Upregulated PD-1 Signaling is an Important Antagonist to Glomerular Health in Aged Kidneys

Kidney aging and its contribution to disease and its underlying mechanisms are not well understood. With an aging population, kidney health becomes an important medical and socioeconomic factor. We previously showed that podocytes isolated from aged mice exhibit increased expression of Programed Cell Death Protein 1 (PD-1) surface receptor and its two ligands (PD-L1, PD-L2). PDCD1 transcript increases with age in micro-dissected human glomeruli, which correlates with lower eGFR, and higher segmental glomerulosclerosis and vascular arterial intima to lumen ratio. In vitro studies in podocytes demonstrate a critical role for PD-1 signaling in cell survival and induction of a Senescence-Associated Secretory Phenotype (SASP). To prove PD-1 signaling is critical to podocyte aging, aged mice were injected with anti-PD-1 antibody (aPD-1ab). Treatment significantly improved the aging phenotype in both kidney and liver. In the glomerulus, it increased the life-span of podocytes, but not parietal epithelial, mesangial or endothelial cells. Transcriptomic and immunohistochemistry studies demonstrate that anti-PD-1 treatment improved the health-span of podocytes. It restored the expression of canonical podocyte genes, transcription factors and gene regulatory networks, increased cellular metabolism signatures and lessened SASPs. These results suggest a critical contribution for increased PD-1 signaling towards both kidney and liver aging.

1,25(OH)2D3 Inhibited Ferroptosis in Zebrafish Liver Cells (ZFL) by Regulating Keap1-Nrf2-GPx4 and NF-κB-hepcidin Axis

Ferroptosis is a kind of iron-dependent programed cell death. Vitamin D has been shown to be an antioxidant and a regulator of iron metabolism, but the relationship between vitamin D and ferroptosis is poorly studied in fish. This study used zebrafish liver cells (ZFL) to establish a ferroptosis model to explore the effect of 1,25(OH)2D3 on cell ferroptosis and its mechanism of action. The results showed that different incubation patterns of 1,25(OH)2D3 improved the survival rate of ZFL, mitigated mitochondrial damage, enhanced total glutathione peroxidase (GPx) activity, and reduced intracellular reactive oxygen species (ROS), lipid peroxidation (LPO), and malondialdehyde (MDA), as well as iron ion levels, with the best effect at 200 pM 1,25(OH)2D3 preincubation for 72 h. Preincubation of ZFL at 200 pM 1,25(OH)2D3 for 72 h downgraded keap1 and ptgs2 gene expression, increased nrf2, ho-1, fth1, gpx4a,b expression, and lowered the expression of the nf-κb p65,il-6,il-1β gene, thus reducing the expression of hamp1. The above results indicate that different incubation patterns of 1,25(OH)2D3 have protective effects on ferroptosis of ZFL induced by ferroptosis activator RSL3 and 1,25(OH)2D3 can inhibit ferroptosis of ZFL by regulating Keap1–Nrf2–GPx4 and NF-κB–hepcidin axis.

Circular RNA FNDC3B Protects Oral Squamous Cell Carcinoma Cells From Ferroptosis and Contributes to the Malignant Progression by Regulating miR-520d-5p/SLC7A11 Axis

Oral squamous cell carcinoma (OSCC) is a common head and neck malignancy with increasing mortality and high recurrence. Ferroptosis is an emerging programed cell death and plays an essential role in tumorigenesis. Circular RNAs (circRNAs) have been reported as a type of critical regulators in OSCC development. In this study, we identified the function of circular RNA FNDC3B (circFNDC3B) in regulating ferroptosis during the malignant progression of OSCC. Our data demonstrated that the silencing of circFNDC3B by shRNA inhibited GPX4 and SLC7A11 expression and enhanced ROS, iron, and Fe2+ levels in OSCC cells. CircFNDC3B knockdown reinforced erastin-induced inhibitory effect on OSCC cells. The depletion of circFNDC3B repressed cell proliferation and enhanced cell apoptosis of OSCC cells. Mechanically, circFNDC3B was able to increase SLC7A11 by targeting miR-520d-5p. The overexpression of SLC7A11 reversed circFNDC3B depletion or miR-520d-5p-induced ferroptosis phenotypes of OSCC cells. Moreover, tumorgenicity assays in nude mice showed that the depletion of circFNDC3B repressed OSCC cell growth in vivo. Taken together, we concluded that circFNDC3B attenuated ferroptosis of OSCC cells and contributed to OSCC progression by regulating the miR-520d-5p/SLC7A11 axis. CircFNDC3B, miR-520d-5p, and SLC7A11 may serve as potential therapeutic targets of OSCC.

How Phosphatidylserine Is Exposed on Tumor Cells Determines The Tumor’s Microenvironment and the Success or Failure of Checkpoint Therapy

One constant in all malignant somatic tumors is their continuous growth and it is hypothesized that there are only two types of cell mutations that can cause this and that their microenvironments are determined by how those mutated cells eventually die and by how phosphatidylserine (PS) is exposed on their surface. When a mutation in a cell causes its rate of mitotic cell division to continuously exceed the rate necessary for its replacement after its programed cell death (PCD) a continuously growing tumor will form and all of the tumor cells will expose PS by the Xkr8 transmembrane scramblase molecule when they die causing an inflammatory and immune suppressive microenvironment. When a mutation in a cell eliminates PCD a continuous tumor growth begins because all those cells will continue dividing until they die a senescent death where PS is exposed by the TMEM16F scramblase molecule and causes an inflammatory microenvironment. Inflammation stresses somatic cells to expose checkpoint molecules (CPMs) on them and on immune cells that could potentially eliminate them. Only in tumors where PCD has been eliminated will CPM be exposed and only in them will immune checkpoint inhibitors (ICIs) be effective.

A computational study of co-inhibitory immune complex assembly at the interface between T cells and antigen presenting cells

The activation and differentiation of T-cells are mainly directly by their co-regulatory receptors. T lymphocyte-associated protein-4 (CTLA-4) and programed cell death-1 (PD-1) are two of the most important co-regulatory receptors. Binding of PD-1 and CTLA-4 with their corresponding ligands programed cell death-ligand 1 (PD-L1) and B7 on the antigen presenting cells (APC) activates two central co-inhibitory signaling pathways to suppress T cell functions. Interestingly, recent experiments have identified a new cis-interaction between PD-L1 and B7, suggesting that a crosstalk exists between two co-inhibitory receptors and the two pairs of ligand-receptor complexes can undergo dynamic oligomerization. Inspired by these experimental evidences, we developed a coarse-grained model to characterize the assembling of an immune complex consisting of CLTA-4, B7, PD-L1 and PD-1. These four proteins and their interactions form a small network motif. The temporal dynamics and spatial pattern formation of this network was simulated by a diffusion-reaction algorithm. Our simulation method incorporates the membrane confinement of cell surface proteins and geometric arrangement of different binding interfaces between these proteins. A wide range of binding constants was tested for the interactions involved in the network. Interestingly, we show that the CTLA-4/B7 ligand-receptor complexes can first form linear oligomers, while these oligomers further align together into two-dimensional clusters. Similar phenomenon has also been observed in other systems of cell surface proteins. Our test results further indicate that both co-inhibitory signaling pathways activated by B7 and PD-L1 can be down-regulated by the new cis-interaction between these two ligands, consistent with previous experimental evidences. Finally, the simulations also suggest that the dynamic and the spatial properties of the immune complex assembly are highly determined by the energetics of molecular interactions in the network. Our study, therefore, brings new insights to the co-regulatory mechanisms of T cell activation.

A case of pembrolizumab induced distal renal tubular acidosis

Immunotherapy has become a mainstay therapeutic in a variety of malignancies. Checkpoint inhibitors are used to enhance the endogenous immune response to target malignancy. The primary targets of checkpoint inhibitors include programed cell death receptor 1 (PD-1), programed cell death ligand 1 (PD-L1), and cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4). Despite clinical benefits, immune checkpoint inhibitors are associated with side effects termed immune-related adverse events (irAEs). We report a case of the PD-1 inhibitor (pembrolizumab) causing severe distal renal tubular acidosis (RTA). The patient presented with altered mental status and was found to have a severe non-anion gap metabolic acidosis after other potential etiologies were ruled out. We review the etiology of immune checkpoint inhibitor-induced RTA and review the case reports that have been described in the literature.

PD-L1 and TP-53 mRNA and microRNAs Expression in Liquid Biopsy of NSCLC Patients.

Introduction The expression of PD-L1 (programed cell death ligand 1) protein on neoplastic cells is a factor qualifying cancer patients for immunotherapy. However, the status of PD-L1 mRNA expression in plasma or serum has not been well studied in cancer patients. TP-53 (Tumor Protein p53) as tumor suppressor affects the expression of many genes, including microRNAs that regulate PD-L1 expression. The purpose of our study was to evaluate usefulness of analysis of PD-L1 mRNA, microRNAs and TP-53 mRNA expression in liquid biopsy in non-invasive diagnosis of non-small cell lung cancer patients (NSCLC). Material and methods We examined the expression the expression of TP-53 and PD-L1 mRNA as well as seven microRNAs (miR-17, miR-93, miR-142, miR-519, miR-526, miR-34a-5p and miR-34a-3p) in plasma obtained from 80 NSCLC patients and 39 healthy volunteers. We used quantitative PCR preceded by reverse transcription method. Results We observed PD-L1 mRNA expression only in 6 (7.5%) NSCLC patients. We showed that expression of TP-53 mRNA and each tested microRNA were significantly higher in healthy individuals than in NSCLC patients. Based on the Receiver Operating Characteristic (ROC) analysis, we found that TP-53 mRNA and each of the examined microRNAs expression were good diagnostic markers for non-invasive diagnosis of NSCLC. We found a significant, negative correlation between TP-53 mRNA and miR-17 (R=-045, p = 0.0005) as well as miR-34a-5p (R=-0.32, p = 0.04) expression in patients with advanced NSCLC. Conclusion The decreased expression of TP-53 mRNA may influence the disruption of microRNAs which could be involved in the regulation of PD-L1 expression in NSCLC patients

Maize Plants Chimeric for an Autoactive Resistance Gene Display a Cell Autonomous Hypersensitive Response but Non-Cell Autonomous Defense Signaling.

The maize gene Rp1-D21 is a mutant form of the gene Rp1-D that confers resistance to common rust. Rp1-D21 triggers a spontaneous defense response that occurs in the absence of the pathogen and includes a programed cell death called the hypersensitive response (HR). Eleven plants heterozygous for Rp1-D21, in four different genetic backgrounds, were identified that had chimeric leaves with lesioned sectors showing HR abutting green non-lesioned sectors lacking HR. The Rp1-D21 sequence derived from each of the lesioned portions of leaves was unaltered from the expected sequence whereas the Rp1-D21 sequences from nine of the non-lesioned sectors displayed various mutations and we were unable to amplify Rp1-D21 from the other two non-lesioned sectors. In every case, the borders between the sectors were sharp with no transition zone, suggesting that HR and chlorosis associated with Rp1-D21 activity was cell-autonomous. Expression of defense response marker genes was assessed in the lesioned and non-lesioned sectors as well as in near-isogenic plants lacking and carrying Rp1-D21. Defense gene expression was somewhat elevated in non-lesioned sectors abutting sectors carrying Rp1-D21 compared to near-isogenic plants lacking Rp1-D21. This suggests that while the HR itself was cell autonomous, other aspects of the defense response initiated by Rp1-D21 were not.

The Periphery of Salivary Gland Carcinoma Tumors Reveals a PD-L1/PD-1 Biomarker Niche for the Evaluation of Disease Severity and Tumor—Immune System Interplay

The treatment options for patients with advanced salivary gland cancers (SGCs) are limited. Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment. However, the response to ICI immunotherapy is largely driven by the immune cell signatures within the tumor tissue and the para-tumoral tissue compartments. To date, there are no data on the expression of programed cell death protein-1/programed cell death protein-ligand 1 (PD-1/PD-L1) in SGC, which may enable the implementation of ICI immunotherapy for this disease. Thus, we performed an immunohistochemical analysis of PD-1 and PD-L1 expression in tumor cells and tumor-infiltrating immune cells (TIICs) in the tumor center and periphery of 62 SGC patients. The tumor periphery showed significantly higher expression of PD-L1 in tumor cells than in TIICs. Moreover, peripheral TIICs had significantly higher PD-1 expression than peripheral tumor cells. PD-1-positive tumor cells were detected exclusively in the tumor center of high-grade tumors, and most importantly, the presence of lymph node (LN) metastases and primary tumor stage significantly correlated with the presence of PD-L1-positive tumor cells in the tumor periphery. The PD-1/PD-L1 molecular signatures in SGC are clustered predominantly in the tumor periphery, reflect disease severity, and may predict the response to ICI immunotherapy in SGC patients.