Identification of myocarditogenic peptides derived from cardiac myosin capable of inducing experimental allergic myocarditis in the Lewis rat. The utility of a class II binding motif in selecting self-reactive peptides

Cardiac myosin (CM) has been implicated as an autoantigen in the induction of experimental allergic myocarditis (EAM). At the present time no myocarditogenic peptides of CM have been identified. To identify CM peptides with myocarditogenic properties we have made use of a putative binding motif for the MHC class II molecule RT1.BI in the rat. The amino acid sequence of CM alpha-chain was scanned and found to contain nine peptides that contain this binding motif, three peptides found only in the cardiac form of myosin were chosen for further study. This manuscript describes the identification of two CM peptides capable of inducing EAM in the Lewis rat. In doing so this study demonstrates the utility of an MHC class II binding motif to (correctly) predict pathogenic, autoimmunity inducing, peptides. Peptides, CM 1, and CM 2 are the first peptides described that are capable of inducing EAM in rats. The utilization of CM 2 peptide has permitted the establishment of a long term, Ag specific cell line capable of adoptively transferring EAM. Moreover, the establishment of CM 2 specific T lymphocyte lines has permitted the description of a detailed proliferative response of a myocarditogenic cell line to a specific cardiac Ag. The identification of CM 1 and 2 formally proves that CM, and not a co-purified contaminant, is an Ag in EAM. Finally, this report documents that experimentally induced giant cell myocarditis is not a separate disease entity arising from a distinct cardiac Ag or CM epitope from regular myocarditis.

Identification of an N-terminally acetylated encephalitogenic epitope in myelin proteolipid apoprotein for the Lewis rat

Proteolipid apoprotein (PLP) is a major component of the central nervous system myelin. As such, it is capable of inducing experimental allergic encephalomyelitis (EAE) in many subhuman species. On the basis of a putative MHC class II binding motif in Lewis rats (RT-1B1) recently identified in our laboratory, the present study identifies one pathogenic T cell epitope of PLP for the Lewis rat, located in the area between amino acid residues 217 and 240. Four overlapping synthetic peptides derived from this region were tested for their antigenicity and encephalitogenicity. Although the longer peptides could not induce EAE in the Lewis rats in their "theoretically" native form after immunization, they were endowed with encephalitogenic ability when modified by N-terminal acetylation. All animals immunized with N-acetylated peptides PLP 217-233 and PLP 224-240 developed inflammation in the lower spinal cord, but with very low incidence of clinical EAE (1 of 12). In contrast, none of the animals immunized with nonacetylated peptides developed either clinical or histologic EAE. Mild inflammation of the spinal cord was also found in two of four rats immunized with N-acetylated peptide PLP 220-234. The animals immunized with the decapeptide, N-acetylated PLP 224-233, did not develop inflammation of the spinal cord. Despite the low incidence of clinical disease, it was possible to generate vigorous T cell lines against all the peptides synthesized from this region of PLP.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased expression of ICAM-1 during reoxygenation in brain endothelial cells

BACKGROUND AND PURPOSE

Thrombolysis is a promising therapy for acute ischemic stroke. However, there is evidence that neutrophils may physically plug cerebral microvessels on reperfusion, preventing the full benefit of thrombolysis. We undertook this study to determine whether there was increased endothelial expression of the intercellular adhesion molecule-1 (ICAM-1) gene during hypoxia-reoxygenation.

METHODS

We isolated and cultured human brain microvascular endothelial cells and subjected them to hypoxia (PO2 < 10 mm Hg) in an anaerobic chamber followed by variable periods of reoxygenation.

RESULTS

Twenty-hour periods of hypoxia did not lead to endothelial cytotoxicity as measured by a chromium-release assay. By Northern blot analysis, ICAM-1 mRNA transcripts were dramatically increased at 4 hours of reoxygenation but fell toward baseline (normoxia) by 12 and 24 hours. Hypoxia alone did not lead to an increase in mRNA levels. Western blot analysis showed an increased expression of ICAM-1 at 4, 12, and 24 hours of reoxygenation. The 4-hour increase in mRNA levels was not attenuated by pretreatment with 100 mumol/L allopurinol but was reduced by 30% with the addition of 20 mmol/L N-acetyl-L-cysteine at the time of reoxygenation and completely prevented by pretreatment with N-acetyl-L-cysteine.

CONCLUSIONS

Hypoxia-reoxygenation leads to an increase in ICAM mRNA levels that peaks at 4 hours in human brain microvascular endothelial cells. Pretreatment with N-acetyl-L-cysteine can completely block the increase in ICAM-1 mRNA levels.

Increased TGF-beta and decreased oncogene expression by omega-3 fatty acids in the spleen delays onset of autoimmune disease in B/W mice

This study was designed to investigate the mechanisms by which marine lipids rich in long chain omega-3 fatty acids inhibit autoimmune disease and prolong the survival rate in female (NZB/NZW) F1 (B/W) mice, an animal model for human SLE. Nutritionally adequate semipurified diets containing at 10% either corn oil (CO) or fish oil (FO) were fed from 1 mo of age and were monitored for proteinuria and survival. Proteinuria was detected earlier and became progressively severe in CO-fed mice. The average life span was significantly shortened by the CO diet (266.7 days +/- 12.5), whereas FO extended the survival significantly (402.1 days +/- 26.1; p < 0.001). A cross-sectional study at 6.5 mo of age revealed an increased proliferative response to T cell mitogens including bacterial superantigens and decreased serum anti-dsDNA Ab titers in the FO group compared with the CO group. Furthermore, splenocytes from the FO group when stimulated with Con A had higher IL-2 and lower IL-4 production similar to that of young (3.5 mo) mice. Flow cytometric analyses of splenocytes revealed lower Ig+, higher lymphocyte endothelial cell adhesion molecule-1, and lower Pgp-1+ cells within CD4+ and CD8+ subsets in FO-fed mice. Also, elevated IL-2 and IL-4 and significantly higher TGF-beta 1 and lower c-myc and c-ras mRNA expression and higher TGF-beta 1 and significantly lower c-Myc and c-Ha-Ras proteins were detected in spleens of FO-fed mice. Fatty acid analysis revealed significantly higher linoleic (18:2 omega-6) and arachidonic (20:4 omega-6) acid levels in splenocytes of the CO-fed group and higher eicosapentaenoic (20:5 omega-3) and docosahexanoic (22:6 omega-3) acid levels in the FO-fed group, indicating that changes in membrane fatty acid composition may contribute to the altered immune function and gene expression during the development of murine SLE.

Increased TGF-beta and decreased oncogene expression by omega-3 fatty acids in the spleen delays onset of autoimmune disease in B/W mice

This study was designed to investigate the mechanisms by which marine lipids rich in long chain omega-3 fatty acids inhibit autoimmune disease and prolong the survival rate in female (NZB/NZW) F1 (B/W) mice, an animal model for human SLE. Nutritionally adequate semipurified diets containing at 10% either corn oil (CO) or fish oil (FO) were fed from 1 mo of age and were monitored for proteinuria and survival. Proteinuria was detected earlier and became progressively severe in CO-fed mice. The average life span was significantly shortened by the CO diet (266.7 days +/- 12.5), whereas FO extended the survival significantly (402.1 days +/- 26.1; p &lt; 0.001). A cross-sectional study at 6.5 mo of age revealed an increased proliferative response to T cell mitogens including bacterial superantigens and decreased serum anti-dsDNA Ab titers in the FO group compared with the CO group. Furthermore, splenocytes from the FO group when stimulated with Con A had higher IL-2 and lower IL-4 production similar to that of young (3.5 mo) mice. Flow cytometric analyses of splenocytes revealed lower Ig+, higher lymphocyte endothelial cell adhesion molecule-1, and lower Pgp-1+ cells within CD4+ and CD8+ subsets in FO-fed mice. Also, elevated IL-2 and IL-4 and significantly higher TGF-beta 1 and lower c-myc and c-ras mRNA expression and higher TGF-beta 1 and significantly lower c-Myc and c-Ha-Ras proteins were detected in spleens of FO-fed mice. Fatty acid analysis revealed significantly higher linoleic (18:2 omega-6) and arachidonic (20:4 omega-6) acid levels in splenocytes of the CO-fed group and higher eicosapentaenoic (20:5 omega-3) and docosahexanoic (22:6 omega-3) acid levels in the FO-fed group, indicating that changes in membrane fatty acid composition may contribute to the altered immune function and gene expression during the development of murine SLE.

[The relationship between the amount of gingival crevicular fluid and periodontitis]

In this paper, we report the results of comparing the amount of GCF, collected from 100 patients suffering from periodontitis and 40 patients suffering from gingivitis with 64 normal control subjects. The results showed that the amount of GCF is independent of sex and where the GCF was collected, ie., either side of the maxillary or mandibular teeth. However, the fluid amount was closely related to inflammation of the periodontium and significantly related to the severity of inflammation and bone destruction. This study provide evidence that the determination of the GCF amount is an essential criteria for detecting periodontal activity.

Dietary regulation of mammary tumorigenesis in RIII/Sa mice: investigation of a possible mechanism

The effects of caloric restriction on the incidence of mammary tumor development, the levels of the expression of mouse mammary tumor virus (MMTV)- and prolactin-RNA, as well as the levels of serum prolactin, were investigated in virgin RIII/Sa mice, a strain known to display a high incidence of spontaneous mammary tumor development. Of the 54 mice fed a low-calorie (LC; 10 kcal/day) diet containing low fat (LF; 5% corn oil) for a period of 72 weeks, only seven mice were found to develop mammary tumors, an incidence of 13%. By contrast, the cumulative tumor incidence in a similar sized group of mice, fed a high-calorie (HC; 16 kcal/day) low fat-containing diet was 73%. Estimation of the relative levels of MMTV-RNA, as determined by Northern and slot blot hybridizations, in the mammary glands of mice fed LCLF and HCLF diets for 8, 10, 16, 28, and 36 weeks revealed that the LCLF diet-fed mice expressed 4-15-fold less RNA than the HCLF diet-fed mice. Interestingly, however, the LCLF diet did not appear to exert any effect on the expression of prolactin RNA even though it reduced the levels of serum prolactin. We suggest that in RII/Sa mice the modulation of MMTV-induced mammary tumors by dietary calorie is linked to the secretion of serum prolactin which, in turn, affects the replication of MMTV required for mammary cell transformation.

Bronchial smooth muscle energetics: effect of iodoacetate and hypoxia

The active pressure (AP) and the oxygen consumption (VO2) of segments of bovine bronchi were measured during a 10 microM carbachol stimulation. VO2 did not increase during the carbachol-induced contraction whereas there was a twofold increase in the lactate production. Addition of the glycolytic blocker, iodoacetate (83 microM), decreased the AP to 68.9 +/- 6.4% of control value (n = 10, P < 0.05) whereas VO2 remained constant. The lactate concentration in the physiological solution decreased significantly (P < 0.05). When the solution was supplemented with pyruvate (10 mM), the effect of iodoacetate was antagonized. Under hypoxic condition, i.e. when the solution was bubbled with 5% CO2 in N2, VO2 decreased sharply to 7.7 +/- 3.1% of control (n = 8, P < 0.05) whereas AP did not change. The combined effect of iodoacetate and hypoxia led to a fall in both AP (12.4 +/- 3.0% of control, n = 7, P < 0.05) and VO2 (21.2 +/- 5.1%, P < 0.05). These results suggest that the energy required by bronchial smooth muscle to generate contraction could be supplied by either the aerobic or the anaerobic pathway.

Prostaglandin E2 level in gingival crevicular fluid and its relation to the periodontal pocket depth in patients with periodontitis

Prostaglandin E2 (PGE2) levels in gingival crevicular fluid (GCF) of 46 normal controls and 90 patients suffering from periodontitis with different periodontal pocket depths were measured by radioimmunoassay (RIA). The results demonstrated that PGE2 levels in the GCF of the periodontal pockets are higher in patients with periodontitis. The PGE2 level rises as the periodontal pocket deepens, especially in cases where the periodontal pocket depth exceeds 6 mm. This study shows that the PGE2 level is significantly related to the severity of bone destruction in periodontitis.

ICAM-1 expression on human brain microvascular endothelial cells

There is evidence that leukocytes play an important role in mediating tissue injury during acute ischemic stroke. Endothelial cell adhesive molecules such as ICAM-1 are required for the migration of leukocytes into the brain. Using an Elisa, we compared the expression of ICAM-1 by human brain microvascular endothelial cells with human umbilical vein endothelial cells. There was constitutive surface expression of ICAM-1 on both brain and umbilical vein endothelial cells. With cytokine (IL-1 beta or TNF) or lipopolysaccaride stimulation, ICAM-1 surface expression increased to a greater extent on brain than on umbilical vein endothelial cells. Dexamethasone at doses up to 100 microM had no effect on inhibiting cytokine-mediated upregulation of ICAM-1 on human brain microvascular endothelial cells.

The amino acid sequence of iguana (Iguana iguana) pancreatic ribonuclease

The pyrimidine-specific ribonuclease superfamily constitutes a group of homologous proteins so far found only in higher vertebrates. Four separate families are found in mammals, which have resulted from gene duplications in mammalian ancestors. To learn more about the evolutionary history of this superfamily, the primary structure and other characteristics of the pancreatic enzyme from iguana (Iguana iguana), a herbivorous lizard species belonging to the reptiles, have been determined. The polypeptide chain consists of 119 amino acid residues. The positions of insertions and deletions in the sequence are identical to those in the enzyme from snapping turtle. However, the two enzymes differ at 54% of the amino acid positions. Iguana ribonuclease contains no carbohydrate, although the enzyme possesses three recognition sites for carbohydrate attachment, and has a high number of acidic residues in a localized part of the sequence.

S-thiolation and irreversible oxidation of sulfhydryls on carbonic anhydrase III during oxidative stress: a method for studying protein modification in intact cells and tissues

S-thiolation of carbonic anhydrase III (CA III) in cultured rat hepatocytes under oxidative stress was studied by immunodetection on nitrocellulose blots of isoelectrofocusing gels. In cells treated with menadione, three S-thiolated forms of CA III were detected, whereas only two forms were observed in hepatocytes treated with t-butyl hydroperoxide. Two "nonreducible" oxidized forms of CA III were also detected on nitrocellulose blots. These forms increased with the amount of stress and were the only modified forms of CA III in buthionine sulfoxide-treated hepatocytes containing 10-fold less glutathione than control hepatocytes. These experiments support the concept that S-thiolation protects CA III from irreversible oxidation during oxidative stress. Partly and fully S-thiolated forms of CA III were easily detected in both male and female hepatocytes by the immunoblotting method, although female cells contained 15-fold less CA III than did male liver. S-thiolated forms of CA III were also detected in rat skeletal muscle and heart showing the utility of this method for determining the effect of oxidative stress on specific S-thiolatable protein in several tissues in vivo.

The primary structure of pancreatic ribonuclease from mole rat superspecies Spalax leucodon

The primary structure of pancreatic ribonuclease of the superspecies Spalax leucodon has been determined. Only one difference with the previously determined sequence of the superspecies Spalax ehrenbergi was detected; the proline residue at position 42 has been replaced by alanine. Proline-42 is a well-conserved residue in mammalian pancreatic ribonucleases; the only other species with alanine at this position is the three-toed sloth. As the Muridae and the Spalacidae diverged 20-40 million years ago and the superspecies S. leucodon and S. ehrenbergi about 1-2 million years ago, and as pancreatic ribonuclease exhibits 24 substitutions in the line from the Muridae/Spalacidae ancestor to Spalax, a difference of one amino residue between the sequences of the two Spalax superspecies is what may be expected.

Gap junctions modulate tissue contractility and alpha 1 adrenergic agonist efficacy in isolated rat aorta

Immunocytochemical analysis, using antibodies directed against connexin43, revealed abundant gap junctions between smooth muscle cells in intact aorta from Fischer 344 rats. Therefore, the authors evaluated the potential contribution of these intercellular junctions to contractile responses elicited by alpha 1 adrenergic receptor activation in rat aortic rings. Preincubation with the selective junctional uncoupling agent heptanol (200 microM) diminished the magnitude of contractions induced by the low-efficacy partial agonist oxymetazoline (1-3 microM) by 50.6 +/- 4.5% (P < .01; n = 16 rings from 16 rats) but had no effect on equivalent contractions induced by the high-efficacy agonist phenylephrine (0.1 microM; n = 16 rings from 16 animals). Reduced phenylephrine contractility was observed at higher heptanol concentrations (500 microM). However, neither 200 nor 500 microM heptanol altered the magnitude of contractions elicited by 60 mM KCl, indicating that tissue contractility per se was unaffected by heptanol. In calcium-free solution, the magnitude of the phasic contraction induced by phenylephrine was three-fold greater than the magnitude of the oxymetazoline-induced phasic contraction (P < .001) but the phasic responses to both agonists were unaffected by the same heptanol concentrations that significantly diminished their steady-state responses. Because heptanol, at the concentrations used, has selective pharmacological actions on gap junctions, these studies provide additional support for a role of gap junctions in the maintenance and modulation of vasomotor tone. In rat aorta, junctional transfer of alpha 1 adrenergic-receptor activated second-messenger molecules appears to be an important modulator of tissue contractility and agonist efficacy.

Nitric oxide mediates IL-1 beta-induced islet dysfunction and destruction: prevention by dexamethasone

Nitric oxide has recently been implicated as a cellular molecule that mediates interleukin-1 beta (IL-1 beta)-induced inhibition of glucose-stimulated insulin secretion by islets of Langerhans. In this study evidence is presented which demonstrates that islets contain both the cytokine inducible and the constitutive isoforms of nitric oxide synthase as determined by NADPH diaphorase staining and immunohistochemical localization. Untreated islets contain NADPH diaphorase activity, and the intensity of NADPH diaphorase staining is dramatically increased after culture for 18 hrs with IL-1 beta. Both control and IL-1 beta-induced NADPH diaphorase staining of islets is inhibited by the nitric oxide synthase inhibitor NG-monomethyl-L-arginine (NMMA). Importantly, approximately 60-70% of islet cells stained positive for NADPH diaphorase (under both IL-1 beta treated and control conditions), suggesting that a subset of islet cells contain nitric oxide synthase. The beta-cell appears to be the endocrine cell type which contains constitutive nitric oxide synthase as demonstrated by immunohistochemical co-localization of constitutive nitric oxide synthase and insulin. IL-1 beta is believed to stimulate the expression of cytokine inducible nitric oxide synthase because the synthetic glucocorticoid, dexamethasone, prevents IL-1 beta induced inhibition of glucose stimulated insulin secretion and cGMP accumulation by islets. Both dexamethasone, and the nitric oxide synthase inhibitors NMMA and aminoguanidine also prevent IL-1 beta induced islet degeneration. These results indicate that nitric oxide produced by the inducible isoform of nitric oxide synthase mediates cytokine induced islet dysfunction and destruction, and that the beta-cell is the islet endocrine cellular source of constitutive nitric oxide synthase.

Registration and three-dimensional reconstruction of autoradiographic images by the disparity analysis method

Quantitative autoradiography is a powerful radioisotopic-imaging method for neuroscientists to study local cerebral blood flow and glucose-metabolic rate at rest, in response to physiologic activation of the visual, auditory, somatosensory, and motor systems, and in pathologic conditions. Most autoradiographic studies analyze glucose utilization and blood flow in two-dimensional (2D) coronal sections. With modern digital computer and image-processing techniques, a large number of closely spaced coronal sections can be stacked appropriately to form a three-dimensional (3D) image. 3D autoradiography allows investigators to observe cerebral sections and surfaces from any viewing angle. A fundamental problem in 3D reconstruction is the alignment (registration) of the coronal sections. A new alignment method based on disparity analysis is presented, which can overcome many of the difficulties encountered by previous methods. The disparity analysis method can deal with asymmetric, damaged, or tilted coronal sections under the same general framework, and it can be used to match coronal sections of different sizes and shapes. Experimental results on alignment and 3D reconstruction are presented.

Varieties of inhibition in the processing and control of processing in the mammalian cochlear nucleus

Seven-barrel micropipettes were used to apply drugs microiontophoretically to single units in the dorsal cochlear nucleus (DCN) in chloralose-anaesthetised guinea-pigs. While both agonists and antagonists of putative neurotransmitters in the cochlear nucleus have been investigated in these experiments, the main thrust has been to explore the influence of specific antagonists on cells' spectral and temporal properties, thus elucidating the effects of naturally occurring inhibitory transmitters. At least five types of inhibition appear to be pharmacologically/physiologically separable: (1) Stimulus-evoked tonic "lateral/sideband" inhibition: glycinergic; (blocked by strychnine); responsible for the lateral inhibition of dorsal cochlear nucleus (DCN) type III and IV cells. Strychnine has its predominant effect on sustained (lateral) inhibition compared with the more transient forms of inhibition. Subtraction of receptive field maps enables us to visualise the extent of the inhibitory receptive field. It extends virtually throughout the unit's response field for both these classes but is generally, especially in type IV cells, maximal at the characteristic frequency (CF). This type of inhibition will primarily be responsible for enhancing spectral contrasts in the way that, in the visual system, surround inhibition enhances visual contrast. Furthermore, lateral inhibitory sidebands can "bias" the "working point" of a cell's response so that the dynamic range of effective stimuli and response can be extended. (2) "Background" tonic inhibition: GABAAergic; (blocked by bicuculline). Blocking this inhibition generally results in an increase in the background (i.e., spontaneous) activity. This inhibition is probably responsible for adjusting excitatory-inhibitory contrasts in both spectral and temporal domains. (3) Stimulus-related off-inhibition appears to be neither glycinergic nor GABAAergic. Blocking these receptors actually enhances off-inhibition. Nicotinic cholinergic blockers may have a small effect on off-inhibition, but so far we have not been able to block it entirely. This off-inhibition is important for enhancing temporal contrast. This inhibition must, therefore, be mediated by other transmitters, yet undetermined, or by a local feedback circuit or, less likely, be a membrane-based after-effect of stimulation. (4) Pre-synaptic inhibition, mediated by GABAB receptors presumed to act on primary afferent terminals, thus controlling afferent input to DCN principal cells. (5) Short-latency contralateral inhibition, mediated by glycine.