The gene defective in Huntington's disease encodes a protein, huntingtin, with unknown function. Antisera generated against three separate regions of huntingtin identified a single high molecular weight protein of approximately 320 kDa on immunoblots of human neuroblastoma extracts. The same protein species was detected in human and rat cortex synaptosomes and in sucrose density gradients of vesicle-enriched fractions, where huntingtin immunoreactivity overlapped with the distribution of vesicle membrane proteins (SV2, transferrin receptor, and synaptophysin). Immunohistochemistry in human and rat brain revealed widespread cytoplasmic labeling of huntingtin within neurons, particularly cell bodies and dendrites, rather than the more selective pattern of axon terminal labeling characteristic of many vesicle-associated proteins. At the ultrastructural level, immunoreactivity in cortical neurons was detected in the matrix of the cytoplasm and around the membranes of the vesicles. The ubiquitous cytoplasmic distribution of huntingtin in neurons and its association with vesicles suggest that huntingtin may have a role in vesicle trafficking.

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A growing body of evidence suggests that interaction of epithelial and immune cells via neuropeptides, hormones, and cytokines participate in the pathophysiology of diarrhea and intestinal inflammation (reviewed in ref. 1). Neurotensin (NT), a bioactive peptide (2) with a primary distribution in the brain and the gastrointestinal tract, has been localized by immunohistochemistry to endocrine cells (N cells) and neurons in the intestinal mucosa, submucosa, and muscularis of animals and humans (3). A wide range of biological activities has been described for NT with actions on the cardiovascular, gastrointestinal, reproductive, and central nervous systems (3). The known intestinal effects of this peptide include trophic effects on small and large bowel, pancreas, and stomach; inhibition of small bowel and gastric motility; and stimulation of colonic motor activity (3). Studies in animals (3, 4, 5) and humans (3, 6) also demonstrate that NT may modulate fluid secretion in the intestinal tract and that its secretory effects in the ileum may be mediated through a nervous reflex in the enteric nervous system (5).Several lines of evidence indicate that NT may also participate in inflammatory reactions. Intravenous administration of NT to rats causes mast cell degranulation (7) and increases vascular permeability and levels of histamine and leukotriene C4 in the plasma (8); these effects can be inhibited by a specific NT receptor antagonist (9).NT also interacts in vitro with immune and inflammatory cells, including leukocytes (10), peritoneal mast cells (7), and macrophages (11,12). Although these studies point to a role for NT in inflammatory reactions, the possibility that this peptide participates in the pathogenesis of colonic inflammation has not been examined.NT exerts its effects by interacting with specific receptors (NTR) on cell surfaces. Two specific receptors for NT (NTR1 and NTR2), which belong to the seven transmembrane G protein-linked superfamily, have been identified and cloned (13,14). NTR1-mRNA and NT binding sites have been identified in the brain (15), small and large intestine of animals and humans (13, 15), human colonic epithelial cell lines (16,17), human blood mononuclear cells (11), and endothelial cells (18). Recently, we demonstrated the presence of NTR1 mRNA in the rat colonic mucosa, including colonic epithelial cells (19). We also showed that administration of the specific NT receptor nonpeptide antagonist SR-48,692 to rats attenuated colonic mucin secretion and mast cell activation following immobilization stress, indicating a critical role for NT in stress-related colonic responses (19).Clostridium difficile is the primary pathogenic factor of antibiotic-associated diarrhea in humans and animals The neuropeptide neurotensin mediates several intestinal functions, including chloride secretion, motility, and cellular growth. However, whether this peptide participates in intestinal inflammation is not known. Toxin A, an enterotoxin from Clostridium difficile, mediates pseudomembranous col...

The etiology and mechanisms of pathogenesis of human peripartum cardiomyopathy (PPCM) remain unknown. The incidence and prevalence of this disease is rare in some parts of the world and more common in others. The purpose of this review is to summarize our current knowledge of the factors that have been entertained which may contribute to the pathogenesis of PPCM with special emphasis on more recent data from our laboratory that provide support to the view that this disease is an autoimmune disease with multiple contributing factors and effector mechanisms. This is supported by the fact that sera from PPCM patients contain high titers of auto-antibodies against normal human cardiac tissue proteins of 37, 33, and 25 kD that was not present in the sera of patients with idiopathic cardiomyopathy (IDCM), indicating for the first time that PPCM is distinct from IDCM. In addition to the autoantibodies, the PBMC's from PPCM patients demonstrate a heightened level of fetal microchimerism, an abnormal cytokine profile, decreased levels of CD4+ CD25lo regulatory T cells, and a significant reduction in the plasma levels of progesterone, estradiol and relaxin in PPCM patients as compared with other normal pregnant non-PPCM patients. A potential role for reduced plasma levels of selenium in the pathogenesis of select PPCM patients was also noted. These findings for the first time suggest that such abnormalities may in concert lead to the initiation and perpetuation of an autoimmune process, which leads to cardiac failure and disease. Identification of the precise nature of the cardiac tissue autoantigens (currently in progress) will pave the way for the delineation of mechanism of this autoimmune disease. A working model for the pathogenesis of this disease is also described herein.

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SUMMARY1. Neurotensin stimulated histamine release and granule extrusion when applied to isolated rat peritoneal mast cells.2. This secretary response was prevented by the removal of calcium or energy and was not accompanied by the release of lactic dehydrogenase.3. The secretary response produced by neurotensin was prevented by prior treatment of mast cells with cromoglycate.4. The intravenous injection of neurotensin into anaesthetized rats produced a rapid and significant increase in the level of blood histamine that was dependent upon the dose of neurotensin.5. Treatment of rats with compound 48/80, 24 hr before neurotensin, abolished the elevation in blood histamine caused by neurotensin. The intravenous injection of cromoglyeate 1-2 min before neurotensin greatly reduced the response to neurotensin.6. The intradermal injection of neurotensin (0-03-30 p-mole) increased capillary permeability in rats pre-treated intravenously with Evans Blue. This response was abolished by the antihistamine, diphenhydramine. Increasing the dose of neurotensin to 300 p-mole partially overcame this inhibition by diphenhydramine.7. Our results demonstrate that neurotensin can elicit an exocytotic secretary response from isolated rat peritoneal mast cells and elevate histamine levels in blood.

A trinucleotide repeat (CAG) expansion in the huntingtin gene causes Huntington's disease (HD). In brain tissue from HD heterozygotes with adult onset and more clinically severe juvenile onset, where the largest expansions occur, a mutant protein of equivalent intensity to wild-type huntingtin was detected in cortical synaptosomes, indicating that a mutant species is synthesized and transported with the normal protein to nerve endings. The increased size of mutant huntingtin relative to the wild type was highly correlated with CAG repeat expansion, thereby linking an altered electrophoretic mobility of the mutant protein to its abnormal function. Mutant huntingtin appeared in gray and white matter with no difference in expression in affected regions. The mutant protein was broader than the wild type and in 6 of 11 juvenile cases resolved as a complex of bands, consistent with evidence at the DNA level for somatic mosaicism. Thus, HD pathogenesis results from a gain of function by an aberrant protein that is widely expressed in brain and is harmful only to some neurons.

The binding of neurotensin to synaptic membranes from rat brain was studied at 24°with the use of [3HJ neurotensin. The binding was found to be highly specific, saturable, and reversible. Values for KD of 2 nM and 0.9 nM were derived from equilibrium and kinetic experiments, respectively. Virtually no degradation of neurotensin was observed in the incubation medium after exposure to synaptic membranes under the conditions of the binding studies. Competitive inhibition of [3Hlneurotensin binding by partial sequences of neurotensin revealed that the addition of the residue arginine-8 to the neurotensin(9-13)pentapeptide increases about 500-fold the relative binding potency, whereas the remaining portion of the NH2-terminal region is mainly responsible for full pharmacological potency; the COOH-terminal leucyl residue is essential for bin ing.