Rac1 conditional deletion attenuates retinal ganglion cell apoptosis by accelerating autophagic flux in a mouse model of chronic ocular hypertension

Müller cells under hydrostatic pressure modulate retinal cell survival via TRPV1/PLCγ1 complex-mediated calcium influx in experimental glaucoma

Glaucoma, an irreversible blinding eye disease, is currently unclear whose pathological mechanism is. This study investigated how transient receptor potential cation channel subfamily V member 1 (TRPV1), 1-phosphatidylinositol 4,5-bisphosphate phosphodiesterase gamma-1 (PLCγ1), and P2X purinoceptor 7 (P2X7) modulate the levels of intracellular calcium ions (Ca2+ ) and adenosine triphosphate (ATP) in Müller cells and retinal ganglion cells (RGCs) under conditions of elevated intraocular pressure (IOP). Müller cells were maintained at hydrostatic pressure (HP). TRPV1- and PLCG1-silenced Müller cells and P2X7-silenced RGCs were constructed by transfection with short interfering RNA (siRNAs). RGCs were cultured with the conditioned media of Müller cells under HP. A mouse model of chronic ocular hypertension (COH) was established and used to investigate the role of TRPV1 in RGCs in vivo. Müller cells and RGCs were analyzed by ATP release assays, intracellular calcium assays, CCK-8 assays, EdU (5-ethynyl-2'-deoxyuridine) staining, TUNEL staining, flow cytometry, and transmission electron microscopy. In vivo changes in inner retinal function were evaluated by hematoxylin and eosin (H&E) staining and TUNEL staining. Western blot analyses were performed to measure the levels of related proteins. Our data showed that HP increased the levels of ATP and Ca2+ influx in Müller cells, and those increases were accompanied by the upregulation of TRPV1 and p-PLCγ1 expression. Suppression of TRPV1 or PLCG1 expression in Müller cells significantly decreased the ATP levels and intracellular Ca2+ accumulation induced by HP. Knockdown of TRPV1, PLCG1, or P2X7 significantly decreased apoptosis and autophagy in RGCs cultured in the conditioned media of HP-treated Müller cells. Moreover, TRPV1 silencing decreased RGC apoptosis and autophagy in the in vivo model of COH. Collectively, inhibition of TRPV1/PLCγ1 and P2X7 expression may be a useful therapeutic strategy for managing RGC death in glaucoma.

Selective deletion of zinc transporter 3 in amacrine cells promotes retinal ganglion cell survival and optic nerve regeneration after injury

Vision depends on accurate signal conduction from the retina to the brain through the optic nerve, an important part of the central nervous system that consists of bundles of axons originating from retinal ganglion cells. The mammalian optic nerve, an important part of the central nervous system, cannot regenerate once it is injured, leading to permanent vision loss. To date, there is no clinical treatment that can regenerate the optic nerve and restore vision. Our previous study found that the mobile zinc (Zn²⁺) level increased rapidly after optic nerve injury in the retina, specifically in the vesicles of the inner plexiform layer. Furthermore, chelating Zn²⁺ significantly promoted axonal regeneration with a long-term effect. In this study, we conditionally knocked out zinc transporter 3 (ZnT3) in amacrine cells or retinal ganglion cells to construct two transgenic mouse lines (VGAT^CreZnT3^fl/fl and VGLUT2^CreZnT3^fl/fl, respectively). We obtained direct evidence that the rapidly increased mobile Zn²⁺ in response to injury was from amacrine cells. We also found that selective deletion of ZnT3 in amacrine cells promoted retinal ganglion cell survival and axonal regeneration after optic nerve crush injury, improved retinal ganglion cell function, and promoted vision recovery. Sequencing analysis of reginal ganglion cells revealed that inhibiting the release of presynaptic Zn²⁺ affected the transcription of key genes related to the survival of retinal ganglion cells in postsynaptic neurons, regulated the synaptic connection between amacrine cells and retinal ganglion cells, and affected the fate of retinal ganglion cells. These results suggest that amacrine cells release Zn²⁺ to trigger transcriptomic changes related to neuronal growth and survival in reginal ganglion cells, thereby influencing the synaptic plasticity of retinal networks. These results make the theory of zinc-dependent retinal ganglion cell death more accurate and complete and provide new insights into the complex interactions between retinal cell networks.

GGT1 Suppresses the Development of Ferroptosis and Autophagy in Mouse Retinal Ganglion Cell Through Targeting GCLC

Background

Glaucoma is a neurodegenerative disorder characterized with optic nerve injury and the loss of retinal ganglion cells (RGCs). Ferroptosis has been proved to be associated with the degradation of RGCs. The aim of this study is to elucidate the relationship between ferroptosis and glaucoma pathogenesis, and unveil the underlying mechanism.

Methods

Methyl thiazolyl tetrazolium (MTT) assay was used to evaluate the proliferation of RGCs. The accumulation of cellular iron was measured by Iron assay kit, and the level of reactive oxygen species (ROS) was detected by fluorescence probe. The mitochondrial morphology and autophagosomes were analysed by using transmission electron microscopy (TEM). The contents of glutathione (GSH) and malondialdehyde (MDA) were tested by a GSH assay kit and an MDA detection kit, respectively. The expression of autophagy-related proteins was detected by Western blotting.

Results

A serious cell damage, aberrant iron homeostasis, and oxidative stress was shown in RGC-5 after oxygen-glucose deprivation/reoxygenation (OGD/R) treatment and gamma-Glutamyl transpeptidase 1 (GGT1) knockdown, but these effects were significantly alleviated by overexpression of GGT1 or ferroptosis inhibitors. The TEM and immunofluorescent results indicated that mitochondria impairment and autophagosome accumulation in OGD/R-treated cells was improved after GGT1 overexpression, while the phenomenon in GGT1-silenced cells was aggravated. Furthermore, we found that GGT1 can interact with glutamate cysteine ligase catalytic subunit (GCLC) to inhibit autophagy and ferroptosis in RGC-5 cells.

Conclusion

GGT1 represses autophagy in RGC-5 cells by targeting GCLC, which further restrains the development of ferroptosis in cells.

High glucose dialysate-induced peritoneal fibrosis: Pathophysiology, underlying mechanisms and potential therapeutic strategies

Peritoneal dialysis is an efficient renal replacement therapy for patients with end-stage kidney disease. However, continuous exposure of the peritoneal membrane to dialysate frequently leads to peritoneal fibrosis, which alters the function of the peritoneal membrane and results in withdrawal from peritoneal dialysis in patients. Among others, high glucose dialysate is considered as a predisposing factor for peritoneal fibrosis in patients on peritoneal dialysis. Glucose-induced inflammation, metabolism disturbance, activation of the renin-angiotensin-aldosterone system, angiogenesis and noninflammation-induced reactive oxygen species are implicated in the pathogenesis of high glucose dialysate-induced peritoneal fibrosis. Specifically, high glucose causes chronic inflammation and recurrent peritonitis, which could cause migration and polarization of inflammatory cells, as well as release of cytokines and fibrosis. High glucose also interferes with lipid metabolism and glycolysis by activating the sterol-regulatory element-binding protein-2/cleavage-activating protein pathway and increasing hypoxia inducible factor-1α expression, leading to angiogenesis and peritoneal fibrosis. Activation of the renin-angiotensin-aldosterone system and Ras-mitogen activated protein kinase signaling pathway is another contributing factor in high glucose dialysate-induced fibrosis. Ultimately, activation of the transforming growth factor-β1/Smad pathway is involved in mesothelial-mesenchymal transition or epithelial-mesenchymal transition, which leads to the development of fibrosis. Although possible intervention strategies for peritoneal dialysate-induced fibrosis by targeting the transforming growth factor-β1/Smad pathway have occasionally been proposed, lack of laboratory evidence renders clinical decision-making difficult. We therefore aim to revisit the upstream pathways of transforming growth factor-beta1/Smad and propose potential therapeutic targets for high glucose-induced peritoneal fibrosis.

Autophagy deficiency protects against ocular hypertension and neurodegeneration in experimental and spontanous glaucoma mouse models

Glaucoma is a group of diseases that leads to chronic degeneration of retinal ganglion cell (RGC) axons and progressive loss of RGCs, resulting in vision loss. While aging and elevated intraocular pressure (IOP) have been identified as the main contributing factors to glaucoma, the molecular mechanisms and signaling pathways triggering RGC death and axonal degeneration are not fully understood. Previous studies in our laboratory found that overactivation of autophagy in DBA/2J::GFP-LC3 mice led to RGC death and optic nerve degeneration with glaucomatous IOP elevation. We found similar findings in aging GFP-LC3 mice subjected to chronic IOP elevation. Here, we further investigated the impact of autophagy deficiency on autophagy-deficient DBA/2J-Atg4bko and DBA/2J-Atg4b+/- mice, generated in our laboratory via CRISPR/Cas9 technology; as well as in Atg4bko mice subjected to the experimental TGFβ2 chronic ocular hypertensive model. Our data shows that, in contrast to DBA/2J and DBA/2J-Atg4b+/- littermates, DBA/2J-Atg4bko mice do not develop glaucomatous IOP elevation. Atg4b deficiency also protected against glaucomatous IOP elevation in the experimental TGFβ2 chronic ocular hypertensive model. Atg4 deletion did not compromise RGC or optic nerve survival in Atg4bko mice. Moreover, our results indicate a protective role of autophagy deficiency against RGC death and ON atrophy in the hypertensive DBA/2J-Atg4b+/- mice. Together, our data suggests a pathogenic role of autophagy activation in ocular hypertension and glaucoma.

Modulation of Rac1/PAK1/connexin43-mediated ATP release from astrocytes contributes to retinal ganglion cell survival in experimental glaucoma

Connexin43 (Cx43) is a major gap junction protein in glial cells. Mutations have been found in the gap-junction alpha 1 gene encoding Cx43 in glaucomatous human retinas, suggestive of the involvement of Cx43 in the pathogenesis of glaucoma. However, how Cx43 is involved in glaucoma is still unknown. We showed that increased intraocular pressure in a glaucoma mouse model of chronic ocular hypertension (COH) downregulated Cx43, which was mainly expressed in retinal astrocytes. Astrocytes in the optic nerve head where they gather and wrap the axons (optic nerve) of retinal ganglion cells (RGCs) were activated earlier than neurons in COH retinas and the alterations in astrocytes plasticity in the optic nerve caused a reduction in Cx43 expression. A time course showed that reductions of Cx43 expression were correlated with the activation of Rac1, a member of the Rho family. Co-immunoprecipitation assays showed that active Rac1, or the downstream signaling effector PAK1, negatively regulated Cx43 expression, Cx43 hemichannel opening and astrocyte activation. Pharmacological inhibition of Rac1 stimulated Cx43 hemichannel opening and ATP release, and astrocytes were identified to be one of the main sources of ATP. Furthermore, conditional knockout of Rac1 in astrocytes enhanced Cx43 expression and ATP release, and promoted RGC survival by upregulating the adenosine A3 receptor in RGCs. Our study provides new insight into the relationship between Cx43 and glaucoma, and suggests that regulating the interaction between astrocytes and RGCs via the Rac1/PAK1/Cx43/ATP pathway may be used as part of a therapeutic strategy for managing glaucoma.

Autophagy in glaucoma pathogenesis: Therapeutic potential and future perspectives

Glaucoma is a common blinding eye disease characterized by progressive loss of retinal ganglion cells (RGCs) and their axons, progressive loss of visual field, and optic nerve atrophy. Autophagy plays a pivotal role in the pathophysiology of glaucoma and is closely related to its pathogenesis. Targeting autophagy and blocking the apoptosis of RGCs provides emerging guidance for the treatment of glaucoma. Here, we provide a systematic review of the mechanisms and targets of interventions related to autophagy in glaucoma and discuss the outlook of emerging ideas, techniques, and multidisciplinary combinations to provide a new basis for further research and the prevention of glaucomatous visual impairment.

mTOR Signalling Pathway: A Potential Therapeutic Target for Ocular Neurodegenerative Diseases

Recent advances in the research of the mammalian target of the rapamycin (mTOR) signalling pathway demonstrated that mTOR is a robust therapeutic target for ocular degenerative diseases, including age-related macular degeneration (AMD), diabetic retinopathy (DR), and glaucoma. Although the exact mechanisms of individual ocular degenerative diseases are unclear, they share several common pathological processes, increased and prolonged oxidative stress in particular, which leads to functional and morphological impairment in photoreceptors, retinal ganglion cells (RGCs), or retinal pigment epithelium (RPE). mTOR not only modulates oxidative stress but is also affected by reactive oxygen species (ROS) activation. It is essential to understand the complicated relationship between the mTOR pathway and oxidative stress before its application in the treatment of retinal degeneration. Indeed, the substantial role of mTOR-mediated autophagy in the pathogenies of ocular degenerative diseases should be noted. In reviewing the latest studies, this article summarised the application of rapamycin, an mTOR signalling pathway inhibitor, in different retinal disease models, providing insight into the mechanism of rapamycin in the treatment of retinal neurodegeneration under oxidative stress. Besides basic research, this review also summarised and updated the results of the latest clinical trials of rapamycin in ocular neurodegenerative diseases. In combining the current basic and clinical research results, we provided a more complete picture of mTOR as a potential therapeutic target for ocular neurodegenerative diseases.

Antiviral Effects of ABMA and DABMA against Influenza Virus In Vitro and In Vivo via Regulating the Endolysosomal Pathway and Autophagy

Influenza virus is an acute and highly contagious respiratory pathogen that causes great concern to public health and for which there is a need for extensive drug discovery. The small chemical compound ABMA and its analog DABMA, containing an adamantane or a dimethyl-adamantane group, respectively, have been demonstrated to inhibit multiple toxins (diphtheria toxin, Clostridium difficile toxin B, Clostridium sordellii lethal toxin) and viruses (Ebola, rabies virus, HSV-2) by acting on the host’s vesicle trafficking. Here, we showed that ABMA and DABMA have antiviral effects against both amantadine-sensitive influenza virus subtypes (H1N1 and H3N2), amantadine-resistant subtypes (H3N2), and influenza B virus with EC₅₀ values ranging from 2.83 to 7.36 µM (ABMA) and 1.82 to 6.73 µM (DABMA), respectively. ABMA and DABMA inhibited the replication of influenza virus genomic RNA and protein synthesis by interfering with the entry stage of the virus. Molecular docking evaluation together with activity against amantadine-resistant influenza virus strains suggested that ABMA and DABMA were not acting as M2 ion channel blockers. Subsequently, we found that early internalized H1N1 virions were retained in accumulated late endosome compartments after ABMA treatment. Additionally, ABMA disrupted the early stages of the H1N1 life cycle or viral RNA synthesis by interfering with autophagy. ABMA and DABMA protected mice from an intranasal H1N1 challenge with an improved survival rate of 67%. The present study suggests that ABMA and DABMA are potential antiviral leads for the development of a host-directed treatment against influenza virus infection.

Rapamycin and Resveratrol Modulate the Gliotic and Pro-Angiogenic Response in Müller Glial Cells Under Hypoxia

Hypoxia and hypoxia-reoxygenation are frequently developed through the course of many retinal diseases of different etiologies. Müller glial cells (MGCs), together with microglia and astrocytes, participate firstly in response to the injury and later in the repair of tissue damage. New pharmacological strategies tend to modulate MGCs ability to induce angiogenesis and gliosis in order to accelerate the recovery stage. In this article, we investigated the variation in autophagy flux under hypoxia during 4 h, employing both gas culture chamber (1% O₂) and chemical (CoCl₂) hypoxia, and also in hypoxia-reoxygenation. Then, we delineated a strategy to induce autophagy with Rapamycin and Resveratrol and analysed the gliotic and pro-angiogenic response of MGCs under hypoxic conditions. Our results showed an increase in LC3B II and p62 protein levels after both hypoxic exposure respect to normoxia. Moreover, 1 h of reoxygenation after gas hypoxia upregulated LC3B II levels respect to hypoxia although a decreased cell survival was observed. Exposure to low oxygen levels increased the protein expression of the glial fibrillary acid protein (GFAP) in MGCs, whereas Vimentin levels remained constant. In our experimental conditions, Rapamycin but not Resveratrol decreased GFAP protein levels in hypoxia. Finally, supernatants of MGCs incubated in hypoxic conditions and in presence of the autophagy inductors inhibited endothelial cells (ECs) tubulogenesis. In agreement with these results, reduced expression of vascular endothelial growth factor (VEGF) mRNA was observed in MGCs with Rapamycin, whereas pigment epithelium-derived factor (PEDF) mRNA levels significantly increased in MGCs incubated with Resveratrol. In conclusion, this research provides evidence about the variation of autophagy flux under hypoxia and hypoxia-reoxygenation as a protective mechanism activated in response to the injury. In addition, beneficial effects were observed with Rapamycin treatment as it decreased the gliotic response and prevented the development of newly formed blood vessels.

P2X7/P2X4 Receptors Mediate Proliferation and Migration of Retinal Microglia in Experimental Glaucoma in Mice

Microglia are involved in the inflammatory response and retinal ganglion cell damage in glaucoma. Here, we investigated how microglia proliferate and migrate in a mouse model of chronic ocular hypertension (COH). In COH retinas, the microglial proliferation that occurred was inhibited by the P2X7 receptor (P2X7R) blocker BBG or P2X7R knockout, but not by the P2X4R blocker 5-BDBD. Treatment of primary cultured microglia with BzATP, a P2X7R agonist, mimicked the effects of cell proliferation and migration in COH retinas through the intracellular MEK/ERK signaling pathway. Transwell migration assays showed that the P2X4R agonist CTP induced microglial migration, which was completely blocked by 5-BDBD. In vivo and in vitro experiments demonstrated that ATP, released from activated Müller cells through connexin43 hemichannels, acted on P2X7R to induce microglial proliferation, and acted on P2X4R/P2X7R (mainly P2X4R) to induce microglial migration. Our results suggest that inhibiting the interaction of Müller cells and microglia may attenuate microglial proliferation and migration in glaucoma.

Recruitment of LC3 by Campylobacter jejuni to Bacterial Invasion Site on Host Cells via the Rac1-Mediated Signaling Pathway

Campylobacter jejuni is a leading cause of food-borne disease worldwide. The pathogenicity of C. jejuni is closely associated with the internalization process in host epithelial cells, which is related to a host immune response. Autophagy indicates a key role in the innate immune system of the host to exclude invasive pathogens. Most bacteria are captured by autophagosomes and degraded by autophagosome-lysosome fusion in host cells. However, several pathogens, such as Salmonella and Shigella, avoid and/or escape autophagic degradation to establish infection. But autophagy involvement as a host immune response to C. jejuni infection has not been clarified. This study revealed autophagy association in C. jejuni infection. During infection, C. jejuni activated the Rho family small GTPase Rac1 signaling pathway, which modulates actin remodeling and promotes the internalization of this pathogen. In this study, we found the LC3 contribution to C. jejuni invasion signaling via the Rac1 signaling pathway. Interestingly, during C. jejuni invasion, LC3 was recruited to bacterial entry site depending on Rac1 GTPase activation just at the early step of the infection. C. jejuni infection induced LC3-II conversion, and autophagy induction facilitated C. jejuni internalization. Also, autophagy inhibition attenuated C. jejuni invasion step. Moreover, Rac1 recruited LC3 to the cellular membrane, activating the invasion of C. jejuni. Altogether, our findings provide insights into the new function of LC3 in bacterial invasion. We found the interaction between the Rho family small GTPase, Rac1, and autophagy-associated protein, LC3.

Loss of JNK-Associated Leucine Zipper Protein Promotes Peritoneal Dialysis-Related Peritoneal Fibrosis

BACKGROUND

Peritoneal dialysis-related peritoneal fibrosis is the leading cause of peritoneal ultrafiltration failure. Multitude factors and pathological processes have been implicated in peritoneal fibrosis development and progression, whereas the intrinsic anti-fibrotic mechanism has rarely been explored. JNK-associated leucine zipper protein (JLP) has been recently found possessing powerful anti-fibrotic merits of overall antagonizing TGF-β-induced profibrotic effects.

OBJECTIVES

We wondered whether JLP is expressed in the peritoneum, and if so, whether it exerts the anti-fibrotic effects similar to those in the kidney.

METHOD

Here, we examined and confirmed JLP expression in peritoneum tissue of mice. Then, we established a peritoneal fibrosis model in Jlp wild-type and Jlp global deficient mice and observed the different effects of Jlp on peritoneal fibrosis progression. In vitro studies were performed on peritoneal mesothelial HMrSV5 cells with or without Jlp knockdown to investigate the underlying mechanism by which Jlp exerts anti-fibrotic effects.

RESULTS

We found that the expression of JLP decreased in a high-glucose peritoneal dialysis solution (HGPDS)-induced peritoneal fibrosis mouse model and in HGPDS-treated peritoneal mesothelial cell HMrSV5. JLP deletion exacerbated HGPDS-induced peritoneal fibrosis in peritoneal fibrosis mice, and knockdown of JLP resulted in an increased profibrotic response to HGPDS stimulation in HMrSV5 cells, which was associated with epithelial-to-mesenchymal transition, elevated autophagy, and apoptosis, as well as enhanced TGF-β1/Smad signaling activation.

CONCLUSIONS

Our findings revealed a new anti-fibrotic factor of Jlp involved in peritoneal fibrosis induction and shed light on novel therapeutic targets in peritoneal ultrafiltration failure.

The interplay of autophagy and oxidative stress in the pathogenesis and therapy of retinal degenerative diseases

Oxidative stress is mainly caused by intracellular reactive oxygen species (ROS) production, which is highly associated with normal physiological homeostasis and the pathogenesis of diseases, particularly ocular diseases. Autophagy is a self-clearance pathway that removes oxidized cellular components and regulates cellular ROS levels. ROS can modulate autophagy activity through transcriptional and posttranslational mechanisms. Autophagy further triggers transcription factor activation and degrades impaired organelles and proteins to eliminate excessive ROS in cells. Thus, autophagy may play an antioxidant role in protecting ocular cells from oxidative stress. Nevertheless, excessive autophagy may cause autophagic cell death. In this review, we summarize the mechanisms of interaction between ROS and autophagy and their roles in the pathogenesis of several ocular diseases, including glaucoma, age-related macular degeneration (AMD), diabetic retinopathy (DR), and optic nerve atrophy, which are major causes of blindness. The autophagy modulators used to treat ocular diseases are further discussed. The findings of the studies reviewed here might shed light on the development and use of autophagy modulators for the future treatment of ocular diseases.

Interplay between Müller cells and microglia aggravates retinal inflammatory response in experimental glaucoma

Background

Glaucoma, the leading cause of irreversible blindness, is a retinal neurodegenerative disease, which results from progressive apoptotic death of retinal ganglion cells (RGCs). Although the mechanisms underlying RGC apoptosis in glaucoma are extremely complicated, an abnormal cross-talk between retinal glial cells and RGCs is generally thought to be involved. However, how interaction of Müller cells and microglia, two types of glial cells, contributes to RGC injury is largely unknown.

Methods

A mouse chronic ocular hypertension (COH) experimental glaucoma model was produced. Western blotting, immunofluorescence, quantitative real-time polymerase chain reaction (q-PCR), transwell co-culture of glial cells, flow cytometry assay, ELISA, Ca²⁺ image, and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) techniques were employed to investigate the interaction of Müller cells and microglia, and its underlying mechanisms in COH retina.

Results

We first showed that Müller cell activation in mice with COH induced microglia activation through the ATP/P2X7 receptor pathway. The activation of microglia resulted in a significant increase in mRNA and protein levels of pro-inflammatory factors, such as tumor necrosis factor-α and interleukin-6. These inflammatory factors in turn caused the up-regulation of mRNA expression of pro-inflammatory factors in Müller cells through a positive feedback manner.

Conclusions

These findings provide robust evidence, for the first time, that retinal inflammatory response may be aggravated by an interplay between activated two types of glial cells. These results also suggest that to reduce the interplay between Müller cells and microglia could be a potential effective strategy for preventing the loss of RGCs in glaucoma.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02366-x.

Ligustrazine protects against chronic hypertensive glaucoma in rats by inhibiting autophagy via the PI3K-Akt/mTOR pathway

PURPOSE

Glaucoma is a leading cause of global irreversible blindness, and characterized by the progressive loss of retinal ganglion cells (RGCs). Ligustrazine (TMP) is a natural product that has shown beneficial effects on various diseases. This study aimed to determine whether ligustrazine produces a therapeutic effect on glaucoma and to investigate its underlying mechanisms.

METHODS

A rat chronic hypertensive glaucoma model was induced by episcleral vein cauterization (EVC). Adult Sprague-Dawley (SD) rats were intraperitoneally administered TMP at a dose of 80 mg/kg once a day, from two days before EVC to one month after EVC. To elucidate the role of the mammalian target of rapamycin (mTOR) and phosphoinositide 3-kinase (PI3K), TMP-treated experimental rats were co-treated with the mTOR inhibitor rapamycin (5 mg/kg) or the PI3K inhibitor Ly294002 (10 mg/kg). The intraocular pressure (IOP) of the experimental and control rats was measured every six days. Retinal cells were examined by hematoxylin-eosin and terminal deoxynucleotidyltransferase-mediated biotinylated UTP nick end labeling (TUNEL) staining, as well as transmission electron microscopy. Immunohistochemistry and western blot analysis were performed to measure proteins involved in apoptosis and autophagy.

RESULTS

Ligustrazine protected retinal cells from death in experimental glaucoma rats, which was not due to the lowering of IOP, but could be attributable to direct suppression of retinal cell apoptosis. In glaucoma rats, autophagy was markedly activated in retina cells, as evidenced by increased numbers of autophagosomes and the expression of autophagy-related proteins (ATG5 and LC3-II/I). Notably, such alterations in glaucoma rats were almost completely reversed by ligustrazine. The suppressive effects of ligustrazine on apoptosis and autophagy of retina cells were markedly attenuated by the mTOR inhibitor rapamycin or the PI3K inhibitor Ly294002. Additionally, ligustrazine significantly increased the protein levels of phosphorylated PI3K (p-PI3K), protein kinase B (p-Akt), and mTOR (p-mTOR) in glaucoma rats, whereas such increases were attenuated by rapamycin or Ly294002.

CONCLUSIONS

These results demonstrate that ligustrazine is protective in experimental glaucoma by inhibiting autophagy via the activation of the PI3K-Akt/mTOR pathway, providing compelling evidence that ligustrazine is potentially therapeutic for patients with glaucoma.

Berberine ameliorates vascular dysfunction by a global modulation of lncRNA and mRNA expression profiles in hypertensive mouse aortae

Objective

The current study investigated the mechanism underlying the therapeutic effects of berberine in the vasculature in hypertension.

Methods

Angiotensin II (Ang II)-loaded osmotic pumps were implanted in C57BL/6J mice with or without berberine administration. Mouse aortae were suspended in myograph for force measurement. Microarray technology were performed to analyze expression profiles of lncRNAs and mRNAs in the aortae. These dysregulated expressions were then validated by qRT-PCR. LncRNA-mRNA co-expression network was constructed to reveal the specific relationships.

Results

Ang Ⅱ resulted in a significant increase in the blood pressure of mice, which was suppressed by berberine. The impaired endothelium-dependent aortic relaxation was restored in hypertensive mice. Microarray data revealed that 578 lncRNAs and 554 mRNAs were up-regulated, while 320 lncRNAs and 377 mRNAs were down-regulated in the aortae by Ang Ⅱ; both were reversed by berberine treatment. qRT-PCR validation results of differentially expressed genes (14 lncRNAs and 6 mRNAs) were completely consistent with the microarray data. GO analysis showed that these verified differentially expressed genes were significantly enriched in terms of “cellular process”, “biological regulation” and “regulation of biological process”, whilst KEGG analysis identified vascular function-related pathways including cAMP signaling pathway, cGMP-PKG signaling pathway, and calcium signaling pathway etc. Importantly, we observed that lncRNA ENSMUST00000144849, ENSMUST00000155383, and AK041185 were majorly expressed in endothelial cells.

Conclusion

The present results suggest that the five lncRNAs ENSMUST00000144849, NR_028422, ENSMUST00000155383, AK041185, and uc.335+ might serve critical regulatory roles in hypertensive vasculature by targeting pivotal mRNAs and subsequently affecting vascular function-related pathways. Moreover, these lncRNAs were modulated by berberine, therefore providing the novel potential therapeutic targets of berberine in hypertension. Furthermore, lncRNA ENSMUST00000144849, ENSMUST00000155383, and AK041185 might be involved in the preservation of vascular endothelial cell function.

Neuroprotective effect of the somatostatin receptor 5 agonist L-817,818 on retinal ganglion cells in experimental glaucoma

Somatostatin plays important roles in modulating neuronal functions by activating the five specific G-protein coupled receptors (sst1-sst5). Previous studies have demonstrated that sst5 were expressed in retinal ganglion cells (RGCs) and sst5 agonist attenuated the α-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid-induced retinal neurotoxicity. In this study, we investigated effects and underlying mechanisms of the sst5 agonist L-817,818 on RGC injury induced by elevated intraocular pressure (COH) in experimental glaucoma. Our results showed that intraperitoneal administration of L-817,818 significantly reduced RGC loss and decreased the number of terminal deoxynucleotidyl transferase mediated dUTP nick-end labeling (TUNEL)-positive RGCs in COH retinas, suggesting that L-817,818 may attenuate RGC apoptosis. Consistently, in COH retinas with L-817,818 administration, both the down-regulated mRNA and protein levels of anti-apoptotic Bcl-2 and the up-regulated mRNA and protein levels of pro-apoptotic Bax were partially reversed. L-817,818 administration downregulated the expression of apoptosis-related proteins caspase-9 and caspase-3 in COH retinas. In addition, L-817,818 administration reduced the concentrations of reactive oxygen species/reactive nitrogen species and malondialdehyde, and ameliorated the functions of mitochondrial respiratory chain complex (MRCC). Our results imply that administration of the sst5 agonist L-817,818 reduces RGC loss in COH rats through decreasing RGC apoptosis, which is mediated by regulating Bcl-2/Bax balance, reducing oxidative stress and rescuing activities of MRCC. Activation of sst5 may provide neuroprotective roles for RGCs in glaucoma.