Epidermal Growth Factor Removal or Tyrphostin AG1478 Treatment Reduces Goblet Cells & Mucus Secretion of Epithelial Cells from Asthmatic Children Using the Air-Liquid Interface Model

RATIONALE: Epithelial remodelling in asthma is characterised by goblet cell hyperplasia and mucus hypersecretion for which no therapies exist. Differentiated bronchial air-liquid interface cultures from asthmatic children display high goblet cell numbers. Epidermal growth factor and its receptor have been implicated in goblet cell hyperplasia.

OBJECTIVES: We hypothesised that EGF removal or tyrphostin AG1478 treatment of differentiating air-liquid interface cultures from asthmatic children would result in a reduction of epithelial goblet cells and mucus secretion.

METHODS: In Aim 1 primary bronchial epithelial cells from non-asthmatic (n = 5) and asthmatic (n = 5) children were differentiated under EGF-positive (10ng/ml EGF) and EGF-negative culture conditions for 28 days. In Aim 2, cultures from a further group of asthmatic children (n = 5) were grown under tyrphostin AG1478, a tyrosine kinase inhibitor, conditions. All cultures were analysed for epithelial resistance, markers of differentiation using immunocytochemistry, ELISA for MUC5AC mucin secretion and qPCR for MUC5AC mRNA.

RESULTS: In cultures from asthmatic children the goblet cell number was reduced in the EGF negative group (p = 0.01). Tyrphostin AG1478 treatment of cultures from asthmatic children had significant reductions in goblet cells at 0.2μg/ml (p = 0.03) and 2μg/ml (p = 0.003) as well as mucus secretion at 2μg/ml (p = 0.04).

CONCLUSIONS: We have shown in this preliminary study that through EGF removal and tyrphostin AG1478 treatment the goblet cell number and mucus hypersecretion in differentiating air-liquid interface cultures from asthmatic children is significantly reduced. This further highlights the epidermal growth factor receptor as a potential therapeutic target to inhibit goblet cell hyperplasia and mucus hypersecretion in asthma.

Identification of lactic acid bacteria strains modulating incretin hormone secretion and gene expression in enteroendocrine cells

Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are incretin hormones released from intestinal enteroendocrine (EE) cells and have well-established glucose-lowering actions. Lactic acid bacteria (LAB) colonise the human intestine, but it is unknown whether LAB and EE cells interact. Acute co-culture of LAB with EE cells showed that certain LAB strains elicit GLP-1 and GIP secretion (13-194-fold) and upregulate their gene expression. LAB-induced incretin hormone secretion did not appear to involve nutrient mechanisms, nor was there any evidence of cytolysis. Instead PCR array studies implicated signalling agents of the toll-like receptor system, e.g. adaptor protein MyD88 was decreased 23-fold and cell surface antigen CD14 was increased 17-fold. Mechanistic studies found that blockade of MyD88 triggered significant GLP-1 secretion. Furthermore, blocking of CD14 completely attenuated LAB-induced secretion. A recent clinical trial clearly shows that LAB have potential for alleviating type 2 diabetes, and further characterisation of this bioactivity is warranted.

De novo sequencing of two novel peptides homologous to calcitonin-like peptides, from skin secretion of the Chinese Frog, Odorrana schmackeri

An MS/MS based analytical strategy was followed to solve the complete sequence of two new peptides from frog (Odorrana schmackeri) skin secretion. This involved reduction and alkylation with two different alkylating agents followed by high resolution tandem mass spectrometry. De novo sequencing was achieved by complementary CID and ETD fragmentations of full-length peptides and of selected tryptic fragments. Heavy and light isotope dimethyl labeling assisted with annotation of sequence ion series. The identified primary structures are GCD[I/L]STCATHN[I/L]VNE[I/L]NKFDKSKPSSGGVGPESP-NH2 and SCNLSTCATHNLVNELNKFDKSKPSSGGVGPESF-NH2, i.e. two carboxyamidated 34 residue peptides with an aminoterminal intramolecular ring structure formed by a disulfide bridge between Cys2 and Cys7. Edman degradation analysis of the second peptide positively confirmed the exact sequence, resolving I/L discriminations. Both peptide sequences are novel and share homology with calcitonin, calcitonin gene related peptide (CGRP) and adrenomedullin from other vertebrates. Detailed sequence analysis as well as the 34 residue length of both O. schmackeri peptides, suggest they do not fully qualify as either calcitonins (32 residues) or CGRPs (37 amino acids) and may justify their classification in a novel peptide family within the calcitonin gene related peptide superfamily. Smooth muscle contractility assays with synthetic replicas of the S–S linked peptides on rat tail artery, uterus, bladder and ileum did not reveal myotropic activity.

pLR-HL: a novel amphibian Bowman-Birk-type trypsin inhibitor from the skin secretion of the broad-folded frog, Hylarana latouchii

In this study, we report a novel heptadecapeptide (LIGGCWTKSIPPKPCLV) of the pLR/ranacyclin family, named pLR-HL, whose structure was deduced from its biosynthetic precursor-encoding cDNA cloned from the skin secretion-derived cDNA library of the broad-folded frog, Hylarana latouchii, by employing a "shotgun" cloning technique. It contains a disulphide loop between Cys5 and Cys15 which is consistent with Bowman-Birk-type protease inhibitors. The primary structure of pLR-HL deduced from the cDNA sequence was confirmed by fractionating the skin secretion using reverse phase HPLC and subsequent analysis using MALDI-TOF mass spectrometry and LC/MS/MS fragmentation sequencing. On the basis of the establishment of unequivocal amino acid sequence, a synthetic replicate was synthesised by solid-phase Fmoc chemistry, and it displayed a moderately potent trypsin inhibition with a Ki of 143 nM. The substitution of Lys-8 by Phe (Phe8 -pLR-HL) resulted in abolition of trypsin inhibition but generation of modest inhibition on chymotrypsin with a Ki of 2.141 μM. Additionally, both the disulphide loops of pLR-HL and Phe8 -pLR-HL were synthesised and tested. Both of the catalytic loops retained similar inhibitory potencies towards trypsin or chymotrypsin in comparison with the original intact molecules. Thus, the replacement of reactive site residues could alter the specificity of these protease inhibitors, while the canonical reactive loop alone can independently constitute biologically-active moiety.

PH-sauvagine from the skin secretion of Phyllomedusa hypochondrialis: a novel CRF-like peptide with smooth muscle contraction activity

Amphibian skin, and particularly that of south/Central American phyllomedusine frogs, is supposed to be "a huge factory and store house of a variety of active peptides". The 40 amino acid amphibian CRF-like peptide, sauvagine, is a prototype member of a unique family of these Phyllomedusa skin peptides. In this study, we describe for the first time the structure of a mature novel peptide from the skin secretion of the South American orange-legged leaf frog, Phyllomedusa hypochondrialis, which belongs to the amphibian CRF/sauvagine family. Partial amino acid sequence from the N-terminal was obtained by automated Edman degradation with the following structure: pGlu-GPPISIDLNMELLRNMIEI-. The biosynthetic precursor of this novel sauvagine peptide, consisted of 85 amino acid residues and was deduced from cDNA library constructed from the same skin secretion. Compared with the standard sauvagine from the frog, Phyllomedusa sauvagei, this novel peptide was found to exert similar contraction effects on isolated guinea-pig colon and rat urinary bladder smooth muscle preparations.

Quantification of Type VI secretion system activity in macrophages infected with Burkholderia cenocepacia

The Gram-negative bacterial type VI Secretion System (T6SS) delivers toxins to kill orinhibit the growth of susceptible bacteria, while others target eukaryotic cells. Deletionof atsR, a negative regulator of virulence factors in B. cenocepacia K56-2, increasesT6SS activity. Macrophages infected with a K56-2 ΔatsR mutant display dramaticalterations in their actin cytoskeleton architecture that rely on the T6SS, which isresponsible for the inactivation of multiple Rho-family GTPases by an unknownmechanism. We employed a strategy to standardize the bacterial infection ofmacrophages and densitometrically quantify the T6SS-associated cellular phenotype,which allowed us to characterize the phenotype of systematic deletions of each genewithin the T6SS cluster and ten vgrG encoding genes in K56-2 ΔatsR. None of thegenes from the T6SS core cluster and the individual vgrGs were directly responsiblefor the cytoskeletal changes in infected cells. However, a mutant strain with all vgrGgenes deleted was unable to cause macrophage alterations. Despite not being able toidentify a specific effector protein responsible for the cytoskeletal defects inmacrophages, our strategy resulted in the identification of the critical core componentsand accessory proteins of the T6SS assembly machinery and provides a screeningmethod to detect T6SS effectors targeting the actin cytoskeleton in macrophages byrandom mutagenesis.

Phylloseptin-PBa—A Novel Broad-Spectrum Antimicrobial Peptide from the Skin Secretion of the Peruvian Purple-Sided Leaf Frog (Phyllomedusa Baltea) Which Exhibits Cancer Cell Cytotoxicity

Antimicrobial peptides from amphibian skin secretion display remarkable broad-spectrum antimicrobial activity and are thus promising for the discovery of new antibiotics. In this study, we report a novel peptide belonging to the phylloseptin family of antimicrobial peptides, from the skin secretion of the purple-sided leaf frog, Phyllomedusa baltea, which was named Phylloseptin-PBa. Degenerate primers complementary to putative signal peptide sites of frog skin peptide precursor-encoding cDNAs were designed to interrogate a skin secretion-derived cDNA library from this frog. Subsequently, the peptide was isolated and identified using reverse phase HPLC and MS/MS fragmentation. The synthetic replicate was demonstrated to have activity against S. aureus, E. coli and C. albicans at concentrations of 8, 128 and 8 mg/L, respectively. In addition, it exhibited anti-proliferative activity against the human cancer cell lines, H460, PC3 and U251MG, but was less active against a normal human cell line (HMEC). Furthermore, a haemolysis assay was performed to assess mammalian cell cytotoxicity of Phylloseptin-PBa. This peptide contained a large proportion of α-helical domain, which may explain its antimicrobial and anticancer activities.

Naturally-occurring TGR5 agonists modulating glucagon-like peptide-1 biosynthesis and secretion

Selective GLP-1 secretagogues represent a novel potential therapy for type 2 diabetes mellitus. This study examined the GLP-1 secretory activity of the ethnomedicinal plant, Fagonia cretica, which is postulated to possess anti-diabetic activity. After extraction and fractionation extracts and purified compounds were tested for GLP-1 and GIP secretory activity in STC-1 pGIP/neo cells. Intracellular levels of incretin hormones and their gene expression were also determined. Crude F. cretica extracts stimulated both GLP-1 and GIP secretion, increased cellular hormone content, and upregulated gene expression of proglucagon, GIP and prohormone convertase. However, ethyl acetate partitioning significantly enriched GLP-1 secretory activity and this fraction underwent bioactivity-guided fractionation. Three isolated compounds were potent and selective GLP-1 secretagogues: quinovic acid (QA) and two QA derivatives, QA-3β-O-β-D-glycopyranoside and QA-3β-O-β-D-glucopyranosyl-(28→1)-β-D-glucopyranosyl ester. All QA compounds activated the TGR5 receptor and increased intracellular incretin levels and gene expression. QA derivatives were more potent GLP-1 secretagogues than QA. This is the first time that QA and its naturally-occurring derivatives have been shown to activate TGR5 and stimulate GLP-1 secretion. These data provide a plausible mechanism for the ethnomedicinal use of F. cretica and may assist in the ongoing development of selective GLP-1 agonists.