Molecular,Viral and Clinical Features of Alcohol- and Non-Alcohol-Induced Liver Injury

Hepatic cells are sensitive to internal and external signals. Ethanol is one of the oldest and most widely used drugs in the world. The focus on the mechanistic engine of the alcohol-induced injury has been in the liver, which is responsible for the pathways of alcohol metabolism. Ethanol undergoes a phase I type of reaction, mainly catalyzed by the cytoplasmic enzyme, alcohol dehydrogenase (ADH), and by the microsomal ethanol-oxidizing system (MEOS). Reactive oxygen species (ROS) generated by cytochrome (CYP) 2E1 activity and MEOS contribute to ethanol-induced toxicity. We aimed to: (1) Describe the cellular, pathophysiological and clinical effects of alcohol misuse on the liver; (2) Select the biomarkers and analytical methods utilized by the clinical laboratory to assess alcohol exposure; (3) Provide therapeutic ideas to prevent/reduce alcohol-induced liver injury; (4) Provide up-to-date knowledge regarding the Corona virus and its affect on the liver; (5) Link rare diseases with alcohol consumption. The current review contributes to risk identification of patients with alcoholic, as well as non-alcoholic, liver disease and metabolic syndrome. Additional prevalence of ethnic, genetic, and viral vulnerabilities are presented.     

The TolC protein of Escherichia coli serves as a cell-surface receptor for the newly characterized TLS bacteriophage

The TolC protein of Escherichia coli is implicated in a variety of diverse cellular functions, including antibiotic efflux and alpha-hemolysin secretion. An incidental role of TolC is to facilitate the entry of the bacteriophage TLS and colicin E1 into the bacterial cell. Despite the resolution of TolC's atomic structure, the roles of specific residues in its diverse functions are unknown. Here, we describe a genetic strategy for isolating missense tolC mutations that abolish the bacteriophage receptor activity of the TolC protein without influencing its role in antibiotic efflux. These spontaneous mutations affected two regions of the TolC protein and included base-pair substitutions, insertions, and deletions. Comparison of the TolC sequence with those of its homologues revealed two hypervariable stretches that were predicted to represent loops. Interestingly, all but one of the TolC alterations preventing phage binding were located in these two hypervariable regions, which are likely to be exposed on the cell surface. This was substantiated by the recently solved three-dimensional structure of TolC. Curiously, all the phage-resistant TolC mutants showed varying degrees of resistance to colicin E1, suggesting the involvement of overlapping regions of TolC in colicin E1 import and phage binding.The phage used in this study, TLS, was earlier reported as a strain of U3. However, we show here that, unlike the previously reported lipopolysaccharide-specific U3 phage, this phage displays a distinctly different host range and discrete morphological features and, in addition to utilizing TolC as receptor, it requires the inner core of a lipopolysaccharide.     

Relationships among seizures, extracellular amino acid changes, and neurodegeneration induced by 4-aminopyridine in rat hippocampus: a microdialysis and electroencephalographic study

4-Aminopyridine is a powerful convulsant that induces the release of neurotransmitters, including glutamate. We report the effect of intrahippocampal administration of 4-aminopyridine at six different concentrations through microdialysis probes on EEG activity and on concentrations of extracellular amino acids and correlate this effect with histological changes in the hippocampus. 4-Aminopyridine induced in a concentration-dependent manner intense and frequent epileptic discharges in both the hippocampus and the cerebral cortex. The three highest concentrations used induced also a dose-dependent enhancement of extracellular glutamate, aspartate, and GABA levels and profound hippocampal damage. Neurodegenerative changes occurred in CA1, CA3, and CA4 subfields, whereas CA2 was spared. In contrast, microdialysis administration of a depolarizing K+ concentration and of tetraethylammonium resulted in increased amino acid levels but no epileptic activity and no or moderate neuronal damage. These results suggest that seizure activity induced by 4-aminopyridine is due to a combined action of excitatory amino acid release and direct stimulation of neuronal firing, whereas neuronal death is related to the increased glutamate release but is independent of seizure activity. In addition, it is concluded that the glutamate release-inducing effect of 4-aminopyridine results in excitotoxicity because it occurs at the level of nerve endings, thus permitting the interaction of glutamate with its postsynaptic receptors, which is probably not the case after K+ depolarization.     

On the stability of a model of testosterone dynamics

We prove the global asymptotic stability of a well-known delayed negative-feedback model of testosterone dynamics, which has been proposed as a model of oscillatory behavior. We establish stability (and hence the impossibility of oscillations) even in the presence of delays of arbitrary length.Supported in part by AFOSR Grant F49620-01-1-0063, NIH Grant P20 GM64375, and Dimacs.E.D. Sontag: Supported in part by AFOSR Grant F49620-01-1-0063 and NIH Grant R01 GM46383.Acknowledgement We would like to thank Augusto Ponce for useful suggestions.     

Progressive iron accumulation induces a biphasic change in the glutathione content of neuroblastoma cells

Glutathione (GSH) constitutes the single most important antioxidant in neurons, whereas iron causes oxidative stress that leads to cell damage and death. Although GSH and iron produce opposite effects on redox cell status, no mechanistic relationships between iron and GSH metabolism are known. In this work, we evaluated in SH-SY5Y neuroblastoma cells the effects of iron accumulation on intracellular GSH metabolism. After 2 d exposure to increasing concentrations of iron, cells underwent concentration-dependent iron accumulation and a biphasic change in intracellular GSH levels. Increasing iron from 1 to 5 microM resulted in a marked increase in intracellular oxidative stress and increased GSH levels. Increased GSH levels were due to increased synthesis. Further increases in iron concentration led to significant reduction in both reduced (GSH) and total (GSH + (2 x GSSG)) glutathione. Cell exposure to high iron concentrations (20-80 microM) was associated with a marked decrease in the GSH/GSSG molar ratio and the GSH half-cell reduction potential. Moreover, increasing iron from 40 to 80 microM resulted in loss of cell viability. Iron loading did not change GSH reductase activity but induced significant increases in GSH peroxidase and GSH transferase activities. The changes in GSH homeostasis reported here recapitulate several of those observed in Parkinson's disease substantia nigra. These results support a model by which progressive iron accumulation leads to a progressive decrease in GSH content and cell reduction potential, which finally results in impaired cell integrity.     

Immunohistochemical detection of [corrected] TrkB in the enteric nervous system of the small intestine in pigeon (Columba livia)

The presence and cell localization of TrkB, the main receptor for the neurotrophins (NTs), was investigated immunohistochemically in the small intestine of adult pigeons, with special reference to the enteric nervous system (ENS). Several neuronal (neurofilament proteins and PGP 9.5) and glial cell (S100 protein) markers were studied in parallel. TrkB immunoreactivity (TrkB-IR) was found to be restricted to immunohistochemically-identified glial cells present in the enteric plexuses, and to Schwann cells forming the perivascular plexus. Also, TrkB-IR was detected in enterochromaffin cells and in unidentified dendritic cells within the gut-associated lymphoid tissue. The present results demonstrate that as for mammals, TrkB in the ENS is restricted to the glial cells. The possible function of the TrkB ligands, however, remains to be established.     

Evidence that xeroderma pigmentosum cells do not perform the first step in the repair of ultraviolet damage to their DNA. 1969

Xeroderma pigmentosum (XP) is a recessively transmitted disorder of man characterized by increased sensitivity to ultraviolet light. Homozygous, affected individuals, upon exposure to sunlight, sustain severe damage to the skin; this damage is characteristically followed by multiple basal and squamous cell carcinomas and not uncommonly by other malignant neoplasia. A tissue culture cell line was derived from the skin of a man with XP. Our measurements of ultraviolet-induced pyrimidine dimers in cellular DNA show that normal diploid human skin fibroblasts excise up to 70 per cent of the dimers 24 hours, but that fibroblasts derived from the individual with XP excise less than 20 per cent in 48 hours. Alkaline gradient sedimentation experiments show that during the 24 hours after irradiation of normal cells a large number of single-stranded breaks appear and then disappear. Such changes are not observed in XP cells. XP cells apparently fail to start, the excision process because they lack the required function of an ultraviolet-specific endonuclease. These findings, plus earlier ones of Cleaver on the lack of repair replication in XP cells, raise the possibility that unexcised pyrimidine dimers can be implicated in the oncogenicity of ultraviolet radiation.     

Synthesis of dihydronaphthofurandiones and dihydrofuroquinolinediones with trypanocidal activity and analysis of their stereoelectronic properties

The synthesis of dihydronaphthofurandione and dihydrofuroquinolinedione derivatives 4-11 was performed through Diels-Alder reactions of dihydrobenzofurandione 1 with several carbodienes and acrolein N,N-dimethylhydrazone. Then, the use of 5-bromobenzofurandione 2 toward 1,3-pentadiene and the 1-azadiene afforded quinones 6 and 11 with a total regioselectivity. All the prepared quinones were tested for trypanocidal activity in vitro against Trypanosoma epimastigotes, Tulahuen strain. Among the tested compounds, the furoquinolinediones 10 and 11 have shown potent trypanocidal activities but, only the 1,5-regioisomer (11) was found active as a redox cycling agent. Calculation of their stereoelectronic properties by the density-functional theory method provided a new insight for the trypanocidal activity of these heterocyclic quinones.