PubMed Health⌕ Search

Biomedical subjects

Lars Iversen

Publications and source records attributed to Lars Iversen.

At least 19 recordsLinked to original sources
PubMed2006

Atomic force microscope studies on the interactions of Candida rugosa lipase and supported lipidic bilayers.

Using the Langmuir-Blodgett technique we prepared substrate supported well-defined lipid/phospholipid (1-mono-palmitoyl-rac-glycerol (MPG)/l,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC)) bilayers in which the MPG lipid leaflet was exposed to the aqueous phase. Hydrolysis of MPG performed by Candida rugosa lipase (CRL) on the upper MPG layer of these supported bilayers on mica was imaged by real time atomic force microscope (AFM) using a liquid cell, so that the area increase of the initial structural defects could be followed over time. Our data strongly suggest that the edges of the initial structural defects are the preferred activation sites for CRL once the enzyme is adsorbed onto these interfaces. When a 2.5nM bulk concentration of CRL was assayed on this planar lipid substrate, we found a long lag phase before a sharp increase of catalytic activity. The lag-burst kinetic behaviour was related to the interfacial activation phenomenon although we propose that it is also dependent on the gel-phase state of this interface.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Mitogen- and stress-activated protein kinase 1 is activated in lesional psoriatic epidermis and regulates the expression of pro-inflammatory cytokines.

Mitogen- and stress-activated protein kinase 1 (MSK1) is a downstream target of both the p38 and extracellular signal-regulated kinase 1/2 (ERK1/2) mitogen-activated protein kinases (MAPKs). MSK1 stimulates transcription of different pro-inflammatory genes through activation of transcription factors. The purpose of this study was to investigate the expression and activation of MSK1 in lesional psoriatic skin and its role in cytokine production in cultured normal human keratinocytes. Western blotting revealed a consistent and significant increase in phosphorylated (activated) MSK1(Ser376) in lesional psoriatic skin. Immunofluorescence staining revealed the phosphorylated MSK1(Thr581) to be localized in the basal layers of the epidermis in lesional psoriatic skin. No staining was found in non-lesional psoriatic skin. Cultured human keratinocytes incubated with anisomycin or IL-1beta resulted in the phosphorylation of the p38 MAPK and MSK1(Ser376). MSK1(Ser376) phosphorylation was inhibited by pre-incubation with the p38 inhibitor SB 202190. Transfection of the keratinocytes with specific MSK1 small interfering RNA resulted in 80% reduction of MSK1 expression and 51, 40, and 31% decrease in IL-6, IL-8, and tumor necrosis factor-alpha protein production, respectively. This study demonstrates for the first time the expression of MSK1 in epidermal keratinocytes and increased activation focally in psoriatic epidermis. As MSK1 regulates the production of pro-inflammatory cytokines, it may play a role in the pathogenesis of psoriasis.

Adult↗
PubMed2006

Protein expression of TNF-alpha in psoriatic skin is regulated at a posttranscriptional level by MAPK-activated protein kinase 2.

Alterations in specific signal transduction pathways may explain the increased expression of proinflammatory cytokines seen in inflammatory diseases such as psoriasis. We reveal increased TNF-alpha protein expression, but similar TNF-alpha mRNA levels, in lesional compared with nonlesional psoriatic skin, demonstrating for the first time that TNF-alpha expression in lesional psoriatic skin is regulated posttranscriptionally. Increased levels of activated MAPK-activated protein kinase 2 (MK2) together with increased MK2 kinase activity were found in lesional compared with nonlesional psoriatic skin. Immunohistochemical analysis showed that activated MK2 was located in the basal layers of the psoriatic epidermis, whereas no positive staining was seen in nonlesional psoriatic skin. In vitro experiments demonstrated that both anisomycin and IL-1beta caused a significant activation of p38 MAPK and MK2 in cultured normal human keratinocytes. In addition, TNF-alpha protein levels were significantly up-regulated in keratinocytes stimulated with anisomycin or IL-1beta. This increase in TNF-alpha protein expression was completely blocked by the p38 inhibitor, SB202190. Transfection of cultured keratinocytes with MK2-specific small interfering RNA led to a significant decrease in MK2 expression and a subsequent significant reduction in the protein expression of the proinflammatory cytokines TNF-alpha, IL-6, and IL-8, whereas no change in the expression of the anti-inflammatory cytokine IL-10 was seen. This is the first time that MK2 expression and activity have been investigated in an inflammatory disease such as psoriasis. The results strongly suggest that increased activation of MK2 is responsible for the elevated and posttranscriptionally regulated TNF-alpha protein expression in psoriatic skin, making MK2 a potential target in the treatment of psoriasis.

Adult↗
PubMed2005

Tumor necrosis factor-alpha-induced CTACK/CCL27 (cutaneous T-cell-attracting chemokine) production in keratinocytes is controlled by nuclear factor kappaB.

CTACK/CCL27 is pivotal in mediating the migration of lymphocytes into the skin, through the binding to the chemokine receptor CCR10. CCL27 is continuously expressed by keratinocytes, but highly upregulated in inflammatory skin diseases such as atopic dermatitis and psoriasis. CCL27 can be induced in cultured keratinocytes by tumor necrosis factor (TNF)-alpha, which is also known to induce activity of the transcription factor NF-kappaB. NF-kappaB plays a vital role in controlling inflammation through its regulation of transcription of chemokines and pro-inflammatory cytokines. We show here that inhibition of NF-kappaB with the non-specific NF-kappaB inhibitors SSC (sodium salicylate), DCIC (3,4-dichloroisocoumarin) and PAO (phenylarsine oxide) results in a downregulation of TNF-alpha-induced CCL27 production. To substantiate the result and to investigate the role of NF-kappaB we investigated if specific antisense oligonucleotides against the p50 and p65 subunits of NF-kappaB had the same effect. Inhibition of either p50 or p65 production with antisense oligonucleotides resulted in a significant downregulation of TNF-alpha-induced CCL27 production. These results indicate that CCL27 expression is under the control of NF-kappaB, and that NF-kappaB, as indicated by others, may be an attractive target for therapy in inflammatory skin diseases.

Base Sequence↗
PubMed2005

A randomized clinical trial of hospital-based, comprehensive cardiac rehabilitation versus usual care for patients with congestive heart failure, ischemic heart disease, or high risk of ischemic heart disease (the DANREHAB trial)--design, intervention, and population.

BACKGROUND: Current guidelines broadly recommend comprehensive cardiac rehabilitation (CR), although evidence for this is still limited. It is not known whether evidence from before 1995 is still valid. STUDY DESIGN: The DANish Cardiac ReHABilitation (DANREHAB) trial was designed as a centrally randomized clinical trial to clarify whether hospital-based comprehensive CR is superior to usual care for patients with congestive heart failure, ischemic heart disease, or high risk for ischemic heart disease. A combined primary outcome measure included total mortality, myocardial infarction, or readmissions due to heart disease based on linkage to public registries. The CR was an individually tailored, multidisciplinary program (6 weeks of intensive CR and 12 months of follow-up) including patient education, exercise training, dietary counseling, smoking cessation, psychosocial support, risk factor management, and clinical assessment. STUDY POPULATION: Of 5060 discharged patients, 1614 (32%) were eligible for the trial and 770 patients were randomized (47% of those eligible). Participants were younger (P < .001) and had less comorbidity than nonparticipants (P < .03). CONCLUSION: Our trial shows that a large-scale, centrally randomized clinical trial on comprehensive CR can be conducted among a broadly defined patient group, but reaching the stipulated number of 1800 patients was difficult. Although the study included relatively many women and older people, elderly patients and patients with high comorbidity were underrepresented, which may influence the external validity.

Adult↗
PubMed2005

Generalized cellular hypertrophy is induced by a dual-acting PPAR agonist in rat urinary bladder urothelium in vivo.

Some developmental dual-acting PPARalpha/gamma agonists, such as ragaglitazar, have shown carcinogenic effects in the rodent urinary bladder urothelium after months-years of dosing. We examined early (precancerous) changes in the bladder urothelium of rats orally dosed with ragaglitazar, using a newly developed flow cytometric method. Following 3 weeks of oral ragaglitazar dosing, increases in physical size occurred in a generalized fashion in rat bladder urothelial cells, determined by flow cytometry. Protein/DNA measurements confirmed increased protein content of urothelial cells in the bladder, and hypertrophy was observed in the kidney pelvis urothelium by histopathology. In animals exhibiting urothelial hypertrophy, no cell cycle changes were detected in parallel samples of bladder urothelium. Interestingly, urothelial cells from normal rats were found to constitute a unique type of noncycling population, with high G2/M fractions. In summary, our findings showed that in the urothelium of ragaglitazar-treated animals, hypertrophy (increased size and protein content per cell) was an early change, that affected the whole bladder urothelial cell population. The urothelial hypertrophy was primary, i.e., occurred in the absence of similarly pronounced changes in cell cycle distributions. To our knowledge, this is the first report of a direct hypertrophic effect of a PPAR agonist. Urothelial hypertrophy might be a relevant early biological endpoint in mechanistic studies regarding the bladder-carcinogenic effect of PPAR agonists.

Animals↗
PubMed2005

Inverse regulation of the nuclear factor-kappaB binding to the p53 and interleukin-8 kappaB response elements in lesional psoriatic skin.

Nuclear factor-kappaB (NF-kappaB) is an inducible nuclear transcription factor regulating a range of cellular processes. An imbalance of the DNA binding activity of NF-kappaB may, therefore, be part of the pathophysiological mechanisms in psoriasis. The purpose of this study was to determine the NF-kappaB DNA binding activity in psoriatic skin using three different kappaB sites and to determine how DNA binding activity was modulated by the anti-psoriatic drug calcipotriol. By electrophoretic mobility shift assay, we demonstrated that the NF-kappaB DNA binding to the p53 kappaB site was decreased, whereas the NF-kappaB DNA binding to the interleukin-8 (IL-8) kappaB site was increased in lesional psoriatic skin compared with non-lesional psoriatic skin. No regulation was seen on the NF-kappaB DNA binding to the major histocompatibility complex class I kappaB site. These changes were paralleled by a similar decrease in p53 expression and an increase in IL-8 expression in involved psoriatic skin compared with uninvolved skin as determined by quantitative RT-PCR. The alteration in NF-kappaB DNA binding activity was neither accompanied by any change in the expression of the inhibitor kappaB (IkappaB) kinases, IKKalpha, IKKbeta, and IKKgamma nor in the expression of the NF-kappaB inhibitor proteins, IkappaBalpha and IkappaBbeta. Immunofluorescence analysis revealed that p65 was sequestered in the cytoplasm of keratinocytes, whereas p50 exhibited a cytoplasmic as well as a nuclear localization. Interestingly, this distribution of p50 and p65 was similar in lesional and non-lesional psoriatic skin. Topical application of calcipotriol to lesional psoriatic skin for 4 d resulted in increased NF-kappaB binding to the p53 kappaB site and decreased NF-kappaB binding to the IL-8 kappaB site. Taken together, our data demonstrate that the NF-kappaB DNA binding activity is regulated in a specific manner in psoriatic skin depending on the kappaB sites investigated, and that topical treatment of psoriatic skin normalizes the abnormal NF-kappaB binding activity seen in lesional psoriatic skin.

Administration, Cutaneous↗
PubMed2004

1alpha,25(OH)(2)D(3) regulates NF-kappaB DNA binding activity in cultured normal human keratinocytes through an increase in IkappaBalpha expression.

NF-kappaB is a dimeric transcription factor which regulates transcription of a number of different genes including IL-8 and p53. In resting cells NF-kappaB is usually retained in an inactive state in the cytoplasm through binding to a member of the inhibitory kappaB (IkappaB) protein family. The purpose of this study was to determine the effect of 1alpha,25(OH)(2)D(3) on NF-kappaB activation in both unstimulated and stimulated (IL-1alpha) cultured normal human keratinocytes. NF-kappaB DNA binding activity was determined by EMSA using two different oligonucleotides containing the kappaB sequence from either the IL-8 or the p53 promoter. IkappaBalpha and p53 expression was determined by Western blotting and IL-8 expression by ELISA. In unstimulated keratinocytes no NF-kappaB binding to the IL-8 kappaB binding sequence was detectable, whereas stimulation with IL-1alpha (10 ng/ml) led to a significant ( P<0.05) induction of NF-kappaB binding. In contrast NF-kappaB binding to the p53 kappaB binding sequence was detectable in unstimulated cells, although it was significantly increased after IL-1alpha (10 ng/ml) stimulation. Incubation with 1alpha,25(OH)(2)D(3) (10(-8)-10(-7) M) was shown to significantly ( P<0.05) stimulate the expression of IkappaBalpha and in parallel experiments with normal human keratinocytes stimulated with IL-1alpha (10 ng/ml) a significant ( P<0.05) time and dose-dependent decrease in NF-kappaB binding to the IL-8 kappaB binding sequence and in IL-8 expression were seen. A less-pronounced decrease in NF-kappaB binding to the p53 kappaB response element was seen after preincubation with 1alpha,25(OH)(2)D(3) and IL-1alpha stimulation, and it did not result in any change in p53 expression. These results demonstrate that 1alpha,25(OH)(2)D(3) inhibits NF-kappaB binding to the IL-8 kappaB binding sequence more potently than binding to the p53 kappaB binding sequence. We propose that this selectivity may be mediated through an increased expression of IkappaBalpha which leads to an inhibition of specific NF-kappaB subunits resulting in a selective regulation of NF-kappaB-induced gene transcription.

Adult↗
PubMed2004

Lysophosphatidylcholine induces keratinocyte differentiation and upregulation of AP-1- and NF-kappaB DNA-binding activity.

Lysophosphatidylcholine (lysoPC) is generated by the action of phospholipase A2 on membrane phosphatidylcholine, the most abundant cellular phospholipid. In vitro, lysoPC has pro-inflammatory properties, as it upregulates the expression of adhesion molecules and is a chemoattractant to monocytes and T lymphocytes. It upregulates the expression of a variety of genes including genes encoding growth factors and cyclooxygenase-2 and modulates other cellular responses like proliferation and differentiation. A role for lysoPC as an intracellular messenger transducing signals from membrane-associated receptors has also been suggested. However, the mechanisms behind the diverse actions of lysoPC are poorly understood. In this study we found that lysoPC in non-toxic concentrations caused increased activator protein-1 (AP-1) DNA-binding activity and transglutaminase-1 expression in cultured human keratinocytes. The effects on transglutaminase-1 and AP-1 were dependent on protein kinase C and mitogen-activated protein kinase kinase. In addition, lysoPC caused a rapid and transient increase in DNA-binding activity of nuclear factor-kappaB.

Cell Differentiation↗
PubMed2004

A survey of occupational hand eczema in Denmark.

Occupational hand eczema (OHE) is the most frequently recognized work-related disease in Denmark and the annual cost to society is high. Understanding of the epidemiology of OHE is essential to be able to give appropriate recommendations for its prevention. The study comprised 758 persons, 490 females and 268 males with recognized OHE in the period October 2001 to November 2002. Data were obtained prospectively from the National Board of Industrial Industry Registry and from a self-administered questionnaire (response rate, 82%). The most frequently recognized diagnosis was irritant contact dermatitis (ICD), mainly caused by wet occupations. The proportion of occupational ICD was equal for males and females, 59.7% and 63.1%, respectively. The estimated rates of OHE were high for bakers, hairdressers and dental surgery assistants, and a high proportion of apprentices were found among hairdressers. The prevalence of atopic dermatitis was low (16.4%) compared to previous studies among hand eczema patients. The prevalence of occupational allergic contact dermatitis in the study population was substantially higher among males than females, and the most frequent causes among males were allergy to chromium (leather exposure), rubber additives (gloves) and nickel due to exposure from work tools and metalworking industry.

Adult↗
PubMed2003

Humicola lanuginosa lipase hydrolysis of mono-oleoyl-rac-glycerol at the lipid-water interface observed by atomic force microscopy.

A new type of planar lipid substrate for Humicola lanuginosa lipase (HLL) has been prepared by depositing a monolayer of 1-mono-oleoyl-rac-glycerol (MOG) on top of a monolayer of dipalmitoyl-phosphatidylcholine (DPPC) on mica by the Langmuir-Blodgett (LB) technique. The bilayer was subsequently exposed to HLL in a liquid cell of an atomic force microscope (AFM) allowing the time course of the lipolytic degradation to be observed. By analysing a series of AFM images, we find that enzymes are preferentially activated at the edge of nano-scale defects present in the bilayer prior to enzyme injection, while defect-free areas of the substrate are surprisingly stable towards enzyme degradation. The initial rate of hydrolysis is found to be proportional to the perimeter length, P, of the initial nano-scale defects as well as the bulk enzyme concentration, c(HLL); d(lipid)/dt=k P c(HLL). We estimate the specific rate of MOG hydrolysis by HLL to be 2.5x10(4) MOG molecules/(minute x molecule of HLL).

1,2-Dipalmitoylphosphatidylcholine↗