Retinal vasculitis is a rare and potentially sight-threatening condition that affects the retinal vasculature. Recognizing the pathogenesis of retinal vasculitis is critical for devising effective therapies and improving patient outcomes [1]. Previous research has identified several risk factors and potential triggers for retinal vasculitis, such as autoimmune disorders, infections, and environmental factors [2,3]. Despite these findings, the precise mechanisms underlying retinal vasculitis remain uncertain, and there is a scarcity of research on the role of inflammatory markers in this condition [4]. Investigating the complex processes behind retinal vasculitis, a new study carried out at a tertiary care hospital concentrated on the functions of Macrophage Inflammatory Protein-1β (MIP-1β) and Monocyte Chemoattractant Protein-1 (MCP-1) [1-4]. Because of its complicated etiology and perhaps blinding effects, retinal vasculitis which is typified by inflammation of the retina's blood vessels presents serious diagnostic and therapeutic difficulties [5]. Leading the study team were renowned ophthalmologists and immunologists who sought to clarify how MIP-1β and MCP-1 contribute to the development of retinal vasculitis [6,7]. To create a baseline, they carefully recruited patients and collected vitreous fluid samples from those with retinal vasculitis and compared them with samples from non-inflammatory ocular disorders [8]. By means of cutting-edge molecular biology methods including polymerase chain reaction (PCR) and enzyme-linked immunosorbent assays (ELISA), the researchers measured the MIP-1β and MCP-1 expression levels in the vitreous humor of the study subjects [9]. Their results showed that both chemokines were much upregulated in people with retinal vasculitis than in controls, suggesting that they are essential in coordinating the inflammatory cascade in the retinal microenvironment [10].

The study clarified the complicated interaction between different immune cells and signaling molecules involved in the pathogenesis of retinal vasculitis, offering a strong basis for next studies aiming at deciphering the nuances of ocular inflammatory illnesses [7,8]. Through clarification of the molecular pathways underlying retinal vasculitis, this work opens the door to the creation of novel therapeutic approaches designed to tackle the particular immunological issues raised by this crippling disease [5,6]. Hence, this study aims to investigate the expression and significance of macrophage inflammatory protein-1β (MIP-1β) and monocyte chemoattractant protein-1 (MCP-1) in retinal vasculitis. Research Question of the present study is what is the expression and significance of MIP-1β and MCP-1 in retinal vasculitis? The aim of this study is to determine the expression and significance of MIP-1β and MCP-1 in retinal vasculitis. We hypothesize that MIP-1β and MCP-1 play a crucial role in the pathogenesis of retinal vasculitis and that their expression levels are associated with disease severity.

Following approval from the Institutional Ethics Committee, the current study commenced. One hundred cases of retinal vasculitis that were presented at the vitro-retinal clinic of the Regional Institute of Ophthalmology, SCBMCH, Cuttack, over a two-year period (October 2019 to September 2021) were enlisted in this prospective study. All cases of retinal vasculitis that met the inclusion criteria were as follows: age greater than 18 years and the presence of vessel wall staining on FFA, in addition to sheathing, perivascular inflammation, superficial and profound hemorrhages, or vessel wall inflammation. Individuals who had previously suffered from glaucoma, venous occlusion, artery occlusion, or diabetic retinopathy and were under the age of eighteen were ineligible.

All patients who sought care at the Retina Clinic were registered, evaluated, and followed up with throughout the duration of the trial. An exhaustive medical history was obtained, in addition to conducting fundus examination, intraocular pressure measurements, and visual acuity assessments. Fundus fluorescein angiography and optical coherence tomography were performed on patients lacking clear media. A comprehensive hemogram, a Mantoux test, random blood sugar, a VDRL, and an HIV ELISA were all standard procedures performed on every patient. All patients were referred to the corresponding departments that were located at SCBMCH Cuttack. Patients were allocated to receive either conservative therapy or surgical intervention, contingent upon their presentation. Patients diagnosed with peripheral vasculitis who exhibited adequate visual acuity without retinal nonperfusion were advised to undergo periodic observation. Patients exhibiting satisfactory visual acuity and retinal non-perfusion measuring less than 5 DD were initiated on systemic corticosteroids (Tablet Prednisolone 1 mg/kg/day). These corticosteroids gradually tapered off. Refractory cases, defined as those that exhibited no response to steroid therapy after a period of eight weeks, were prescribed immunosuppressants (azathioprine 2 mg/kg/day). Anti-VEGF injections were administered to patients who were presented with CME as a result of vasculitis. It was advised that patients who were presented with peripheral vasculitis and retinal hypoperfusion exceeding 5 DD undergo laser photocoagulation. Those diagnosed with vitreous hemorrhage were advised to undergo routine follow-up care and surveillance. It is recommended that patients who present with non-clearing vitreous hemorrhage and tractional retinal detachment undergo vitrectomy with endo-photocoagulation. An extensive assessment of the present condition was conducted, including direct and indirect ophthalmoscopy, fundus fluorescein angiography, optical coherence tomography, B scan, slit lamp biomicroscope of the anterior segment, and Goldmann Applanation tonometer intraocular pressure measurement. An analysis of the blood was conducted. The concentrations of MCP-1 and MIP-1β were assessed using commercially available ELISA assays (R&D Systems, UK). In summary, one hundred microliters of serum was added to duplicate wells containing 100 µl of assay diluent for MIP-1β and MCP-1 followed by two hours of incubation at room temperature. An evaluation of the outcomes was conducted after three months.

In our study, we observed that the incidence of retinal vasculitis was higher in males (80%) than that in females (20%).  Of the 62 patients with primary vasculitis, 60 were male and only 2 were female. Of the 8 patients with retinal vasculitis secondary to ocular disease, 6 were male and 2 were female. Of the 30 patients with retinal vasculitis secondary to systemic disease, 15 were males and 15 were females. We also observed cases due to primary retinal vasculitis were maximum (62%), followed by those due to systemic diseases (30%) and due to ocular disease (8%). We observed laterality predominantly in both eyes (54%), followed by the right eye (30%) and left eye (16%).

Table 1: Treatment modalities in the study patients.

Table 2: Levels of MIP-1β, MCP-1, and BCVA in pre- and post-treatment patients.

From retinal vasculitis patients, serum samples were collected, and ELISA was used to quantify the chemokines monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1β (MIP-1β). Chemokine levels were linked for every sample to the state of the disease and the medication being used at the moment. Not treated patients with retinal vasculitis had much higher serum MIP-1β levels than patients who received treatment after three months (P < 0.05). MIP-1β and MCP-1 levels were associated with prednisolone levels in patients receiving this medication alone and with disease activity in some patients. While not all samples had measurable MIP-1α levels, those from patients with pre-treated retinal vasculitis had far higher levels than those from individuals who had received treatment after three months.

This study examined for the first time the location of the chemokines MIP-1β and MCP-1 as an autoimmune inflammatory disease in the form of retinal vasculitis. Of the two chemokines investigated, MIP-1β appeared to be most closely associated with the development of retinal vasculitis. It was present most frequently and most extensively, particularly in disease before treatment, but also was detectable in the disease after the treatment for three months.

The location of chemokines during retinal vasculitis was examined, rather than their site of production. In retinal vasculitis inflammatory cells produce MIP-1β [7-9]. MIP-1β, in addition to its detection, specifically associated with cells, was also shown to be associated with acellular exudates in the subretinal space. These acellular exudates are a result of lysis and fragmentation of the photoreceptors and vessel leakage during peak disease, and areas of fibrin deposition may be present [7,8]. The ability of MIP-1β to bind to proteoglycans may account for its association with these exudates [9].

In retinal vasculitis, mRNA expression for a variety of chemokines including MIP-1β, MIP-1β, and MCP-1 has been detected before the onset of clinical disease and throughout acute clinical disease [10].  As with our findings in retinal vasculitis, MIP-1β expression appeared to be of particular significance in the pathogenesis of some models. In inflammation induced by transfer of proteolipid protein (PLP)-specific T cells into SJL/J mice, antibodies to MIP-1β, but not to MCP-1, could inhibit the development of acute and relapsing retinal vasculitis, as well as the infiltration of mononuclear cells into the central nervous system [11,12]. However, using DNA vaccines in a model in which Lewis rats were immunized with myelin basic protein, it was shown that vaccines for MIP-1β or MCP-1 prevented inflammation, whereas vaccine had no effect [13]. 

We observed higher amount of MIP-1β and MCP-1 in pre-treatment patients of retinal vasculitis patients. Further evidence for a role for MCP-1 in autoimmune inflammatory disease has been provided by the anterior uveitis develops in Lewis rats. In this model MCP-1 was detected preclinically in the iris-ciliary body and lumbar spinal cord, increasing as disease developed and coinciding with expression of IL-2 and IFNγ [14].  It was suggested that MCP-1 contributed to the initial recruitment of inflammatory cells into both the eye and CNS. However, in our study MIP-1β rather than MCP-1 appeared more likely to be important in early recruitment, because it was detected before MCP-1, at day 8 after immunization. This difference may be linked to the less acute nature of posterior uveitis. 

We observed higher amount of MIP-1β and MCP-1 in pre-treatment patients and the same molecules were reduced when compared with post-treatment patients.  Both MIP-1β and MCP-1 were detected in association with choroidal and retinal vessels, both with endothelial and perivascular cells. However, dual-immunofluorescence microscopy indicated that they did not localize to the same cells. Similar findings have been described at the blood–brain barrier, where separate binding domains for MIP-1β and MCP-1 have been identified on the parenchymal surface of brain microvessels [14].

Interferons detection in the tissue sections paralleled disease development and also MIP-1β production. As with MIP-1β, interferons was also detectable in the choroid after immunization, extensive at peak disease, and much reduced after a fortnight post-immunization. This supports earlier studies on interferon mRNA expression in retinal vasculitis [15].  IFNγ is produced by T cells, but dual-immunofluorescence staining clearly showed that MIP-1β was produced by other cells in addition to T cells. IFNγ production by T cells may be stimulating MIP-1β production by macrophages. In contrast, in rheumatoid arthritis T cells from synovial fluid express MIP-1β and RANTES in the absence of IL-2 and IFN-γ, and the investigators speculate that these chemokines downregulate the expression of specific T-cell–secreted cytokines, such as IL-2 and IFN-γ, which can alter the Th1-to-Th2 balance [13-16].  There is no evidence to suggest that this happens in retinal vasculitis. 

The present study provides noteworthy insights into the role of MIP-1β and MCP-1 in the context of retinal vasculitis, suggesting their potential as biomarkers for the early diagnosis and treatment of this condition. However, due to the intricate mechanisms by which chemokines exert their effects, further research could concentrate on the potential therapeutic benefits of targeting MIP-1β and MCP-1 in retinal vasculitis, as well as the examination of other inflammatory markers that may be involved in this condition.

Conflict of interest:

There is no conflict of interest among the present study authors.

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