Systemic exposure to CpG-ODN elicits low-grade inflammation in the retina

Toll-Like Receptor Signalling Pathways and the Pathogenesis of Retinal Diseases

There is growing evidence that the pathogenesis of retinal diseases such as diabetic retinopathy (DR) and age-related macular degeneration (AMD) have a significant chronic inflammatory component. A vital part of the inflammatory cascade is through the activation of pattern recognition receptors (PRR) such as toll-like receptors (TLR). Here, we reviewed the past and current literature to ascertain the cumulative knowledge regarding the effect of TLRs on the development and progression of retinal diseases. There is burgeoning research demonstrating the relationship between TLRs and risk of developing retinal diseases, utilising a range of relevant disease models and a few large clinical investigations. The literature confirms that TLRs are involved in the development and progression of retinal diseases such as DR, AMD, and ischaemic retinopathy. Genetic polymorphisms in TLRs appear to contribute to the risk of developing AMD and DR. However, there are some inconsistencies in the published reports which require further elucidation. The evidence regarding TLR associations in retinal dystrophies including retinitis pigmentosa is limited. Based on the current evidence relating to the role of TLRs, combining anti-VEGF therapies with TLR inhibition may provide a longer-lasting treatment in some retinal vascular diseases.

The roles of microRNAs played in lung diseases via regulating cell apoptosis

MicroRNAs (miRNAs) are a type of endogenous non-coding short-chain RNA, which plays a crucial role in the regulation of many essential cellular functions, including cellular migration, proliferation, invasion, autophagy, oxidative stress, apoptosis, and differentiation. The lung can be damaged by pathogenic microorganisms, as well as physical or chemical factors. Research has confirmed that miRNAs and lung cell apoptosis can affect the development and progression of several lung diseases. This article reviews the role of miRNAs in the development of lung disease through regulating host cell apoptosis.

Myeloid Cells in the Mouse Retina and Uveal Tract Respond Differently to Systemic Inflammatory Stimuli

Purpose

In spite of clear differences in tissue function and significance to ocular disease, little is known about how immune responses differ between the retina and uveal tract. To this end we compared the effects of acute systemic inflammation on myeloid cells within the mouse retina, iris-ciliary body, and choroid.

Methods

Systemic inflammation was induced in Cx3cr1gfp/gfp and CD11c-eYFP Crb1wt/wtmice by intraperitoneal lipopolysaccharide (LPS). In vivo fundus imaging was performed at two, 24, and 48 hours after LPS, and ocular tissue wholemounts were immunostained and studied by confocal microscopy. Flow cytometry was used to investigate the expression of activation markers (MHC class II, CD80, CD86) on myeloid cell populations at 24 hours. For functional studies, retinal microglia were isolated from LPS-exposed mice and cocultured with naïve OT-II CD4+ T-cells and ovalbumin peptide. T-cell proliferation was measured by flow cytometry and cytokine assays.

Results

Systemic LPS altered the density and morphology of retinal microglia; however, retinal microglia did not upregulate antigen presentation markers and failed to stimulate naïve CD4+ T-cell proliferation in vitro. In contrast, uveal tract myeloid cells displayed a phenotype consistent with late-activated antigen-presenting cells at 24 hours. Systemic LPS induced remodeling of myeloid populations within the uveal tract, particularly in the choroid, where dendritic cells were partially displaced by macrophages at 24 hours.

Conclusions

The disparate myeloid cell responses in the retina and uveal tract after systemic LPS highlight differential regulation of innate immunity within these tissue environments, observations that underpin and advance our understanding of ocular immune privilege.

Effects of age on retinal macrophage responses to acute elevation of intraocular pressure

There is accumulating evidence that aging shifts the central nervous system milieu towards a proinflammatory state, with increased reactivity of microglia in the aging eye and brain having been implicated in the development of age-related neurodegenerative conditions. Indeed, alterations to microglial morphology and function have been recognized as a part of normal aging. Here, we sought to assess the effects of age on the retinal microglial and macrophage response to acute intraocular pressure (IOP) elevation. Further, we performed experiments whereby bone marrow from young or middle-aged mice was used to reconstitute the bone marrow of whole-body irradiated 12 month old mice. Bone marrow chimeric mice then underwent cannulation and IOP elevation 8 weeks after whole-body irradiation and bone marrow transplantation in order to determine whether the age of bone marrow alters the macrophage response to retinal injury. Our data show retinal macrophage reactivity and microglial morphological changes were enhanced in older mice when compared to younger mice in response to injury. When IOP elevation was performed after whole-body irradiation and bone marrow rescue, we noted subretinal macrophage accumulation and glial reactivity was reduced compared to non-irradiated mice that had also undergone IOP elevation. This effect was evident in both groups of chimeric mice that had received either young or middle-aged bone marrow, suggesting irradiation itself may alter the macrophage and glial response to injury rather than the age of bone marrow.