Consideration of T-cell profile in the examination of statin efficacy in inflammatory diseases, neurodegeneration, and neurocognitive performance.

Statins are a cornerstone in the medical management of cardiovascular disease, yet their efficacy varies greatly between individuals. In this commentary, we outline evidence for the role of CD4+CD28null T-cell expansion as a critical moderator of the effects of statins in preventing cardiovascular events via the reduction of pathological inflammation. Given this relationship, we argue that T-cell profiles should be considered as a patient characteristic in clinical and pre-clinical studies examining statin efficacy in other age- and inflammation-related pathologies. We discuss the implications this may have for studies of statin use in numerous disease processes - notably, dementia and neurocognitive dysfunction - and the potential for T-cell profiles to be used as a prognosticator for statin efficacy in rheumatoid arthritis, Alzheimer's disease, and multiple sclerosis.

Cellular rejuvenation protects neurons from inflammation mediated cell death.

In multiple sclerosis (MS), the invasion of the central nervous system by peripheral immune cells is followed by the activation of resident microglia and astrocytes. This cascade of events results in demyelination, which triggers neuronal damage and death. The molecular signals in neurons responsible for this damage are not yet fully characterized. In MS, retinal ganglion cell neurons (RGCs) of the central nervous system (CNS) undergo axonal injury and cell death. This phenomenon is mirrored in the experimental autoimmune encephalomyelitis (EAE) mouse model of MS. To understand the molecular landscape, we isolated RGCs from mice subjected to the EAE protocol. RNA-sequencing and ATAC-sequencing analyses were performed. Pathway analysis of the RNA-sequencing data revealed that RGCs displayed a molecular signature, similar to aged neurons, showcasing features of senescence. Single-nucleus RNA-sequencing analysis of neurons from human MS patients revealed a comparable senescence-like phenotype., which was supported by immunostaining RGCs in EAE mice. These changes include alterations to the nuclear envelope, modifications in chromatin marks, and accumulation of DNA damage. Transduction of RGCs with an Oct4 - Sox2 - Klf4 transgene to convert neurons in the EAE model to a more youthful epigenetic and transcriptomic state enhanced the survival of RGCs. Collectively, this research uncovers a previously unidentified senescent-like phenotype in neurons under pathological inflammation and neurons from MS patients. The rejuvenation of this aged transcriptome improved visual acuity and neuronal survival in the EAE model supporting the idea that age rejuvenation therapies and senotherapeutic agents could offer a direct means of neuroprotection in autoimmune disorders.

To grow and to stay, both controlled by RhoA: Opposing cellular effects on axon regeneration.

In this issue of Neuron, Stern et al. (2021) demonstrate that cell-type-specific ablation of RhoA differentially affects axon regeneration outcomes in spinal cord injury models. Their findings highlight the importance of considering cell-type-specific strategies to promote axon regeneration.

Decreasing Surgical Site Infections in Plastic Surgery: A Systematic Review and Meta-analysis of Level 1 Evidence.

BACKGROUND: Although many interventions are implemented to prevent surgical site infections (SSIs) in plastic surgery, their supporting evidence is inconsistent. OBJECTIVES: The goal of this study was to assess the efficacy of methods for decreasing SSIs in plastic surgery. METHODS: A systematic review and meta-analysis were performed to compare the effects of SSI prevention methods. All the studies were assessed for quality of evidence according to the GRADE assessment. RESULTS: Fifty Level 1 randomized controlled trials were included. The most common interventions for preventing SSIs were antibiotic prophylaxis, showering, prepping, draping, and the use of dressings. Current evidence suggests that antibiotic prophylaxis is largely unnecessary and overused in many plastic surgical procedures, with the exception of head and neck oncologic, oral craniofacial, and traumatic hand surgeries. CONCLUSIONS: Efficacy of antibiotic prophylaxis in plastic surgery is dependent on surgery type. There is a lack evidence that showering and prepping with chlorohexidine and povidone reduces SSIs.

Tau protein phosphorylation at Thr175 initiates fibril formation via accessibility of the N-terminal phosphatase-activating domain.

One of the neuropathological hallmarks of the tauopathies is the formation of neuronal cytoplasmic inclusions and fibrils of microtubule-associated tau protein (tau). The phosphorylation of Thr175 of tau (pThr175 tau) appears to be sufficient for fibril formation in vitro and in vivo, but the mechanism by which this initiates fibril formation is unknown. Using transient transfections of tau mutants into HEK293T cells, we determined that the phosphorylation of Thr175 leads to exposure of the tau N-terminal phosphatase-activating domain (PAD). The exposed PAD is known to interact with protein phosphatase-1 (PP1) resulting in glycogen synthase kinase 3ß (GSK3ß) activation. In vivo, a single traumatic controlled cortical injury in rats also resulted in the phosphorylation of Thr175 and increased exposure of tau PAD followed by pathological tau fibril formation. Taken together, these data suggest that neurotoxicity may be precipitated by phosphorylation at Thr175 and subsequent tau PAD exposure, GSK3ß activation and tau fibril formation. Cover Image for this issue: doi: 10.1111/jnc.14767.

Phosphorylation of Threonine 175 Tau in the Induction of Tau Pathology in Amyotrophic Lateral Sclerosis-Frontotemporal Spectrum Disorder (ALS-FTSD). A Review.

Approximately 50-60% of all patients with amyotrophic lateral sclerosis (ALS) will develop a deficit of frontotemporal function, ranging from frontotemporal dementia (FTD) to one or more deficits of neuropsychological, speech or language function which are collectively known as the frontotemporal spectrum disorders of ALS (ALS-FTSD). While the neuropathology underlying these disorders is most consistent with a widespread alteration in the metabolism of transactive response DNA-binding protein 43 (TDP-43), in both ALS with cognitive impairment (ALSci) and ALS with FTD (ALS-FTD; also known as MND-FTD) there is evidence for alterations in the metabolism of the microtubule associated protein tau. This alteration in tau metabolism is characterized by pathological phosphorylation at residue Thr175 (pThr175 tau) which in vitro is associated with activation of GSK3ß (pTyr216GSK3ß), phosphorylation of Thr231tau, and the formation of cytoplasmic inclusions with increased rates of cell death. This putative pathway of pThr175 induction of pThr231 and the formation of pathogenic tau inclusions has been recently shown to span a broad range of tauopathies, including chronic traumatic encephalopathy (CTE) and CTE in association with ALS (CTE-ALS). This pathway can be experimentally triggered through a moderate traumatic brain injury, suggesting that it is a primary neuropathological event and not secondary to a more widespread neuronal dysfunction. In this review, we discuss the neuropathological underpinnings of the postulate that ALS is associated with a tauopathy which manifests as a FTSD, and examine possible mechanisms by which phosphorylation at Thr175tau is induced. We hypothesize that this might lead to an unfolding of the hairpin structure of tau, activation of GSK3ß and pathological tau fibril formation through the induction of cis-Thr231 tau conformers. A potential role of TDP-43 acting synergistically with pathological tau metabolism is proposed.