ApoE ε4 and IL-6-174G/C Polymorphism may Lead to Early Onset of Alzheimer's Disease with Atypical Presentation.

BACKGROUND: Alzheimer's disease (AD) is the most common cause of dementia. Although genetic mutations are known in rare familial form, exact cause of neurodegeneration in sporadic AD is still unknown. While ApoE ε4 and IL-6 C-174G/C patterns have been found to increase the risk of AD in Caucasians, the results are inconsistent in other ethnic groups. OBJECTIVE: The aim of this study was to evaluate the effect of ApoE and IL-6-174G/C polymorphisms among patients of AD in the Eastern part of India. MATERIALS AND METHODS: Consecutive patients of probable AD diagnosed as per National Institute on Aging-Alzheimer's Association (NIA-AA) criteria with age, gender, and education-matched healthy controls were recruited between December 2015 and September 2018. Patients were clinically evaluated and along with controls were genotyped for ApoE and IL-6-174G/C polymorphisms by the polymerase chain reaction method. RESULTS: A total 115 patients and 162 controls showed a similar pattern of ApoE and IL-6-174G/C polymorphism pattern. While ε3ε3 and GG patterns were the commonest, followed by ε3ε4 and GC pattern in ApoE and IL-6 respectively, the effect of ApoE ε4 and IL-6-174 C allele on AD symptoms could not be established. However, patients with onset before 50 years were found to have significantly higher proportion of ApoE ε4 and C allele of IL-6-174 in comparison to patients with onset above 50. These young patients were also having more atypical presentation than their older counterpart. CONCLUSION: Our study revealed a novel role of both ApoE ε4 and C allele of IL-6-174 together in developing early onset AD with more atypical clinical features.

Hedgehog dysregulation contributes to tissue-specific inflammaging of resident macrophages.

Age-associated low-grade sterile inflammation, commonly referred to as inflammaging, is a recognized hallmark of aging, which contributes to many age-related diseases. While tissue-resident macrophages are innate immune cells that secrete many types of inflammatory cytokines in response to various stimuli, it is not clear whether they have a role in driving inflammaging. Here we characterized the transcriptional changes associated with physiological aging in mouse resident macrophage populations across different tissues and sexes. Although the age-related transcriptomic signatures of resident macrophages were strikingly tissue-specific, the differentially expressed genes were collectively enriched for those with important innate immune functions such as antigen presentation, cytokine production, and cell adhesion. The brain-resident microglia had the most wide-ranging age-related alterations, with compromised expression of tissue-specific genes and relatively exaggerated responses to endotoxin stimulation. Despite the tissue-specific patterns of aging transcriptomes, components of the hedgehog (Hh) signaling pathway were decreased in aged macrophages across multiple tissues. In vivo suppression of Hh signaling in young animals increased the expression of pro-inflammatory cytokines, while in vitro activation of Hh signaling in old macrophages, in turn, suppressed the expression of these inflammatory cytokines. This suggests that hedgehog signaling could be a potential intervention axis for mitigating age-associated inflammation and related diseases. Overall, our data represent a resourceful catalog of tissue-specific and sex-specific transcriptomic changes in resident macrophages of peritoneum, liver, and brain, during physiological aging.

Assaying Homodimers of NF-κB in Live Single Cells.

NF-κB is a family of heterodimers and homodimers which are generated from subunits encoded by five genes. The predominant classical dimer RelA:p50 is presumed to operate as "NF-κB" in many contexts. However, there are several other dimer species which exist and may even be more functionally relevant in specific cell types. Accurate characterization of stimulus-specific and tissue-specific dimer repertoires is fundamentally important for understanding the downstream gene regulation by NF-κB proteins. In vitro assays such as immunoprecipitation have been widely used to analyze subunit composition, but these methods do not provide information about dimerization status within the natural intracellular environment of intact live cells. Here we apply a live single cell microscopy technique termed Number and Brightness to examine dimers translocating to the nucleus in fibroblasts after pro-inflammatory stimulation. This quantitative assay suggests that RelA:RelA homodimers are more prevalent than might be expected. We also found that the relative proportion of RelA:RelA homodimers can be perturbed by small molecule inhibitors known to disrupt the NF-κB pathway. Our findings show that Number and Brightness is a useful method for investigating NF-κB dimer species in live cells. This approach may help identify the relevant targets in pathophysiological contexts where the dimer specificity of NF-κB intervention is desired.

Ezh2 Regulates Activation-Induced CD8+ T Cell Cycle Progression via Repressing Cdkn2a and Cdkn1c Expression.

Transition from resting to cell cycle in response to antigenic stimulation is an essential step for naïve CD8+ T cells to differentiate to effector and memory cells. Leaving the resting state requires dramatic changes of chromatin status in the key cell cycle inhibitors but the details of these concerted events are not fully elucidated. Here, we showed that Ezh2, an enzymatic component of polycomb repressive complex 2 (PRC2) catalyzing the trimethylation of lysine 27 on histone 3 (H3K27me3), regulates activation induced naïve CD8+ T cells proliferation and apoptosis. Upon deletion of Ezh2 during thymocyte development (Ezh2fl/flCd4Cre+ mice), naive CD8+ T cells displayed impaired proliferation and increased apoptosis in response to antigen stimulation. However, naive CD8+ T cells only had impaired proliferation but no increase in apoptosis when Ezh2 was deleted after activation (Ezh2fl/flGzmBCre+ mice), suggesting cell cycle and apoptosis are temporally separable events controlled by Ezh2. We then showed that deletion of Ezh2 resulted in the increase in expression of cyclin-dependent kinase inhibitors Cdkn2a (p16 and Arf) and Cdkn1c (p57) in activated naïve CD8+ T cells as the consequence of reduced levels of H3K27me3 at these two gene loci. Finally, with real time imaging, we observed prolonged cell division times of naïve CD8+ T cells in the absence of Ezh2 post in vitro stimulation. Together, these findings reveal that repression of Cdkn1c and Cdkn2a by Ezh2 plays a critical role in execution of activation-induced CD8+ T cell proliferation.