1. Coupling Plant-Derived Cyclotides to Metal Surfaces: An Antibacterial and Antibiofilm Study
Pan Cao, Ying Yang, Fidelia Ijeoma Uche, Sarah Ruth Hart, Wen-Wu Li, Chengqing Yuan Int J Mol Sci. 2018 Mar 9;19(3):793. doi: 10.3390/ijms19030793.
Modification of metal surfaces with antimicrobial peptides is a promising approach to reduce bacterial adhesion. Here, cyclic peptides or cycloids, possessing remarkable stability and antimicrobial activities, were extracted and purified from Viola philippica Cav., and identified using mass spectrometry. Cyclotides were subsequently utilized to modify stainless steel surfaces via polydopamine-mediated coupling. The resulting cyclotide-modified surfaces were characterized by Fourier transform infrared (FTIR) spectroscopy and contact angle analysis. The antibacterial capacity of these cyclotides against Staphylococcus aureus was assessed by Alamar blue assay. The antibiofilm capacity of the modified surfaces was assessed by crystal violet assay, and scanning electron microscopy (SEM). A composite of Kalata b1, Varv A, Viba 15 and Viba 17 (P1); Varv E (P2); and Viphi G (P3) were isolated and identified. FTIR analysis of the modified surfaces demonstrated that cyclotides bound to the surfaces and induced reduction of contact angles. Antimicrobial effects showed an order P3 > P1 and P2, with P3-treated surfaces demonstrating the strongest antibiofilm capacity. SEM confirmed reduced biofilm formation for P3-treated surfaces. This study provides novel evidence for cyclotides as a new class for development of antibacterial and antibiofilm agents.
2. Functional adaptation of venous smooth muscle response to vasoconstriction in proximal, distal, and varix segments of varicose veins
Joseph D Raffetto, Xiaoying Qiao, Katie G Beauregard, Alain F Tanbe, Abhinav Kumar, Virak Mam, Raouf A Khalil J Vasc Surg. 2010 Apr;51(4):962-71. doi: 10.1016/j.jvs.2009.11.037.
Background: Varicose veins (VarVs) are a common disorder of venous dilation and tortuosity with unclear mechanism. The functional integrity and the ability of various regions of the VarVs to constrict is unclear. This study tested the hypothesis that the different degrees of venodilation in different VarV regions reflect segmental differences in the responsiveness to receptor-dependent vasoconstrictive stimuli and/or in the postreceptor signaling mechanisms of vasoconstriction. Methods: Varix segments and adjacent proximal and distal segments were obtained from patients undergoing VarV stripping. Control great saphenous vein specimens were obtained from patients undergoing lower extremity arterial bypass and coronary artery bypass grafting. Circular vein segments were equilibrated under 2 g of tension in a tissue bath, and changes in isometric constriction in response to angiotensin II (AngII, 10(-11)-10(-7) M), phenylephrine (PHE, 10(-9)-10(-4) M), and KCl (96 mM) were recorded. The amount of angiotensin type 1 receptor (AT(1)R) was measured in vein tissue homogenate. Results: AngII caused concentration-dependent constriction in control vein (max 35.3 +/- 9.6 mg/mg tissue, pED(50) 8.48 +/- 0.34). AngII caused less contraction and was less potent in proximal (max 7.9 +/- 2.5, pED(50) 6.85 +/- 0.61), distal (max 5.7 +/- 1.2, pED(50) 6.74 +/- 0.68), and varix segments of VarV (max 7.2 +/- 2.0, pED(50) 7.11 +/- 0.50), suggesting reduced AT(1)R-mediated contractile mechanisms. VarVs and control veins had similar amounts of AT(1)R. alpha-adrenergic receptor stimulation with PHE caused concentration-dependent constriction in control veins (max 73.0 +/- 13.9 mg/mg tissue, pED(50) 5.48 +/- 0.12) exceeding that of AngII. PHE produced similar constriction and was equally potent in varix and distal segments but produced less constriction and was less potent in proximal segments of VarVs (max 32.1 +/- 6.4 mg/mg tissue, pED(50) 4.89 +/- 0.13) vs control veins. Membrane depolarization by 96 mM KCl, a receptor-independent Ca(2+)-dependent response, produced significant constriction in control veins and similar contractile response in proximal, distal, and varix VarV segments, indicating tissue viability and intact Ca(2+)-dependent contraction mechanisms. Conclusions: Compared with control veins, different regions of VarV display reduced AngII-mediated venoconstriction, which may be involved in the progressive dilation in VarVs. Postreceptor Ca(2+)-dependent contraction mechanisms remain functional in VarVs. The maintained alpha-adrenergic responses in distal and varix segments, and the reduced constriction in the upstream proximal segments, may represent a compensatory adaptation of human venous smooth muscle to facilitate venous return from the dilated varix segments of VarV.
3. Seven novel macrocyclic polypeptides from Viola arvensis
U Göransson, T Luijendijk, S Johansson, L Bohlin, P Claeson J Nat Prod. 1999 Feb;62(2):283-6. doi: 10.1021/np9803878.
Seven novel macrocyclic polypeptides, designated as varv peptides B-H, have been isolated from the aerial parts of Viola arvensis. Their primary structures have been elucidated by automated Edman degradation and mass spectrometry. They all consist of 29 or 30 amino acid residues, covalently cyclized via the amide backbone and by three internal disulfide bridges. Their amino acid sequences are as follows: varv peptide B, cyclo-(TCFGGTCNTPGCSCDPWPMCSRNGLPVCGE); varv peptide C, cyclo-(TCVGGTCNTPGCSCSWPVCTRNGVPICGE); varv peptide D, cyclo-(TCVGGSCNTPGCSCSWPVCTRNGLPICGE); varv peptide E, cyclo-(TCVGGTCNTPGCSCSWPVCTRNGLPICGE); varv peptide F, cyclo-(TCTLGTCYTAGCSCSWPVCTRNGVPICGE); varv peptide G, cyclo-(TCFGGTCNTPGCSCDPWPVCSRNGVPVCGE); and varv peptide H, cyclo-(TCFGGTCNTPGCSCETWPVCSRNGLPVCGE). The varv peptides B-H exhibited high degrees of homology with the hitherto known macrocyclic peptides varv peptide A, kalata B1, violapeptide I, circulins A and B, and cyclopsychotride A.
