Ocular Surface Expression andIn VitroActivity of Antimicrobial Peptides

Abstract

Purpose-Human ocular surface epithelia express four antimicrobial peptides (APs): β-defensin (hBD) 1-3 and LL-37. Here the expression of additional APs (hBD 4-6, HE2β1; histatin-1, -3; liver expressed antimicrobial peptide-1, -2; macrophage inflammatory protein (MIP)-3α, and thymosin (T)β-4) was sought and activity against common ocular pathogens studied.Methods-AP expression was determined in human corneal and conjunctival epithelial cells (HCEC, HCjEC) by RT-PCR and in corneal sections by immunostaining. Antimicrobial assays were performed to assess peptide (hBD 1-3, LL-37, MIP-3α, and Tβ4) activity against Pseudomonas aeruginosa (PA), Staphylococcus aureus (SA), and Staphylococcus epidermidis (SE) in the presence of NaCl or tears.Results-HCEC and HCjEC expressed MIP-3α and Tβ4. hBD 1-3, MIP-3α, and Tβ4 showed activity against PA. hBD-3 had potent activity against SA and SE, whereas hBD-2, MIP-3α and Tβ4 had moderate activity and hBD-1 had none. NaCl markedly attenuated, and tears almost completely inhibited the activity of hBD 1-2 and Tβ4, but not that of hBD-3. Conclusions-The ocular surface epithelia additionally express MIP-3α and Tβ4 which have moderate antimicrobial activity. The current data support a role for hBD-3 as an antimicrobial peptide in vivo, but call in to question the effectiveness of some other APs. However, further study is required to conclusively elucidate the physiological role of each AP.

In Vitro Activity of Human β-Defensin 2 againstPseudomonas aeruginosain the Presence of Tear Fluid

“…One obvious extrapolation from the current study is that the MUC5AC within tears may reduce the activities of other cationic antimicrobial peptides; however, we have previously reported that human tears do not inhibit the activity of LL-37 (31) or hBD-3 (30), which suggests that not all antimicrobial peptides are susceptible to the effects of tears in terms of their antimicrobial functions. This is also supported by evidence from a recent study showing the differential effects of tears on two rabbit ␣-defensins (36).…”

“…Antimicrobial activity assays were performed to compare the activity of hBD-2 against P. aeruginosa (ATCC 27853) under our previously described conditions (30) with that in the presence of tear fluid, a more physiologically relevant condition. As shown in Fig.…”

“…Defensins also modulate cytokine production in various cell types (7,67) and simulate histamine release from mast cells (5,46). Human ␤-defensin-2 (hBD-2) has been identified at the ocular surface (34,35,43), and we have recently reported that it exerts activity against common ocular microbial pathogens in in vitro experiments conducted with 10 mM phosphate buffer (30). The expression of hBD-2 can be modulated; for example, it has been shown that hBD-2 expression by human corneal epithelial cells is upregulated by exposure to bacterial products such as lipopolysaccharide (37).…”

Role of Defensins in Corneal Epithelial Barrier Function against Pseudomonas aeruginosa Traversal

“…Since AMPs can impact the viability of P. aeruginosa (21), and because preexposure to P. aeruginosa antigens enhances AMP expression by corneal epithelia (15,35) while increasing resistance to bacterial traversal, we hypothesized that AMPs participate in epithelial defense against bacterial traversal. Small interfering RNA (siRNA) was used to knock down four different AMPs known to be expressed by human corneal epithelium (human ␤-defensins [hBD-1 to hBD3] and the cathelicidin LL-37).…”

Exposure of a Corneal Epithelial Cell Line (hTCEpi) to Demodex-Associated Bacillus Proteins Results in an Inflammatory Response

“…[35][36][37] It has been shown to be upregulated by the cytokines IL-1b and TNF-a in cornea. 38 The exposure of hTCEpi cells to Bacillus proteins induced the increased expression and activity of MMP-9. Matrix metalloproteinase-9 is expressed during cell migration and matrix remodeling in cornea wound repair by the cornea FIGURE 8.…”