Abstract
Purpose :
RPE cells play an important role in different fundamental processes for the maintenance of the neuroretina homeostasis. Indeed, malfunctions of the RPE have been associated with various eye diseases, such as age-related macular degeneration (AMD). One particularly important function of RPE is the regulation of immune activity within the retina, to maintain the immune privilege that characterizes the eye. However, the exact regulatory mechanisms of RPE and their effects on the neuroretina are not yet fully understood.
Methods :
12 week-old C57BL/6J mice were treated i.p. with lipopolysaccharide (LPS), to induce systemic inflammation, or phosphate buffered saline (PBS) as a control. 24 hours after the immune challenge, the neuroretina and RPE layer were collected and used to perform proteomic analysis. Briefly, the samples were digested to extract the proteins, and then analyzed by nano-liquid chromatography coupled to timsTOF Pro mass spectrometry, to investigate differential protein expression between RPE and retina in response to systemic inflammation.
Results :
The separately processed RPE and neuroretina samples exhibited distinct proteomic signatures, containing specific protein markers, such as TTR, PMEL, and RPE65 in the RPE, and PDE6, RHO and NR2E3 in the neuroretina. Moreover, the proteomic analysis revealed the expression of a broad range of immunomodulatory proteins, such as those pertaining to the complement system, namely complement proteins C1, C2, C3, and C4, their receptors CR3 and CR4 as well as other integrins, and components of the Toll-like receptors (TLRs) pathways in both RPE and neuroretina. Upon an inflammatory stimulus however, the modulation of these factors differs between the neuroretina and the RPE, with the latter showing a more specific and stronger response.
Conclusions :
Proteomic, applied to both the RPE and the neuroretina, is a powerful tool to assess their different response during systemic inflammation, as well as in other pathological conditions. Interestingly, the activation of the complement cascade and of other branches of the immune system, seem to be peculiar of the RPE. Moreover, these results shed new light on the role of the RPE in immunomodulation, and in the communication with the neuroretina in response to systemic inflammation, paving the way for a deeper investigation on the mechanisms involved in their interaction.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.