Inherited retinal degeneration refers to untreatable blinding diseases characterized by progressive photoreceptor loss. Photoreceptor degeneration is often associated with an excessive activation of poly(ADP-ribose) polymerase and Ca 2+ -dependent calpain-type proteases. To explore the interplay between poly(ADP-ribose) polymerase and calpain activity, we employed organotypic retinal explant cultures derived from wild-type mice and from the rd1 mouse model for inherited retinal degeneration. Retinae were treated with the poly(ADP-ribose) polymerase inhibitors INO1001 or Olaparib, the poly(ADP-ribose) glycohydrolase inhibitor JA2131, or the transient receptor potential channel M2 blocker 8-Br-ADPR. Readouts included the terminal deoxynucleotidyl transferase dUTP nick end labeling assay to detect cell death, in situ activity assays for histone-deacetylases, poly(ADP-ribose) polymerase, and calpain, as well as immunostaining for activated calpain-2, and poly(ADP-ribose). Poly(ADP-ribose) polymerase, poly(ADP-ribose) glycohydrolase, and transient receptor potential channel M2 inhibition reduced calpain activity and calpain-2 activation. Poly(ADP-ribose) polymerase activity was decreased by poly(ADP-ribose) polymerase and transient receptor potential channel M2 inhibitors but not by poly(ADP-ribose) glycohydrolase inhibition. Remarkably, the poly(ADP-ribose) polymerase inhibitor INO1001 increased histone-deacetylase activity unlike any of the other compounds. When combined with the poly(ADP-ribose) glycohydrolase inhibitor JA2131, INO1001 reduced photoreceptor cell death in a synergistic fashion, although such synergy was not observed for calpain or poly(ADP-ribose) polymerase activity. Moreover, synergistic photoreceptor preservation was not observed when JA2131 was combined with the poly(ADP-ribose) polymerase inhibitor Olaparib. Overall, these results indicate that in rd1 photoreceptors, poly(ADPribose) polymerase controls calpain activity via poly(ADP-ribose) glycohydrolase and transient receptor potential channel M2-induced Ca 2+ influx. We also characterized INO1001 as potentially more beneficial for inherited retinal degeneration treatment than Olaparib. Our study details the complexity of poly(ADP-ribose) polymerase-signaling in photoreceptors and identifies poly(ADP-ribose) glycohydrolase and transient receptor potential channel M2 as new targets for inherited retinal degeneration therapy development.

In retinopathy of prematurity (ROP), preventing avascular dysplasia may be more critical than inhibiting abnormal neovascularization. While hypoxia-inducible factors (HIFs) are implicated in angiogenesis, their role in preventing ROP remains unclear. Oxygen-induced retinopathy (OIR) model and hyperoxic cell model were used in this study. Immunofluorescence, western blot, ELISA, cell counting kit-8 (CCK-8), and flow cytometry were applied to assess the effects of hyperoxia on the astrocytes. Co-culture of astrocytes with retinal microvascular endothelial cells (RMECs) was used to observe the effects of astrocyte inactivation on the RMECs. Overexpression of HIFs in astrocytes was used to investigate the mechanism. The OIR model revealed a decreased number of retinal astrocytes and the expression of dystrophin and R-cadherin in hyperoxic environments (P12), which was reversed after room air rearing (P17-P21), with an upward trend in RMECs (P21). In vitro hyperoxia induced significant apoptosis in astrocytes at 24 h. Moreover, the expression of angiogenesis-related factors (VEGF and ANGPTL4), vascular stabilization, and development-related factors (Laminin-β2, Dystrophin, R-cadherin) was decreased. Co-culture of astrocytes and RMECs yielded similar conclusions, with astrocyte inactivation decreasing the tube-forming capacity of RMECs. Overexpression of HIFs in astrocytes promoted the expression of VEGF, ANGPTL4, and Laminin-β2 under hyperoxic conditions. Emphatically, HIF-1α was more effective than HIF-2α in promoting the expression of integrin β1, dystrophin, and R-cadherin. Overexpression of HIFs in astrocytes reverses hyperoxia-induced retinal astrocyte inactivation and retinal vascular structural disruption and dysplasia. Strikingly, HIF-1α is a more suitable therapeutic target for ROP prevention than HIF-2α.

Retinitis Pigmentosa (RP) is a group of rare, inherited, neurodegenerative diseases of the retina that primarily affect rod photoreceptors. The initial loss of rods is followed by a secondary cone photoreceptor degeneration and eventually legal blindness. Despite several attempts, RP still remains essentially untreatable. In recent years, inhibition of poly (ADP-ribose) polymerase (PARP) has been proposed as a potential therapeutic strategy for autosomal-recessive RP, based on promising work in preclinical animal models. However, the effects of PARP inhibitors in autosomal-dominant RP are still largely unknown. Here, we employed a novel, human-homologous rhodopsin-mutant RhoI255del/+ mouse model for autosomal dominant RP to assess the impact of different PARP inhibitors on the progression of photoreceptor degeneration. The PARP inhibitors used -olaparib, saruparib, INO1001, and nicotinamide-target different PARP isoforms, and their potentially differential effects were evaluated in organotypic retinal explants cultivated under entirely defined conditions. Readouts comprised in situ activity assays for PARP and calpain-type proteases, the TUNEL assay for cell death, as well as immunostaining for activated calpain-2, activated caspase-3, rhodopsin, and cone arrestin-3. Unexpectedly, and in contrast to previous findings in animal models for recessive RP, all of the PARP inhibitors used led to marked and dose-dependent rod photoreceptor toxicity in the RhoI255del dominant RP model. Furthermore, this effect appeared to be independent of rhodopsin expression. On the other hand, cone photoreceptors were apparently unaffected by PARP inhibition. The present study thus demonstrates the importance of PARP activity for rod photoreceptor viability in a dominant rhodopsin mutant, highlights the need for a deeper understanding of the mechanisms underlying photoreceptor degeneration in different RP forms, and cautions against the indiscriminate use of PARP inhibitors for the treatment of RP.

Retinitis pigmentosa (RP) is an inherited retinal degenerative disorder characterized by progressive photoreceptor loss and irreversible blindness. Increasing evidence implicates neuroinflammation as a contributor to photoreceptor degeneration extending beyond the initial genetic insult. Although estrogen has been reported to exert anti-inflammatory effects in the central nervous system, its role in RP remains controversial, with some studies suggesting a paradoxical exacerbation of retinal pathology. To address this discrepancy, we identify estrogen receptor alpha (Esr1) as a central immunoregulatory hub in RP. Transcriptomic analyses of rd1 and rd10 revealed upregulation of estrogen-responsive and inflammatory pathways, with Esr1 expression markedly elevated during degeneration. TUNEL assays demonstrated that systemic estradiol (E2) exerted divergent effects, protective in rd1 yet deleterious in rd10, whereas selective pharmacological activation of Esr1 with propyl pyrazole triol (PPT) consistently reduced photoreceptor death, preserved dark-adapted ERG responses, and downregulated inflammatory mediators including Tnf-α, Cx3cl1/Cx3cr1, Cd68, and Iba1. Mechanistically, Esr1 activation repressed microglial Tnf transcription and disrupted a self-sustaining Cx3cl1/Cx3cr1–Tnf-α signaling loop driving microglial recruitment, activation and neurotoxicity in the outer nuclear layer (ONL). Targeted interventions confirmed tumor necrosis factor receptor 1 (Tnfr1) as the principal mediator of Tnf-induced photoreceptor death: selective inhibition with R7050 conferred superior protection compared with broad-spectrum Tnf-α inhibitors (etanercept, infliximab). Cx3cr1 blockade likewise suppressed microglial activation and improved visual outcomes. Collectively, our findings establish Esr1 activation as not merely an external intervention but the amplification of an intrinsic self-protective program, positioning Esr1, Tnfr1, and Cx3cr1 as actionable therapeutic targets to suppress neuroinflammation and preserve vision in RP.

Retinitis pigmentosa (RP) is a group of inherited diseases characterized by a primary rod photoreceptor dysfunction and progressive rod and cone cell death. Due to their very high energy demand, the degeneration of photoreceptors may be linked to insufficient energy supply or metabolic imbalance. Critical transcription factors that regulate metabolism such as peroxisome proliferator-activated receptors (PPARs) and their co-activator PGC-1α have been found to play important roles in neurodegenerative diseases, but their potential roles in RP have yet not been disclosed. In this study, we used organotypic retinal explant cultures derived from the rd1 mouse model for RP to investigate the effects of PPARα, PPARγ, PPARβ/δ agonists, as well as PGC-1α activation and inhibition. Photoreceptor death in the outer nuclear layer (ONL) of the retina was quantified using the TUNEL assay, while in situ activity assays were used to monitor effects of PPARs and PGC-1α on poly (ADP-ribose) polymerase (PARP) and calpain activity. In addition, we performed immunostainings to evaluate poly (ADP-ribose) (PAR) generation and activation of calpain-1 and calpain-2. We found that PPARβ/δ agonists had limited effects, while activation of PPARα, PPARγ, and PGC-1α significantly reduced photoreceptor death and PARP activity in rd1 retina. Conversely, inhibition of PGC-1α had a strong detrimental effect on photoreceptor viability. Activation of the histone deacetylase sirtuin-1, an upstream agonist of PGC-1α, had no effect unless it was combined with simultaneous inhibition of PARP. Furthermore, PPARγ and PGC-1α effectively suppressed overall calpain activity and overactivation of calpain-2, alleviating photoreceptor degeneration caused by Ca2+ imbalance. In summary, our data supports the concept of a PARP–sirtuin-1–PGC-1α–PPAR–PARP feedback control that connects defective energy metabolism to photoreceptor degeneration. Specifically, our findings suggest that PPARα, PPARγ, and PGC-1α cooperate to preserve photoreceptor viability, highlighting PPAR-signaling as a promising target for future therapeutic interventions. ### Competing Interest Statement The authors have declared no competing interest. Charlotte and Tistou Kerstan Foundation China Scholarship Council, https://ror.org/04atp4p48 Yunnan Provincial Health Commission Clinical Medicine Center Research Project, No.2024YNLCYXZX0326, No.2024YNLCYXZX0339 Yunnan Fundamental Research Kunming Medical University Projects, No.202501AY070001-217 Yunnan University Medical Research Foundation, YDYXJJ2024-0004 Key Project of Yunnan Fundamental Research Projects, 202301AS070046

Retinitis pigmentosa (RP) is an inherited retinal degenerative disorder characterized by progressive photoreceptor loss and irreversible blindness. Increasing evidence implicates neuroinflammation as a contributor to photoreceptor degeneration extending beyond the initial genetic insult. Although estrogen has been reported to exert anti-inflammatory effects in the central nervous system, its role in RP remains controversial, with some studies suggesting a paradoxical exacerbation of retinal pathology. To address this discrepancy, we identify estrogen receptor alpha (Esr1) as a central immunoregulatory hub in RP. Transcriptomic analyses of rd1 and rd10 revealed upregulation of estrogen-responsive and inflammatory pathways, with Esr1 expression markedly elevated during degeneration. TUNEL assays demonstrated that systemic estradiol (E2) exerted divergent effects, protective in rd1 yet deleterious in rd10, whereas selective pharmacological activation of Esr1 with propyl pyrazole triol (PPT) consistently reduced photoreceptor death, preserved dark-adapted ERG responses, and downregulated inflammatory mediators including Tnf-α, Cx3cl1/Cx3cr1, Cd68, and Iba1. Mechanistically, Esr1 activation repressed microglial Tnf transcription and disrupted a self-sustaining Cx3cl1/Cx3cr1–Tnf-α signaling loop driving microglial recruitment, activation and neurotoxicity in the outer nuclear layer (ONL). Targeted interventions confirmed tumor necrosis factor receptor 1 (Tnfr1) as the principal mediator of Tnf-induced photoreceptor death: selective inhibition with R7050 conferred superior protection compared with broad-spectrum Tnf-α inhibitors (etanercept, infliximab). Cx3cr1 blockade likewise suppressed microglial activation and improved visual outcomes. Collectively, our findings establish Esr1 activation as not merely an external intervention but the amplification of an intrinsic self-protective program, positioning Esr1, Tnfr1, and Cx3cr1 as actionable therapeutic targets to suppress neuroinflammation and preserve vision in RP and related retinal disorders. ### Competing Interest Statement The authors have declared no competing interest. the National Natural Science Foundation of China, 82360604 the Medical Leading Talents Training Program of Yunnan Provincial Health Commission, L-2019029 the Yunnan Provincial Health Commission Clinical Medicine Center Research Project, 2024YNLCYXZX0326, 2024YNLCYXZX0339 the Yunnan Science and Technology Plan Project, 202105AF150067, 202401AT070454 the Project of Yunnan Fundamental research Projects, 202401AT070453 the Open Project of National Clinical key Specialty, ZKF2024046 the Yunnan Fundamental Research Kunming Medical University Projects, 202501AY070001-217, 202501AY070001-209

Inherited retinal degeneration (IRD) refers to untreatable blinding diseases characterized by progressive photoreceptor loss. Photoreceptor degeneration is often associated with an excessive activation of poly (ADP-ribose) polymerase (PARP) and Ca2+-dependent calpain-type proteases. To explore the interplay between PARP and calpain activity, we employed organotypic retinal explant cultures derived from wild-type mice and from the rd1 mouse model for IRD. Retinae were treated with the PARP inhibitors INO1001 or Olaparib, the poly (ADP-ribose) glycohydrolase (PARG) inhibitor JA2131, or the transient receptor potential channel M2 (TRPM2) blocker 8-Br-ADPR. Readouts included the TUNEL assay to detect cell death, in situ activity assays for histone-deacetylases (HDAC), PARP, and calpain, as well as immunostaining for activated calpain-2, and poly (ADP-ribose) (PAR). PARP, PARG, and TRPM2 inhibition reduced calpain activity and calpain-2 activation. PARP activity was decreased by PARP and TRPM2 inhibitors but not by PARG inhibition. Remarkably, the PARP inhibitor INO1001 increased HDAC activity unlike any of the other compounds. When combined with the PARG inhibitor JA2131, INO1001 reduced photoreceptor cell death in a synergistic fashion, although such synergy was not observed for calpain or PARP activity. Moreover, synergistic photoreceptor preservation was not observed when JA2131 was combined with the PARP inhibitor Olaparib. Overall, these results indicate that in rd1 photoreceptors, PARP controls calpain activity via PARG and TRPM2-induced Ca2+ influx. We also characterize INO1001 as potentially more beneficial for IRD treatment than Olaparib. Our study details the complexity of PARP-signalling in photoreceptors and identifies PARG and TRPM2 as new targets for IRD therapy development. ### Competing Interest Statement The authors have declared no competing interest.

Retinitis Pigmentosa (RP) is the most common inherited retinal degeneration, characterized by an initial loss of rod photoreceptor cells. Photoreceptor cell death has been associated with high levels of cyclic guanosine-3′, 5′- monophosphate (cGMP) in animal models of autosomal recessive RP (ARRP) and autosomal dominant RP (ADRP). cGMP analogues inhibiting protein kinase G (PKG) have been found to prevent rod degeneration in ARRP disease models, but their effects on ADRP are unknown. Here, we used the recently generated rhodopsin-mutant RhoI255d/+ ADRP mouse model to study cGMP-signaling and the effects of cGMP analogues targeting PKG. cGMP accumulation was investigated by retinal immunostaining in wild-type (WT), RhoI255d/+, and RhoI255d/I255d mice. The therapeutic efficacy of the cGMP analogues CN03 and CN238 was evaluated on organotypic retinal explant cultures derived from WT and RhoI255d/+ mice. Readouts included the TUNEL assay and immunostaining for cone arrestin-3. Downstream effectors of cell death were visualized using calpain, poly-ADP-ribose polymerase (PARP), and histone deacetylase (HDAC) in situ assays, as well as caspase-3 immunostaining. Photoreceptor function was assessed using micro-electroretinogram (µERG) recordings. When compared with WT, RhoI255d photoreceptors displayed cGMP accumulation in outer segments. In the RhoI255d/+ ADRP model, CN03 and CN238 significantly reduced the number of dying photoreceptors. However, the relatively small number of photoreceptors exhibiting caspase-3 activity was not changed by the treatment. Remarkably, CN238 effectively provided long-lasting neuroprotection of cone photoreceptors and preserved retinal light responsiveness of RhoI255d/+ retina. Overall, this study suggests caspase-independent but cGMP-dependent cell death as a dominant degenerative mechanism in the RhoI255d/+ ADRP mouse model. PKG inhibition demonstrated robust neuroprotection of both rod and cone photoreceptors, while the marked preservation of retinal function, especially with the compound CN238, highlighted cGMP analogues for the treatment of ADRP.

Retinitis Pigmentosa (RP) is an inherited neurodegenerative disease which leads to loss of retinal photoreceptors and blindness. Histone deacetylases (HDAC) were previously found to be involved in photoreceptor cell death, and HDAC inhibitors have shown protective effects in animal models for autosomal recessive RP. However, whether HDAC inhibitors can protect photoreceptors in autosomal dominant RP (ADRP) remains unclear. Here, we utilized the recently generated human homologous RhoI255d/+ ADRP mouse model to investigate degenerative mechanisms and the therapeutic potential of HDAC inhibitors. To visualize photoreceptor HDAC activity, we applied an in situ HDAC activity assay on post-natal (P) day 20 wild type (WT) and RhoI255d/+ retina. Treatment with the HDAC class I/II inhibitor Trichostatin A and the HDAC class III inhibitor nicotinamide (NAM) suggested that most HDAC activity detected in RhoI255d/+ photoreceptors was related to class I/II isoforms. The therapeutic potential of different HDAC inhibitors, targeting different HDAC isoforms, was evaluated in vitro, on organotypic retinal explants cultured under completely controlled conditions. HDAC inhibitors tested included SAHA (Vorinostat), MPT0G211, ACY-957, and NAM. Readouts comprised the TUNEL assay, immunostaining for activated calpain-2 and caspase-3, cone arrestin-3, and bromodeoxyuridine (BrdU)-labeling. Among the compounds tested, MPT0G211, targeting predominantly cytoplasmic HDAC-6, exhibited the strongest protective effect on both rod and cone photoreceptors. Remarkably, high-dose ACY-957, inhibiting nuclear HDAC-1/-2, induced both photoreceptor cell death and cell proliferation. High levels of NAM, blocking mitochondrial and nuclear HDACs, caused selective rod cell death, without affecting cones. All HDAC inhibitors tested had no or only minor effects on neurons of the inner retina. Our study highlights the complexity and ambiguity of HDAC activity during photoreceptor neurodegeneration and cautions against the use of unspecific inhibitors. At the same time, it showcases important differences between rod and cone photoreceptors and suggests especially HDAC-6 as a potential target for future therapy development.

BACKGROUND:Choroidal neovascularization (CNV) is a key manifestation of intraocular neovascularization, and it is considered one of the main causes of blindness in ophthalmology. Additionally, multiple anti-vascular endothelial growth factor (VEGF) drugs have been used as first-line treatment for CNV. However, several issues posed challenges to the anti-VEGF drugs, which were mainly composed of short duration of action, requirement for repeated injections, and complications. Thrombospondin-1 (TSP-1) is an endogenous protein that was found to regulate multiple biological processes within the body, and it has been proven to exhibit an inhibitory effect on neovascularization. Besides, the function of TSP-1 during the inhibition of neovascularization was currently considered to mainly focus on its type Ⅰ repeats (TSRs), which was attributed to the large molecular weight, complex structure, and possible unknown functions of TSP-1. Therefore, TSRs can be applied as targets and research directions for the further development and exploration of potential therapeutic drugs. OBJECTIVES:Based on the type I repeats (TSRs) of thrombospondin-1 (TSP-1), amino acid sequences of different lengths were designed and synthesized in this study, named as VR-9 VR-10、VR-11、VR-12、VR-13. The objective was to explore the effects of the above five peptides on angiogenesis in Chori-retinal neovascularization, alongside the screening of the best peptides and the deep exploration into the underlying mechanism, aimed to provide a basis for the development and application of peptide drugs in the treatment of CNV. METHODS:Wound healing, CCK-8, and 5-ethynyl-2'-deoxyuridine (EdU) assays were employed to evaluate the proliferation and migration ability of cells. CRISPR-Cas9 technology was utilized to establish CD36 knockdown cell lines, alongside the conduction of qPCR to verify the efficiency of gene knockdown. The expression levels of VEGF and CD31 in RF/6A cells and rats were assessed by Western blot. Additionally, Hematoxylin and eosin (HE) staining was performed to examine the structural integrity of the rat retina, while Fluorescein Isothiocyanate-Dextran Cardiac Perfusion (FITC) labeling was used to observe the occurrence and development of choroidal neovascularization (CNV). RESULTS:According to the wound-healing and CCK-8 assays, VR-13 was the most effective in inhibiting the proliferation and migration of endothelial cells. Furthermore, VR-13 peptide effectively inhibited the pathological development of CNV without the detection of retinal toxicity in the rat CNV model. CONCLUSIONS:Overall, it was found that VR-13 exhibit significant effects on the inducing of apoptosis and the inhibition of the progression of angiogenesis by regulating the expression of VEGF and CD31 via CD36 signaling pathway.

Inherited retinal degeneration (IRD) is a debilitating condition characterized by progressive loss of photoreceptor cells. However, the underlying mechanisms remain largely unclear. This study investigated the role of DNA topoisomerase II alpha (TOP2A) and its interplay with protein kinase G (PKG) and histone deacetylase (HDAC) in the rd1 mouse model for IRD. Immunofluorescence and quantitative western blotting analyses were performed to evaluate the expression of TOP2A, PKG1, PKG2, HDAC1, and other related markers. TSC24 and suberoylanilide hydroxamic acid were used to specifically inhibit TOP2A and HDAC, respectively, in organotypic retinal explant cultures derived from wild-type or rd1 mice. Furthermore, we examined the effect of PKG activity on TOP2A phosphorylation using KT5823. Significant upregulation of TOP2A was observed in the rd1 mouse retina compared with wild-type controls, especially in the outer nuclear layer. Phosphorylation levels of TOP2A strongly correlated with photoreceptor cell death. Treatment with TSC24 significantly reduced TOP2A-positive and TUNEL-positive cells. TOP2A phosphorylation was accompanied by HDAC activation, which was mitigated by TSC24. PKG inhibition by KT5823 reduced TOP2A phosphorylation at specific residues and photoreceptor HDAC activity. Our findings position TOP2A in the PKG-TOP2A-HDAC photoreceptor degenerative pathway, offering new potential therapeutic targets for combating IRD-type diseases.

PurposeTo investigate the role of the lamina cribrosa (LC) astrocytes in the autoregulatory capacity of optic nerve head (ONH) vessels and to explore the underlying molecular mechanisms.MethodsThe Oxygen-glucose deprivation/reperfusion model (OGD/R) in vitro was constructed to examine the changes in cell morphology and protein expression in LC astrocytes. LC astrocytes were co-cultured with vascular smooth muscle cells (VSMCs) to detect the role of LC astrocytes in the autoregulatory function of vessels.ResultsThe partial pressure of oxygen (PO2) in the supernatant of LC astrocytes was significantly lower following OGD, and this reduction was more pronounced with longer OGD durations. OGD inhibited proliferation and promoted apoptosis in LC astrocytes, with longer OGD durations correlating with decreased proliferation and increased apoptosis. Reoxygenation following 1 h of OGD led to upregulation of GFAP, mTOR, cPLA2 protein expression and supernatant PGE2 concentration in LC astrocytes, an effect that can be attenuated by the mTOR inhibitor. Co-culturing with LC astrocyte resulted in increased expression of MYPT1 protein in VSMCs, and the VSMCs exhibited a relaxed morphology.ConclusionUnder in vitro OGD/R conditions, LC astrocyte were activated through the mTOR pathway, leading to increased secretion of PGE2, which locally regulates the dilation of VSMCs. In conclusion, LC astrocytes may regulate local blood flow in the ONH.

Inherited retinal degenerations (IRDs) are a group of untreatable and commonly blinding diseases characterized by progressive photoreceptor loss. IRD pathology has been linked to an excessive activation of cyclic nucleotide-gated channels (CNGC) leading to Na+- and Ca2+-influx, subsequent activation of voltage-gated Ca2+-channels (VGCC), and further Ca2+ influx. However, a connection between excessive Ca2+ influx and photoreceptor loss has yet to be proven. Here, we used whole-retina and single-cell RNA-sequencing to compare gene expression between the rd1 mouse model for IRD and wild-type (wt) mice. Differentially expressed genes indicated links to several Ca2+-signalling related pathways. To explore these, rd1 and wt organotypic retinal explant cultures were treated with the intracellular Ca2+-chelator BAPTA-AM or inhibitors of different Ca2+-permeable channels, including CNGC, L-type VGCC, T-type VGCC, Ca2+-release-activated channel (CRAC), and Na+/Ca2+ exchanger (NCX). Moreover, we employed the novel compound NA-184 to selectively inhibit the Ca2+-dependent protease calpain-2. Effects on the retinal activity of poly(ADP-ribose) polymerase (PARP), sirtuin-type histone-deacetylase, calpains, as well as on activation of calpain-1, and − 2 were monitored, cell death was assessed via the TUNEL assay. While rd1 photoreceptor cell death was reduced by BAPTA-AM, Ca2+-channel blockers had divergent effects: While inhibition of T-type VGCC and NCX promoted survival, blocking CNGCs and CRACs did not. The treatment-related activity patterns of calpains and PARPs corresponded to the extent of cell death. Remarkably, sirtuin activity and calpain-1 activation were linked to photoreceptor protection, while calpain-2 activity was related to degeneration. In support of this finding, the calpain-2 inhibitor NA-184 protected rd1 photoreceptors. These results suggest that Ca2+ overload in rd1 photoreceptors may be triggered by T-type VGCCs and NCX. High Ca2+-levels likely suppress protective activity of calpain-1 and promote retinal degeneration via activation of calpain-2. Overall, our study details the complexity of Ca2+-signalling in photoreceptors and emphasizes the importance of targeting degenerative processes specifically to achieve a therapeutic benefit for IRDs.

Astrocyte patterns affect the normal development of the retinal vascular network in retinopathy of prematurity (ROP), which is associated with VEGF secretion. However, the role of the astrocyte polarization in this process remains unknown. Therefore, this study aimed to track the status of A1/A2 reactive astrocytes in the retinas of the oxygen-induced retinopathy (OIR) model and their association with VEGF expression. The C57BL/6 mouse OIR model was constructed to characterize the pathological changes in ROP. Immunofluorescence of iB4 and GFAP staining was performed to observe changes in the vascular network and astrocyte pattern at different time points (P0, P7, P12, P17, and P21). C3-labeled A1 reactive and S100A10-labeled A2 reactive astrocytes and VEGF were also observed. The pattern of GFAP-labeled astrocyte was altered concurrently with the iB4-positive vascular network during OIR. Astrocyte activity was significantly weakened at P12 and significantly enhanced at P17. Notably, the number of C3-labeled A1 reactive astrocytes was significantly increased at P12, decreased at P17, and normalized at P21 in OIR models. S100A10-labeled A2 reactive astrocytes were significantly increased at P17 but did not change significantly at P12 or P17. VEGF levels were decreased at P7-P12 and increased at P12-P17. The expression pattern of VEGF was opposite to that of C3-labeled A1 reactive astrocytes and identical to that of S100A10-labeled A2 reactive astrocytes. In conclusion, the astrocyte pattern and vascular network exhibited similar changes during the OIR process, and the periods of vaso-obliteration and neo-vascularization display an abnormal activation in A1- and A2-reactive astrocytes.

Inherited retinal degeneration (IRD) represents a diverse group of gene mutation-induced blinding diseases. In IRD, the loss of photoreceptors is often connected to excessive activation of histone-deacetylase (HDAC), poly-ADP-ribose-polymerase (PARP), and calpain-type proteases (calpain). Moreover, the inhibition of either HDACs, PARPs, or calpains has previously shown promise in preventing photoreceptor cell death, although the relationship between these enzyme groups remains unclear. To explore this further, organotypic retinal explant cultures derived from wild-type mice and rd1 mice as a model for IRD were treated with different combinations of inhibitors specific for HDAC, PARP, and calpain. The outcomes were assessed using in situ activity assays for HDAC, PARP, and calpain, immunostaining for activated calpain-2, and the TUNEL assay for cell death detection. We confirmed that inhibition of either HDAC, PARP, or calpain reduced rd1 mouse photoreceptor degeneration, with the HDAC inhibitor Vorinostat (SAHA) being most effective. Calpain activity was reduced by inhibition of both HDAC and PARP whereas PARP activity was only reduced by HDAC inhibition. Unexpectedly, combined treatment with either PARP and calpain inhibitors or HDAC and calpain inhibitors did not produce synergistic rescue of photoreceptors. Together, these results indicate that in rd1 photoreceptors, HDAC, PARP, and calpain are part of the same degenerative pathway and are activated in a sequence that begins with HDAC and ends with calpain.

Purpose This research aimed to ascertain the neuroprotective effect of histone deacetylase (HDAC) inhibition on retinal photoreceptors in Pde6brd1 mice, a model of retinitis pigmentosa (RP). Methods Single-cell RNA-sequencing (scRNA-seq) explored HDAC and poly (ADP-ribose) polymerase (PARP)-related gene expression in both Pde6b-mutant rd1 and wild-type (WT) mice. The CUT&Tag method was employed to examine the functions of HDAC in rd1 mice. Organotypic retinal explant cultures from WT and rd1 mice were exposed to the HDAC inhibitor SAHA (suberoylanilide hydroxamic acid) postnatally, from day 5 to day 11. The terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) assay was applied to quantify the percentage of photoreceptor loss in the outer nuclear layer (ONL). HDAC activity was confirmed to be inhibited by SAHA through an HDAC activity assay. Moreover, the study evaluated PARP activity, a key driver of the initial response to DNA damage during photoreceptor degeneration, following HDAC inhibition. Results The scRNA-seq revealed that diverse roles of HDAC and PARP isoforms in photoreceptor cell death. HDAC-related genes appeared to regulate cell death and primary immunodeficiency. Alterations in HDAC activity were consistent with the TUNEL-positive cells in the ONL at different time points. Notably, SAHA significantly postponed photoreceptor loss and decreased HDAC and PARP activity, thereby implicating both in the same degenerative pathway. Conclusions This study highlights that the interaction between HDAC inhibition and PARP can delay photoreceptor cell death, proposing a promising therapeutic approach for RP.

Retinitis pigmentosa (RP) is a group of inherited retinal dystrophies that typically results in photoreceptor cell death and vision loss. Here, we explored the effect of early growth response-1 (EGR1) expression on photoreceptor cell death in Pde6brd1 (rd1) mice and its mechanism of action. To this end, single-cell RNA-seq (scRNA-seq) was used to identify differentially expressed genes in rd1 and congenic wild-type (WT) mice. Chromatin immunoprecipitation (ChIP), the dual-luciferase reporter gene assay, and western blotting were used to verify the relationship between EGR1 and poly (ADP-ribose) polymerase-1 (PARP1). Immunofluorescence staining was used to assess PARP1 expression after silencing or overexpression of EGR1. Photoreceptor cell death was assessed using the TUNEL assay following silencing/overexpression of EGR1 or administration of MAPK/c-Jun pathway inhibitors tanzisertib and PD98059. Our results showed differential expression of ERG1 in rd1 and WT mice via scRNA-seq analysis. The ChIP assay demonstrated EGR1 binding to the PARP1 promoter region. The dual-luciferase reporter gene assay and western blotting results revealed that EGR1 upregulated PARP1 expression. Additionally, the TUNEL assay showed that silencing EGR1 effectively reduced photoreceptor cell death. Similarly, the addition of tanzisertib and PD98059 reduced the expression of c-Jun and EGR1 and decreased photoreceptor cell death. Our study revealed that inhibition of the MAPK/c-Jun pathway reduced the expression of EGR1 and PARP1 and prevented photoreceptor cell death. These results highlight the importance of EGR1 for photoreceptor cell death and identify a new avenue for therapeutic interventions in RP.

一例获得性免疫缺陷综合征伴多重感染患者,右眼视物模糊20余日,经眼部检查发现右眼脉络膜巨大隆起病灶,玻璃体腔出现黄白色脓样物质,根据肺结核病史及眼底表现诊断为右眼脉络膜结核瘤(干酪样坏死型并破溃),予全身抗结核治疗2个月后脓样物质大部分吸收;半年后脉络膜病变范围较前扩大,再次系统抗结核治疗3个月后眼部及全身情况稳定.

The cellular mechanisms underlying hereditary photoreceptor degeneration are still poorly understood. The aim of this study was to systematically map the transcriptional changes that occur in the degenerating mouse retina at the single cell level. To this end, we employed single-cell RNA-sequencing (scRNA-seq) and retinal degeneration-1 (rd1) mice to profile the impact of the disease mutation on the diverse retinal cell types during early post-natal development. The transcriptome data allowed to annotate 43,979 individual cells grouped into 20 distinct clusters. We further characterized cluster-specific metabolic and biological changes in individual cell types. Our results highlight Ca2+-signaling as relevant to hereditary photoreceptor degeneration. Although metabolic reprogramming in retina, known as the ‘Warburg effect’, has been documented, further metabolic changes were noticed in rd1 mice. Such metabolic changes in rd1 mutation was likely regulated through mitogen-activated protein kinase (MAPK) pathway. By combining single-cell transcriptomes and immunofluorescence staining, our study revealed cell type-specific changes in gene expression, as well as interplay between Ca2+-induced cell death and metabolic pathways.

Hereditary retinal degeneration (RD) is characterized by progressive photoreceptor cell death. Overactivation of the cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG) pathway in photoreceptor cells causes photoreceptor cell death, especially in models harboring phosphodiesterase 6b (PDE6b) mutations. Previous studies on RD have used mainly murine models such as rd1 or rd10 mice. Given the genetic and physiological differences between mice and humans, it is important to understand to which extent the retinas of primates and rodents are comparable. Macaques share a high level of genetic similarity with humans. Therefore, wild-type macaques (aged 1-3 years) were selected for the in vitro culture of retinal explants that included the retina-retinal pigment epithelium (RPE)-choroid complex. These explants were treated with different concentrations of the PDE6 inhibitor zaprinast to induce the cGMP-PKG signaling pathway and simulate RD pathogenesis. cGMP accumulation and cell death in primate retinal explants were subsequently verified using immunofluorescence and the TUNEL assay. The primate retinal model established in this study may serve for relevant and effective studies into the mechanisms of cGMP-PKG-dependent RD, as well as for the development of future treatment approaches.