Summary
Background
The role of skin microbiota in acne remains to be fully elucidated. Initial culture‐based investigations were hampered by growth rate and selective media bias. Even with less ...biased genomic methods, sampling, lysis and methodology, the task of describing acne pathophysiology remains challenging. Acne occurs in sites dominated by Cutibacterium acnes (formerly Propionibacterium acnes) and Malassezia species, both of which can function either as commensal or pathogen.
Objectives
This article aims to review the current state of the art of the microbiome and acne.
Methods
The literature regarding the microbiome and acne was reviewed.
Results
It remains unclear whether there is a quantitative difference in microbial community distribution, making it challenging to understand any community shift from commensal to pathogenic nature. It is plausible that acne involves (i) change in the distribution of species/strains, (ii) stable distribution with pathogenic alteration in response to internal (intermicrobe) or external stimuli (host physiology or environmental) or (iii) a combination of these factors.
Conclusions
Understanding physiological changes in bacterial species and strains will be required to define their specific roles, and identify any potential intervention points, in acne pathogenesis and treatment. It will also be necessary to determine whether any fungal species are involved, and establish whether they play a significant role. Further investigation using robust, modern analytic tools in longitudinal studies with a large number of participants, may make it possible to determine whether the microbiota plays a causal role, is primarily involved in exacerbation, or is merely a bystander. It is likely that the final outcome will show that acne is the result of complex microbe–microbe and community–host interplay.
What's already known about this topic?
Acne is among the most common skin disorders, but little is known about its aetiology.
While a role for the skin microbiome is postulated, its involvement remains unclear.
What does this study add?
This review outlines what is known about the role of skin microbes in acne.
This article describes the use of multiple methodologies for sampling and analysis of microbiology in acne studies.
Positives and negatives of each methodology are reviewed and key needs are defined.
Linked Editorial: Van Steensel. Br J Dermatol 2019; 181:647–648.
Linked Comment: Ochsendorf. Br J Dermatol 2019; 181:657–658.
Highlights • We examine changes of over 1000 miRNAs in human neural cells by Toxoplasma infection. • MiR-132 is highly upregulated by all three prototype Toxoplasma strains. • Dopamine receptor ...signaling is predicted to be the most regulated by miR-132. • Several members of dopamine receptor pathway have been repressed in mice infection. • An elevation in the concentrations of dopamine and its metabolites occurred.
Stroke is a major cause of mortality and morbidity worldwide. Extracellular glutamate accumulation leading to overstimulation of the ionotropic glutamate receptors mediates neuronal injury in stroke ...and in neurodegenerative disorders. Here we show that miR-223 controls the response to neuronal injury by regulating the functional expression of the glutamate receptor subunits GluR2 and NR2B in brain. Overexpression of miR-223 lowers the levels of GluR2 and NR2B by targeting 3′-UTR target sites (TSs) in GluR2 and NR2B, inhibits NMDA-induced calcium influx in hippocampal neurons, and protects the brain from neuronal cell death following transient global ischemia and excitotoxic injury. MiR-223 deficiency results in higher levels of NR2B and GluR2, enhanced NMDA-induced calcium influx, and increased miniature excitatory postsynaptic currents in hippocampal neurons. In addition, the absence of MiR-223 leads to contextual, but not cued memory deficits and increased neuronal cell death following transient global ischemia and excitotoxicity. These data identify miR-223 as a major regulator of the expression of GluR2 and NR2B, and suggest a therapeutic role for miR-223 in stroke and other excitotoxic neuronal disorders.
c-Abl is activated in the brain of Parkinson's disease (PD) patients and in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-intoxicated mice where it inhibits parkin through tyrosine ...phosphorylation leading to the accumulation of parkin substrates, and neuronal cell death. In the present study, we evaluated the in vivo efficacy of nilotinib, a brain penetrant c-Abl inhibitor, in the acute MPTP-induced model of PD. Our results show that administration of nilotinib reduces c-Abl activation and the levels of the parkin substrate, PARIS, resulting in prevention of dopamine (DA) neuron loss and behavioral deficits following MPTP intoxication. On the other hand, we observe no reduction in the tyrosine phosphorylation of parkin and the parkin substrate, AIMP2 suggesting that the protective effect of nilotinib may, in part, be parkin-independent or to the pharmacodynamics properties of nilotinib. This study provides a strong rationale for testing other brain permeable c-Abl inhibitors as potential therapeutic agents for the treatment of PD.
Poly(ADP-ribose) polymerase-1 (PARP-1) plays a pivotal role in multiple neurologic diseases by mediating caspase-independent cell death, which has recently been designated parthanatos to distinguish ...it from other forms of cell death such as apoptosis, necrosis and autophagy. Mitochondrial apoptosis-inducing factor (AIF) release and translocation to the nucleus is the commitment point for parthanatos. This process involves a pathogenic role of poly(ADP-ribose) (PAR) polymer. It generates in the nucleus and translocates to the mitochondria to mediate AIF release following lethal PARP-1 activation. PAR polymer itself is toxic to cells. Thus, PAR polymer signaling to mitochondrial AIF is the key event initiating the deadly crosstalk between the nucleus and the mitochondria in parthanatos. Targeting PAR-mediated AIF release could be a potential approach for the therapy of neurologic disorders.
Mitochondrial dynamics and mitophagy have been linked to cardiovascular and neurodegenerative diseases. Here, we demonstrate that the mitochondrial division dynamin Drp1 and the Parkinson's ...disease‐associated E3 ubiquitin ligase parkin synergistically maintain the integrity of mitochondrial structure and function in mouse heart and brain. Mice lacking cardiac Drp1 exhibited lethal heart defects. In Drp1KO cardiomyocytes, mitochondria increased their connectivity, accumulated ubiquitinated proteins, and decreased their respiration. In contrast to the current views of the role of parkin in ubiquitination of mitochondrial proteins, mitochondrial ubiquitination was independent of parkin in Drp1KO hearts, and simultaneous loss of Drp1 and parkin worsened cardiac defects. Drp1 and parkin also play synergistic roles in neuronal mitochondrial homeostasis and survival. Mitochondrial degradation was further decreased by combination of Drp1 and parkin deficiency, compared with their single loss. Thus, the physiological importance of parkin in mitochondrial homeostasis is revealed in the absence of mitochondrial division in mammals.
Synopsis
In vivo analysis reveals a synergistic role of mitochondrial fission protein Drp1 and Parkinson's disease‐associated ligase parkin in the regulation of ubiquitination and degradation of mitochondria in the heart and brain.
Mitochondria divide in cardiomyocytes.
Drp1 deficiency causes mitochondrial dysfunction, lethal heart failure and neurodegeneration due to defects in mitophagy.
Mitochondria enlarge and accumulate ubiquitinated outer membrane proteins and mitophagy adaptor protein p62 independently of parkin.
Parkin is dispensable for mitochondrial respiration, heart function and neuronal survival in the presence of Drp1‐regulated mitophagy.
Simultaneous loss of Drp1 and parkin increases mitophagy defects.
In vivo analysis reveals a synergistic role of mitochondrial fission protein Drp1 and Parkinson's disease‐associated ligase parkin in the regulation of ubiquitination and degradation of mitochondria in the heart and brain.
The pathologic accumulation and aggregation of α-synuclein (α-syn) underlies Parkinson's disease (PD). The molecular mechanisms by which pathologic α-syn causes neurodegeneration in PD are not known. ...Here, we found that pathologic α-syn activates poly(adenosine 5'-diphosphate-ribose) (PAR) polymerase-1 (PARP-1), and PAR generation accelerates the formation of pathologic α-syn, resulting in cell death via parthanatos. PARP inhibitors or genetic deletion of PARP-1 prevented pathologic α-syn toxicity. In a feed-forward loop, PAR converted pathologic α-syn to a more toxic strain. PAR levels were increased in the cerebrospinal fluid and brains of patients with PD, suggesting that PARP activation plays a role in PD pathogenesis. Thus, strategies aimed at inhibiting PARP-1 activation could hold promise as a disease-modifying therapy to prevent the loss of dopamine neurons in PD.
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
Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1) and PARK2/Parkin mutations cause autosomal recessive forms of Parkinson's disease. Upon a loss of mitochondrial membrane ...potential ( $\Delta \Psi _m$ ) in human cells, cytosolic Parkin has been reported to be recruited to mitochondria, which is followed by a stimulation of mitochondrial autophagy. Here, we show that the relocation of Parkin to mitochondria induced by a collapse of $\Delta \Psi _m$ relies on PINK1 expression and that overexpression of WT but not of mutated PINK1 causes Parkin translocation to mitochondria, even in cells with normal $\Delta \Psi _m$ We also show that once at the mitochondria. Parkin is in close proximity to PINK1, but we find no evidence that Parkin catalyzes PINK1 ubiquitinationorthatPINKI phosphorylates Parkin. However, co-overexpression of Parkin and PINK1 collapses the normal tubular mitochondrial network into mitochondrial aggregates and/or large perinuclear clusters, many of which are surrounded by autophagic vacuoles. Our results suggest that Parkin, together with PINK1, modulates mitochondrial trafficking, especially to the perinuclear region, a subcellular area associated with autophagy. Thus by impairing this process, mutations in either Parkin or PINK1 may alter mitochondrial turnover which, in turn, may cause the accumulation of defective mitochondria and, ultimately, neurodegeneration in Parkinson's disease.
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