Induction of clusterin Expression by Neuronal Cell Death in Zebrafish

Clusterin, a protein associated with multiple functions, is expressed in a wide variety of mammalian tissues. Although clusterin is known to be involved in neurodegenerative diseases, ageing, and tumorigenesis, a detailed analysis of the consequences of gain- or loss-of-function approaches has yet to be performed to understand the underlying mechanisms of clusterin functions. Since clusterin levels change in neurological diseases, it is likely that clusterin contributes to cell death and degeneration in general. Zebrafish was investigated as a model system to study human diseases. During development, zebrafish clusterin was expressed in the notochord and nervous system. Embryonic overexpression of clusterin by mRNA microinjection did not affect axis formation, whereas its knock-down by anti-sense morpholino treatment resulted in neuronal cell death. To analyze the function of clusterin in neurodegeneration, a transgenic zebrafish was investigated, in which nitroreductase expression is regulated under the control of a neuron-specific huC promoter which is active between the stages of early neuronal precursors and mature neurons. Nitroreductase turns metronidazole into a cytotoxic agent that induces cell death within 12 h. After metronidazole treatment, transgenic zebrafish showed neuron-specific cell death. Interestingly, we also observed a dramatic induction of clusterin expression in the brain and spinal cord in these fish, suggesting a direct or indirect role of clusterin in neuronal cell death and thus, more generally, in neurodegeneration.     

Crohn's disease of the appendix

Granulomatous inflammation typifying Crohn''s disease was centred within or confined to appendices in six patients, two of whom developed lesions attributable to Crohn''s disease elsewhere in the gut. The remaining four patients have remained symptom-free for periods varying from two to six years. Histological evidence of Crohn''s disease was also present in five of 46 appendices available for re-examination in a survey of 63 cases of Crohn''s enterocolitis. It is adduced that appendiceal involvement in Crohn''s disease is not uncommon.     

Telocytes in Crohn's disease

Crohn's disease (CD) is a relapsing chronic inflammatory disorder that may involve all the gastrointestinal tract with a prevalence of terminal ileum. Intestinal lesions have a characteristic discontinuous and segmental distribution and may affect all layers of the gut wall. Telocytes (TC), a peculiar type of stromal cells, have been recently identified in a variety of tissues and organs, including gastrointestinal tract of humans and mammals. Several roles have been proposed for TC, including mechanical support, spatial relationships with different cell types, intercellular signalling and modulation of intestinal motility. The aim of our study was to investigate the presence and distribution of TC in disease‐affected and ‐unaffected ileal specimens from CD patients compared with controls. TC were identified by CD34/PDGFRα immunohistochemistry. In affected CD specimens TC disappeared, particularly where fibrosis and architectural derangement of the intestinal wall were observed. In the thickened muscularis mucosae and submucosa, few TC entrapped in the fibrotic extracellular matrix were found. A discontinuous network of TC was present around smooth muscle bundles, ganglia and enteric strands in the altered muscularis propria. At the myenteric plexus, the loss of TC network was paralleled by the loss of interstitial cells of Cajal network. In the unaffected CD specimens, TC were preserved in their distribution. Our results suggest that in CD the loss of TC might have important pathophysiological implications contributing to the architectural derangement of the intestinal wall and gut dysmotility. Further functional studies are necessary to better clarify the role of TC loss in CD pathophysiology.     

Genetics of clusterin isoform expression and Alzheimer's disease risk

The minor allele of rs11136000 within CLU is strongly associated with reduced Alzheimer's disease (AD) risk. The mechanism underlying this association is unclear. Here, we report that CLU1 and CLU2 are the two primary CLU isoforms in human brain; CLU1 and CLU2 share exons 2-9 but differ in exon 1 and proximal promoters. The expression of both CLU1 and CLU2 was increased in individuals with significant AD neuropathology. However, only CLU1 was associated with the rs11136000 genotype, with the minor "protective" rs11136000T allele being associated with increased CLU1 expression. Since CLU1 and CLU2 are predicted to encode intracellular and secreted proteins, respectively, we compared their expression; for both CLU1 and CLU2 transfected cells, clusterin is present in the secretory pathway, accumulates in the extracellular media, and is similar in size to clusterin in human brain. Overall, we interpret these results as indicating that the AD-protective minor rs11136000T allele is associated with increased CLU1 expression. Since CLU1 and CLU2 appear to produce similar proteins and are increased in AD, the AD-protection afforded by the rs11136000T allele may reflect increased soluble clusterin throughout life.     

Serum clusterin levels are not increased in presymptomatic Alzheimer's disease

Increased plasma levels of clusterin have recently been found to be associated with severity and progression in Alzheimer's disease (AD). We have investigated clusterin levels in serum of elderly people with presymptomatic AD from a population-based prospective cohort study. During 10 years follow-up, 43 participants were diagnosed with AD after on average 4.2 years (±2.6 years SD) after the initial blood sampling. At the time of blood sampling, these participants showed normal cognitive function. For each presymptomatic AD case, a control was matched on gender and age. Furthermore, the selected controls had to remain dementia-free and still be alive at the end of follow-up. Quantitative serum clusterin levels were measured with a newly developed multiple reaction monitoring (MRM) assay. Results of the assay showed no significant difference in clusterin levels between presymptomatic AD and controls (p-value 0.54). In conclusion, serum clusterin is not an early, presymptomatic biomarker for AD.     

Growth in paediatric Crohn's disease

Growth failure (GF) is one of the major complications affecting children with inflammatory bowel disease. The faltering is temporary in 40-50% of cases and prolonged in 10-20% in Crohn's disease (CD). Such failure is rare in children with ulcerative colitis (5%). This complication is often associated with retarded bone development and delayed onset of sexual maturation. The delayed linear growth has a variety of causes including insufficient intake due to anorexia and the inflammatory process with increased energy and protein expenditure. Other factors are increased intestinal loss, secondary hypopituitarism and treatment with steroids. Therapeutic strategies of CD in children have changed this last decade by introducing new therapeutic agents such as topic steroids, immunosuppressors, anti-TNF (antibody and notably in children enteral nutrition which has shown its efficacy in inducing remissions of active CD, restoring nutritional status and stimulation of linear growth. The results of a recent prospective multicentric study over 2 years in 82 CD show that severe GF (-2 SD) is initially present in 15% (n = 12), among them 11 remain < -2SD after 2 years of follow-up. Six patients who were on the normal range initially increased their GF during the follow-up (< -2SD) (total 21% < -2SD (n = 17) at 2 years). At inclusion in this group there was no difference in growth velocity, used of steroids, enteral nutrition or severity of CD as compared to the group with no GF. It suggests that new treatment strategy should be developed in the future for this specific complication of paediatric CD.