Oxidative Stress and Inflammation-Related mRNAs Are Elevated in Serum of a Finnish Wet AMD Cohort

Abstract

Purpose: Localized diseases can be affected by and affect the systemic environment via blood circulation. In this study, we explored the differences in circulating serum mRNAs between patients with wet AMD (wAMD) and controls.

Methods: Blood samples were obtained from 60 Finnish patients with wAMD and 64 controls. After serum preparation and RNA sequencing, the count data was examined for differentially expressed genes (DEGs) and further checked for enriched molecular pathways and ontology terms as well as links to clinical data.

Results: We found many DEGs and some enriched pathways, including the inflammation and cell survival-associated pathway tumour necrosis factor alpha (TNF-α) signaling via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). The related DEGs were oxidized low-density lipoprotein receptor 1 (OLR1), salt inducible kinase 1 (SIK1), and coagulation factor III (F3). DEGs from degradative macular and retinal processes were also examined, many of which were also related to cardiovascular disease and maintenance. Additionally, DEG counts were inspected in relation to clinical and anti-VEGF treatment parameters, and glutamine amidotransferase-like class 1 domain-containing 3A (GATD3A) levels were found to be significantly lower in patients with wAMD treated with anti-VEGF.

Conclusions: Differentially expressed systemic mRNAs that are linked to mitochondrial function, oxidative stress, and inflammation may have a role in the pathology of wAMD. Our observations provide new data for the understanding of the progression of wAMD.

Figure 1.

Optical coherence tomography images of healthy to severely atrophied retinas. Yellow arrows indicate outer retina damage and the thick green arrow indicates RPE level changes. cORA, complete outer retinal atrophy; iRORA, incomplete RPE and outer retinal atrophy; RPE, retinal pigment epithelium.

Figure 2.

Frequency of zero counts for each filtered protein-coding gene. There were 12,451 genes left after filtering.

Figure 3.

PC analysis plot of wAMD and control samples. All genes after filtering were used (12,451 in total). The ellipses cover the 95% confidence level areas of the groupings (green = controls, red = patients with wAMD).

Figure 4.

Volcano plot of the wAMD vs. control DEG results. The labeled genes represent the ten most upregulated and downregulated genes (white label background), as well as the genes that were found to be of interest and discussed based on later calculations and selections (yellow label background). DEG, differentially expressed gene; LFC, log₂-fold change; wAMD, wet age-related macular degeneration.

Figure 5.

Multilevel and permutation method gene set enrichment analysis results for wAMD vs. control DEGs. Enriched gene sets with an adjusted P value of less than or equal to 0.050 are shown. Calculations based on the stat value (fgsea default). NES, normalized enrichment score.

Figure 6.

Scatter plot of the results of the qPCR analysis of (A) SIK1 and (B) GATD3A mRNA expression in the serum of wAMD vs. control patients. Results are shown as a scatter dot plot with median. GATD3A, glutamine amidotransferase-like class 1 domain-containing 3A; SIK1, salt inducible kinase 1; ns, not statistically significant. *P ≤ 0.050, Mann–Whitney U test.

Figure 7.

Venn diagram of the overlap of DEGs in our and three other studies related to AMD research.