Minocycline inhibits PARP‑1 expression and decreases apoptosis in diabetic retinopathy

Minocycline and Diacetyl Minocycline Eye Drops Reduce Ocular Neovascularization in Mice

Purpose

To evaluate the efficacy of minocycline and a novel, modified minocycline analogue that lacks antimicrobial action, diacetyl minocycline (DAM), on choroidal neovascularization (CNV) in mice of both sexes.

Methods

CNV was induced via laser injury in female and male C57BL/6J mice. Minocycline, DAM, or saline was administered via topical eye drops twice a day for 2 weeks starting the day after laser injury. CNV volume was measured using immunohistochemistry labeling and confocal microscopy.

Results

Minocycline reduced lesion volume by 79% (P ≤ 0.0004) in female and male mice. DAM reduced lesion volume by 73% (P ≤ 0.001) in female and male mice. There was no significant difference in lesion volume between minocycline and DAM treatment groups or between female and male mice.

Conclusions

Both minocycline and DAM eye drops significantly reduced laser-induced CNV lesion volume in female and male mice. While oral tetracyclines have been shown to mitigate pathologic neovascularization in both preclinical studies and clinical trials, the present data are the first to suggest that tetracycline derivatives may be effective to reduce pathologic CNV when administered via topical eye drops. However, the action is unrelated to antimicrobial action. Targeted delivery of these medications via eye drops may reduce the potential for systemic side effects.

Translational Relevance

Topical administration of minocycline and/or DAM via eye drops may represent a novel therapeutic strategy for disorders involving pathologic CNV.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.

UPRmt activation improves pathological alterations in cellular models of mitochondrial diseases

Background

Mitochondrial diseases represent one of the most common groups of genetic diseases. With a prevalence greater than 1 in 5000 adults, such diseases still lack effective treatment. Current therapies are purely palliative and, in most cases, insufficient. Novel approaches to compensate and, if possible, revert mitochondrial dysfunction must be developed.

Results

In this study, we tackled the issue using as a model fibroblasts from a patient bearing a mutation in the GFM1 gene, which is involved in mitochondrial protein synthesis. Mutant GFM1 fibroblasts could not survive in galactose restrictive medium for more than 3 days, making them the perfect screening platform to test several compounds. Tetracycline enabled mutant GFM1 fibroblasts survival under nutritional stress. Here we demonstrate that tetracycline upregulates the mitochondrial Unfolded Protein Response (UPR^mt), a compensatory pathway regulating mitochondrial proteostasis. We additionally report that activation of UPR^mt improves mutant GFM1 cellular bioenergetics and partially restores mitochondrial protein expression.

Conclusions

Overall, we provide compelling evidence to propose the activation of intrinsic cellular compensatory mechanisms as promising therapeutic strategy for mitochondrial diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-022-02331-8.

The Molecular Mechanism of Long Non-Coding RNA (LncRNA) Regulation of Notch Signaling in Glucose-Induced Apoptosis of Human Retinal Vascular Endothelial Cell

Diabetes, a global health concern, affects the health of more than 500 million adults. The absence of Notch protein can cause an imbalance in the retinal vascular environment and cause retinal vascular disease. Long noncoding RNA (lncRNA) is known to be involved in the regulation of many signaling pathways. We hope to understand the specific mechanism of apoptosis in retinal vascular endothelial cells (RVECs) by exploring the regulatory effect of lncRNA on the Notch pathway. In this study, we found that RVECs treated with glucose showed increased levels of Notch transcript and protein expression. The lentiviral interference with Notch RNAi reversed this response. When Notch activity decreased, oxidative stress also decreased, accompanied by increased levels of Caspase-9 and Caspase-3 and an increased rate of apoptosis. Therefore, we believe that Notch is involved in the development of diabetic retinopathy and loss of expression promotes apoptosis of human RVECs. By inhibiting the Notch pathway, lncRNA promotes apoptosis of human RVECs in a high-glucose environment.

Neurovascular unit in diabetic retinopathy: pathophysiological roles and potential therapeutical targets

Diabetic retinopathy (DR), one of the common complications of diabetes, is the leading cause of visual loss in working-age individuals in many industrialized countries. It has been traditionally regarded as a purely microvascular disease in the retina. However, an increasing number of studies have shown that DR is a complex neurovascular disorder that affects not only vascular structure but also neural tissue of the retina. Deterioration of neural retina could precede microvascular abnormalities in the DR, leading to microvascular changes. Furthermore, disruption of interactions among neurons, vascular cells, glia and local immune cells, which collectively form the neurovascular unit, is considered to be associated with the progression of DR early on in the disease. Therefore, it makes sense to develop new therapeutic strategies to prevent or reverse retinal neurodegeneration, neuroinflammation and impaired cell-cell interactions of the neurovascular unit in early stage DR. Here, we present current perspectives on the pathophysiology of DR as a neurovascular disease, especially at the early stage. Potential novel treatments for preventing or reversing neurovascular injuries in DR are discussed as well.

Retinal Inflammation, Cell Death and Inherited Retinal Dystrophies

Inherited retinal dystrophies (IRDs) are a group of retinal disorders that cause progressive and severe loss of vision because of retinal cell death, mainly photoreceptor cells. IRDs include retinitis pigmentosa (RP), the most common IRD. IRDs present a genetic and clinical heterogeneity that makes it difficult to achieve proper treatment. The progression of IRDs is influenced, among other factors, by the activation of the immune cells (microglia, macrophages, etc.) and the release of inflammatory molecules such as chemokines and cytokines. Upregulation of tumor necrosis factor alpha (TNFα), a pro-inflammatory cytokine, is found in IRDs. This cytokine may influence photoreceptor cell death. Different cell death mechanisms are proposed, including apoptosis, necroptosis, pyroptosis, autophagy, excessive activation of calpains, or parthanatos for photoreceptor cell death. Some of these cell death mechanisms are linked to TNFα upregulation and inflammation. Therapeutic approaches that reduce retinal inflammation have emerged as useful therapies for slowing down the progression of IRDs. We focused this review on the relationship between retinal inflammation and the different cell death mechanisms involved in RP. We also reviewed the main anti-inflammatory therapies for the treatment of IRDs.

Minocycline reduces inflammatory response and cell death in a S100B retina degeneration model

BACKGROUND

Previous studies noted that intravitreal injection of S100B triggered a glaucoma-like degeneration of retina and optic nerve as well as microglia activation after 14 days. The precise role of microglia in our intravitreal S100B model is still unclear. Hence, microglia were inhibited through minocycline. The aim is to investigate whether microglia have a significant influence on the degeneration process or whether they are only a side effect in the model studied here.

METHODS

Minocycline was applied daily in rats by intraperitoneal injection using two different concentrations (13.5 mg/kg body weight, 25 mg/kg body weight). One day after treatment start, S100B or PBS was intravitreally injected in one eye per rat. The naïve groups received no injections. This resulted in a total of five groups (naïve n = 14, PBS n = 14, S100B n = 13, 13.5 mg/kg mino n = 15, 25 mg/kg mino n = 15). At day 14, electroretinogram measurements were performed, followed by immunofluorescence and label-free quantitative proteomics analysis. The focus of these investigations was on the survival of RGCs as well as their axons, the response of the microglia, and the identification of further pathological modes of action of S100B.

RESULTS

The best signal transmission was detected via ERG in the 13.5 mg/kg mino group. The inhibition of the microglia protected optic nerve neurofilaments and decreased the negative impact of S100B on RGCs. However, the minocycline treatment could not trigger complete protection of RGCs. Furthermore, in retina and optic nerve, the minocycline treatment reduced the number and activity of S100B-triggered microglia in a concentration-dependent manner. Proteomics analysis showed that S100B application led to numerous metabolic functions and cellular stress, mainly an increased inflammatory response, glycolysis, and mitochondrial dysfunction, which caused oxidative stress in the retina. Importantly, the protective capability of lower dose of minocycline was unraveled by suppressing the apoptotic, inflammatory, and the altered metabolic processes caused by S100B insult in the retina.

CONCLUSION

Intravitreally injected S100B not only led to a pro-inflammatory microglial reaction, but also a mitochondrial and metabolic dysfunction. Also, these results suggest that an excessive microglial response may be a significant degenerative factor, but not the only trigger for increased cell death.

A combination of inhibiting microglia activity and remodeling gut microenvironment suppresses the development and progression of experimental autoimmune uveitis

Noninfectious (autoimmune and immune-mediated) uveitis is an ocular inflammatory disease which can lead to blindness in severe cases. Due to the potential side effects of first-line drugs for clinical uveitis, novel drugs and targets against uveitis are still urgently needed. In the present study, using rat experimental autoimmune uveitis (EAU) model, we first found that minocycline treatment can substantially inhibit the development of EAU and improve the retinal function by suppressing the retinal microglial activation, and block the infiltration of inflammatory cells, including Th17, into the retina by decreasing the major histocompatibility complex class II (MHC II) expression in resident and infiltrating cells. Moreover, we demonstrated that minocycline treatment can remodel the gut microenvironment of EAU rats by restoring the relative abundance of Ruminococcus bromii, Streptococcus hyointestinalis, and Desulfovibrio sp. ABHU2SB and promoting a functional shift in the gut via reversing the levels of L-proline, allicin, aceturic acid, xanthine, and leukotriene B4, and especially increasing the production of propionic acid, histamine, and pantothenic acid. At last, we revealed that minocycline treatment can significantly attenuate the progression of EAU after inflammation onset, which may be explained by the role of minocycline in the remodeling of the gut microenvironment since selective elimination of retinal microglia on the later stages of EAU was shown to have little effect. These data clearly demonstrated that inhibition of microglial activation and remodeling of the gut microenvironment can suppress the development and progression of experimental autoimmune uveitis. Considering the excellent safety profile of minocycline in multiple clinical experiments, we suggest that minocycline may have therapeutic implications for clinical uveitis.

Differential effects of minocycline on microvascular complications in murine models of type 1 and type 2 diabetes

Diabetes is a global healthcare problem associated with enormous healthcare and personal costs. Despite glucose lowering agents that control glycaemia, both type 1 (T1D) and type (T2D) diabetes patients often develop microvascular complications that increase morbidity and mortality. Current interventions rely on careful glycemic control and healthy lifestyle choices, but these are ineffective at reversing or completely preventing the major microvascular complications, diabetic peripheral neuropathy (DPN), diabetic retinopathy (DR), and diabetic kidney disease (DKD). Minocycline, a tetracycline antibiotic with anti-inflammatory and anti-apoptotic properties, has been proposed as a protective agent in diabetes. However, there are no reported studies evaluating the therapeutic efficacy of minocycline in T1D and T2D models for all microvascular complications (DPN, DR, and DKD). Therefore, we performed metabolic profiling in streptozotocin-induced T1D and db/db T2D models and compared the efficacy of minocycline in preventing complications to that of insulin and pioglitazone in both models. Minocycline partially ameliorated DR and DKD in T1D and T2D animals, but was less effective than insulin or pioglitazone, and failed to improve DPN in either model. These results suggest that minocycline is unlikely to improve outcomes beyond that achieved with current available therapies in patients with T1D or T2D associated microvascular complications.

Neuroprotective effects of minocycline on focal cerebral ischemia injury: a systematic review

To review the neuroprotective effects of minocycline in focal cerebral ischemia in animal models. By searching in the databases of PubMed, ScienceDirect, and Scopus, and considering the inclusion and exclusion criteria of the study. Studies were included if focal cerebral ischemia model was performed in mammals and including a control group that has been compared with a minocycline group. Written in languages other than English; duplicate data; in vitro studies and combination of minocycline with other neuroprotective agents were excluded. Neurological function of patients was assessed by National Institute of Health Stroke Scale, modified Rankin Scale, and modified Barthel Index. Neuroprotective effects were assessed by detecting the expression of inflammatory cytokines. We examined 35 papers concerning the protective effects of minocycline in focal cerebral ischemia in animal models and 6 clinical trials which had evaluated the neuroprotective effects of minocycline in ischemic stroke. These studies revealed that minocycline increases the viability of neurons and decreases the infarct volume following cerebral ischemia. The mechanisms that were reported in these studies included anti-inflammatory, antioxidant, as well as anti-apoptotic effects. Minocycline also increases the neuronal regeneration following cerebral ischemia. Minocycline has considerable neuroprotective effects against cerebral ischemia-induced neuronal damages. However, larger clinical trials may be required before using minocycline as a neuroprotective drug in ischemic stroke.

Microglia in Retinal Degeneration

The retina is a complex tissue with multiple cell layers that are highly ordered. Its sophisticated structure makes it especially sensitive to external or internal perturbations that exceed the homeostatic range. This necessitates the continuous surveillance of the retina for the detection of noxious stimuli. This task is mainly performed by microglia cells, the resident tissue macrophages which confer neuroprotection against transient pathophysiological insults. However, under sustained pathological stimuli, microglial inflammatory responses become dysregulated, often worsening disease pathology. In this review, we provide an overview of recent studies that depict microglial responses in diverse retinal pathologies that have degeneration and chronic immune reactions as key pathophysiological components. We also discuss innovative immunomodulatory therapy strategies that dampen the detrimental immunological responses to improve disease outcome.

Modulation of three key innate immune pathways for the most common retinal degenerative diseases

This review highlights the role of three key immune pathways in the pathophysiology of major retinal degenerative diseases including diabetic retinopathy, age‐related macular degeneration, and rare retinal dystrophies. We first discuss the mechanisms how loss of retinal homeostasis evokes an unbalanced retinal immune reaction involving responses of local microglia and recruited macrophages, activity of the alternative complement system, and inflammasome assembly in the retinal pigment epithelium. Presenting these key mechanisms as complementary targets, we specifically emphasize the concept of immunomodulation as potential treatment strategy to prevent or delay vision loss. Promising molecules are ligands for phagocyte receptors, specific inhibitors of complement activation products, and inflammasome inhibitors. We comprehensively summarize the scientific evidence for this strategy from preclinical animal models, human ocular tissue analyses, and clinical trials evolving in the last few years.

Diabetic retinopathy: a complex pathophysiology requiring novel therapeutic strategies

INTRODUCTION

Diabetic retinopathy (DR) is the leading cause of vision loss in the working age population of the developed world. DR encompasses a complex pathology, and one that is reflected in the variety of currently available treatments, which include laser photocoagulation, glucocorticoids, vitrectomy and agents which neutralize vascular endothelial growth factor (VEGF). Whilst these options demonstrate modest clinical benefits, none is yet to fully attenuate clinical progression or reverse damage to the retina. This has led to an interest in developing novel therapies for the condition, such as mediators of angiopoietin signaling axes, immunosuppressants, nonsteroidal anti-inflammatory drugs (NSAIDs), oxidative stress inhibitors and vitriol viscosity inhibitors. Further, preclinical research suggests that gene therapy treatment for DR could provide significant benefits over existing treatments options.

AREAS COVERED

Here we review the pathophysiology of DR and provide an overview of currently available treatments. We then outline recent advances made towards improved patient outcomes and highlight the potential of the gene therapy paradigm to revolutionize DR management.

EXPERT OPINION

Whilst significant progress has been made towards our understanding of DR, further research is required to enable the development of a detailed spatiotemporal model of the disease. In addition, we hope that improvements in our knowledge of the condition facilitate therapeutic innovations that continue to address unmet medical need and improve patient outcomes, with a focus on the development of targeted medicines.

Low-dose minocycline mediated neuroprotection on retinal ischemia-reperfusion injury of mice

PURPOSE

The aim of this study was to investigate the effect of minocycline (MC) on the survival of retinal ganglion cells (RGCs) in an ischemic-reperfusion (I/R) injury model of retinal degeneration.

METHODS

Retinal I/R injury was induced in the left eye of mice for 60 min by maintaining intraocular pressure at 90 mmHg. Low- or high-dose MC (20 or 100 mg/kg, respectively) was administered by intravenous injection at 5 min after the retinal ischemic insult and then administered once daily until the mice were euthanized. RGCs and microglial cells were counted using immunofluorescence staining. Functional changes in the RGCs were evaluated using electroretinography. The visual function was assessed using an optokinetic test.

RESULTS

The data demonstrated that the effect of MC was dose dependent. Low-dose MC showed protective effects, with reduced RGC loss and microglial activation, while the high-dose MC showed damage effects, with more RGC loss and microglial activation when compared with the vehicle group. The electroretinography and optokinetic test results were consistent with the morphologic observations.

CONCLUSIONS

These data suggested that appropriate concentrations of MC can protect the retina against retinal ischemic-reperfusion injury, while excessive MC has detrimental effects.

The Beta Adrenergic Receptor Blocker Propranolol Counteracts Retinal Dysfunction in a Mouse Model of Oxygen Induced Retinopathy: Restoring the Balance between Apoptosis and Autophagy

In a mouse model of oxygen induced retinopathy (OIR), beta adrenergic receptor (BAR) blockade has been shown to recover hypoxia-associated retinal damages. Although the adrenergic signaling is an important regulator of apoptotic and autophagic processes, the role of BARs in retinal cell death remains to be elucidated. The present study was aimed at investigating whether ameliorative effects of BAR blockers may occur through their coordinated action on apoptosis and autophagy. To this aim, retinas from control and OIR mice untreated or treated with propranolol, a non-selective BAR1/2 blocker, were characterized in terms of expression and localization of apoptosis and autophagy markers. The effects of propranolol on autophagy signaling were also evaluated and specific autophagy modulators were used to get functional information on the autophagic effects of BAR antagonism. Finally, propranolol effects on neurodegenerative processes were associated to an electrophysiological investigation of retinal function by recording electroretinogram (ERG). We found that retinas of OIR mice are characterized by increased apoptosis and decreased autophagy, while propranolol reduces apoptosis and stimulates autophagy. In particular, propranolol triggers autophagosome formation in bipolar, amacrine and ganglion cells that are committed to die by apoptosis in response to hypoxia. Also our data argue that propranolol, through the inhibition of the Akt-mammalian target of rapamycin pathway, activates autophagy which decreases retinal cell death. At the functional level, propranolol recovers dysfunctional ERG by recovering the amplitude of a- and b-waves, and oscillatory potentials, thus indicating an efficient restoring of retinal transduction. Overall, our results demonstrate that BAR1/2 are key regulators of retinal apoptosis/autophagy, and that BAR1/2 blockade leads to autophagy-mediated neuroprotection. Reinstating the balance between apoptotic and autophagic machines may therefore be viewed as a future goal in the treatment of retinopathies.

Quinalizarin exerts an anti-tumour effect on lung cancer A549 cells by modulating the Akt, MAPK, STAT3 and p53 signalling pathways

Quinalizarin may be a potential chemical agent for cancer therapy, as it exerts anti‑tumour effects against a variety of different types of cancer. However, the underlying regulatory mechanism and signalling pathways of quinalizarin in lung cancer cells remains unknown. The present study sought to investigate the effects of quinalizarin on proliferation, apoptosis and reactive oxygen species (ROS) generation in lung cancer. MTT assays were used to evaluate the effects of quinalizarin on the viability of lung cancer A549, NCI‑H460 and NCI‑H23 cells. Flow cytometry was employed to evaluate the effects of quinalizarin on the cell cycle, apoptosis and ROS generation in A549 cells. Western blotting was performed to detect cell cycle and apoptosis‑associated protein expression levels in A549 cells. Quinalizarin inhibited A549, NCI‑H460 and NCI‑H23 cell proliferation and induced A549 cell cycle arrest at the G0/G1 phase. Quinalizarin induced apoptosis by upregulating the expression of B‑cell lymphoma 2 (Bcl‑2)‑associated agonist of cell death, cleaved‑caspase‑3 and cleaved‑poly (adenosine diphosphate‑ribose) polymerase, and downregulating the expression of Bcl‑2. Furthermore, quinalizarin activated mitogen‑activated protein kinase (MAPK) and p53, and inhibited the protein kinase B and signal transducer and activator of transcription‑3 (STAT3) signalling pathways. In addition, quinalizarin increased ROS generation. The ROS scavenger N‑acetyl‑L‑cysteine restored quinalizarin‑induced cell apoptosis, and inactivated the MAPK and STAT3 signalling pathways. The results of the present study demonstrated that quinalizarin induces G0/G1 phase cell cycle arrest and apoptosis via ROS mediated‑MAPK and STAT3 signalling pathways.

Inhibiting the microglia activation improves the spatial memory and adult neurogenesis in rat hippocampus during 48 h of sleep deprivation

BACKGROUND

Sleep deprivation (SD) leads to cognitive impairment. Neuroinflammation could be a significant contributing factor in the same. An increase in regional brain pro-inflammatory cytokines induces cognitive deficits, however, the magnitude of the effect under SD is not apparent. It is plausible that microglia activation could be involved in the SD-induced cognitive impairment by modulation of neuronal cell proliferation, differentiation, and brain-derived neuronal factor (BDNF) level. The present study aimed to evaluate the possible beneficial effect of minocycline in amelioration of spatial memory decline during SD by its anti-inflammatory and neuroprotective actions. We scrutinized the effect of minocycline on the inflammatory cytokine levels associated with glial cells (microglia and astrocytes) activity and neurogenesis markers crucial for behavioral functions during SD.

METHODS

Male Sprague-Dawley rats weighing 230-250 g were sleep deprived for 48 h using automated cage shaking apparatus. The spatial memory was tested using MWM apparatus immediately after completion of SD with and without minocycline. The animals were euthanized, blood was collected, and brain was extracted for neuroinflammation and neurogenesis studies. The set of experiments were also conducted with use of temozolomide, a neurogenesis blocker.

RESULTS

Minocycline treatment increased the body weight, food intake, and spatial memory performance which declined during SD. It reduced the pro-inflammatory and increased the anti-inflammatory cytokine levels in hippocampus and plasma and inhibited the reactive gliosis in the hippocampus evidenced by improved cell count, morphology, and immunoreactivity. Additionally, minocycline administration promoted neurogenesis at different stages: proliferation (BrdU, Ki-67), differentiation (DCX) cells and growth factor (BDNF). However, no significant change was observed in maturation (NeuN) during SD. In addition, molecules related to behavior, inflammation, and neurogenesis were shown to be more affected after temozolomide administration during SD, and changes were restored with minocycline treatment. We observed a significant correlation of neurogenesis with microglial activation, cytokine levels, and spatial memory during SD.

CONCLUSION

The present study demonstrated that the SD-induced decline in spatial memory, neuronal cells proliferation, differentiation, and BDNF level could be attributed to upregulation of neuroinflammatory molecules, and minocycline may be an effective intervention to counteract these changes. Microglial activation is involved in SD-induced changes in inflammatory molecules, neurogenesis, and spatial memory.

Impact of minocycline on vascularization and visual function in an immature mouse model of ischemic retinopathy

The role of microglia in the pathophysiology of ischemic retinal diseases has been extensively studied. Retinal microglial activation may be correlated with retinal neovascularization in oxygen-induced retinopathy (OIR), an animal model that has been widely used in retinopathy of prematurity (ROP) research. Minocycline is an antibiotic that decreases microglial activation following hyperoxic and hypoxic-ischemic phases in neonatal rodents. Here, we investigated the effects of minocycline on vascularization and visual function. In our results, we found that after the administration of minocycline, microglial reactivity was reduced in the retina, which was accompanied by an increase in the avascular area at P12, P14 and P17. Although microglial reactivity was reduced at P17, minocycline treatment did not attenuate retinal neovascularization. A changing trend in microglial number was observed, and the apoptosis and proliferation states on different days partly contributed to this change. Further study also revealed that although minocycline downregulated the levels of proinflammatory factors, visual function appeared to be significantly worsened. Collectively, we demonstrated that minocycline disturbed the physiological vascularization of the avascular area and exacerbated visual dysfunction, indicating that minocycline may not be an effective drug and may even be detrimental for the treatment of ischemic retinopathy in immature mammals.

Opportunities for the repurposing of PARP inhibitors for the therapy of non-oncological diseases

The recent clinical availability of the PARP inhibitor olaparib (Lynparza) opens the door for potential therapeutic repurposing for non-oncological indications. Considering (a) the preclinical efficacy data with PARP inhibitors in non-oncological diseases and (b) the risk-benefit ratio of treating patients with a compound that inhibits an enzyme that has physiological roles in the regulation of DNA repair, we have selected indications, where (a) the severity of the disease is high, (b) the available therapeutic options are limited, and (c) the duration of PARP inhibitor administration could be short, to provide first-line options for therapeutic repurposing. These indications are as follows: acute ischaemic stroke; traumatic brain injury; septic shock; acute pancreatitis; and severe asthma and severe acute lung injury. In addition, chronic, devastating diseases, where alternative therapeutic options cannot halt disease development (e.g. Parkinson's disease, progressive multiple sclerosis or severe fibrotic diseases), should also be considered. We present a preclinical and clinical action plan for the repurposing of PARP inhibitors.

LINKED ARTICLES

This article is part of a themed section on Inventing New Therapies Without Reinventing the Wheel: The Power of Drug Repurposing. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.2/issuetoc.

Minocycline targets multiple secondary injury mechanisms in traumatic spinal cord injury

Minocycline hydrochloride (MH), a semi-synthetic tetracycline derivative, is a clinically available antibiotic and anti-inflammatory drug that also exhibits potent neuroprotective activities. It has been shown to target multiple secondary injury mechanisms in spinal cord injury, via its anti-inflammatory, anti-oxidant, and anti-apoptotic properties. The secondary injury mechanisms that MH can potentially target include inflammation, free radicals and oxidative stress, glutamate excitotoxicity, calcium influx, mitochondrial dysfunction, ischemia, hemorrhage, and edema. This review discusses the potential mechanisms of the multifaceted actions of MH. Its anti-inflammatory and neuroprotective effects are partially achieved through conserved mechanisms such as modulation of p38 mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3K)/Akt signaling pathways as well as inhibition of matrix metalloproteinases (MMPs). Additionally, MH can directly inhibit calcium influx through the N-methyl-D-aspartate (NMDA) receptors, mitochondrial calcium uptake, poly(ADP-ribose) polymerase-1 (PARP-1) enzymatic activity, and iron toxicity. It can also directly scavenge free radicals. Because it can target many secondary injury mechanisms, MH treatment holds great promise for reducing tissue damage and promoting functional recovery following spinal cord injury.

Moving Past Anti-VEGF: Novel Therapies for Treating Diabetic Retinopathy

Diabetic retinopathy is the leading cause of blindness in working age adults, and is projected to be a significant future health concern due to the rising incidence of diabetes. The recent advent of anti-vascular endothelial growth factor (VEGF) antibodies has revolutionized the treatment of diabetic retinopathy but a significant subset of patients fail to respond to treatment. Accumulating evidence indicates that inflammatory cytokines and chemokines other than VEGF may contribute to the disease process. The current review examines the presence of non-VEGF cytokines in the eyes of patients with diabetic retinopathy and highlights mechanistic pathways in relevant animal models. Finally, novel drug targets including components of the kinin-kallikrein system and emerging treatments such as anti-HPTP (human protein tyrosine phosphatase) β antibodies are discussed. Recognition of non-VEGF contributions to disease pathogenesis may lead to novel therapeutics to enhance existing treatments for patients who do not respond to anti-VEGF therapies.