TAR DNA-binding protein 43 (TDP-43) is a highly conserved nuclear RNA/DNA-binding protein involved in the regulation of RNA processing. The accumulation of TDP-43 aggregates in the central nervous system is a common feature of many neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), Alzheimer’s disease (AD), and limbic predominant age-related TDP-43 encephalopathy (LATE). Accumulating evidence suggests that prion-like spreading of aberrant protein aggregates composed of tau, amyloid-β, and α-synuclein is involved in the progression of neurodegenerative diseases such as AD and PD. Similar to those of prion-like proteins, pathological aggregates of TDP-43 can be transferred from cell-to-cell in a seed-dependent and self-templating manner. Here, we review clinical and experimental studies supporting the prion-like spreading of misfolded TDP-43 and discuss the molecular mechanisms underlying the propagation of these pathological aggregated proteins. The idea that misfolded TDP-43 spreads in a prion-like manner between cells may guide novel therapeutic strategies for TDP-43-associated neurodegenerative diseases.

Background Cytoplasmic inclusions of transactive response DNA binding protein of 43 kDa (TDP-43) in neurons and astrocytes are a feature of some neurodegenerative diseases, such as frontotemporal lobar degeneration with TDP-43 (FTLD-TDP) and amyotrophic lateral sclerosis (ALS). However, the role of TDP-43 in astrocyte pathology remains largely unknown. Methods To investigate whether TDP-43 overexpression in primary astrocytes could induce inflammation, we transfected primary astrocytes with plasmids encoding Gfp or TDP-43-Gfp. The inflammatory response and upregulation of PTP1B in transfected cells were examined using quantitative RT-PCR and immunoblot analysis. Neurotoxicity was analysed in a transwell coculture system of primary cortical neurons with astrocytes and cultured neurons treated with astrocyte-conditioned medium (ACM). We also examined the lifespan, performed climbing assays and analysed immunohistochemical data in pan-glial TDP-43-expressing flies in the presence or absence of a Ptp61f RNAi transgene. Results PTP1B inhibition suppressed TDP-43-induced secretion of inflammatory cytokines (interleukin 1 beta (IL-1β), interleukin 6 (IL-6) and tumour necrosis factor alpha (TNF-α)) in primary astrocytes. Using a neuron-astrocyte coculture system and astrocyte-conditioned media treatment, we demonstrated that PTP1B inhibition attenuated neuronal death and mitochondrial dysfunction caused by overexpression of TDP-43 in astrocytes. In addition, neuromuscular junction (NMJ) defects, a shortened lifespan, inflammation and climbing defects caused by pan-glial overexpression of TDP-43 were significantly rescued by downregulation of ptp61f (the Drosophila homologue of PTP1B) in flies. Conclusions These results indicate that PTP1B inhibition mitigates the neuronal toxicity caused by TDP-43-induced inflammation in mammalian astrocytes and Drosophila glial cells.

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Photodynamic therapy (PDT), consisting of photosensitizer, light, and oxygen has been used for the treatment of various diseases including cancers, microbial infections and skin disorders. In this study, we examined the anti-inflammatory effect of chlorin e6-mediated PDT in P. acnes-infected HaCaT cells using photosensitizer chlorin e6 (Ce6) and halogen light. The live and heat-killed P. acnes triggered an upregulation of inflammatory molecules such as iNOS, NO, and inflammatory cytokine in HaCaT cells and mouse model. Ce6-mediated PDT notably downregulated the expression of these inflammatory molecules in vitro and in vivo. Similarly, chlorin e6-mediated PDT was capable of regulating inflammatory response in both live and heat killed S. epidermidis exposed HaCaT cells. Moreover, phosphorylation of p38, JNK, and ERK were reduced by Ce6-mediated PDT. Ce6-mediated PDT also reduced the phosphorylation of IKKα/β, IĸBα and NFκB p65 in P. acnes-stimulated HaCaT cells. In addition, the dramatic increase in the nuclear translocation of NFκB p65 observed upon stimulation with P. acnes was markedly impaired by Ce6-based PDT. This is the first suggestion that Ce6-mediated PDT suppresses P. acnes-induced inflammation through modulating NFκB and MAPKs signaling pathways.

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