Abstract
BackgroundSubstance P (SP) is a nociceptive tachykinin which regulates the immune inflammatory reactions including monocyte chemoattractant protein 1 (MCP-1) production. Sequential second-eye cataract surgery patients often suffer more pain than the first one partly because of the MCP-1 increase in aqueous humor (AH). This study aims to illustrate whether SP is involved in sympathetic inflammatory responses in the contralateral eye in patients with or without type 2 diabetes.MethodsThis prospective randomized clinical study included 51 cataract patients (22 with diabetes and 29 without). Bilateral sequential cataract surgeries were conducted with 1-day or 1-week interval randomly. More than 100 μl of AH were obtained before surgery and stored for later analysis using magnetic Luminex assays to detect interleukin (IL)-1β, IL-1ra,IL-6, IL-8, IL-10, MCP-1, vascular endothelial growth factor, spinal macrophage inflammatory protein (MIP-1a), interferon-inducible protein 10 (IP-10), regulated on activation, normal T expressed and secreted (RANTES), as well as the enzyme-linked immunosorbent assay for SP.ResultsAmong the 4 groups, no significant differences were found in age, sex distribution, the R/L ration of the first surgery eye, or the lens nucleus hardness (P ≥ 0.802). Over 100 μl of AH samples were collected safely in all cases without intraoperative complications. SP and MCP-1 levels were both increased significantly in the second eye of the diabetic patients with 1-day and 1-week interval (P ≤ 0.040). The SP increase in the second eye of the diabetic patients were significantly higher than that of the patients without diabetes (P ≤ 0.030) both in the groups with 1-day and 1-week interval. Similarly, the MCP-1 increase was significantly higher in the diabetic patients in the group with 1-week interval (P = 0.042).ConclusionsSubstance P and MCP-1 productions elevated in the AH of the contralateral eye after the first-eye cataract surgery in diabetic patients, indicating that SP and MCP-1 were involved in the sympathetic inflammatory responses. Diabetic patients are susceptible to noninfectious inflammation after cataract surgery, and perceive more pain in the second-eye phacoemulsification.Trial registrationChinese Clinical Trial Registry, ChiCTR1900028374, retrospectively registered on 20th December, 2019.
Highlights
Substance P (SP) is a nociceptive tachykinin which regulates the immune inflammatory reactions including monocyte chemoattractant protein 1 (MCP-1) production
The previous studies focused on the changes of the pain-related inflammatory cytokines such as interleukin (IL)-1, IL-6,12 IL-8, spinal macrophage inflammatory protein (MIP), MCP-1, vascular endothelial growth factor (VEGF), and regulated on activation, normal T expressed and secreted (RANTES) before and after cataract surgery of the first eye, the neuropeptide SP has not been identified
Substance P level increased in the 2nd surgical eye in Diabetes mellitus (DM) patients For the age-related cataract (ARC) patients in group 1, the substance P level was 1.97 ± 0.09 pg/ml in the first surgical eye, and 1.99 ±
Summary
Substance P (SP) is a nociceptive tachykinin which regulates the immune inflammatory reactions including monocyte chemoattractant protein 1 (MCP-1) production. Substance P (SP) is an undecapeptide member of the tachykinin family, acting as an neurotransmitter or neuromodulator in a wide range of physiological and pathophysiological processes in the central nervous system and peripheral tissues It is mainly secreted by neurons, and a variety of nonneuronal cells including microglia, epithelial cells, endothelial cells, and immune cells [1]. SP plays a role in regulating the immune system, including inflammation [2, 3], apoptosis [4], and induction of the expression of the production of chemokines and pro-inflammatory cytokines [1, 5] It is involved in the pain nervous system as an important neurotransmitter mediating nociceptive transmission [6]. In the current study we aimed to illustrate whether SP participated in the inflammatory reaction in the contralateral eye after the first-eye cataract surgery in patients with or without type 2 diabetes, which might illuminate the mechanism of sympathetic immune responses
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