Biomedical subjects

J Kwakkel

Publications and source records attributed to J Kwakkel.

9 recordsLinked to original sources

PubMed2006

PGC-1alpha regulates the isoform mRNA ratio of the alternatively spliced thyroid hormone receptor alpha transcript.

Transcripts derived from the thyroid hormone receptor alpha (TRalpha) gene are alternatively spliced resulting in a functional receptor TRalpha1 and a non-T3-binding variant TRalpha2 that can exert a dominant negative effect on the transactivation functions of other TRs. There is evidence that the ratio of TRalpha isoform transcripts can be modulated and here, we investigate whether the PPARgamma co-activator alpha (PGC-1alpha) has an effect on this splicing process. PGC-1alpha was discovered not only as a transcriptional co-activator, but also has certain motifs characteristic of splicing factors. We demonstrate that PGC-1alpha alters the ratio of endogenously expressed TRalpha isoform transcripts in HepG2 cells, by decreasing TRalpha1 mRNA levels twofold. This change in isoform ratio is accompanied by a decrease in 5'-deiodinase expression, whereas no differences were found in TRbeta1 expression. Deletion of the RNA-processing domain of PGC-1alpha abrogated the effect on the TRalpha splicing, whereas expression of only the RNA-processing domain favored TRalpha1 expression. PGC-1alpha showed a similar effect on the splicing of a TRalpha minigene containing only the last four exons and introns of the TRalpha gene. These data suggest that PGC-1alpha is involved in the RNA processing of TRalpha transcripts.

Alternative Splicing↗

PubMed2006

Differential involvement of nuclear factor-kappaB and activator protein-1 pathways in the interleukin-1beta-mediated decrease of deiodinase type 1 and thyroid hormone receptor beta1 mRNA.

One of the hallmarks of the sick euthyroid syndrome or non-thyroidal illness is a decrease of serum triiodothyronine, caused mainly by a decrease in liver deiodinase type 1 (D1) mRNA and activity. Proinflammatory cytokines like interleukin (IL)-1beta are likely involved in this disease, but are also known to inhibit thyroid hormone receptor (TR)-beta1 gene expression, which is of interest as the D1 promoter contains TREs. The aim of the present study was to evaluate whether the IL-1beta-induced decrease of D1 and TRbeta1 mRNA is mediated by the same cytokine signalling pathways in a human hepatoma cell line (HepG2). We observed a downregulation of both D1 and TRbeta1 mRNA after 4 h of incubating the cells with IL-1beta. Sulfasalazine was used to inhibit the nuclear factor-kappaB (NFkappaB) pathway and SP600125, a chemical inhibitor of the c-Jun N-terminal kinase, was used as an inhibitor of the activator protein-1 (AP-1) pathway. AP-1 inhibition did not affect the decrease of D1 and TRbeta1 mRNA, but the TRbeta1 mRNA decrease was completely abolished after inhibiting NFkappaB, while D1 mRNA was unaffected. Only simultaneous inhibition of both the NFkappaB and AP-1 pathways abolished the D1 mRNA decrease. We concluded that IL-1beta stimulation of HepG2 cells results in a marked decrease of D1 and TRbeta1 mRNA. The decrease of TRbeta1 mRNA is exclusively mediated by the NFkappaB pathway, while the decrease of D1 mRNA requires inhibition of both the AP-1 and the NFkappaB pathways.

Anthracenes↗

PubMed2006

Differential effects of leptin and refeeding on the fasting-induced decrease of pituitary type 2 deiodinase and thyroid hormone receptor beta2 mRNA expression in mice.

Profound changes in thyroid hormone metabolism occur in the central part of the hypothalamus-pituitary-thyroid (HPT) axis during fasting. Hypothalamic changes are partly reversed by leptin administration, which decreases during fasting. It is unknown to what extent leptin affects the HPT axis at the level of the pituitary. We, therefore, studied fasting-induced alterations in pituitary thyroid hormone metabolism, as well as effects of leptin administration on these changes. Because refeeding rapidly increased serum leptin, the same parameters were studied after fasting followed by refeeding. Fasting for 24 h decreased serum T(3) and T(4) and pituitary TSHbeta, type 2deiodinase (D2), and thyroid hormone receptor beta2 (TRbeta2) mRNA expression. The decrease in D2 and TRbeta2 mRNA expression was prevented when 20 mug leptin was administered twice during fasting. By contrast, the decrease in TSHbeta mRNA expression was unaffected. A single dose of leptin given after 24 h fasting did not affect decreased TSHbeta, D2, and TRbeta2 mRNA expression, while 4 h refeeding resulted in pituitary D2 and TRbeta2 mRNA expression as observed in control mice. Serum leptin, T(3), and T(4) after refeeding were similar compared with leptin administration. We conclude that fasting decreases pituitary TSHbeta, D2, and TRbeta2 mRNA expression, which (with the exception of TSHbeta) can be prevented by leptin administration during fasting. Following 24 h fasting, 4 h refeeding completely restores pituitary D2 and TRbeta2 mRNA expression, while a single leptin dose is ineffective. This indicates that other postingestion signals may be necessary to modulate rapidly the fasting-induced decrease in pituitary D2 and TRbeta2 mRNA expression.

Animals↗

PubMed2006

Chronic local inflammation in mice results in decreased TRH and type 3 deiodinase mRNA expression in the hypothalamic paraventricular nucleus independently of diminished food intake.

During illness, changes in thyroid hormone metabolism occur, known as nonthyroidal illness and characterised by decreased serum triiodothyronine (T3) and thyroxine (T4) without an increase in TSH. A mouse model of chronic illness is local inflammation, induced by a turpentine injection in each hind limb. Although serum T3 and T4 are markedly decreased in this model, it is unknown whether turpentine administration affects the central part of the hypothalamus-pituitary-thyroid axis (HPT-axis). We therefore studied thyroid hormone metabolism in hypothalamus and pituitary of mice during chronic inflammation induced by turpentine injection. Using pair-fed controls, we could differentiate between the effects of chronic inflammation per se and the effects of restricted food intake as a result of illness. Chronic inflammation increased interleukin (IL)-1beta mRNA expression in the hypothalamus more rapidly than in the pituitary. This hypothalamic cytokine response was associated with a rapid increase in local D2 mRNA expression. By contrast, no changes were present in pituitary D2 expression. TSHbeta mRNA expression was altered compared with controls. Comparing chronic inflamed mice with pair-fed controls, both preproTSH releasing hormone (TRH) and D3 mRNA expression in the paraventricular nucleus were significantly lower 48 h after turpentine administration. The timecourse of TSHbeta mRNA expression was completely different in inflamed mice compared with pair-fed mice. Turpentine administration resulted in significantly decreased TSHbeta mRNA expression only after 24 h while later in time it was lower in pair-fed controls. In conclusion, central thyroid hormone metabolism is altered during chronic inflammation and this cannot solely be attributed to diminished food intake.

Abscess↗

PubMed2005

Induction of type 3 deiodinase activity in inflammatory cells of mice with chronic local inflammation.

During illness, changes in thyroid hormone metabolism occur, so-called nonthyroidal illness (NTI). NTI has been characterized by a fall of serum T(3) due to decreased extrathyroidal conversion of T(4) into T(3) by liver type 1 deiodinase (D1), without an increase in serum TSH. Type 3 deiodinase (D3) was thought not to play an important role during NTI, but recently it has been shown that D3 activity is up-regulated in liver and skeletal muscle of critically ill patients related to hypoxia. We studied D3 gene expression and activity in liver and muscle/subcutis of mice during illness, which was induced by two different stimuli: bacterial endotoxin (lipopolysaccharide) administration, resulting in an acute systemic response, and a turpentine injection in each hindlimb, resulting in a local sc abscess. Lipopolysaccharide induced a rapid decrease in liver D1 and D3 activity but not skeletal muscle of hindlimb. In contrast, local inflammation induced by turpentine did not decrease liver D1 and D3 activity but increased markedly D3 activity in the muscle/subcutis sample containing the abscess, associated with strongly increased IL-1beta and IL-6 mRNA expression. Inflammatory cells, surrounding the abscess showed D3 and T(3)-transporter monocarboxylate transporter-8 immunoreactivity, whereas muscle cells did not show any immunoreactivity. In conclusion, local inflammation strongly induces D3 activity in inflammatory cells, especially in invading polymorphonuclear granulocytes, suggesting enhanced local degradation of T(3).

Abscess↗

PubMed2004

Contribution of interleukin-12 to the pathogenesis of non-thyroidal illness.

Changes in both central and peripheral thyroid hormone (TH) metabolism occur during illness. These changes, known collectively as non-thyroidal illness, are apparently mediated by the proinflammatory cytokines IL-6, TNFalpha and IFNgamma. IL-12 is involved in regulation of IFNgamma and TNFalpha. The aim of this study was to evaluate the role of IL-12 in TH metabolism during illness. We studied TH metabolism both centrally (in the pituitary) and peripherally (in the liver) in IL-12 knock-out (IL-12 (-/-)) and wild type (WT) mice during illness induced by administration of bacterial endotoxin (LPS). LPS induced a similar decrease in serum T (3), T (4) and liver 5'-DI mRNA expression in IL-12 (-/-) and WT mice with the exception of a smaller reduction of serum T (4) in IL-12 (-/-) mice. In the pituitary, the LPS-induced decline in 5'-DI activity in WT mice was not observed in IL-12 (-/-) mice (p < 0.001), whereas the decrease in DII activity tended to be smaller in IL-12 (-/-) mice (p = 0.066). The lower decrease in pituitary activity of both DI and DII in IL-12 (-/-) mice is possibly related to the lower LPS-induced T (4) decrease. In conclusion, IL-12 is involved in the central regulation of the HPT axis during illness but not in the peripheral regulation.

Animals↗

PubMed2004

Simultaneous changes in central and peripheral components of the hypothalamus-pituitary-thyroid axis in lipopolysaccharide-induced acute illness in mice.

During illness, major changes in thyroid hormone metabolism and regulation occur; these are collectively known as non-thyroidal illness and are characterized by decreased serum triiodothyronine (T(3)) and thyroxine (T(4)) without an increase in serum TSH. Whether alterations in the central part of the hypothalamus-pituitary-thyroid (HPT) axis precede changes in peripheral thyroid hormone metabolism instead of vice versa, or occur simultaneously, is presently unknown. We therefore studied the time-course of changes in thyroid hormone metabolism in the HPT axis of mice during acute illness induced by bacterial endotoxin (lipopolysaccharide; LPS).LPS rapidly induced interleukin-1beta mRNA expression in the hypothalamus, pituitary, thyroid and liver. This was followed by almost simultaneous changes in the pituitary (decreased expression of thyroid receptor (TR)-beta2, TSHbeta and 5'-deiodinase (D1) mRNAs), the thyroid (decreased TSH receptor mRNA) and the liver (decreased TRbeta1 and D1 mRNA). In the hypothalamus, type 2 deiodinase mRNA expression was strongly increased whereas preproTRH mRNA expression did not change after LPS. Serum T(3) and T(4) fell only after 24 h. Our results suggested almost simultaneous involvement of the whole HPT axis in the downregulation of thyroid hormone metabolism during acute illness.

Acute Disease↗

PubMed2002

Influence of respiratory syncytial virus infection on cytokine and inflammatory responses in allergic mice.

BACKGROUND: Th2 lymphocyte responses are associated with inflammation and disease during allergic responses. Exposure to particular environmental factors during the expression of allergy could result in more pronounced Th2-like immune responses and more severe disease. One factor might be a respiratory virus infection. OBJECTIVE: The aim of our study was to investigate the influence of respiratory syncytial virus (RSV) infection on the expression of ovalbumin (OVA)-induced allergy in BALB/c mice. METHODS: We determined OVA-specific IgE in serum, cytokine profiles and histopathological lesions in lungs of OVA-allergic mice after RSV infection. RESULTS: OVA sensitization and challenge induced OVA-specific IgE in serum, Th2 cytokine mRNA expression, and mononuclear and eosinophilic inflammation in the lungs. RSV inoculation during the challenge period enhanced OVA-induced IL-4 and IL-5 mRNA expression in lung tissue. RSV further enhanced the OVA-induced hypertrophy of mucous cells and eosinophilic infiltration in lung tissue. Surprisingly, RSV infection decreased Th2 cytokine secretion and eosinophilic influx in bronchoalveolar lavage of OVA-allergic mice. Because inactivated RSV did not influence these responses, replication of RSV appeared essential for the modification of OVA-induced Th2 cytokine expression. RSV did not change OVA-specific IgE levels in serum. Furthermore, the RSV-induced IL-12 mRNA expression in lung tissue of OVA-allergic mice was diminished, but IFN-gamma mRNA expression was not affected. CONCLUSION: RSV infection enhanced particular OVA-induced Th2 cytokine mRNA responses and pulmonary lesions in allergic mice and thus aggravated allergic respiratory disease.

Animals↗

PubMed2000

Both immunisation with a formalin-inactivated respiratory syncytial virus (RSV) vaccine and a mock antigen vaccine induce severe lung pathology and a Th2 cytokine profile in RSV-challenged mice.

Respiratory syncytial virus (RSV) is the most important cause of bronchiolitis and pneumonia in infants and young children. Immunopathology may play a role in RSV-induced disease and a severe RSV infection may also be associated with an increased risk of developing asthma. Vaccination with formalin-inactivated RSV (FI-RSV) prior to infection resulted both in human and in the mouse model in extensive lung pathology. In the mouse model, it has been shown that this aggravation of disease was associated with a shift in the balance between Th1 and Th2 cytokines towards a Th2-type response. The aim of the present study was to characterise the immunological and inflammatory responses in BALB/c mice upon RSV infection with or without prior vaccination with aluminium-adjuvanted FI-RSV or control antigens (FI-Mock). As previously reported by others, we also observed that a primary RSV infection in BALB/c mice resulted in a predominant Th1-type cytokine response, which was associated with slight bronchiolitis and alveolitis. FI-RSV vaccination prior to RSV challenge prevented virus replication and was associated with an aggravation of pulmonary histopathology and a shift towards a Th2-type response. Vaccination with FI-Mock did not prevent RSV replication in the lung but resulted in an even more pronounced Th2 response after infection while these mice were not sensitised to specific viral antigens. Thus, viral replication in a Th2 responding animal (induced by aluminium-adjuvanted mock vaccine) appears to boost the Th2 response upon RSV infection.

Animals↗