Glycoconjugation: An approach to cancer therapeutics

Cancer constitutes the second leading cause of death globally and is considered to have been responsible for an estimated 9.6 million fatalities in 2018. Although treatments against gastrointestinal tumors have recently advanced, those interventions can only be applied to a minority of patients at the time of diagnosis. Therefore, new therapeutic options are necessary for advanced stages of the disease. Glycosylation of antitumor agents, has been found to improve pharmacokinetic parameters, reduce side effects, and expand drug half-life in comparison with the parent compounds. In addition, glycosylation of therapeutic agents has been proven to be an effective strategy for their targeting tumor tissue, thereby reducing the doses of the glycodrugs administered to patients. This review focusses on the effect of the targeting properties of glycosylated antitumor agents on gastrointestinal tumors.

Secretory Autophagy and Its Relevance in Metabolic and Degenerative Disease

Proteins to be secreted through so-called "conventional mechanisms" are characterized by the presence of an N-terminal peptide that is a leader or signal peptide, needed for access to the endoplasmic reticulum and the Golgi apparatus for further secretion. However, some relevant cytosolic proteins lack of this signal peptides and should be secreted by different unconventional or "non-canonical" processes. One form of this unconventional secretion was named secretory autophagy (SA) because it is specifically associated with the autophagy pathway. It is defined by ATG proteins that regulate the biogenesis of the autophagosome, its representative organelle. The canonical macroautophagy involves the fusion of the autophagosomes with lysosomes for content degradation, whereas the SA pathway bypasses this degradative process to allow the secretion. ATG5, as well as other factors involved in autophagy such as BCN1, are also activated as part of the secretory pathway. SA has been recognized as a new mechanism that is becoming of increasing relevance to explain the unconventional secretion of a series of cytosolic proteins that have critical biological importance. Also, SA may play a role in the release of aggregation-prone protein since it has been related to the autophagosome biogenesis machinery. SA requires the autophagic pathway and both, secretory autophagy and canonical degradative autophagy are at the same time, integrated and highly regulated processes that interact in ultimate cross-talking molecular mechanisms. The potential implications of alterations in SA, its cargos, pathways, and regulation in human diseases such as metabolic/aging pathological processes are predictable. Further research of SA as potential target of therapeutic intervention is deserved.

Initial Steps in Mammalian Autophagosome Biogenesis

During the last decade, autophagy has been pointed out as a central process in cellular homeostasis with the consequent implication in most cellular settings and human diseases pathology. At present, there is significant data available about molecular mechanisms that regulate autophagy. Nevertheless, autophagy pathway itself and its importance in different cellular aspects are still not completely clear. In this article, we are focused in four main aspects: (a) Induction of Autophagy: Autophagy is an evolutionarily conserved mechanism induced by nutrient starvation or lack of growth factors. In higher eukaryotes, autophagy is a cell response to stress which starts as a consequence of organelle damage, such as oxidative species and other stress conditions. (b) Initiation of Autophagy; The two major actors in this signaling process are mTOR and AMPK. These multitasking protein complexes are capable to summarize the whole environmental, nutritional, and energetic status of the cell and promote the autophagy induction by means of the ULK1-Complex, that is the first member in the autophagy initiation. (c) ULK1-Complex: This is a highly regulated complex responsible for the initiation of autophagosome formation. We review the post-transductional modifications of this complex, considering the targets of ULK1. (d)The mechanisms involved in autophagosome formation. In this section we discuss the main events that lead to the initial structures in autophagy. The BECN1-Complex with PI3K activity and the proper recognition of PI3P are one of these. Also, the transmembrane proteins, such as VMP1 and ATG9, are critically involved. The membrane origin and the cellular localization of autophagosome biogenesis will be also considered. Hence, in this article we present an overview of the current knowledge of the molecular mechanisms involved in the initial steps of mammalian cell autophagosome biogenesis.

The HMG-I/Y-related protein p8 binds to p300 and Pax2 trans-activation domain-interacting protein to regulate the trans-activation activity of the Pax2A and Pax2B transcription factors on the glucagon gene promoter

p8 is a nuclear DNA-binding protein, which was identified because its expression is strongly activated in response to several stresses. Biochemical and biophysical studies revealed that despite a weak sequence homology p8 is an HMG-I/Y-like protein, suggesting that p8 may be involved in transcription regulation. Results reported here strongly support this hypothesis. Using a pull-down approach, we found that p8 interacts with the general co-activator p300. We also found that, similar to the HMG proteins, p300 was able to acetylate recombinant p8 in vitro, although the significance of such modification remains to be determined. Then a screening by the two-hybrid system, using p8 as bait, allowed us to identify the Pax2 trans-activation domain-interacting protein (PTIP) as another partner of p8. Transient transfection studies revealed that PTIP is a strong inhibitor of the trans-activation activities of Pax2A and Pax2B on the glucagon gene promoter, which was chosen as a model because it is a target of the Pax2A and Pax2B transcription factors. This effect is completely abolished by co-transfection of p8 in glucagon-producing InRIG9 cells, indicating that p8 binding to PTIP prevents inhibition of the glucagon gene promoter. This was not observed in NIH3T3 fibroblasts that do not express glucagon. Finally, expression of p8 enhances the effect of p300 on Pax2A and Pax2B trans-activation of the glucagon gene promoter. These observations suggest that in glucagon-producing cells p8 is a positive cofactor of the activation of the glucagon gene promoter by Pax2A and Pax2B, both by recruiting the p300 cofactor to increase the Pax2A and Pax2B activities and by binding the Pax2-interacting protein PTIP to suppress its inhibition.

Nitric oxide and apoptosis induced in Peyer's patches by attenuated strains of Salmonella enterica serovar Enteritidis

Nitric oxide (NO) is a toxic molecule of the immune system which contributes to the control of microbial pathogens. Additional functions of NO in innate and adaptive immunity have recently been described; these functions include the modulation of the cytokine response of lymphocytes and the regulation of immune cell apoptosis. In addition to direct microbicidal actions, NO has immunoregulatory effects relevant to the control of infections. In turn, infected macrophages and macrophage-regulating lymphocytes may undergo apoptosis during infection by Salmonella spp. In this work we investigated the ability of attenuated strains of Salmonella enterica serovar Enteritidis with different protective capacities to induce intestinal inducible nitric oxide synthase (iNOS) and apoptosis in Peyer's patches (PP) in mice. Results showed that the intestinal iNOS activity correlated with increased apoptosis in PP. Furthermore, the ability to induce intestinal NO production and apoptosis within the first few hours after immunization seemed to correlate with the protective capacity of mutant E/1/3 of S. enterica serovar Enteritidis. It was found that nonprotective mutant C/2/2, which was unable to induce intestinal NO production, also failed to induce apoptosis in PP. Moreover, aminoguanidine treatment at the time of immunization resulted in inhibition of the NO production and apoptosis induced by protective mutant E/1/3 and completely abolished protection against challenge. These results suggest that the induction of iNOS in the intestinal mucosa by attenuated mutant E/1/3 of S. enterica serovar Enteritidis at the time of immunization is necessary to generate a protective immune response.

Molecular and functional characterization of the stress-induced protein (SIP) gene and its two transcripts generated by alternative splicing. SIP induced by stress and promotes cell death

We have used a quantitative fluorescent cDNA microarray hybridization approach to identify pancreatic genes induced by the cellular stress promoted by acute pancreatitis in the mouse. We report the cloning and characterization of one of them that encodes the stress-induced proteins (SIP). The mouse SIP gene is organized into five exons and expands over approximately 20 kilobase pairs. Exon 4 (38 base pairs) is alternatively spliced to generate two transcripts. Northern blot and in situ hybridization showed that both SIP mRNAs are rapidly and strongly induced in acinar cells of the pancreas with acute pancreatitis. They are also constitutively expressed in several other tissues, although with different ratios. They encode proteins of 18 and 27 kDa (SIP(18) and SIP(27)). SIP(27) is identical to the thymus-expressed acidic protein (TEAP) protein, formerly described as a thymus-specific protein. Expression of the SIP(18) and SIP(27)/EGFP or V5 fusion proteins showed that both are nuclear factors. We monitored SIP expression in NIH3T3 cells submitted to various stress agents. UV stress, base damaging, mutagenic stress, ethanol, heat shock, and oxidative stress induced the concomitant expression of SIP(18) and SIP(27) mRNAs. Finally, transient transfection of SIP(18) and SIP(27) expression plasmids induced death by apoptosis in COS7 cells as measured by terminal deoxynucleotidyltransferase-mediated dUTP nick end-labeling staining. In conclusion, the SIP gene is an important element of cellular stress response. It is expressed in many tissues and induced by a variety of stress agents affecting many cellular pathways. SIP generates, by alternative splicing, two nuclear proteins that can promote cell death by apoptosis.

Expression profiling in pancreas during the acute phase of pancreatitis using cDNA microarrays

Most attacks of acute pancreatitis are self-limiting, suggesting that the pancreatic cells adapt their phenotype to prevent progression of the disease. Such phenotypic change must involve a coordinated modification in the expression of numerous genes. To identify differentially expressed genes, high-density mouse cDNA microarrays were hybridized with cDNA probes from both healthy pancreas and pancreas affected by acute pancreatitis. From the 7981 mouse genes analyzed, 239 showed significant changes in their expression during the acute phase of pancreatitis. Among them, 107 genes were up-regulated whereas 132 were down-regulated. They include genes whose function was not previously related to pancreatitis, suggesting that they are involved in some way into the acute pancreatic response. Finally, 40% of differentially expressed genes corresponded to ESTs. Demonstration that a large quantity of unexpected or yet uncharacterized genes showed altered expression during acute pancreatitis underscores the interest of a genome-based investigation. Some of these genes are certainly involved in the cellular defense against pancreatitis and, as such, deserve being studied further.

Cloning and expression of the mouse PIP49 (Pancreatitis Induced Protein 49) mRNA which encodes a new putative transmembrane protein activated in the pancreas with acute pancreatitis

We have used a microarray-based strategy to characterize, at the molecular level, the pancreatic emergency program set up by the pancreatic cells in response to pancreatitis. In this strategy, the phenotype of the pancreatitis-affected pancreas is established by characterization of a large number of its transcripts using a high-density mouse cDNA microarray. This method allows identification of transcripts differentially expressed during pancreatitis. We describe here the cloning, sequencing, and expression analysis of a new gene, named PIP49 (Pancreatitis Induced Protein 49). Its very strong expression is specific of acinar cells and occurs rapidly after initiation of the acute phase of pancreatitis. Analysis of its primary and secondary structures strongly suggests that PIP49 encodes a putative transmembrane protein.

Lipopolysaccharide directly affects pancreatic acinar cells: implications on acute pancreatitis pathophysiology

We have explored whether lipopolysaccharide (LPS, endotoxin) induces pancreatic injury on pancreatic acinar cells both in vivo and in vitro. Wistar male rats were treated with four intraperitoneal injections of 10 mg/kg LPS, and AR4-2J cells were exposed to increasing doses of LPS. Expression of pancreatitis-associated-protein (PAP) mRNA was strongly induced in AR4-2J cells exposed to LPS, while amylase mRNA was reduced. LPS also induced apoptosis and expression of TNF-alpha, IL-1beta, and IL-8 mRNA in AR4-2J cells. The in vivo effect of LPS showed structural signs of cellular damage, including numerous cytoplasmic vacuoles, severe nuclear alterations, and high expression of PAP mRNA. This study demonstrated that LPS induced pancreatic damage by directly affecting the pancreatic acinar cells. The role of LPS in the pathophysiology of acute pancreatitis may be partly due to the effect LPS has on the acinar cell.

Pancreatic acinar cells submitted to stress activate TNF-alpha gene expression

To elucidate whether pancreatic acinar cell submitted to stress is able to express TNF-alpha, we studied TNF-alpha mRNA expression by Northern blot and in situ hybridization in healthy pancreas, in tissue from caerulein-induced pancreatitis and after lipopolysaccharide (LPS) treatment. In specimens from normal pancreas, TNF-alpha mRNA expression, as judged by both Northern blot and in situ hybridization, was negative, whereas a strong but transient expression was observed in acinar cells from caerulein pancreatitis and LPS treatment. TNF-alpha mRNA appeared as rapidly as 30 min after treatment, and was maximal 6 h after. At this time, there was mild infiltration consisting mostly of polymorphonuclear leukocytes (PMNL) and no signal of TNF-alpha transcript was found in their cytoplasm. Our results strongly indicate that pancreatic acinar cell is the source of TNF-alpha early in the course of acute pancreatitis and LPS treatment, and suggest that the expression of this cytokine is a part of a general response of the acinar cell to aggression.

Lipopolysaccharides induce p8 mRNA expression in vivo and in vitro

Systemic LPS endotoxin is associated with acute pancreatic damage. Whether damage results from direct interaction of LPS with pancreatic cells is unknown. We addressed that question by monitoring p8 expression in reponse to LPS, in vivo and in vitro, because overexpression of the p8 protein is a sensitive marker of pancreatic agression. For in vivo studies, rats were sacrificed at different times after a single intraperitoneal injection of LPS, and pancreas, liver, kidney, lung, brain, and intestine were processed for RNA preparation. In vitro, pancreatic acinar AR4-2J cells were cultivated with 0.1, 1, or 10 micrograms/ml LPS for 6, 12, or 24 h. p8 mRNA expression was monitored by Northern blotting. In vivo, it was strongly increased in the pancreas after 12 h of treatment and remained elevated after 24 h. It was also induced in kidney and liver, with a maximum at 6 and 12 h, respectively, but not in lung, brain, or intestine. In AR4-2J cells, basal p8 mRNA expression was very low and increased in a time- and dose-dependent manner after treatment with LPS. LPS-induced overexpression of p8 mRNA in vivo confirmed the adverse effect of endotoxemia on pancreas and its overexpression in vitro demonstrated a direct interaction of LPS with pancreatic cells.

Clusterin overexpression in rat pancreas during the acute phase of pancreatitis and pancreatic development

Molecular mechanisms associated with apoptosis in pancreas remain largely unknown. Clusterin mRNA is induced in several tissues in response to most apoptotic stimuli. In these tissues, clusterin has an antiapoptotic activity. The aim of this work was to test whether clusterin, which is not expressed in normal pancreas, was induced in pancreas during pancreatitis and pancreatic development. Clusterin mRNA levels were strongly increased 6 h after pancreatitis induction. Maximal expression happened between 24-48 h and decreased progressively to undetectable levels at day 5. Clusterin mRNA was expressed with similar intensity in oedematous caerulein-induced pancreatitis and in response to various degrees of necrohaemorrhagic taurocholate-induced pancreatitis, indicating a maximal gene activity in all types of pancreatitis; in situ hybridization showed that the acinar cells and some ducts expressed clusterin mRNA. A single band of about 35-38 kDa was detected by western blot in pancreatic homogenates and in pancreatic juice from rats with acute pancreatitis, but not from control rats. Clusterin mRNA expression was strong in late fetal life and remains high until day 11 post-partum, then decreased progressively with a minimum from 35 to 90 days post-partum. Clusterin mRNA levels were strongly induced in pancreatic acinar AR4-2J cells in response to various apoptotic stimuli (i.e., cycloheximide, staurosporine, ceramide and H2O2) but not with interleukin (IL)-1, IL-4 or IL-6 or heat shock, which do not induce apoptosis in AR4-2J cells. In conclusion, we demonstrated that clusterin is synthesized and released by the pancreas. Its strong expression during acute pancreatitis suggests its involvement in the pancreatic response to injury. Clusterin is also induced during pancreatic development. Because these situations are associated with apoptosis and clusterin was shown to protect against apoptosis, we speculate that clusterin could be involved in the control of acinar cell apoptosis.

The effect of chronic intraperitoneal infusion of bacterial endotoxin on exocrine pancreas function in rats

CONCLUSION

This study demonstrated that LPS infusion can induce tissue lesions and impair the exocrine protein secretion of the pancreas in rats.

BACKGROUND

The effect of chronic ip infusion of lipopolysaccharide (LPS) on the exocrine pancreas function was studies in rats.

METHODS

Four milligrams per kilogram per day of Salmonella typhi LPS were infused intraperitoneally by means of surgically implanted osmotic pumps. Rats were studied after 7-d LPS infusion.

RESULTS

Plasma fibrinogen and amylase activity increased significantly in LPS-treated rats when compared with control rats. Histological examination of the pancreas showed congestion, infiltration, and focal necrosis in LPS-treated rats. The pancreas wet weight, as well as DNA and total soluble protein contents were significantly increased in LPS-treated animals when compared with controls. The pancreas protein output was significantly decreased in pure pancreatic juice, whereas the pancreatic juice flow rate was significantly increased in LPS-treated animals, when compared with controls. Electrophoretic patterns showed a marked decrease in digestive enzyme contents, whereas there was an increased content of 15 kDa protein.

Effect of ethanol intake on pancreatic exocrine secretion in mice

Swiss mice were fed conventional lab chow and 10% ethanol or water as drinking fluid for 2 weeks. Pancreatic juice was obtained by cannulation of the bile pancreatic common duct of mice anesthetized with urethane. Isolated pancreatic lobules were also obtained. The flow rate and the amylase output were determined in pure pancreatic juice. The release of amylase was measured in pancreatic lobule preparations. The basal pancreatic juice flow rate and the amylase output were significantly increased by ethanol consumption. The magnitude of the pancreatic juice flow rate and the amylase output responses to increasing doses of bethanechol, a cholinergic agent, was significantly decreased in ethanol-fed mice. The amount of spontaneously released amylase was higher in pancreatic lobule preparations from ethanol-fed animals than that from control mice, and the difference was abolished by addition of atropine to the incubation media. The amylase release rate in response to increasing doses of bethanechol was significantly reduced in lobule preparations from the ethanol-fed group. These data indicate that ethanol intake in mice has a stimulating effect on the spontaneous pancreatic secretion and lends support to the hypothesis that ethanol consumption increases the intrapancreatic cholinergic tone.

Changes in pancreatic exocrine secretion after repeated haloperidol administration

The effect of repeated administration of haloperidol on the pancreatic secretion was studied in urethane-anesthetized Swiss mice. Haloperidol (2 mg/kg) injected daily i.p. for 7 days, increase the volume and protein content of the basal pancreatic juice significantly. This secretory activity was partially blocked by i.p. injection of atropine (5 mg/kg), both in control and treated animals. The volume of the secretory response to bethanechol, a cholinergic agonist, was decreased by haloperidol without any change in amylase release. From these findings it is concluded that repeated haloperidol treatment produces an increase of basal pancreatic secretion, which is probably the result of changes in the sensitivity of dopamine receptors of the gland.

Serum isoamylase activities in cystic fibrosis patients, determined by an inhibitory assay

Serum isoamylase activities were determined in patients with either cystic fibrosis (CF) or celiac disease and in age-matched healthy children by means of an inhibitory assay suitable for routine application. The percentage pancreatic isoamylase (PIA) activity was significantly decreased in CF patients when compared with that of patients with celiac disease. Cystic fibrosis patients with steatorrhea had lower absolute values of PIA activity and higher values of salivary isoenzyme activity than control individuals. There was no overlapping between values obtained from CF patients and either celiac patients or healthy individuals. These results suggest that determination of PIA activity may be a useful adjunct test for the diagnosis of CF in patients with steatorrhea.

An experimental model to perform dynamic studies of exocrine pancreatic secretion in mice

An experimental model to perform dynamic studies of exocrine pancreatic secretion from mice has been developed. It consists of a microsurgical procedure in anesthetized mice using a stereoscopic microscope. The bile-pancreatic common duct was individualized, isolated and cannulated. A specially calibrated capillary tube was placed in the free end of the cannula and put on a millimetrical rule. Readings of pure pancreatic juice flow rate were performed minute by minute to obtain a flow rate curve. The procedure allowed the discrimination among increasing betanechol doses of 0.1, 0.2, and 0.4 microgram/g body weight.

Kallikrein and amylase contents in tissues from a mutant mouse model for human cystic fibrosis

Kallikrein and amylase activities are decreased in the pancreas and salivary glands from cri/cri homozygote mutant mice. Kallikrein is decreased in the cri/cri kidney too. With reference to nucleic acid concentrations there is no difference between control and mutant mice. The previously described electrolyte abnormalities of the cribriform degeneration (cri) mutant mouse, could be due to the abnormal activity of the kallikrein-kinin system on the transport mechanism of tubular cells in the organs mentioned. These findings represent a new step on our efforts to develop a useful animal model for human cystic fibrosis research.

An experimental model to study bile and exocrine pancreatic secretion from mice

An in vivo experimental model to obtain exocrine pancreatic secretion and bile from mice has been developed. It consists of a microsurgical procedure in anesthetized mice. The bile-pancreatic common duct and the duodenum were individualized, isolated, and cannulated using a stereoscopic microscope to obtain pure pancreatic juice, pure bile, bile-pancreatic juice, and duodenal contents. Intravenous injection of secretin as a pancreatic secretion stimulant was used with this experimental model. Fluid color an enzymatic activity were used as indicators of the fluid purity. In order to evaluate the overall procedure, mortality under surgery and volumes of samples obtained (expressed as microliters/30 minutes) before and after administration of secretin was measured. Results from a total of 524 mice of the BALB/c and DBA/2J-cri inbred strains were evaluated.