Cytoplasmic expression of human telomerase catalytic protein (hTERT) in neutrophils: an immunoelectron microscopy study

Generation of an immortalized human choroid endothelial cell line (iChEC-1) using an endothelial cell specific promoter

Age-related macular degeneration (AMD) is a common cause of blindness worldwide. While recent studies have revealed that the loss of choroidal endothelial cells (ChECs) is critical to the disease pathogenesis of dry AMD, in vitro studies are needed to fully elucidate the disease mechanism. However, these studies remain hindered due to the lack of publically available human ChEC lines. To address this need, ChECs were harvested form donor tissue and enriched for by using magnetic cell separation using anti-CD31 conjugated microbeads. Next, lenti-viral vectors with endothelial-specific promoters driving genes necessary for immortalization, CDH5p-hTERT and CDH5p TAg, were generated. Stable integration of both gene cassettes allowed cells to maintain their proliferative state and yielded an immortalized cell line (iChEC-1). Immunocytochemical analysis of iChEC-1 confirmed the expression of important ChEC markers such as CA4, a marker of choriocapillaris endothelial cells, CDH5, and CD34, pan-endothelial cell markers. qRT-PCR analysis of expanded clones from iChEC-1 further showed that the line maintained expression of other important endothelial markers, vWF, PECAM1, and PLVAP, similar to primary cells. Functional responses were characterized by tube-forming assays and repopulation of decellularized choroid with the immortalized cell line. In conclusion, the iChEC-1 line presents a suitable immortalized human ChEC line for future in vitro studies of AMD.

Murine regulatory T cells induce death of effector T, B, and NK lymphocytes through a contact-independent mechanism involving telomerase suppression and telomere-associated senescence

Regulatory T cells (Tregs) suppress the activity of effector T, B and NK lymphocytes and sustain immunological tolerance, but the proliferative activity of suppressed cells remains unexplored. In the present study, we report that mouse Tregs can induce replicative senescence and the death of responder mouse CD4⁺CD25^- T cells, CD8⁺ T cells, B cells and NK cells in vitro and in vivo. Contact-independent in vitro co-cultivation with Tregs up-regulated endonuclease G (EndoG) expression and its translocation to the nucleus in responder cells. EndoG localization in the nucleus induced alternative mRNA splicing of the telomerase catalytic subunit Tert and telomerase inhibition. The lack of telomerase activity in proliferating cells led to telomere loss followed by the development of senescence and cell death. Injection of Tregs into mice resulted in EndoG-associated alternative splicing of Tert, telomerase inhibition, telomere loss, senescence development and increased cell death in vivo. The present study describes a novel contact-independent mechanism by which Tregs specify effector cell fate and provides new insights into cellular crosstalk related to immune suppression.

Chronic Inflammation in Immune Aging: Role of Pattern Recognition Receptor Crosstalk with the Telomere Complex?

Age-related decline in immunity is characterized by stem cell exhaustion, telomere shortening, and disruption of cell-to-cell communication, leading to increased patient risk of disease. Recent data have demonstrated that chronic inflammation exerts a strong influence on immune aging and is closely correlated with telomere length in a range of major pathologies. The current review discusses the impact of inflammation on immune aging, the likely molecular mediators of this process, and the various disease states that have been linked with immunosenescence. Emerging findings implicate NF-κB, the major driver of inflammatory signaling, in several processes that regulate telomere maintenance and/or telomerase activity. While prolonged triggering of pattern recognition receptors is now known to promote immunosenescence, it remains unclear how this process is linked with the telomere complex or telomerase activity. Indeed, enzymatic control of telomere length has been studied for many decades, but alternative roles of telomerase and potential influences on inflammatory responses are only now beginning to emerge. Crosstalk between these pathways may prove to be a key molecular mechanism of immunosenescence. Understanding how components of immune aging interact and modify host protection against pathogens and tumors will be essential for the design of new vaccines and therapies for a wide range of clinical scenarios.

Nuclear translocation of telomerase reverse transcriptase is a critical process in lymphatic metastasis of nasopharyngeal carcinoma

Telomerase reverse transcriptase (TERT) is the predominant functional unit of telomerase and maintains the telomere length and the stability of chromosomes. Recently, TERT has been shown to be a critical factor in a number of other biological processes, including cell proliferation and cancer metastasis. In addition, although numerous studies have been conducted, the subcellular localization of the TERT protein and the association of such with cancer metastasis remains unclear. To investigate the involvement of TERT in in vivo metastasis, quantum dots-based immunofluorescence and western blot analysis were conducted to detect changes in the subcellular localization of TERT in human nasopharyngeal carcinoma (NPC) tissues and metastatic lymph nodes. To further investigate, metastatic and non-metastatic models of NPC were generated using 5-8F (high metastasis capability) and 6-10B (low metastasis capability) cell lines, respectively. It was found that TERT protein was overexpressed in NPC tissue samples and metastatic lymph nodes and TERT was predominantly located in the cytoplasm of primary NPC tissues, while TERT was predominantly located in the nucleus of the metastatic lymph nodes. The ratio of cytoplasmic TERT/nuclear TERT for the primary tumor of the 6-10B cell line was almost six-fold higher than that of the metastatic lymph nodes of the 5-8F cell line. TERT translocation from the cytoplasm to nucleus may present a critical step in the lymphatic metastasis of NPC. Thus, TERT translocation may be more useful than TERT expression level and telomerase activity for predicting the metastasis of NPC.