Excessive Plasmin Compromises Hepatic Sinusoidal Vascular Integrity After Acetaminophen Overdose

The serine protease plasmin degrades extracellular matrix (ECM) components both directly and indirectly through activation of matrix metalloproteinases. Excessive plasmin activity and subsequent ECM degradation cause hepatic sinusoidal fragility and hemorrhage in developing embryos. We report here that excessive plasmin activity in a murine acetaminophen (APAP) overdose model likewise compromises hepatic sinusoidal vascular integrity in adult animals. We found that hepatic plasmin activity is up-regulated significantly at 6 hours after APAP overdose. This plasmin up-regulation precedes both degradation of the ECM component fibronectin around liver vasculature and bleeding from centrilobular sinusoids. Importantly, administration of the pharmacological plasmin inhibitor tranexamic acid or genetic reduction of plasminogen, the circulating zymogen of plasmin, ameliorates APAP-induced hepatic fibronectin degradation and sinusoidal bleeding. Conclusion: These studies demonstrate that reduction of plasmin stabilizes hepatic sinusoidal vascular integrity after APAP overdose. (Hepatology 2018; 00:1-13).

Hepatic mitochondrial DNA/Toll-like receptor 9/MicroRNA-223 forms a negative feedback loop to limit neutrophil overactivation and acetaminophen hepatotoxicity in mice

Acetaminophen (APAP) overdose is a leading cause of acute liver failure worldwide, in which mitochondrial DNA (mtDNA) released by damaged hepatocytes activates neutrophils through binding of Toll-like receptor 9 (TLR9), further aggravating liver injury. Here, we demonstrated that mtDNA/TLR9 also activates a negative feedback pathway through induction of microRNA-223 (miR-223) to limit neutrophil overactivation and liver injury. After injection of APAP in mice, levels of miR-223, the most abundant miRNAs in neutrophils, were highly elevated in neutrophils. Disruption of the miR-223 gene exacerbated APAP-induced hepatic neutrophil infiltration, oxidative stress, and injury and enhanced TLR9 ligand-mediated activation of proinflammatory mediators in neutrophils. An additional deletion of the intercellular adhesion molecule 1 (ICAM-1) gene ameliorated APAP-induced neutrophil infiltration and liver injury in miR-223 knockout mice. In vitro experiments revealed that miR-223-deficient neutrophils were more susceptible to TLR9 agonist-mediated induction of proinflammatory mediators and nuclear factor kappa B (NF-κB) signaling, whereas overexpression of miR-223 attenuated these effects in neutrophils. Moreover, inhibition of TLR9 signaling by either treatment with a TLR9 inhibitor or by disruption of TLR9 gene partially, but significantly, suppressed miR-223 expression in neutrophils post-APAP injection. In contrast, activation of TLR9 up-regulated miR-223 expression in neutrophils in vivo and in vitro. Mechanistically, activation of TLR9 up-regulated miR-223 by enhancing NF-κB binding on miR-223 promoter, whereas miR-223 attenuated TLR9/NF-κB-mediated inflammation by targeting IκB kinase α expression. Collectively, up-regulation of miR-223 plays a key role in terminating the acute neutrophilic response and is a therapeutic target for treatment of APAP-induced liver failure. (Hepatology 2017;66:220-234).

Acute and chronic effects of IL-22 on acetaminophen-induced liver injury

Acetaminophen (APAP)-induced liver injury (AILI) accounts for half of the acute liver failure cases in the United States. A better understanding of the underlying mechanisms of AILI is necessary for the development of novel antidotes. We found that pretreatment with IL-22 protected mice from APAP-mediated hepatotoxicity. The protection was dependent on STAT3, as IL-22 failed to reduce APAP hepatotoxicity in liver-specific STAT3 knockout mice. In contrast to the acute exposure to IL-22, the endogenous chronic overexpression of IL-22 in IL-22 transgenic (TG) mice or IL-22 adenovirus treatment for 6 wk resulted in a markedly increased susceptibility to AILI. Furthermore, the hepatic expression levels of cytochrome 2E1 (Cyp2E1) and Cyp1A2 were much higher in IL-22TG mice. Ablation of Cyp2E1 but not hepatic STAT3 abolished AILI and protein-adduct formation in IL-22TG mice. Finally, hepatic expression of HNF-1α, a transcriptional factor that is known to control Cyp2E1 expression, was elevated in IL-22TG mice compared with wild-type mice. Upregulation of hepatic Cyp2E1 was only observed in mice with constitutive overexpression of IL-22 but not with short-term treatment with one dose of IL-22 or multiple doses of IL-22 for 2 wk. In conclusion, short-term acute IL-22 exposure protects mice against AILI through STAT3 activation; however, chronic constitutive overexpression of IL-22 exacerbates AILI by increasing Cyp2E1 and toxic reactive APAP metabolite production. These findings may not only enhance our understanding of the effects of chronic inflammation on AILI in patients with liver disease, but are also helpful to identify novel therapeutic targets for the treatment of AILI.

New and unconventional treatments for obstructive sleep apnea

Although continuous positive airway pressure, oral appliances and surgical modifications of the airway are considered as part of the routine management of patients with obstructive sleep apnea, many new and unconventional therapies exist. Many of the trials using these new alternatives have been limited by insufficient data, poor trial design, small sample size, unclear inclusion criteria, lack of randomization, and lack of blinding, and on occasion are biased by retrospective design. Bariatric surgery, positional therapy, auto-titrating positive airway pressure, serotonin agents, wake promoting agents, genioglossus stimulation surgery, supplemental oxygen, nasal dilators, nasal expiratory resistor devices and oropharyngeal exercises will be reviewed. As obstructive sleep apnea impacts the individual and society at large, further research is needed to explore new therapeutic treatment options for obstructive sleep apnea. Therapeutic trials for obstructive sleep apnea must be of rigorous design to prove clinical effectiveness while taking into account both patient satisfaction and cost effectiveness.

Unrecognized acetaminophen toxicity as a cause of indeterminate acute liver failure

Despite extensive investigations, the cause of liver injury in 14% of patients with acute liver failure remains unknown (indeterminate). In a pilot study using a novel assay, highly specific acetaminophen-cysteine adducts were detected in 7 of 36 indeterminate patients (19%). To extend these observations, sera from 110 subjects enrolled in the Acute Liver Failure Study Group registry with indeterminate acute liver failure were analyzed with a similar but more efficient and sensitive adduct assay. As positive controls, another 199 patients with known or presumed acetaminophen-induced liver failure were assessed for the presence and quantity of adducts. Clinical, laboratory, and outcome data were compared for the two groups. On the basis of previous data for known therapeutic exposures and acetaminophen overdoses, an adduct concentration ≥1.0 nmol/mL of serum indicated a definite acetaminophen overdose. Among the 110 indeterminate cases, 18% had assay values ≥1.0 with a median level of 9.2 nmol/mL; 94.5% of the positive controls (known acetaminophen cases) had values ≥1.0 nmol/mL. Regardless of the initial diagnosis, subjects with elevated adduct levels demonstrated the clinical profile and hyperacute biochemical injury pattern associated with acetaminophen overdose: a predominance of female gender, very high aminotransferase levels, and low bilirubin levels.

CONCLUSION

These data confirm and extend previous observations regarding the high (18%) prevalence of unrecognized or uncertain acetaminophen toxicity among subjects with indeterminate acute liver failure. N-Acetylcysteine use was limited in this group, presumably because of the lack of a specific diagnosis of acetaminophen toxicity.

Agreement between 95th percentile pressure based on a 7-night auto-adjusting positive airway pressure trial vs. equation-based predictions in sleep apnea

STUDY OBJECTIVES

to analyze the agreement between effective CPAP-determined on the basis of a 7-night auto-adjusting positive airway pressure (APAP) trial at home with that obtained through 5 different predictive equations.

METHODS

Data were collected from consecutive CPAP-naive patients with OSA who underwent a 7-night non-attended home-setting APAP trial. The 95th percentile APAP pressure was considered as the effective CPAP and also as the reference variable against which the equation-based predictions were compared. All patients fulfilled the following criteria: residual respiratory disturbances index (RDI) < 10 events/h, average air leak < 0.4 L/sec and > 4 h of use per night during the APAP trial.

RESULTS

A total of 100 consecutive patients (70 men) with the following characteristics were included: mean age 49 +/- 11 years, body mass index 34 +/- 4 kg/m2, diagnostic Epworth Sleepiness Scale score 14 +/- 7, diagnostic RDI 56 +/- 28 events/h, 95th percentile APAP 11 +/- 2 cm H2O, hours of use per night 6.2 +/- 1.3, and residual RDI 5 +/- 2 events/h. A poor level of agreement between the 95th percentile pressure and the pressures obtained through 5 predictive equations was observed (the intra-class correlation coefficient ranged from 0.17 to 0.32).

CONCLUSIONS

The disagreement observed between the effective CPAP determined through a 7-night APAP trial and the pressures obtained by the predictive equations suggest that long-term CPAP prescriptions based on predictive equations may be improper.

Autoadjusting positive pressure trial in adults with sleep apnea assessed by a simplified diagnostic approach

STUDY OBJECTIVES

To describe our clinical experience with autoadjusting positive airway pressure (APAP) trials carried out on patients with moderate-to-severe obstructive sleep apnea (OSA).

METHODS

Consecutive CPAP-naive adults underwent a non-attended home APAP trial (ResMed, Autoset, Spirit). Diagnoses of OSA were established by simplified polygraphy.

RESULTS

Data from 208 men and 71 women. The median age (interquartile range) was 51 years (41-59), with an Epworth Sleepiness Scale score of 13.5 (9-19), body mass index of 33 kg/m2 (29-38) and respiratory disturbance index (RDI) of 53 events/h (35-74). The APAP trial results included: hours used per night, 5.5 (4-7); 95th percentile pressure, 10.6 cm H2O (9.4-11.7); 95th percentile leak, 0.3 UL/sec (0.1-0.6); residual RDI, 6.2 events/h (3.9-11.4); and percentage change in RDI, 87% (74-93). The proportion of patients with residual RDI >10 events/h was 29% (95% CI 23.6-34.3). Adherence (> 70% of nights and > 4 h/night) was observed in 72.4% of subjects (95% CI 67-78). Patients with APAP adherence tended to require higher CPAP pressures, had higher rates of residual RDI, and had a lower percentage change in RDI than those with no adherence. As the 95th percentile CPAP pressure increased so too did residual RDI.

CONCLUSIONS

The APAP trial was effective in decreasing RDI with an acceptable adherence rate; however, residual OSAwas a frequent finding. Our results support that in up to one-third of patients evaluated by a simplified diagnostic approach, CPAP titration based on 95th percentile pressure may not be sufficient if residual RDI < 10 events/h is considered as a therapeutic target.