Insulin-like growth factor I is a possible pathogenic mechanism in nasal polyps

Quercetin, a natural flavonoid, protects against hepatic ischemia-reperfusion injury via inhibiting Caspase-8/ASC dependent macrophage pyroptosis

INTRODUCTION

Hepatic ischemia-reperfusion injury (IRI) is an inevitable adverse event following liver surgery, leading to liver damage and potential organ failure. Despite advancements, effective interventions for hepatic IRI remain elusive, posing a significant clinical challenge. The innate immune response significantly contributes to the pathogenesis of hepatic IRI by promoting an inflammatory cytotoxic cycle. We have reported that blocking GSDMD-induced pyroptosis in innate immunity cells protected hepatic IRI from inflammatory injury. However, the search for effective pyroptosis inhibitors continues.

OBJECTIVES

This study aims to evaluate whether quercetin, a natural flavonoid, can inhibit GSDMD-induced pyroptosis and mitigate hepatic IRI.

METHODS

We established the hepatic IRI murine model and cellular pyroptosis model to evaluate the efficacy of quercetin.

RESULTS

Quercetin effectively alleviated hepatic IRI-induced tissue necrosis and inflammation. We found that during hepatic IRI, the cleavage of GSDMD occurred in hepatic macrophages, but not in other non-parenchymal cells. Quercetin inhibited the cleavage of GSDMD in macrophages. Moreover, we found that quercetin blocked the ASC assembly to inhibit the formation of NLRP3 inflammasomes and AIM2 inflammasomes, suppressing macrophage pyroptosis. Co-immunoprecipitation experiments confirmed that quercetin inhibited the interaction between ASC and Caspase-8, which is the mechanism of ASC complex and inflammasome formation. Overexpression of Caspase-8 abolished the anti-pyroptosis effect of quercetin in NLRP3 and AIM2 inflammasome signaling. Furthermore, we found that the hepatoprotective activity of quercetin was reduced in myelocytic GSDMD-deficient mice.

CONCLUSION

Our findings suggest that quercetin has beneficial effects on hepatic IRI. Quercetin could attenuate hepatic IRI and target inhibition of macrophage pyroptosis via blocking Caspase-8/ASC interaction. We recommend that quercetin might serve as a targeted approach for the prevention and personalized treatment of hepatic IRI in perioperative patients.

Significant polyomic and functional upregulation of the PAPP-A/IGFBP-4/5/IGF-1 axis in chronic rhinosinusitis with nasal polyps

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) is associated with epithelial expansion and polyp survival. However, the molecular mechanism of this aberrant proliferation is unclear. The purpose of this study was to interrogate derangements of the pappalysin-A/insulin-like growth factor binding protein/insulin-like growth factor-1 (PAPP-A/IGFBP-4/5/IGF-1 axis) as a major contributing factor to polyp growth in CRSwNP.

METHODS

Matched tissue and exosomal proteomic arrays including PAPP-A, IGFBP-4, IGFBP-5, and IGF-1 were quantified using aptamer-based methods/Western blots for proteomic analysis and whole-transcriptome sequencing/quantitative polymerase chain reaction (qPCR) for transcriptomic analysis in CRSwNP and control patients. Functional PAPP-A assays were then performed in both tissue and exosomes (set 1: n = 20 per group; validation set 2: n = 26 per group).

RESULTS

Tissue and exosomal PAPP-A was significantly overexpressed in CRSwNP compared to controls on both a transcriptomic and proteomic level (p < 0.0001). Known inhibitors of PAPP-A (stanniocalcin-1/-2) were significantly downregulated (p < 0.0001) as were PAPP-A cleavage products (IGFBP-5 p < 0.0001). PAPP-A function was shown to be increased 5-fold to 6-fold in tissue and exosomes.

CONCLUSION

Upregulated tissue and exosomal PAPP-A signaling is significantly associated with CRSwNP and may be an important factor in the promotion of epithelial proliferation and polyp growth. These data lend further support to the emerging concept of exosomal functional and polyomic analyses as a method to study sinonasal pathology.

Differential Effects of Insulin-Like Growth Factors on Scratch Wound Repair in Respiratory Epithelial Cells

Background

Insulin-like growth factors (IGFs) I and II, being potent promoters of cellular growth and differentiation, were investigated for their effectiveness in improving the rate of scratch closure in human respiratory epithelium in vitro.

Methods

Human epithelial cell lines from the nasal, bronchial, and tracheal regions were analyzed for their response to IGF-I and IGF-II, in a confluent monolayer scratch assay. IGF-binding proteins (IGFBPs) produced by certain cells are able to reduce the effectiveness of the IGFs. Consequently, the analogues LongR3 IGF-I, Des1–3 IGF-I and Arg3 IGF-I were investigated also because of their lower affinity for the IGFBPs, while still retaining unaffected affinity for the IGF-I receptor.

Results

All growth factors that were analyzed significantly improved the rate of scratch closure in bronchial and tracheal epithelial cells (p ≤ 0.05). In comparison, scratch closure was markedly slower in nasal epithelial cells and IGF-I was the most effective growth factor at effecting scratch closure in these cells. The IGF-I analogues did not significantly improve scratch closure compared with IGF-I, despite the presence of IGFBP-3 in nasal, bronchial, and tracheal epithelial cells.

Conclusion

Addition of IGF-I to wounded nasal epithelial cells increases the rate of scratch closure and therefore may have potential for improving the healing of the nasal mucosa.

Profibrotic transforming growth factor beta 1 and activin A are increased in nasal polyp tissue and induced in nasal polyp epithelium by cigarette smoke and Toll-like receptor 3 ligation

BACKGROUND

The mechanism of airway remodeling in chronic rhinosinusitis with nasal polyposis (CRSwNP) remains unknown. We wished to determine whether profibrotic transforming growth factor beta 1 (TGF-β1) and activin A and their downstream signaling proteins are increased in CRSwNP and if they are regulated in epithelial cells by noxious or inflammatory stimuli.

METHODS

Frozen tissue from CRSwNP patients, healthy control (HC) middle turbinates, and sinus tissue from CRS without NP (CRSsNP) patients were immunostained for TGF-β1, activin A, and downstream signaling proteins. Primary nasal epithelial cells (PNECs) from HCs and CRSwNP patients were cultured in media, cigarette smoke extract (CSE), or double-stranded RNA (dsRNA) (a ligand for Toll-like receptor-3) and examined for inflammatory and profibrotic genes using real-time polymerase chain reaction (PCR).

RESULTS

CRSwNP patients showed increased TGF-β1 and activin A in the stroma, increased TGF-β1 signaling (phosphorylated Smad2/3) in the stroma and epithelium, and increased Smad3-dependent Snail1 in the stroma. Immunostaining for TGF-β1, pSmad2/3, and Snail1 in CRSwNP patients was highly correlated. Immunostaining for pSmad2/3 and Snail1 was similar in CRSwNP and CRSsNP patients. Compared to HCs, PNECs from CRSwNP patients were more responsive to CSE and dsRNA in terms of TGF-β1 and activin A and more strongly induced by dsRNA in terms of chemokines.

CONCLUSION

Increased TGF-β1 and activin A and increased downstream TGF-β1 signaling is present in CRSwNP patients, primarily in the stroma. This may contribute to features of airway remodeling previously described. PNECs from CRSwNP patients are induced to produce TGF-β1 and activin A by CSE and dsRNA, suggesting that cigarette smoke and viral infection might also contribute to airway remodeling.

Association of the -14C/G MET and the -765G/C COX-2 gene polymorphisms with the risk of chronic rhinosinusitis with nasal polyps in a Polish population

Chronic rhinosinusitis with nasal polyps is strongly associated with other diseases, including asthma and allergy. The following study tested the association of the -765 G/C polymorphism of cyclooxygenase-2 (COX-2) encoding gene and the -14C/G polymorphism of protooncogen MET (MET) encoding gene with a risk of chronic rhinosinusitis with nasal polyps in a Polish population. One hundred ninety-five patients of chronic rhinosinusitis with nasal polyps as well as 200 sex-, age-, and ethnicity-matched control subjects without chronic sinusitis and nasal polyps were enrolled in this study. Among the group of patients, 63 subjects were diagnosed with allergy and 65 subjects with asthma, respectively. DNA was isolated from peripheral blood lymphocytes of patients as well as controls, and gene polymorphisms were analyzed by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR). Ten percent of the samples have been confirmed by a second method single-strand conformation polymorphism (SSCP)-PCR. We reported that the -765 G/C COX-2 (odds ratio [OR] 7.79; 95% confidence interval [CI] 4.88-12.4, p<0.001) and the -14C/G MET (OR 2.83; 95% CI 1.74-4.61, p<0.001) were associated with an increased risk of chronic rhinosinusitis with nasal polyps among analyzed group of patients. Moreover, the group of patients without allergy or asthma indicated the association of the -765 C/G (OR 7.25; 95% CI 4.38-12.1, p<0.001 and OR 7.61; 95% CI 4.47-12.6, p<0.001) genotype of the COX-2 as wells as the -14C/G (OR 2.47; 95% CI 1.46-4.17, p<0.001 and OR 2.59; 95% CI 1.54-4.37, p<0.001) genotype of MET with an increased risk of chronic rhinosinusitis with nasal polyps. Finally, it was also found that the selected group of patients with allergy or asthma indicated a very strong association of the -765 G/C (OR 5.64; 95% CI 2.91-10.9 and OR 4.74; 95% CI 2.49-9.03, p<0.001, respectively) genotype of the COX-2 with an increased risk of chronic rhinosinusitis with nasal polyps. Thus, our results suggest that COX-2 and MET gene polymorphisms may have deep impact on the risk of rhinosinusitis nasal polyp formation, which may also depend on asthma or allergy. Our results showed that the -765 G/C polymorphism of COX-2 gene and the -14C/G polymorphism of the MET gene may be associated with the risk of chronic rhinosinusitis with nasal polyps in a Polish population.

Could cellular proliferation be a predictive index for the relapse of nasal polyposis and down-regulated by nasal steroid treatment?

The aim of this article is to identify the cellular mitotic activity using Ki-67 monoclonal antibody for predicting relapses of nasal polyposis after surgery. A prospective study was conducted at Kartal Training and Research Hospital Otolaryngology Department between January 2006 and September 2008. Nasal polyps were obtained from all patients and pathological materials were analyzed for the Ki-67 staining using immunohistochemistry. Patients were followed after surgery for 12 months for relapse. There was no statistically significant difference between recurrent and nonrecurrent polyps. Polyp recurrence has a multifactorial origin. Ki-67 index alone does not provide sufficient information about polyp recurrence before the operation.

c-MET pathway involvement in chronic rhinosinusitis: a genetic association analysis

OBJECTIVE

The c-MET receptor and its ligand hepatocyte growth factor (HGF) has been shown to be overexpressed in tissue from chronic rhinosinusitis (CRS) patients with nasal polyps compared with that from controls. We assessed the genetic association of polymorphisms in the met proto-oncogene (MET) gene with CRS.

STUDY DESIGN

Case-control genetic association study.

SETTING

Tertiary-care university hospital.

SUBJECTS AND METHODS

A total of 206 unrelated Canadian patients with CRS and 196 control subjects were enrolled. Subjects were genotyped for 33 polymorphisms in the MET gene.

RESULTS

The allelic association analysis showed eight single nucleotide polymorphisms in the MET gene (rs38850, rs38855, rs38857, rs2237717, rs2402118, rs193688, rs1621, rs42336) with a statistically significant association with CRS. The rs38850 T allele showed the strongest association and the highest risk for CRS (P = 0.004; odds ratio 1.65, 95% confidence interval 1.18-2.32); the association did not reach statistical significance after adjustment for genomic control (P = 0.06). The haplotype TGG constructed of markers rs38850, rs38855, and rs38857 represented a risk haplotype, resulting in a P value of 0.003 that remained significant after correction for multiple testing (P = 0.018).

CONCLUSION

These data suggest that polymorphisms in the MET gene may play a role in the susceptibility to develop CRS. Study findings apply to patients with severe CRS unresponsive to surgery.

Intranasal insulin: from nose to brain

BACKGROUND

Intranasal insulin has proven useful to control hyperglycemia in diabetics but its mechanism of action has not been well defined. We attempted to understand several aspects of human insulin metabolism by measurement of and interaction of insulin and its associated moieties in nasal mucus, saliva and blood plasma under various physiological and pathological conditions.

METHODS

Insulin, insulin receptors, insulin-like growth factor 1 (IGF1) and insulin-like growth receptor 3 (IGFR3) were measured in nasal mucus, saliva and blood plasma in normal subjects, in thin and obese subjects and in diabetics under fasting and fed conditions.

RESULTS

There are complex relationships among each of these moieties in each biological fluid. Insulin and its associated moieties are present in both nasal mucus and saliva. These moieties in nasal mucus and saliva report on physiological and pathological changes in glucose metabolism as do these moieties in plasma. Indeed, insulin and its associated moieties in nasal mucus may offer specific data on how insulin enters the brain and thereby play essential roles in control of insulin metabolism.

INTERPRETATION

These data support the concept that insulin is synthesized not only in parotid glands but also in nasal serous glands. They also support the concept that insulin enters the brain following intranasal administration either 1) by direct entry through the cribriform plate, along the olfactory nerves and into brain parenchyma, 2) by entry through specific receptors in blood-brain barrier and thereby into the brain or 3) some combination of 1) and 2). Conversely, data also show that insulin introduced directly into the brain is secreted out of brain into the peripheral circulation. Data in this study demonstrate for the first time that insulin and its associated moieties are present not only in saliva but also in nasal mucus. How these complex relationships among nasal mucus, saliva and plasma occur are unclear but results demonstrate these relationships play separate yet interrelated roles in physiology and pathology of human insulin metabolism.

Identification of Selective Basophil Chemoattractants in Human Nasal Polyps as Insulin-Like Growth Factor-1 and Insulin-Like Growth Factor-2

In a search for novel leukocyte chemoattractants at sites of allergic inflammation, we found basophil-selective chemoattractant activity in extracts of human nasal polyps. The extracts were fractionated by reverse phase HPLC, and the resulting fractions were tested for leukocyte-stimulating activity using sensitive shape change assays. The basophil-selective activity detected was not depleted by a poxvirus CC-chemokine-binding protein affinity column. This activity was further purified by HPLC, and proteins in the bioactive fractions were analyzed by tandem electrospray mass spectrometry. Insulin-like growth factor-2 (IGF-2) was identified in these HPLC fractions, and the basophil-stimulating activity was inhibited by an anti-IGF-2-neutralizing Ab. Recombinant IGF-2 induced a substantial shape change response in basophils, but not eosinophils, neutrophils, or monocytes. IGF-2 stimulated chemokinesis of basophils, but not eosinophils or neutrophils, and synergized with eotaxin-1/CCL11 in basophil chemotaxis. IGF-2 also caused up-regulation of basophil CD11b expression and inhibited apoptosis, but did not stimulate degranulation or Ca(2+) flux. Recombinant IGF-1 exhibited similar basophil-selective effects as IGF-2, and both growth factors were detected in nasal polyp extracts by ELISA. This is the first demonstration of chemokinetic factors that increase the motility of basophils, but do not act on other granulocytes or monocytes. IGF-1 and IGF-2 could play a role in the selective recruitment of basophils in vivo.

Basic fibroblast growth factor expression in recurrent versus non-recurrent nasal polyposis

Various growth factors are expressed in nasal polyps, and some of these have been suggested to play a role in polyp formation. A potential relation between growth factor expression and polyp recurrence, however, is undetermined. Basic fibroblast growth factor (bFGF) is expressed in mononuclear cells, as well as in endothelial and epithelial surface and gland cells of nasal polyps. To determine whether bFGF may play a role in the recurrence of nasal polyps, the present study aimed at a comparison of bFGF expression in recurrent versus non-recurrent polyps. Further, the expression in polyps from asthmatic patients was compared with that from non-asthmatics. Thirty patients with newly diagnosed nasal polyposis were included. Polypectomy was performed at entry to the long-term follow-up study. Fifteen patients only had one polypectomy (no recurrence group, with a median observation time of 81 months). Fifteen patients had a median of 6.4 polypectomies (multiple recurrence group, with a median observation time of 108 months). Five of nine patients with asthma belonged to the non-recurrence group and four to the recurrence group. The polyp from the entrance polypectomy was examined for expression of bFGF by immunohistochemistry, using a polyclonal antibody. A masked semi-quantification of staining intensity was performed in recurrent versus non-recurrent polyps, as well as in asthmatics versus non-asthmatics. bFGF expression was seen as varying staining of the polyp surface and gland epithelium, as well as of some mononuclear cells and some fibroblast-like cell profiles in the polyp stroma. Vascular endothelium was labeled occasionally. Semi-quantification of the staining intensity showed no significant differences between recurrent and non-recurrent polyps, or between asthmatics and non-asthmatics. We conclude that the level of immunohistochemical expression of bFGF in recurrent and non-recurrent nasal polyposis is equivalent. Thus, the level of bFGF expression in the primary polyp can not predict a subsequent recurrence. The expression of bFGF is not up-regulated in patients with asthma. Further studies are needed to determine a potential role of bFGF in nasal polyposis, with special reference to different stages of polyp formation and growth.

Effects of topical budesonide treatment on glucocorticoid receptor mRNA down-regulation and cytokine patterns in nasal polyps

The effects of a topically applied corticosteroid, budesonide, on the expression of glucocorticoid receptor (GR) mRNA and regulation of pro-inflammatory cytokine patterns in patients with nasal polyps were evaluated. All patients were eligible for surgical polypectomy, and a majority of them had been treated with nasal steroids. Patients were given 400 microg b.i.d. (group A, n = 11), 200 microg b.i.d. (group B, n = 10), or no treatment (group C, n = 15) during two months before polypectomy. Morning serum cortisol was analyzed on the day of surgery. Surgically removed polyps were taken for analysis of GR mRNA expression by solution hybridization. Remaining tissue was cryostat-sectioned, whereafter quantification of the cytokines interleukin 1beta, interleukin 2, interleukin 4, interleukin 5, interleukin 6, interleukin 10, tumor necrosis factor alpha, and interferon gamma was made by immunohistochemistry and digitized image analysis. No significant differences among the three groups were found for any of the parameters investigated.

CONCLUSION

nasal polyps do not respond with down-regulation of GR mRNA or cytokines following topical corticosteroid treatment. The proposed corticosteroid resistance may be inherent, or induced by a change of local tissue bioavailability.

Nasal polyposis pathogenesis: a flow cytometric and immunohistochemical study of epithelial cell proliferation

In nasal polyps, constantly associated with chronic inflammation, frequent epithelial morphological changes (squamous metaplasia, secretory hyperplasia) suggest a dysregulation of epithelial cell proliferation. Cell proliferation in nasal respiratory epithelium was therefore evaluated in nasal polyposis. In 20 patients, we compared cell proliferation in mucosa from the inferior turbinate to these in nasal polyps using two methods: Flow cytometry analyzing first the ploidy and the percentage of S-phase cells (propidium iodide DNA labeling), secondly the percentage of Ki-67-labeled cells and the green fluorescent index (fluorescein-conjugated anti-human Ki-67 antigen labeling, and thirdly the percentage of Ki-67-labeled cells being in S-phase. Immunohistochemistry, quantifying the expression of Ki-67 antigen in the epithelium permitting to calculate a Ki-67 index. All cell-populations studied were diploid. Percentages of S-phase cells, Ki-67-labeled cells, Ki-67 labeled cells being in the S-phase and green fluorescence index was significantly higher in nasal polyps than in mucosa Ki-67 index were significantly higher in nasal polyps than in mucosa in the epithelium. Epithelial cell proliferation which is therefore increased in nasal polyp could play an important role in nasal polyposis pathogenesis and its relationships with inflammation can be suggested.

Nasal polyps: medical or surgical management?

Nasal polyposis is considered to be a non-IgE-mediated inflammatory condition of the nose and sinuses, often associated with chronic non-allergic rhinitis, aspirin intolerance and non-allergic asthma. The aetiology of nasal polyposis is unknown. The main symptoms are nasal obstruction and disturbance of the sense of smell. Occlusion of the nasal passage by a few large polyps could be treated by simple polypectomy to help the patient breathe through the nose. Polypectomy per se does not worsen asthma. Other surgical procedures can be performed, depending on the degree of the disease. The aim of surgery is to restore the physiological properties of the nose by making the nose as free from polyps as possible, and to allow drainage of infected sinuses. Complementary medical treatment of polyposis is always necessary, as surgery cannot treat the inflammatory component of the mucosal disease. In this respect, topical corticosteroids have long been the drugs of choice to reduce the size of polyps, to prevent recurrence after surgery, and are often the main treatment for the disease in many patients. Fluticasone propionate has now been shown to be at least as effective as beclomethasone dipropionate as a medical tool in the management of polyposis. Short-term treatment with systemic corticosteroids is an alternative method of inducing remission and controlling nasal polyps. However, in most patients with nasal polyps, treatment consists of both medical and surgical management.

Levels of substance P and IgE decapeptide in nasal polyp fluid and matching sera: a preliminary study

Sixteen unselected patients with nasal polyps had the levels of substance P and IgE decapeptide measured by ELISA in the oedema fluids and their matched sera. All 16 samples had low levels of substance P in their sera and had high level of substance P in eight samples of nasal polyp oedema. There was a considerable variation in the values of IgE decapeptide found in the sera but 14 polyp oedema fluids had high levels of IgE decapeptide. This study supports the idea that there is a linkage between the cellular and neurovascular responses. High levels of IgE decapeptide suggest that mast cell reactions occur in the majority of cases and that IgE may be implicated in the process of mast cell degranulation.

Regulation of T84 cell monolayer permeability by insulin-like growth factors

When grown on permeable supports, the T84 human colonic epithelial cell line forms polarized monolayer cultures with high-resistance tight junctions between adjacent cells. Addition of either insulin-like growth factor (IGF) I or II to the basolateral but not the apical membrane side of established monolayers caused a dose-dependent decrease in transepithelial resistance over a 4-day period. IGF-I was more potent than IGF-II, with half-maximally effective concentrations of 0.7 and 2.2 nM, respectively. Both IGF-I and -II caused a parallel increase in the transepithelial flux rates for Na+ and the extracellular space marker, mannitol, demonstrating that the decrease in electrical resistance was due to increased permeability through the tight junction-regulated paracellular pathway. Simultaneous addition of cycloheximide prevented the decline in electrical resistance, implying that protein synthesis is necessary for the effect of IGF on paracellular permeability. Treatment of monolayers with IGF produced a subtle condensation of the perijunctional actin ring as visualized using rhodamine-labeled phalloidin. These results demonstrate that IGF-I and -II regulate the paracellular permeability of T84 cell monolayers through a receptor-mediated process that probably involves changes in protein synthesis and cytoskeletal structure.

Stimulation of macrophage growth and multinucleated cell formation in rat bone marrow cultures by insulin-like growth factor I

In this study the effects of rhIGF-I on macrophage differentiation and growth have been studied using liquid suspension cultures of rat bone marrow cells. IGF-I stimulated macrophage growth in a dose-dependent manner, a maximum response was found at a concentration of 20 ng/ml. IGF-I effects could be ascribed to stimulation of both postmitotic and proliferating cells. A remarkable finding was that IGF-I induced formation of multinucleated cells (MNC). The MNC resembled macrophage-like cells (AcP, NSE positive). A monoclonal antibody to rhIGF-I significantly inhibited IGF-stimulated macrophage growth and MNC formation. A specific antibody to mouse CSF-1 reduced IGF-stimulated macrophage growth in mouse bone marrow cultures indicating that IGF-I effects could, at least in part, be ascribed to endogenous production of CSF-1. These findings indicate that IGF-I in concert with locally induced CSF-1 can influence the differentiation and growth of bone marrow-derived macrophages.

Insulin regulates the paracellular permeability of cultured intestinal epithelial cell monolayers

The T84 human colonic epithelial cell line retains the ability to produce secretagogue-responsive monolayer cultures with high transepithelial resistance when grown and maintained on collagen-coated permeable supports in media supplemented with 5% newborn calf serum. The addition of highly purified insulin to the basolateral but not the apical membrane side of established monolayers caused the transepithelial resistance to decline more than eightfold over a 3-4-d period. By comparing the transepithelial flux of 22Na with that of the extracellular space marker, [3H]mannitol, the decline in electrical resistance was shown to be due solely to an effect on tight junction-mediated paracellular permeability. The effect of insulin was dose dependent with a half-maximal effect at 3.9 ng/ml (approximately 0.7 nM) and fully reversible over a 10-d time course. Simultaneous addition of 2 microM cycloheximide prevented the insulin-induced decline in resistance; in fact, this combination caused a significant increase in electrical resistance. There was no effect on the short-circuit current response of insulin-treated monolayers to secretagogues so long as media was changed daily. While no gross morphological changes were apparent, there did appear to be a subtle condensation of the perijunctional actin ring as visualized using rhodamine-labeled phalloidin. These results demonstrate that insulin modulates the permeability of the occluding junction in T84 cell monolayers through a receptor mediated process which probably involves changes in protein synthesis and cytoskeletal structure. Insulin was also shown to produce similar effects on two other intestinal epithelial cell lines.

Somatomedin C in the pancreas of young and adult, normal and obese, hyperinsulinemic mice

Immunocytochemical, immunochemical and RNA-hybridization techniques were used to map the distribution of somatomedin C (Sm-C; insulin-like growth factor I; IGF-I) in the pancreas of young and adult lean and obese mice. The D cells in the islets of Langerhans showed intense cytoplasmic Sm-C immunoreactivity, extending into their processes. Only slight Sm-C immunoreactivity was seen in A and B cells, apparently confined to the plasma membranes. In the exocrine pancreas scattered duct cells were immunopositive. Starvation increased, while feeding decreased the Sm-C immunoreactivity in B cells. RNA-hybridization analyses revealed that roughly the same number of Sm-C mRNA molecules, as calculated per DNA amount in the pancreas, could be demonstrated in young and adult, lean and obese mice. Radioimmunoassay (RIA) determinations of total Sm-C showed that there were about equal concentrations in the pancreas of lean and obese mice. There were marked differences between the liver and the pancreas, in that the RIA Sm-C values for the former were twice those in the latter while, in contrast, the corresponding values for the Sm-C mRNA, i.e. the agent determining the synthesis of Sm-C, were about 100 times higher in the liver as compared to that in the pancreas. We interpret our results as follows: The D cells in the islets form and secrete Sm-C in both young and adult, lean and obese mice, while A and B cells bind, but do not necessarily synthesize this peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Transient expression of insulin-like growth factor I immunoreactivity by vascular cells during angiogenesis

The present study was undertaken to investigate whether vascular cells show insulin-like growth factor I (IGF-I; somatomedin C) immunoreactivity under normal conditions and/or during angiogenesis in humans and animals, as the trophic peptide IGF-I is considered important for cell growth and differentiation. In adult animals normal blood vessels, i.e., arteries, veins, and capillaries, did not show any IGF-I immunoreactivity. In newborn animals every vascular cell showed IGF-I immunoreactivity; the frequency and intensity thereafter decreased and eventually vanished as the animals approached maturity. Injury of a tissue or organ rapidly induced extensive blood vessel formation and such new blood vessels transiently expressed IGF-I immunoreactivity. Endothelial cells in budding capillaries showed distinct cytoplasmic IGF-I immunoreactivity, as did endothelial cells, smooth muscle cells, and fibroblast in newly formed arteries and veins. In biopsies of human tissue, transient IGF-I immunoreactivity was evident in vascular cells during angiogenesis after injury, as it also was in granulation tissue, skin wounds, and scar capsules around implants. Increased IGF-I immunoreactivity was further demonstrated in vascular cells in biopsies from patients with other changes involving blood vessel formation, e.g., nasal polyps, and in specimens from patients with arteritis, tendonitis, synovitis, Wegener's granulomatosis, idiopathic midline destructive disease, neurofibromatosis (von Recklinghausen's disease), and muscular dystrophy. It is concluded that during angiogenesis, obviously irrespective of inducing factors and mechanisms, vascular wall cells transiently show IGF-I immunoreactivity.