Publications

Although the migration of hepatic myofibroblasts (HMFs) contributes to the development of fibrosis, the signals regulating migration of these cells are poorly understood. In this study, we tested the hypothesis that HMF migration is stimulated by platelet-derived growth factor-BB (PDGF-BB) through p38 mitogen-activated protein (MAP) kinase and extracellular signal-regulated kinase (ERK) signaling pathways. This hypothesis was addressed by directly visualizing the migration of cultured human HMFs into a wound. PDGF-BB stimulated membrane ruffling, migration, and proliferation. PDGF-BB also induced activation of p38 MAP kinase, its downstream effector, heat shock protein (HSP) 27, ERK 1 and ERK 2, and p125 focal adhesion kinase (FAK). Selective antagonism of p38 MAP kinase blocked PDGF-BB-stimulated HSP 27 phosphorylation, membrane ruffling, and migration, but did not alter PDGF-BB-induced proliferation. Selective antagonism of ERK kinase inhibited PDGF-BB-induced ERK phosphorylation and proliferation, but did not affect PDGF-BB-stimulated migration. Concentrations of PDGF-BB that stimulated migration and proliferation did not influence myosin-dependent contractility. Neither selective inhibition of p38 MAP kinase nor ERKs altered PDGF-BB-induced activation of FAK. In conclusion, these results provide novel evidence indicating that (1) HMF migration is stimulated by PDGF-BB through the regulation of membrane ruffling by a p38 MAP kinase signaling pathway, (2) whereas p38 MAP kinase mediates PDGF-BB-stimulated migration, but not proliferation, ERKs mediate PDGF-induced proliferation, but not migration, and (3) increases in myosin-dependent contractility are not required for PDGF-BB-stimulated migration.

Several genes that are mutated in hereditary forms of intrahepatic cholestasis have been identified or mapped, providing new insights into the process of enterohepatic bile acid circulation in health and disease and new tools with which to study this process. Murine models of several of these disorders have been generated. Unanticipated genetic heterogeneity has been identified.

OBJECTIVES

To improve tobacco control campaigns, we analyzed tobacco industry strategies that encourage young adults (aged 18 to 24) to smoke.

METHODS

Initial searches of tobacco industry documents with keywords (e.g., "young adult") were extended by using names, locations, and dates.

RESULTS

Approximately 200 relevant documents were found. Transitions from experimentation to addiction, with adult levels of cigarette consumption, may take years. Tobacco marketing solidifies addiction among young adults. Cigarette advertisements encourage regular smoking and increased consumption by integrating smoking into activities and places where young adults' lives change (e.g., leaving home, college, jobs, the military, bars).

CONCLUSIONS

Tobacco control efforts should include both adults and youths. Life changes are also opportunities to stop occasional smokers' progress to addiction. Clean air policies in workplaces, the military, bars, colleges, and homes can combat tobacco marketing.

OBJECTIVES

This report describes the history, true goals, and effects of tobacco industry-sponsored youth smoking prevention programs.

METHODS

We analyzed previously-secret tobacco industry documents.

RESULTS

The industry started these programs in the 1980s to forestall legislation that would restrict industry activities. Industry programs portray smoking as an adult choice and fail to discuss how tobacco advertising promotes smoking or the health dangers of smoking. The industry has used these programs to fight taxes, clean-indoor-air laws, and marketing restrictions worldwide. There is no evidence that these programs decrease smoking among youths.

CONCLUSIONS

Tobacco industry youth programs do more harm than good for tobacco control. The tobacco industry should not be allowed to run or directly fund youth smoking prevention programs.

INTRODUCTION

Depression of sinus node function occurs in dogs and in patients after cessation of atrial flutter and fibrillation. We tested whether transient atrial pacing might produce similar changes in humans.

METHODS AND RESULTS

We studied the impact of short-term rapid atrial pacing, simulating atrial tachyarrhythmias, on sinoatrial conduction time (SACT) and corrected sinus node recovery time (CS-NRT) in 10 patients undergoing electrophysiologic study. None had recognizable structural heart disease, history of atrial fibrillation or flutter, autonomic dysfunction, or any tachycardia for at least 24 hours before study. All cardiac drugs were discontinued >5 half-lives prior to study. No patient had significant hypotension during atrial stimulation. SACT and CSNRT were measured at baseline, and sinus node reset zone was determined. Right atrial pacing was performed for 10 to 15 minutes, after which SACT and CSNRT were measured again. Both parameters increased significantly, from 423+/-208 msec to 491+/-214 msec and from 80+/-50 msec to 96+/-53 msec, respectively (P = 0.02 and P < 0.001, respectively).

CONCLUSION

Rapid atrial pacing for only 10 to 15 minutes, simulating transient atrial tachyarrhythmias, alters sinus node function in humans. Additional studies are needed to evaluate the mechanism, but the clinical implication is that even transient episodes of atrial tachyarrhythmias can cause sinus node remodeling in patients.

The basis for the permeability barrier abnormality in lamellar ichthyosis (LI) is not known. LI is caused by mutations in the gene that encodes the enzyme, transglutaminase 1 (TGI), which is responsible for assembly of the cornified envelope (CE). TG1 also has been suggested recently to catalyze the covalent attachment of omega-hydroxyceramides (omega-OHCer) to the CE, forming the corneocyte-lipid envelope (CLE). We first assessed the barrier function and the permeability pathway of the water-soluble tracer, colloidal lanthanum, across the stratum corneum (SC) in patients with LI with absent (n = 4) or low (n = 2) TG1 activity/protein. Increased movement of tracer through the SC correlated with increased transcutaneous water loss, and tracer remained restricted to the SC interstices. Enhanced extracellular permeability, in turn, was explicable by truncation and fragmentation of extracellular lamellar membrane arrays. The resultant clefts in the SC interstices represent the likely pathway for increased water permeability. Moreover, tracer movement remained restricted to the interstices, despite the demonstration of increased corneocyte fragility associated with widespread variations in CE structure. Regardless of variability in CE structure, however, CLE structure and bound omega-OHCer content were normal. The normal CLE in LI may explain both the restriction of tracer to the SC interstices, as well as the presence of foreshortened membrane arrays with near-normal interlamellar dimensions. Finally, the demonstration of a normal CLE in LI also raises questions about the putative role of TG1 in forming the CLE. These results demonstrate: (1) the extracellular nature of increased permeability in LI; (2) discontinuities in extracellular membrane structures that account for the enhanced permeability in LI; (3) that these membrane abnormalities are both associated with and explained by abnormalities in the subjacent CE scaffold; and (4) an intact CLE is present in LI, despite abnormalities in the CE, which may restrict water movement to the SC interstices in LI.

Ets transcription factors are involved in cell growth and angiogenesis. Ets-1 targets include members of the matrix metalloproteinase superfamily. In inflammatory glomerular diseases, the patterns and regulation of Ets expression have not been fully characterized. In the present study, nuclear binding activities to the consensus Ets-1/PEA3 motif were detected in mesangial cells (MC), and the Ets-1 protein was positively identified by Western blotting, reverse transcription PCR (RT-PCR), and DNA-binding studies. The 5' flanking regions of the human and rat gelatinase A genes contain clusters of potential Ets-1 binding motifs, one of which is evolutionarily conserved. Using a series of 5' deletion reporter constructs of the rat gelatinase A gene and an Ets-1 expression plasmid, a concentration-dependent threefold trans-activation of gene expression mapped to the conserved Ets-1 binding motif at -1004/-1053 bps, designated responsive element-2 (RE-2). The RE-2 was operative within the context of the homologous gelatinase A promoter but not with a heterologous simian virus 40 promoter. Specific Ets-1 binding to this sequence was demonstrated by DNA-binding studies. Transient expression of an Ets-1 expression plasmid increased gelatinase A protein expression. Our findings identify an additional matrix metalloproteinase family member, gelatinase A, as an Ets-1 responsive gene in MC that may play a role in the high level expression of this enzyme in inflammatory glomerular diseases.