bims-mideyd 2024-02-04 papers

Issue of 2024‒02‒04
five papers selected by
Raji Shyam, Indiana University Bloomington

Cell Signal. 2024 Jan 28. pii: S0898-6568(24)00037-8. [Epub ahead of print] 111069

The transmembrane protein TMEM97 and the epigenetic reader BAHCC1 constitute an axis that supports pro-inflammatory cytokine expression.

Jing Li, Hongtao Shen, Lian-Wang Guo.

Pro-inflammatory cytokine production by the retinal pigment epithelium (RPE) is a key etiology in retinal degenerative diseases, yet the underlying mechanisms are not well understood. TMEM97 is a scarcely studied transmembrane protein recently implicated in retinal degeneration. BAH domain coiled coil 1 (BAHCC1) is a newly discovered histone code reader involved in oncogenesis. A role for TMEM97 and BAHCC1 in RPE inflammation was not known. Here we found that they constitute a novel axis regulating pro-inflammatory cytokine expression in RPE cells. Transcriptomic analysis using a TMEM97-/- ARPE19 human cell line and the validation via TMEM97 loss- and gain-of-function revealed a profound role of TMEM97 in promoting the expression of pro-inflammatory cytokines, notably IL1β and CCL2, and unexpectedly BAHCC1 as well. Moreover, co-immunoprecipitation indicated an association between the TMEM97 and BAHCC1 proteins. While TMEM97 ablation decreased and its overexpression increased NFκB (p50, p52, p65), the master transcription factor for pro-inflammatory cytokines, silencing BAHCC1 down-regulated NFκB and downstream pro-inflammatory cytokines. Furthermore, in an RPE-damage retinal degeneration mouse model, immunofluorescence illustrated down-regulation of IL1β and CCL2 total proteins and suppression of glial activation in the retina of Tmem97-/- mice compared to Tmem97+/+ mice. Thus, TMEM97 is a novel determinant of pro-inflammatory cytokine expression acting via a previously unknown TMEM97- > BAHCC1- > NFκB cascade. SYNOPSIS: Retinal pigment epithelium (RPE) inflammation can lead to blindness. We identify here a previously uncharacterized cascade that underlies RPE cell production of pro-inflammatory cytokines. Specifically, transmembrane protein TMEM97 positively regulates the recently discovered histone code reader BAHCC1, which in turn enhances pro-inflammatory cytokine expression via the transcription factor NFκB.

Keywords: BAHCC1; NFκB; Pro-inflammatory cytokines; Retinal pigment epithelial cell; TMEM97

DOI: https://doi.org/10.1016/j.cellsig.2024.111069

J Exp Med. 2024 Mar 04. pii: e20231011. [Epub ahead of print]221(3):

Microglia at sites of atrophy restrict the progression of retinal degeneration via galectin-3 and Trem2.

Chen Yu, Eleonora M Lad, Rose Mathew, Nobuhiko Shiraki, Sejiro Littleton, Yun Chen, Jinchao Hou, Kai Schlepckow, Simone Degan, Lindsey Chew, Joshua Amason, Joan Kalnitsky, Catherine Bowes Rickman, Alan D Proia, Marco Colonna, Christian Haass, Daniel R Saban.

Outer retinal degenerations, including age-related macular degeneration (AMD), are characterized by photoreceptor and retinal pigment epithelium (RPE) atrophy. In these blinding diseases, macrophages accumulate at atrophic sites, but their ontogeny and niche specialization remain poorly understood, especially in humans. We uncovered a unique profile of microglia, marked by galectin-3 upregulation, at atrophic sites in mouse models of retinal degeneration and human AMD. In disease models, conditional deletion of galectin-3 in microglia led to phagocytosis defects and consequent augmented photoreceptor death, RPE damage, and vision loss, indicating protective roles. Mechanistically, Trem2 signaling orchestrated microglial migration to atrophic sites and induced galectin-3 expression. Moreover, pharmacologic Trem2 agonization led to heightened protection but in a galectin-3-dependent manner. In elderly human subjects, we identified this highly conserved microglial population that expressed galectin-3 and Trem2. This population was significantly enriched in the macular RPE-choroid of AMD subjects. Collectively, our findings reveal a neuroprotective population of microglia and a potential therapeutic target for mitigating retinal degeneration.

DOI: https://doi.org/10.1084/jem.20231011

Prostaglandins Other Lipid Mediat. 2024 Jan 25. pii: S1098-8823(24)00009-1. [Epub ahead of print] 106815

Lipid Mediators in Glaucoma: Unraveling Their Diverse Roles and Untapped Therapeutic Potential.

D J Mathew, J M Sivak.

Glaucoma is a complex neurodegenerative disease characterized by optic nerve damage and visual field loss and remains a leading cause of irreversible blindness. Elevated intraocular pressure (IOP) is a critical risk factor that requires effective management. Emerging research underscores dual roles of bioactive lipid mediators in both IOP regulation and the modulation of neurodegeneration/neuroinflammation in glaucoma. Bioactive lipids, encompassing eicosanoids, specialized pro-resolving mediators (SPMs), sphingolipids, and endocannabinoids, have emerged as crucial players in these processes, orchestrating inflammation and diverse effects on aqueous humor dynamics and tissue remodeling. Perturbations in these lipid mediators contribute to retinal ganglion cell loss, vascular dysfunction, oxidative stress, and neuroinflammation. Glaucoma management primarily targets IOP reduction via pharmacological agents and surgical interventions, with prostaglandin analogues at the forefront. Intriguingly, additional lipid mediators offer promise in attenuating inflammation and providing neuroprotection. Here we explore these pathways to shed light on their intricate roles, and to unveil novel therapeutic avenues for glaucoma management.

Keywords: Aqueous Humor; Endocannabinoids; Glaucoma; Intraocular Pressure; Leukotrienes; Lipid Mediators; Lipoxins; Maresins; Neuropathy; Prostaglandins; Protectins; Resolvins; Retina; SPMs; Sphingolipids

DOI: https://doi.org/10.1016/j.prostaglandins.2024.106815

J Biosci. 2024 ;pii: 21. [Epub ahead of print]49

Generation and characterization of retinal pigment epithelium from patient iPSC line to model oculocutaneous albinism (OCA)1A disease.

Janavi Subramani, Niharika Patlolla, Rajani Battu, Taslimarif Saiyed, Rajarshi Pal.

Oculocutaneous albinism (OCA) is characterized by reduced melanin biosynthesis affecting the retina, thus impairing visual function. The disease pathology of OCA is poorly understood at the cellular level due to unavailability of suitable biological model systems. This study aimed to develop a disease-specific in vitro model for OCA type 1A, the most severe form caused by TYR (tyrosinase) gene mutations, using retinal pigment epithelium (RPE) differentiated from patient-derived human-induced pluripotent stem cells (hiPSCs). A comparative study between healthy and OCA1A RPE cells revealed that while healthy RPE cells exhibited timely onest of pigmentation during differentiation, OCA1A RPE cells failed to pigment even after an extended culture period. This observation was validated by ultrastructural studies using electron microscopy, hinting at melanosome-specific defects. Immunocytochemistry demonstrated abnormal expression patterns of melanogenesis-specific protein markers in OCA1A RPE cells, indicating reduced or absence of melanin synthesis. Next, a quantitative assay was performed to confirm the absence of melanin production in OCA1A RPE cells. Tyrosinase assay showed no activity in OCA1A compared with healthy RPE, suggesting non-functionality of TYR, further corroborated by western blot analysis showing complete absence of the protein. Gene expression by RNA sequencing of healthy and OCA1A RPE cells uncovered differential gene expression associated with lens development, visual perception, transmembrane transporter activity, and key signaling pathways. This disease-in-a-dish model of OCA1A provides an excellent platform to understand disease mechanism, identify potential therapeutic targets, and facilitate gene therapy or gene correction.

Regen Ther. 2024 Mar;25 238-249

Investigation of the effectiveness of gelatin hydrolysate in human iPS-RPE cell suspension transplantation.

Shohei Kitahata, Michiko Mandai, Hinako Ichikawa, Yuji Tanaka, Toshika Senba, Keisuke Kajita, Sunao Sugita, Kazuaki Kadonosono, Masayo Takahashi.

Introduction: The retinal pigment epithelium (RPE) plays essential roles in maintaining retinal functions as well as choroidal capillaries and can lead to visual disorders if dysfunctional. Transplantation of human-induced pluripotent stem cell-derived RPE (hiPSC-RPE) is a promising therapy for such RPE impaired conditions including age-related macular degeneration. The challenge with cell suspension transplantation is targeted delivery of graft cells and undesired cell reflux. Gelatin hydrolysate, a soluble variant with specific molecular weight distribution, is examined in this study for its potential use in hiPSC-RPE suspension transplantation, particularly in reducing cell reflux and enhancing RPE engraftment.Methods: A retinal bleb model was created using polydimethylsiloxane (PDMS) soft lithography to quantify cellular reflux. We examined the effects of gelatin hydrolysate on the hiPSC-RPE of various aspects of cell behavior and performance such as cell viability, hypoxia reaction, morphology, induction of inflammation and immune responses.
Results: Gelatin hydrolysate at 5 % concentration effectively mitigated cell reflux in vitro mimic, improved cell viability, reduced cell aggregation, and had an inhibitory effect on hypoxic reactions due to cell deposition with hiPSC-RPE. Additionally, gelatin hydrolysate did not affect cell adhesion and morphology, and decreased the expression of major histocompatibility complex class II molecules, which suggests reduced immunogenicity of hiPSC-RPE.
Conclusion: Gelatin hydrolysate is considered a valuable and useful candidate for future regenerative therapies in hiPSC-RPE suspension transplantation.

Keywords: Gelatin; Induced pluripotent stem cells; Regenerative medicine; Retinal pigment epithelium; Suspension transplantation; iPS cell therapy

DOI: https://doi.org/10.1016/j.reth.2023.12.016