Activation of glial cells by advanced glycation endproducts

Projektdetails:

Thematik:	Ursachenforschung
Förderstatus:	abgeschlossen
Art der Förderung:	Research
Institution:	Universität Würzburg, Abteilung Physiologische Chemie
Projektleitung:	Dr. Gerald Münch
Laufzeit:	01. November 1998 - 31. Oktober 2000
Fördersumme:	76.694,00 Euro

Projektbeschreibung

A general phenomenon of ageing, which occurs in the human body throughout life, is the formation of insoluble deposits. These deposits result from an irreversible cross-link between accumulating molecules and the surrounding tissue.

One of the major mechanisms of cross-linking and deposit formation is cross-linking by advanced glycation end products (AGE). AGE are derived from the initial reaction of sugars with proteins. Recent studies have identified a threefold increase in brain AGE levels in Alzheimer’s disease patients. AGE can inflict damage on organisms by physically clogging the blood vessels and on a cellular level by causing oxidative stress by activation of immune cells and inducing chronic inflammation. AGE transmit their signals through a signal pathway involving free oxygen radicals as second messengers.

In this project Dr. Münch has identified several relevant biochemical proteins in the cell, which participate in the AGE-induced signalling process. Model-AGEs including ß-amyloid-AGE (but not unmodified ß-amyloid peptide) upregulate cytokines such as interleukin-1ß, interleukin-6, tumor necrosis factor and also the inducible nitric oxide syntase (iNOS). This response can be attenuated by antioxidants, which scavenge intracellular radicals used as second messengers (thioctic acid, N-acetylcysteine, ß-estradiol). The data suggest that AGE are the cause of the proinflammatory properties of ß-amyloid peptide and that such membrane permeable antioxidants can be used as combined radical scavengers and anti-inflammatory drugs for the treatment of Alzheimer’s disease.

Abschlussbericht

A characteristic feature in Alzheimer's disease is the accumulation of abnormal crosslinked protein deposits, "amyloid plaques" and "neurofibrillary tangles" in certain brain areas. A wide body of evidence has now been collected, that these protein deposits are directly or indirectly responsible for the start or at least for the progression of the disease. One of the major mechanism of protein crosslinking and deposit formation, a general phenomenon of aging and occurring in the human body throughout life, is crosslinking by Advanced Glycation Endproducts (AGEs).

AGEs are derived from the initial reaction of sugars e.g. glucose, fructose, etc. with proteins. This crosslinking process is accelerated in diabetes, where the blood glucose level is increased, as well as in long-term hemodialysis, where the clearance of AGEs from the blood is insufficient during dialysis. Recently studies have identified a threefold increase in brain AGEs levels in Alzheimer's disease patients, also AGE-crosslinking in tangles and ß-amyloid plaques. AGEs can not only inflict damage on organisms by physically clogging the blood vessels, but also on a cellular level by causing oxidative stress by activation of immune cells and inducing chronic inflammation.

Drugs which inhibit AGE formation and protein crosslinking have been tested successfully in a broad range of animal models for diabetic complications. One of them, aminoguanidine, is now in a clinical trial with diabetic patients. In analogy, the AGE-inhibitor tenilsetam was tested in clinical trials with Alzheimer's disease patients and significantly improved clinical and psychometric scores. We have found out that AGEs transmit their signals through a signal pathway involving oxygen free radicals as second messengers. Intracellularly acting oxidants are able to scavenger these radicals and attenuate the activation of brain immune cells and stop the local inflammatory reaction.

We have also discovered that Advanced glycation endproducts induce NF-kB activation, cytokine and iNOS expression in microglia, the immune cells of the brain. Anti-inflammatory antioxidants attenuate the expression of these inflammatory markers and are able to downregulate them including the inducible nitric oxide synthase. Advanced glycation endproducts use a common pathway involving the receptor RAGE, MAP-kinase, and NF-kB for signalling towards pro-inflammatroy cytokines which indicates that a drug interfering with these pathways can protect against inflammation in general.

In addition, we show that ß-amyloid potentiates the inflammatory response induced by LPS, Interferon-g and ß-amyloid which means that every inflammatory process in an AD patient is particularly dangerous. Based on our cell culture results, we introduce alpha-lipoic acid as a new treatment option for Alzheimer type dementia. 600 mg alpha-lipoic acid was given daily to patients with AD and related dementias (receiving a standard treatment with acetylcholinesterase inhibitors) in an open study over an observation period of, on average, 337+l-80 days. The treatment led to a stabilization of cognitive functions in the study group. These trials are ongoing - and a stop of dementia progression up to 24 months has been observed with patients with mild to moderate Alzheimer's disease.

Wissenschaftliche Publikationen auf Basis des geförderten Projekts

Münch G , Shepherd C E , McCann H , Brooks W S , Kwok J B J , Arendt T , Hallupp M , Schofield P R , Martins R N , Halliday G M  (2002).  Intraneuronal advanced glycation endproducts in presenilin-1 Alzheimer’s disease. Neuroreport, 13:601-4.

Gasic-Milenkovic, J., Dukic-Stefanovic, S., Deuther-Conrad, W., Gärtner, U., Münch, G. (2003). ß-amyloid peptide potentiates inflammatory responses induced by lipoplysaccharide, interferon-gamma and ‘advanced glycation endproducts’ in a murine microglia cell line. Eur. J. Neurosci, 17:813-821.

Dukic-Stefanovic, S., Gasic-Milenkovic, J., Deuther-Conrad, W., Münch, G. (2003). Signal transduction pathways in mouse microglia N-11 cells activated by advanced glycation endproducts (AGEs). J Neurochem, 87(1):44-55.

Sajithlal G , Huttunen H , Rauvala H , Münch G  (2002).  Receptor for advanced glycation end products (RAGE) plays a more important role in cellular survival than neurite outgrowth during retinoic acid-induced differentiation of neuroblastoma cells. J Biol Chem, 277: 6888-97.

Münch G , Robinson S R  (2002) Alzheimer's vaccine: a cure as dangerous as the disease? J Neural Transm, 109:537-9.

Gasic-Milenkovic, J., Deuther-Conrad, W., Münch, G. (2002). Glycooxidative stress creates a vicious cycle of neurodegeneration in Alzheimer’s disease – a target for neuroprotective treatment strategies? J. Neural Transm Suppl, 109:1081-1087.

Dukic-Stefanovic S., Schinzel R., Riederer P., Münch G. (2001). AGEs in brain ageing - AGE- inhibitors as neuroprotective and anti-dementia drugs? Biogerontology, 2:19-34 .

Hager K., Marahrens A., Kenklies M., Riederer P., Münch G. (2001). Alpha-Lipoic acid – a new treatment option for Alzheimer type dementia. Arch Gerontol Geriatrics, 32:275-282

Wong A., Lüth H.J., Deuther-Conrad W., Dukic-Stepanovic S., Gasic-Milenkovic J., Arendt Th., Münch G. (2001). Advanced glycation endproducts co-localize with inducible nitric oxide synthase in Alzheimer’s disease. Brain Res, 920:32-40.

Wong A., Schinzel R., Wiesinger H., Riederer P., Münch G. (2001). Anti-inflammatory antioxidants attenuate the expression of inducible nitric oxide synthase mediated by advanced glycation endproducts in murine microglia. Eur J Neurosci, 14:1-8.

Deuther-Conrad W., Loske C., Schinzel R., Dringen R., Riederer P., Münch G. (2001). Advanced glycation endproducts change glutathione redox status in SH-SY5Y neuroblastoma cells by a hydrogen peroxide dependent mechanism. Neurosci Lett, 312:29-32.

Gasic-Milenkovic J , Loske C , Münch G (2001). "AGEing" of a protein ? the cytotoxicity of a glycated protein increases with its degree of AGE modification. Z Gerontol Geriatrie, 34:457-60.

Loske C., Gerdemann A., Schepl W., Wycislo M., Schinzel R., Palm D., Riederer R., Münch G. (2000). Transition metal mediated glycoxidation accelerates crosslinking of ß-amyloid peptide. Eur J Biochem, 267:4171-4178.

Münch G., Lüth H.J., Wong A., Arendt Th., Hirsch E., Ravid R., Riederer P. (2000). Advanced glycation endproducts and a-synuclein colocalize in Lewy bodies in cases with incidental Lewy body disease. J Chem Neuroanat, 20:253-7.

Münch G., Marahrens A., Kenklies M., Riederer P., Hager K (2000). Demenz-Therapie: erste Erfolge mit Alpha-Liponsäure. Geriatrie-Journal 10:21-23.

Neumann, A., Schinzel, R., Palm, D., Riederer, P., Münch, G. (1999). High molecular weight hyaluronic acid inhibits advanced glycation endproduct-induced NF-kappa B activation and cytokine expression. FEBS Letters. 453(3):283-287.