Susceptibility to Infections During Acute Liver Injury Depends on Transient Disruption of Liver Macrophage Niche

Kupffer cell reverse migration into the liver sinusoids mitigates neonatal sepsis and meningitis

In adults, liver-resident macrophages, or Kupffer cells (KCs), reside in the sinusoids and sterilize circulating blood by capturing rapidly flowing microbes. We developed quantitative intravital imaging of 1-day-old mice combined with transcriptomics, genetic manipulation, and in vivo infection assays to interrogate increased susceptibility of newborns to bloodstream infections. Whereas 1-day-old KCs were better at catching Escherichia coli in vitro, we uncovered a critical 1-week window postpartum when KCs have limited access to blood and must translocate from liver parenchyma into the sinusoids. KC migration was independent of the microbiome but depended on macrophage migration inhibitory factor, its receptor CD74, and the adhesion molecule CD44. On the basis of our findings, we propose a model of progenitor macrophage seeding of the liver sinusoids via a reverse transmigration process from liver parenchyma. These results also illustrate the importance of developing newborn mouse models to understand newborn immunity and disease.

Necrotic Liver Lesion Resolution: Another Mode of Liver Regeneration

The liver has the great ability to regenerate after partial resection or injury, and the mechanisms underlying liver regeneration have been extensively investigated. Interestingly, acute liver injuries triggered by various etiologies are associated with the formation of necrotic lesions, and such necrotic lesions are also rapidly resolved. However, how necrotic liver lesions are repaired has not been carefully investigated until recently. In this review, we briefly summarize the spatiotemporal process of necrotic liver lesion resolution in several liver injury models including immune-mediated liver injury and drug-induced liver injury. The roles of liver nonparenchymal cells and infiltrating immune cells in controlling necrotic liver lesion resolution are discussed, which may help identify potential therapies for acute liver injury and failure.

Kupffer cell and recruited macrophage heterogeneity orchestrate granuloma maturation and hepatic immunity in visceral leishmaniasis

In murine models of visceral leishmaniasis (VL), parasitization of resident Kupffer cells (resKCs) is responsible for early growth of Leishmania infantum in the liver, which leads to granuloma formation and eventual parasite control. We employed the chronic VL model, and revealed an open niche established by KCs death and their migration outside of the sinusoids, resulting in their gradual replacement by monocyte-derived KCs (moKCs). While early granulomas were composed of resKCs, late granulomas were found outside of the sinusoids and contained resKC-derived macrophages, and monocyte-derived macrophages (momacs). ResKCs and moKCs within the sinusoids were identified as homeostatic/regulatory cells, while resKC-derived macrophages and momacs within late granulomas were pro-inflammatory. Despite the infection being largely confined to the resKC-derived macrophages, in the absence of monocyte recruitment, parasite control was strongly compromised. Macrophage heterogeneity, involving migration and reprogramming of resKCs, along with recruitment of monocyte-derived cells, is a hallmark of granuloma maturation and hepatic immunity in VL.

Comparison of fungal vs bacterial infections in the medical intensive liver unit: Cause or corollary for high mortality?

BACKGROUND

Due to development of an immune-dysregulated phenotype, advanced liver disease in all forms predisposes patients to sepsis acquisition, including by opportunistic pathogens such as fungi. Little data exists on fungal infection within a medical intensive liver unit (MILU), particularly in relation to acute on chronic liver failure.

AIM

To investigate the impact of fungal infections among critically ill patients with advanced liver disease, and compare outcomes to those of patients with bacterial infections.

METHODS

From our prospective registry of MILU patients from 2018-2022, we included 27 patients with culture-positive fungal infections and 183 with bacterial infections. We compared outcomes between patients admitted to the MILU with fungal infections to bacterial counterparts. Data was extracted through chart review.

RESULTS

All fungal infections were due to Candida species, and were most frequently blood isolates. Mortality among patients with fungal infections was significantly worse relative to the bacterial cohort (93% vs 52%, P < 0.001). The majority of the fungal cohort developed grade 2 or 3 acute on chronic liver failure (ACLF) (90% vs 64%, P = 0.02). Patients in the fungal cohort had increased use of vasopressors (96% vs 70%, P = 0.04), mechanical ventilation (96% vs 65%, P < 0.001), and dialysis due to acute kidney injury (78% vs 52%, P = 0.014). On MILU admission, the fungal cohort had significantly higher Acute Physiology and Chronic Health Evaluation (108 vs 91, P = 0.003), Acute Physiology Score (86 vs 65, P = 0.003), and Model for End-Stage Liver Disease-Sodium scores (86 vs 65, P = 0.041). There was no significant difference in the rate of central line use preceding culture (52% vs 40%, P = 0.2). Patients with fungal infection had higher rate of transplant hold placement, and lower rates of transplant; however, differences did not achieve statistical significance.

CONCLUSION

Mortality was worse among patients with fungal infections, likely attributable to severe ACLF development. Prospective studies examining empiric antifungals in severe ACLF and associations between fungal infections and transplant outcomes are critical.

NEDD4 lactylation promotes APAP induced liver injury through Caspase11 dependent non-canonical pyroptosis

Caspase-11 detection of intracellular lipopolysaccharide mediates non-canonical pyroptosis, which could result in inflammatory damage and organ lesions in various diseases such as sepsis. Our research found that lactate from the microenvironment of acetaminophen-induced acute liver injury increased Caspase-11 levels, enhanced gasdermin D activation and accelerated macrophage pyroptosis, which lead to exacerbation of liver injury. Further experiments unveiled that lactate inhibits Caspase-11 ubiquitination by reducing its binding to NEDD4, a negative regulator of Caspase-11. We also identified that lactates regulated NEDD4 K33 lactylation, which inhibits protein interactions between Caspase-11 and NEDD4. Moreover, restraining lactylation reduces non-canonical pyroptosis in macrophages and ameliorates liver injury. Our work links lactate to the exquisite regulation of the non-canonical inflammasome, and provides a basis for targeting lactylation signaling to combat Caspase-11-mediated non-canonical pyroptosis and acetaminophen-induced liver injury.