthase knock-out mice

Type 2 diabetics have an increased risk of developing atherosclerosis, suggesting the mechanisms that cause this disease are enhanced by insulin resistance. In this study we examined the effects of gene knock-out (KO) of lipocalin-type prostaglandin D(2) synthase (L-PGDS), a protein found at elevated levels in type 2 diabetics, on diet-induced glucose tolerance and atherosclerosis. Our results show that L-PGDS KO mice become glucose-in-tolerant and insulin-resistant at an accelerated rate when compared with the C57BL/6 control strain. Adipocytes were significantly larger in the L-PGDS KO mice compared with controls on the same diets. Cell culture data revealed significant differences between insulin-stimulated mitogen-activated protein kinase phosphatase-2, protein-tyrosine phosphatase-1D, and phosphorylated focal adhesion kinase expression levels in L-PGDS KO vascular smooth muscle cells and controls. In addition, only the L-PGDS KO mice developed nephropathy and an aortic thickening reminiscent to the early stages of atherosclerosis when fed a "diabetogenic" high fat diet. We conclude that L-PGDS plays an important role regulating insulin sensitivity and atherosclerosis in type 2 diabetes and may represent a novel model of insulin resistance, atherosclerosis, and diabetic nephropathy.

Inhibition of cell cycle progression and migration of vascular smooth muscle cells by prostaglandin D2 synthase: resistance in diabetic Goto-Kakizaki rats

The regulation of vascular smooth muscle cell (VSMC) proliferation, migration, and apoptosis plays a clear role in the atherosclerotic process. Recently, we reported on the inhibition of the exaggerated growth phenotype of VSMCs isolated from hypertensive rats by lipocalin-type prostaglandin D2 synthase (L-PGDS). In the present study, we report the differential effects of L-PGDS on VSMC cell cycle progression, migration, and apoptosis in wild-type VSMCs vs. those from a type 2 diabetic model. In wild-type VSMCs, exogenously added L-PGDS delayed serum-induced cell cycle progression from the G1 to S phase, as determined by gene array analysis and the decreased protein expressions of cyclin-dependent kinase-2, p21Cip1, and cyclin D1. Cyclin D3 protein expression was unaffected by L-PGDS, although its gene expression was stimulated by L-PGDS in wild-type cells. In addition, platelet-derived growth factor-induced VSMC migration was inhibited by L-PGDS in wild-type cells. Type 2 diabetic VSMCs, however, were resistant to the L-PGDS effects on cell cycle progression and migration. L-PGDS did suppress the hyperproliferation of diabetic cells, albeit through a different mechanism, presumably involving the 2.5-fold increase in apoptosis and the concomitant 10-fold increase of L-PGDS uptake we observed in these cells. We propose that in wild-type VSMCs, L-PGDS retards cell cycle progression and migration, precluding hyperplasia of the tunica media, and that diabetic cells appear resistant to the inhibitory effects of L-PGDS, which consequently may help explain the increased atherosclerosis observed in diabetes.

Cytoprotection by darbepoetin/epoetin alfa in pig tubular and mouse mesangial cells

BACKGROUND

Erythropoietin has recently been found to have cytoprotective effects in the central nervous system (CNS) and retina. The purpose of this study was to determine if darbepoetin alfa (DA) has cytoprotective properties in renal tissues.

METHODS

DA was studied in LLC/PK1 and mesangial cells. Renal cellular injury was induced in different experiments by prostaglandin D2 synthase (PGDS), camptothecin, hydrogen peroxide, and hypoxia. Cellular proliferation and apoptosis were measured [apoptosis by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) nick end-labeling (TUNEL) assay or by caspase-3 activity]. In a separate experiment, an inactive form of erythropoietin alfa was used to study receptor effects.

RESULTS

DA protected against the antiproliferative effects of PGDS. In both LLC/PK1 (TUNEL and caspase-3) and mesangial cells (TUNEL), DA reduced the apoptotic stimulus of PGDS. Epoetin alfa was also found to reduce apoptosis. In LLC/PK1 cells, DA reduced apoptosis induced by camptothecin, but not hydrogen peroxide. DA reduced LLC/PK1 apoptosis induced by hypoxia when added 24 hours before hypoxia, but not when given concurrent with the hypoxic stimulus. Erythropoietin inactive did not protect against PGDS-induced apoptosis.

CONCLUSION

DA has renal antiapoptotic effects for both toxic and hypoxic stimuli. The effect may be mediated via the Erythropoietin receptor.

Prostaglandin D2 synthase inhibits the exaggerated growth phenotype of spontaneously hypertensive rat vascular smooth muscle cells

Lipocalin-type prostaglandin D2 synthase (L-PGDS) has recently been linked to a variety of pathophysiological cardiovascular conditions including hypertension and diabetes. In this study, we report on the 50% increase in L-PGDS protein expression observed in vascular smooth muscle cells (VSMC) isolated from spontaneously hypertensive rats (SHR). L-PGDS expression also increased 50% upon the differentiation of normotensive control cells (WKY, from Wistar-Kyoto rats). In addition, we demonstrate differential effects of L-PGDS treatment on cell proliferation and apoptosis in VSMCs isolated from SHR versus WKY controls. L-PGDS (50 microg/ml) was able to significantly inhibit VSMC proliferation and DNA synthesis and induce the apoptotic genes bax, bcl-x, and ei24 in SHR but had no effect on WKY cells. Hyperglycemic conditions also had opposite effects, in which increased glucose concentrations (20 mm) resulted in decreased L-PGDS expression in control cells but actually stimulated L-PGDS expression in SHR. Furthermore, we examined the effect of L-PGDS incubation on insulin-stimulated Akt, glycogen synthase kinase-3beta (GSK-3beta), and ERK phosphorylation. Unexpectedly, we found that when WKY cells were pretreated with L-PGDS, insulin could actually induce apoptosis and failed to stimulate Akt/GSK-3beta phosphorylation. Insulin-stimulated ERK phosphorylation was unaffected by L-PGDS pretreatment in both cell lines. We propose that L-PGDS is involved in the balance of VSMC proliferation and apoptosis and in the increased expression observed in the hypertensive state is an attempt to maintain a proper equilibrium between the two processes via the induction of apoptosis and inhibition of cell proliferation.

Elevated L-PGDS activity contributes to PMA-induced apoptosis concomitant with downregulation of PI3-K

Recently we demonstrated the induction of apoptosis by the addition of recombinant lipocalin-type prostaglandin D(2) synthase (L-PGDS) to the culture medium of LLC-PK(1) cells. Because protein kinase C (PKC) has been shown to be involved in the apoptotic process of various cell types, we examined the potential role of L-PGDS in phorbol 12-myristate 13-acetate (PMA)-induced apoptosis. We report here the enzymatic activation and phosphorylation of L-PGDS in response to phorbol ester in cell culture and the direct phosphorylation of recombinant L-PGDS by PKC in vitro. Treatment of cells with PMA or L-PGDS decreased phosphatidylinositol 3-kinase (PI3-K) activity and concomitantly inhibited protein kinase B (PKB/Akt) phosphorylation, which led to the hypophosphorylation and activation of Bad. In addition, hypophosphorylation of retinoblastoma protein was also observed in response to L-PGDS-induced apoptosis. Cellular depletion of L-PGDS levels by using an antisense RNA strategy prevented PI3-K inactivation by phorbol ester and inhibited caspase-3 activation and apoptosis. We conclude that phorbol ester-induced apoptosis is mediated by L-PGDS phosphorylation and activation by PKC and is accompanied by inhibition of the PI3-K/PKB anti-apoptotic signaling pathways.

Contribution of prostaglandin D2 synthase to progression of renal failure and dialysis dementia

This article reviews the possible role of prostaglandin D(2) synthase (PGD(2)S) in the progression of chronic renal failure and dialysis dementia. Such a proposal is based on our observation that PGD(2)S significantly increases the rate of apoptosis in cultured pig kidney proximal tubule LLC-PK1 and rat neuronal PC12 cells. Apoptosis was caspase mediated and inhibitable by PGE(1), PGE(2), PGF(2alpha), platelet-derived growth factor (PDGF), and by PGD(2)S inhibitors, selenium and anti-PGD(2)S antibody. Apoptosis was restored by the addition of downstream metabolic products, PGD(2) and 15 deoxy PG triangle up (12,14)J(2). The proposal that PGD(2)S contributes to progression of renal failure and dialysis dementia is based on: (1) the progressive creatinine-like increase in PGD(2)S levels in blood as renal function decreases, increased renal cyclooxygenase (COX) 2 in chronic renal failure, and reported increase in apoptosis noted in the remnant kidney model, and (2) a 35- to 150-fold increase in blood levels of PGD(2)S in dialysis patients. Both conditions appear to favor shifting the PG metabolic pathway to downstream apoptotic metabolites, PGD(2) and 15 deoxy PG triangle up (12,14)J(2). The diverse role that PGs, growth factors, and COX play in progression of chronic renal failure, their interactions with PGD(2)S, and the status of COX inhibitors in retarding the progression of renal failure are reviewed. In addition, the need for a more systematic longitudinal assessment of dementia in dialysis patients by standardized neuropsychologic testing, testing blood levels and glycosylated isoforms of PGD(2)S, and the effect of COX inhibition and erythropoietin administration on dialysis dementia are discussed.

Prostaglandin D(2) synthase induces apoptosis in pig kidney LLC-PK1 cells

BACKGROUND

Prostaglandin D(2) synthase (PGD(2)S), a unique member of the lipocalin family, is found at elevated levels in the serum of patients with renal impairment and has recently been implicated as a new biochemical marker of renal insufficiency. The aim of this study was to investigate the apoptotic effects of PGD2S on a pig kidney epithelial cell line (LLC-PK1) and to investigate the effects of prostaglandins and growth factors on this process.

METHODS

Apoptosis was detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL), annexin V staining, and electron microscopy.

RESULTS

A four- to fivefold increase in apoptosis was observed in PGD(2)S-treated cells as compared with controls and the apoptosis appeared to act via caspase-3. A cyclooxygenase-2 inhibitor, anti-PGD(2)S antibody, and selenium all significantly inhibited the apoptosis induced by PGD(2)S; however, none had any effect on the apoptosis induced by the known apoptotic inducer camptothecin. Furthermore, prostaglandins E(1) and E(2), known to induce mitogen-activated protein (MAP) kinase phosphorylation and exhibit cytoprotective effects, both inhibited PGD(2)S-induced apoptosis, while prostaglandin H(2) had no significant effect. Growth factors such as insulin, insulin-like growth factor-1, and platelet-derived growth factor also decreased PGD(2)S-induced apoptosis. In addition, PGD(2)S isolated from human serum seemed slightly more effective at inducing apoptosis than recombinantly expressed protein.

CONCLUSIONS

We report on the induction of apoptosis by PGD(2)S in LLC-PK1 pig kidney epithelial cells, and speculate that the accumulation of PGD(2)S in the serum of kidney failure patients may further exacerbate renal problems and is most likely regulated by other prostaglandins and growth factors.

Prostaglandin D2 synthase induces apoptosis in PC12 neuronal cells

Apoptosis of neuronal cells is a proposed cause of certain neurological disorders. Here, we report on a 5- to 6-fold increase in apoptosis by exposure to prostaglandin D2 synthase (PGD2S) in PC12 neuronal cells. Apoptosis was detected by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end-labeling (TUNEL) assay, and appears to be mediated via caspase-3 activation. Neutralization with anti-PGD2S antibody or pre-treatment with selenium, which inhibits PGD2S enzymatic activity, both significantly inhibited the PGD2S-induced apoptosis, however, neither had any effect on the apoptosis induced by the known neuronal apoptotic inducer, glutamate. In addition, prostaglandins E1, E2, and F2alpha all inhibited the PGD2S-induced apoptosis while prostaglandin H2 had no significant effect. Furthermore, PGD2S isolated from human serum was more effective at inducing apoptosis then recombinantly expressed protein, presumably due to glycosylation. This novel role of PGD2S, as an inducer of apoptosis, may have implications in PC12 differentiation and possibly some neurological disorders.

Morphological and functional changes in the colonic epithelial cells in a rabbit model of colitis

A rabbit model of TNBS-colitis was used to study the effect of intestinal inflammation on epithelial cell function. Epithelial cells were isolated using a non-enzymatic isolation method without any apparent contamination with infiltrating immune cells. The isolated cells were found to be viable using dye exclusion studies, unidirectional Na+ -fluxes, proliferation assays and morphological studies. The cells, however, showed morphological changes that suggested the presence of increased number of secretory vesicles. This increase correlated well with the increase observed in ion and water secretion as measured by the short-circuit current. Finally, in the colitic tissue the number of PGE2 receptors was greatly reduced with no changes observed in the affinity of PGE2 to its receptor. The reduced number of PGE2 receptors might be due to sensitization of the receptor. In conclusion, we have demonstrated that morphologically and functionally normal epithelial cells can be isolated from the rabbit inflamed distal colon.

Partial characterization of apoptotic factor in Alzheimer plasma

We have previously demonstrated that a plasma natriuretic factor is present in Alzheimer's disease (AD), but not in multi-infarct dementia (MID) or normal controls (C). We postulated that the natriuretic factor might induce the increased cytosolic calcium reported in AD by inhibiting the sodium-calcium antiporter, thereby activating the apoptotic pathway. To test for a factor in AD plasma that induces apoptosis, we exposed nonconfluent cultured LLC-PK1 cells to plasma from AD, MID, and C for 2 h and performed a terminal transferase-dUTP-nick-end labeling (TUNEL) assay. The plasma from AD increased apoptosis nearly fourfold compared with MID and C. The effect was dose dependent and the peak effect was attained after a 2-h exposure. Additionally, apoptotic morphology was detected by electron microscopy, and internucleosomal DNA cleavage was found. We inhibited apoptosis by removing calcium from the medium, inhibiting protein synthesis with cycloheximide, alternately boiling or freezing and thawing the plasma, and digesting a partially purified fraction with trypsin. Heating AD plasma to 56 degrees C did not deactivate the apoptotic factor. These results demonstrate the presence of an apoptotic factor in the plasma of patients with AD.

Gap junctional communication between murine macrophages and intestinal epithelial cell lines

In intestinal inflammation, inflammatory cells infiltrate the submucosa and are found juxtaposed to intestinal epithelial cell (IEC) basolateral membranes and may directly regulate IEC function. In this study we determined whether macrophage (M phi), P388D1 and J774A.1, are coupled by gap junctions to IEC lines, Mode-K and IEC6. Using flow cytometric analysis, we show bi-directional transfer of the fluorescent dye, calcein (700 Da) between IEC and M phi resulting in a 3.5-20-fold increase in recipient cell fluorescence. Homocellular and heterocellular dye transfer between M phi and/or IEC was detected in cocultures of P388D1, J774A.1, Mode-K, IEC6 and CMT93. However, transfer between P388D1 and Mode-K was asymmetrical in that transfer from P388D1 to Mode-K was always more efficient than transfer from Mode-K to P388D1. Dye transfer was strictly dependent on IEC-M phi adhesion which in turn was dependent on the polarity of IEC adhesion molecule expression. Both calcein dye transfer and adhesion were inhibited by the addition of heptanol to cocultures. Furthermore we demonstrate both IEC homocellular, and M phi-IEC heterocellular propagation of calcium waves in response to mechanical stimulation, typical of gap junctional communication. Finally, areas of close membrane apposition were seen in electron micrographs of IEC-M phi cocultures, suggestive of gap junction formation. These data indicate that IEC and M phi are coupled by gap junctions suggesting that gap junctional communication may provide a means by which inflammatory cells might regulate IEC function.

In vitro expansion of CD13+CD33+ dendritic cell precursors from multipotent progenitors is regulated by a discrete fas-mediated apoptotic schedule

We provide new information on how apoptosis regulates the expansion and survival of dendritic cell (DC) elements during in vitro hematopoiesis. Functionally distinct apoptotic schedules were associated with different phases of DC development when multipotent CD34+ progenitor cells were treated with GM-CSF + TNF +/- SCF (c-kit ligand). During early phases of growth, unselected progenitors underwent apoptosis. During intermediate stages, high levels of apoptosis resulted in the preferential selection of DC precursors, as revealed by the massive expansion of DR+CD33+CD13+ cells. Late apoptosis was associated with the death of mature DCs. Apoptotic events surrounding the earlier periods were related to the exogenous addition of TNF-alpha and appeared to be mediated by fas. In contrast, those events associated with terminally differentiated DCs were fas independent because there was no correlation between fas expression and cell death. The bcl-2 protein family appeared to confer resistance to apoptotic death, as revealed by the high levels of bcl-2 and bclxL during peak DC development and in long-term DC cultures. We demonstrate that activation of distinct apoptotic programs regulates DC development and homeostasis. Although suppression of apoptosis may prolong the survival of late DC elements, an earlier apoptotic schedule appears to be required for the selective expansion of DC elements from multipotent progenitors. Our data also provides insight into the mechanism(s) of myeloid lineage selection by cytokines such as TNF-alpha, which may promote both cell death and survival.

Morphological factors influencing transepithelial conductance in a rabbit model of ileitis

BACKGROUND & AIMS

Infection of rabbits with coccidia (Eimeria magna) causes chronic ileal inflammation and diarrhea. Inflamed ileum also shows decreased transmural conductance. The aim of this study was to characterize morphological factors known to affect paracellular permeability that may alter transmural conductance in inflamed ileum.

METHODS

Ileal mucosa was mounted in Ussing chambers for study of [3H]mannitol and [3H]inulin fluxes. Light and electron microscopy were used for morphometric studies. Alterations in the zonula occludens of epithelial cells were evaluated in freeze-fracture replicas.

RESULTS

Inflamed ileum showed diminished paracellular fluxes. Inoculated rabbits showed marked lymphoplasmocytic infiltration and villus blunting in ileum. Villus linear junctional density was unaffected. However, total villus apical surface area per square centimeter of tissue was reduced in inflamed ileum, causing a diminished total villus linear junctional pathway per square centimeter of apical surface. Villus zonula occludens strand number was reduced in inflamed ileum, whereas the frequency of both villus and crypt lateral surface extrajunctional strands increased.

CONCLUSIONS

Chronic inflammation exerts a profound effect on ileal paracellular permeability. Morphological data suggest that this effect may be caused in part by alterations in inflamed ileal mucosal structure and tight junctional organization and density, particularly on villi.

Increase in blood-brain barrier permeability by altitude decompression

Previous studies indicated that exposure to compression-decompression increases blood-brain barrier (BBB) permeability to vital dyes and antibiotics. This report concerns functional and ultrastructural BBB changes induced by altitude decompression. A 2% trypan blue solution was intravenously injected (4 ml.kg-1) into 29 experimental and 19 control rabbits. Some animals also received horseradish peroxidase. The experimental animals were subjected to 30,000 ft (4.3 psi) for 45 min. Controls were kept at ground level. The animals were sacrificed 90 min postinjection. Gross and microscopic examination and spectrophotometric dye determination revealed significantly greater tracer penetration in experimental brains (mean dye concentration 27.06 +/- 4.42 micrograms.g-1) than in controls (4.52 +/- 1.52 micrograms.g-1). No sex differences were noted. Electron microscopy suggested that the increased BBB permeability was due to transendothelial vesicular transport and, occasionally, to penetration through interendothelial junctions. These observations may have relevance to pharmacotherapy in space and at high altitudes and to the pathogenesis of altitude decompression sickness.

Prevention of cholesterol-induced gallstones by hyodeoxycholic acid in the prairie dog

Prairie dogs of both sexes were fed a semisynthetic diet containing 0.35% cholesterol for a period of 8 weeks. This lithogenic diet induced cholesterol gallstones in ten "lithogenic control animals", five males and five females. Three animals maintained with a high glucose, fat-free diet did not develop gallstones although the cholesterol saturation of their bile approached unity. The formation of gallstones was prevented in four out of five males and all five females fed the lithogenic diet plus 0.1% hyodeoxycholic acid (30 mg per kg body weight per day). The biles of the prairie dogs receiving hyodeoxycholic acid were abnormally colored, cloudy, and highly saturated with cholesterol but contained neither cholesterol crystals nor gallstones (with the exception of one male). Feeding the relatively hydrophilic bile acid, hyodeoxycholic acid, was associated with an increase in hepatic microsomal HMG-CoA reductase activity. Cholesterol 7 alpha-hydroxylase, on the other hand, was inhibited by the administered bile acid. The dietary hyodeoxycholic acid was transformed, in part, to 3 alpha, 6 beta-dihydroxy-5-beta-cholanoic acid and hyocholic acid. It is concluded that hyodeoxycholic acid and its metabolites did not prevent the induced cholelithiasis by causing a decrease in the concentration of biliary cholesterol. Instead, this hydrophilic bile acid apparently increases the amount of cholesterol in the bile, probably in the form of a liquid crystalline mesophase. Hyodeoxycholic acid apparently prevents gallstones by preventing the nucleation and aggregation of cholesterol crystals. The lithogenic diet induced moderate to marked bile duct proliferation together with portal fibrosis and inflammatory infiltration. The addition of hyodeoxycholic acid to the lithogenic diet reduced all of the portal tract changes.