Zoltán Rakonczay

The cholinergic system in alzheimer's disease

The past decade has witnessed an enormous increase in our knowledge of the variety and complexity of neuropathological and neurochemical changes in Alzheimers disease. Although the disease is characterized by multiple deficits of neurotransmitters in the brain, this overview emphasizes the structural and neurochemical localization of the elements of the acetylcholine system (choline acetyltransferase, acetylcholinesterase, and muscarinic and nicotinic acetylcholine receptors) in the non-demented brain and in Alzheimers disease brain samples. The results demonstrate a great variation in the distribution of acetylcholinesterase, choline acetyltransferase, and the nicotinic and muscarinic acetylcholine receptors in the different brain areas, nuclei and subnuclei. When stratification is present in certain brain regions (olfactory bulb, cortex, hippocampus, etc.), differences can be detected as regards the laminar distribution of the elements of the acetylcholine system. Alzheimers disease involves a substantial loss of the elements of the cholinergic system. There is evidence that the most affected areas include the cortex, the entorhinal area, the hippocampus, the ventral striatum and the basal part of the forebrain. Other brain areas are less affected. The fact that the acetylcholine system, which plays a significant role in the memory function, is seriously impaired in Alzheimers disease has accelerated work on the development of new drugs for treatment of the disease of the 20th century.

The role of NF-κB activation in the pathogenesis of acute pancreatitis

Acute pancreatitis is an inflammatory disease of the pancreas which, in its most severe form, is associated with multi-organ failure and death. Recently, signalling molecules and pathways which are responsible for the initiation and progression of this disease have been under intense scrutiny. One important signalling molecule, nuclear factor κB (NF-κB), has been shown to play a critical role in the development of acute pancreatitis. NF-κB is a nuclear transcription factor responsible for regulating the transcription of a wide variety of genes involved in immunity and inflammation. Many of these genes have been implicated as central players in the development and progression of acute pancreatitis. This review discusses recent advances in the investigation of pancreatic and extrapancreatic (lungs, liver, monocytes and macrophages, and endothelial cells) NF-κB activation as it relates to acute pancreatitis.

The role of NF-kappaB activation in the pathogenesis of acute pancreatitis.

Acute pancreatitis is an inflammatory disease of the pancreas which, in its most severe form, is associated with multi-organ failure and death. Recently, signalling molecules and pathways which are responsible for the initiation and progression of this disease have been under intense scrutiny. One important signalling molecule, nuclear factor κB (NF-κB), has been shown to play a critical role in the development of acute pancreatitis. NF-κB is a nuclear transcription factor responsible for regulating the transcription of a wide variety of genes involved in immunity and inflammation. Many of these genes have been implicated as central players in the development and progression of acute pancreatitis. This review discusses recent advances in the investigation of pancreatic and extrapancreatic (lungs, liver, monocytes and macrophages, and endothelial cells) NF-κB activation as it relates to acute pancreatitis.

Variants in CPA1 are strongly associated with early onset chronic pancreatitis

Chronic pancreatitis is an inflammatory disorder of the pancreas. We analyzed CPA1, encoding carboxypeptidase A1, in subjects with nonalcoholic chronic pancreatitis (cases) and controls in a German discovery set and three replication sets. Functionally impaired variants were present in 29/944 (3.1%) German cases and 5/3,938 (0.1%) controls (odds ratio (OR) = 24.9, P = 1.5 × 10−16). The association was strongest in subjects aged ≤10 years (9.7%; OR = 84.0, P = 4.1 × 10−24). In the replication sets, defective CPA1 variants were present in 8/600 (1.3%) cases and 9/2,432 (0.4%) controls from Europe (P = 0.01), 5/230 (2.2%) cases and 0/264 controls from India (P = 0.02) and 5/247 (2.0%) cases and 0/341 controls from Japan (P = 0.013). The mechanism by which CPA1 variants confer increased pancreatitis risk may involve misfolding-induced endoplasmic reticulum stress rather than elevated trypsin activity, as is seen with other genetic risk factors for this disease.

Effects of bile acids on pancreatic ductal bicarbonate secretion in guinea pig

Background and aims: Acute pancreatitis is associated with significant morbidity and mortality. Bile reflux into the pancreas is a common cause of acute pancreatitis and, although the bile can reach both acinar and ductal cells, most research to date has focused on the acinar cells. The aim of the present study was to investigate the effects of bile acids on HCO3− secretion from the ductal epithelium. Methods: Isolated guinea pig intralobular/interlobular pancreatic ducts were microperfused and the effects of unconjugated chenodeoxycholate (CDC) and conjugated glycochenodeoxycholate (GCDC) on intracellular calcium concentration ([Ca2+]i) and pH (pHi) were measured using fluorescent dyes. Changes of pHi were used to calculate the rates of acid/base transport across the duct cell membranes. Results: Luminal administration of a low dose of CDC (0.1 mM) stimulated ductal HCO3− secretion, which was blocked by luminal H2DIDS (dihydro-4,4′-diisothiocyanostilbene-2,2′-disulfonic acid). In contrast, both luminal and basolateral administration of a high dose of CDC (1 mM) strongly inhibited HCO3− secretion. Both CDC and GCDC elevated [Ca2+]i, and this effect was blocked by BAPTA-AM (1,2-bis(o-aminophenoxy)ethane-N,N,N′,N′-tetra-acetic acid), caffeine, xestospongin C and the phospholipase C inhibitor U73122. BAPTA-AM also inhibited the stimulatory effect of low doses of CDC on HCO3− secretion, but did not modulate the inhibitory effect of high doses of CDC. Conclusions: It is concluded that the HCO3− secretion stimulated by low concentrations of bile acids acts to protect the pancreas against toxic bile, whereas inhibition of HCO3− secretion by high concentrations of bile acids may contribute to the progression of acute pancreatitis.

Prosurvival Bcl-2 proteins stabilize pancreatic mitochondria and protect against necrosis in experimental pancreatitis.

Acinar cells in pancreatitis die through apoptosis and necrosis, the roles of which are different. The severity of experimental pancreatitis correlates directly with the extent of necrosis and inversely, with apoptosis. Apoptosis is mediated by the release of cytochrome c into the cytosol followed by caspase activation, whereas necrosis is associated with the mitochondrial membrane potential (DeltaPsim) loss leading to ATP depletion. Here, we investigate the role of Bcl-2 proteins in apoptosis and necrosis in pancreatitis. We found up-regulation of prosurvival Bcl-2 proteins in pancreas in various experimental models of acute pancreatitis, most pronounced for Bcl-xL. This up-regulation translated into increased levels of Bcl-xL and Bcl-2 in pancreatic mitochondria. Bcl-xL/Bcl-2 inhibitors induced DeltaPsim loss and cytochrome c release in isolated mitochondria. Corroborating the results on mitochondria, Bcl-xL/Bcl-2 inhibitors induced DeltaPsim loss, ATP depletion and necrosis in pancreatic acinar cells, both untreated and hyperstimulated with CCK-8 (in vitro pancreatitis model). Together Bcl-xL/Bcl-2 inhibitors and CCK induced more necrosis than either treatment alone. Bcl-xL/Bcl-2 inhibitors also stimulated cytochrome c release in acinar cells leading to caspase-3 activation and apoptosis. However, different from their effect on pronecrotic signals, the stimulation by Bcl-xL/Bcl-2 inhibitors of apoptotic responses was less in CCK-treated than control cells. Therefore, Bcl-xL/Bcl-2 inhibitors potentiated CCK-induced necrosis but not apoptosis. Correspondingly, transfection with Bcl-xL siRNA stimulated necrosis but not apoptosis in the in vitro pancreatitis model. Further, in animal models of pancreatitis Bcl-xL up-regulation inversely correlated with necrosis, but not apoptosis. Results indicate that Bcl-xL and Bcl-2 protect acinar cells from necrosis in pancreatitis by stabilizing mitochondria against death signals. We conclude that Bcl-xL/Bcl-2 inhibition would aggravate acute pancreatitis, whereas Bcl-xL/Bcl-2 up-regulation presents a strategy to prevent or attenuate necrosis in pancreatitis.

The role of nitric oxide in edema formation in L-arginine-induced acute pancreatitis.

Introduction Nitric oxide (NO) has been implicated in the regulation of the pancreatic circulation, the promotion of the capillary integrity, and the inhibition of leukocyte adhesion. Aims To investigate the rates of changes in the pancreatic constitutive NO synthase (cNOS) and inducible NOS (iNOS) activities and the role of NO in the vascular permeability changes during the development of L-arginine (Arg)–induced acute pancreatitis. Methodology Acute pancreatitis was induced in male Wistar rats by injecting 250 mg/100 g body weight of Arg i.p. twice at an interval of 1 hour, as a 20% solution in 0.15 M NaCl (group I). The control rats received the same quantity of glycine (group II). In group III, 30 mg/kg NG-nitro-L-arginine methyl ester (L-NAME) was injected i.p. 19 hours after the first Arg injection. The rats were killed at 6, 12, 24, or 48 hours following Arg administration, and the plasma amylase concentration and the pancreatic weight/body weight (pw/bw) ratios were evaluated. NOS activity was determined via the conversion of L-14C-Arg monohydrochloride to 14C-citrulline. The vascular permeability was examined by means of the extravasation of Evans blue dye (20 mg/kg bw) into the pancreatic tissue. Results The serum amylase level was already increased at 6 hours in group I animals, peaked at 12 hours after the Arg injection (11.800 ± 590 versus 6.618 ± 252 U/L in group II), and returned to the control level at 48 hours. The pw/bw ratio peaked at 24 hours in group I (6.63 ± 0.52 versus 4.02 ± 0.22 mg/g in group II) and returned to the control level at 48 hours. The cNOS activity was depleted at 6 hours in group I (0.02 ± 0.003 versus 0.23 ± 0.02 pmol/min/mg protein in group II); it then gradually increased to a level significantly higher than that in group II and decreased thereafter (0.45 ± 0.03 and 0.13 ± 0.01 pmol/min/mg protein at 24 and 48 hours). The iNOS activity was significantly increased at 24 and 48 hours versus that in group II (0.15 ± 0.05 and 0.07 ± 0.01 versus 0.04 ± 0.01 pmol/min/mg protein). The pancreatic concentration of Evans blue dye was significantly higher in group I than in group II (138.59 ± 11.04 versus 43.57 ± 2.67 (g/dry weight). Treatment with L-NAME significantly reduced the amylase activity, pw/bw, Evans blue concentration, and cNOS activity of the pancreas but did not exert any beneficial effect on the histologic score at 24 hours after the onset of pancreatitis, as compared with those values in group I (6.528 ± 673 U/L, 4.56 ± 0.65 mg/g, 86.84 ± 3.9 (g/dry weight, 0.14 ± 0.04 pmol/min/mg protein). Conclusion Endogenous NO is involved in the formation of pancreatic edema in Arg-induced acute pancreatitis by increasing the vascular permeability and protein extravasation. L-NAME treatment decreased the cNOS activity and edema formation but did not prevent the histologic damage in Arg-induced acute pancreatitis.

Interactions between the Endocrine and Exocrine Pancreas and Their Clinical Relevance

In consequence of the close anatomical and functional links between the exocrine and endocrine pancreas, any disease affecting one of these parts will inevitably affect the other. Pancreatic conditions which might cause diabetes mellitus include acute and chronic pancreatitis, pancreatic surgery, cystic fibrosis and pancreatic cancer. The development of diabetes greatly influences the prognosis and quality of life of patients with exocrine pancreatic diseases. It may cause life-threatening complications, such as hypoglycemia, due to the lack of glucagon and the impaired absorption of nutrients, or the micro- and macrovascular complications may impair the organ functions. Diabetes mellitus is an independent risk factor of mortality in those with exocrine pancreatic diseases. The treatment of pancreatic diabetes, a distinct metabolic and clinical form of diabetes, requires special knowledge. Diet and pancreatic enzyme replacement therapy may be sufficient in the early stages. Oral antidiabetic drugs are not recommended. If the diet proves inadequate to reach the glycemic goals, insulin treatment with multiple injections is required. Impairments of the exocrine pancreatic function and morphology in diabetic patients are frequent and well known. Atrophy of the exocrine tissue may be caused by the lack of trophic insulin, whereas pancreatic fibrosis can result from activation of stellate cells by hyperglycemia, or from microangiopathy and neuropathy. The regulation of the exocrine pancreatic function is also damaged because of the impaired effect of islet hormones. In the event of a proven impairment of the pancreatic exocrine function in diabetes mellitus, pancreatic enzyme replacement therapy is indicated. This may improve the nutritional condition of the patient and decrease the metabolic instability.

The acinar-ductal tango in the pathogenesis of acute pancreatitis

There is an unacceptably high mortality in acute pancreatitis, which is due to the lack of specific treatments for the disease. A major reason stated to account for the inability to develop effective treatments is that there are multiple pathobiologic pathways activated in the acinar cell mediating pancreatitis making it difficult to choose molecular targets for therapeutic strategies. However, this reasoning limits opportunities for therapeutic development because it does include another important participant in pancreatitis - the pancreatic duct cells. The most recent advance in pancreatitis research is that depletion of both glycolytic and oxidative ATP synthesis is a common event in both acinar and ductal cells. Although ATP has a very short half-life in the blood and is hydrolysed to ADP, there is clear evidence that encapsulating ATP into liposomes can effectively drive ATP into the cells which can be effective in protecting them from necrosis. In this review, we will examine the effects of different insults associated with pancreatitis on both the acinar and ductal components of the exocrine pancreas pointing out the role of the ductal epithelial responses in both attenuating and increasing the severity of pancreatitis. In addition, we propose that exogenous ATP administration may restore ductal and acinar function providing therapeutic benefit.

NF-κB activation is detrimental in arginine-induced acute pancreatitis

The transcription factor nuclear factor kappaB (NF-kappaB) has been shown to have a critical role in the pathogenesis of sodium taurocholate- and cerulein-induced acute pancreatitis by regulating the expression of many proinflammatory genes in the pancreas. Heat shock proteins (HSPs), on the other hand, protect the pancreas against cellular damage. The aims of the present study were: (i) to investigate pancreatic NF-kappaB activation, proinflammatory cytokine synthesis, and cytoprotective HSP induction during L-arginine- (Arg-) induced acute pancreatitis in rats, and (ii) to establish whether pretreatment with pyrrolidine dithiocarbamate (PDTC) or methylprednisolone (MP) can block the activation of pancreatic NF-kappaB and determine their effects on the severity of Arg-induced acute pancreatitis. The dose-response (3 or 4 g/kg) and time-effect (0.5-96 h) curves relating to the action of Arg on pancreatic NF-kappaB activation and IL-1beta, TNF-alpha, HSP60, and HSP72 synthesis were evaluated. Various doses of PDTC or MP were administered 1 h before the induction of pancreatitis. We demonstrated that Arg specifically and dose-dependently induces pancreatitis, activates NF-kappaB (only the 3 g/kg dose) and proinflammatory cytokine synthesis, and increases the expressions of HSP60 and HSP72 in the pancreas of rats. The lower dose of Arg induced a less severe pancreatitis, but larger increases in the levels of HSPs. The present work supports and extends earlier observations that NF-kappaB activation is a common mechanism in acute pancreatitis, although it is dose dependent and occurs at a later stage in Arg-induced pancreatitis as compared with other models. PDTC and MP pretreatment dose-dependently blocked NF-kappaB activation and proinflammatory cytokine expression and ameliorated many of the examined laboratory (the pancreatic weight/body weight ratio, the pancreatic myeloperoxidase activity, the pancreatic contents of protein, amylase and trypsinogen, the degrees of lipid peroxidation and protein oxidation, and the nonprotein sulfhydryl group content) and morphological parameters of the disease. These findings suggest that pretreatment with PDTC or MP has an anti-inflammatory effect during Arg-induced pancreatitis, which is at least partly mediated by the inhibition of NF-kappaB activation and proinflammatory cytokine synthesis. The increased levels of HSPs most probably act to limit the severity of the disease.