Etiology of end-stage liver cirrhosis impacts hepatic natural killer cell heterogenicity

PELI2 is a negative regulator of STING signaling that is dynamically repressed during viral infection

The innate immune cGAS-STING pathway is activated by cytosolic double-stranded DNA (dsDNA), a ubiquitous danger signal, to produce interferon, a potent anti-viral and anti-cancer cytokine. However, STING activation must be tightly controlled because aberrant interferon production leads to debilitating interferonopathies. Here, we discover PELI2 as a crucial negative regulator of STING. Mechanistically, PELI2 inhibits the transcription factor IRF3 by binding to phosphorylated Thr354 and Thr356 on the C-terminal tail of STING, leading to ubiquitination and inhibition of the kinase TBK1. PELI2 sets a threshold for STING activation that tolerates low levels of cytosolic dsDNA, such as that caused by silenced TREX1, RNASEH2B, BRCA1, or SETX. When this threshold is reached, such as during viral infection, STING-induced interferon production temporarily downregulates PELI2, creating a positive feedback loop allowing a robust immune response. Lupus patients have insufficient PELI2 levels and high basal interferon production, suggesting that PELI2 dysregulation may drive the onset of lupus and other interferonopathies.

Biomarkers of Innate Immunity and Immunological Susceptibility to Viral Infection in Patients with Alcoholic Cirrhosis

BACKGROUND

The harmful effect of alcohol on the immune system may be due to both a direct action of the alcohol or its metabolites on immune cells as an indirect action modifying the different mechanisms of intercellular interaction. The interplay between stimulatory (aKIR) and inhibitory (iKIR) natural killer (NK) cell receptors and their corresponding human leukocyte antigen (HLA) ligands influences the outcome of virus infection. The aim was to analyze the influence of the KIR/HLA pair genetic profile in male alcoholic cirrhosis (AC) patients with and without viral infections to find susceptibility biomarkers that can help establish the risks and prevent viral infections.

METHODS

A total of 281 male AC patients were analyzed. The sociodemographic characteristics, viral hepatitis C (HCV), hepatitis B (HBV), and cytomegalovirus (CMV) infections were analyzed. Genomic DNA was extracted, and genetic the KIR/HLA profiles were investigated. A total of 6 KIR genes and their corresponding ligands (HLA-C) were analyzed. Patients were grouped into two groups: with and without associated viral infection.

RESULTS

A statistically significant increase in the combination of KIR2DL2+/C1C1 was observed in male AC patients with viral infection compared to those without viral infection (45.9% vs. 24.5%, p = 0.021). The analysis of KIR2DL3+/C1+ showed a high frequency comparing healthy controls and male AC patients without virus infection (85% vs. 76.4%; p = 0.026). The analysis of KIR2DL3+/C2C2 frequency showed a statistically significant increase comparing male AC patients without viral infection and healthy controls (23.6% vs. 15%; p = 0.026).

CONCLUSIONS

The genetic KIR2DL2+/C2C2 profiles may play a significant role in determining the vulnerability of male AC patients to viral infections, providing valuable insights for future research and potential therapeutic interventions.

Beta-lapachone ameliorates the progression of primary sclerosing cholangitis pathogenesis in rodent models

AIMS

Primary sclerosing cholangitis (PSC) is a rare cholestatic liver disease characterized by chronic inflammation and severe fibrosis for which effective treatment options are currently lacking. In this study, we explored the potential of beta-lapachone (βL) as a drug candidate for PSC therapy.

MATERIALS AND METHODS

We employed an animal model fed a diet containing 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) to assess the preventive and therapeutic effects of βL. The beneficial effects of βL on PSC pathogenic characteristics, including blood biomarkers, inflammation, and fibrosis, were determined by assessing relevant parameters. Differential gene expression between each group was analyzed by RNA sequencing of liver tissues. Mdr2-/- mice were utilized to explore the involvement of Abcb4 in the βL-induced improvement of PSC pathogenesis.

KEY FINDINGS

βL effectively inhibited key features of PSC pathogenesis, as demonstrated by reduced blood biomarkers and improved pathogenic characteristics. Treatment with βL significantly mitigated DDC-induced apoptosis, cell proliferation, inflammation, and fibrosis. Analysis of differential gene expression confirmed a new insight that βL could stimulate the expression of genes related to NAD synthesis and Abcb4. Indeed, βL-induced NAD exhibited effective functioning, as evidenced by enhanced sirt1/3 and acetyl-lysine levels, leading to improved mitochondrial stability. The role of Abcb4 in response to βL was confirmed in Mdr2/Abcb4 KO mice, where the beneficial effects of βL were abolished.

SIGNIFICANCE

This study provided a new concept for PSC treatment, suggesting that pharmacological stimulation of the NAD synthetic pathway and Abcb4 via βL ameliorates PSC pathogenesis.

NK cell subsets and dysfunction during viral infection: a new avenue for therapeutics?

In the setting of viral challenge, natural killer (NK) cells play an important role as an early immune responder against infection. During this response, significant changes in the NK cell population occur, particularly in terms of their frequency, location, and subtype prevalence. In this review, changes in the NK cell repertoire associated with several pathogenic viral infections are summarized, with a particular focus placed on changes that contribute to NK cell dysregulation in these settings. This dysregulation, in turn, can contribute to host pathology either by causing NK cells to be hyperresponsive or hyporesponsive. Hyperresponsive NK cells mediate significant host cell death and contribute to generating a hyperinflammatory environment. Hyporesponsive NK cell populations shift toward exhaustion and often fail to limit viral pathogenesis, possibly enabling viral persistence. Several emerging therapeutic approaches aimed at addressing NK cell dysregulation have arisen in the last three decades in the setting of cancer and may prove to hold promise in treating viral diseases. However, the application of such therapeutics to treat viral infections remains critically underexplored. This review briefly explores several therapeutic approaches, including the administration of TGF-β inhibitors, immune checkpoint inhibitors, adoptive NK cell therapies, CAR NK cells, and NK cell engagers among other therapeutics.