PEGylated- l -asparaginase (PEG-ASNase) is a chemotherapeutic agent used to treat pediatric acute lymphoblastic leukemia (ALL). Its use is avoided in adults due to its high risk of liver injury including hepatic steatosis, with obesity and older age considered risk factors of the injury. Our study aims to elucidate the mechanism of PEG-ASNase-induced liver injury. Mice received 1500 U/kg of PEG-ASNase and were sacrificed 1, 3, 5, and 7 days after drug administration. Liver triglycerides were quantified, and plasma bilirubin, ALT, AST, and non-esterified fatty acids (NEFA) were measured. The mRNA and protein levels of genes involved in hepatic fatty acid synthesis, β -oxidation, very low-density lipoprotein (VLDL) secretion, and white adipose tissue (WAT) lipolysis were determined. Mice developed hepatic steatosis after PEG-ASNase, which associated with increases in bilirubin, ALT, and AST. The hepatic genes Ppara , Lcad/Mcad , Hadhb , Apob100 , and Mttp were upregulated, and Srebp-1c and Fas were downregulated after PEG-ASNase. Increased plasma NEFA, WAT loss, and adipose tissue lipolysis were also observed after PEG-ASNase. Furthermore, we found that PEG-ASNase-induced liver injury was exacerbated in obese and aged mice, consistent with clinical studies of ASNase-induced liver injury. Our data suggest that PEG-ASNase-induced liver injury is due to drug-induced lipolysis and lipid redistribution to the liver.

Adipose tissue (AT) expands by a combination of two fundamental cellular mechanisms: hypertrophic growth of existing adipocytes or through generation of new adipocytes also known as hyperplastic growth. Multiple lines of evidence suggest a limited capacity for hyperplastic growth of adipose tissue in adulthood and that adipocyte number is relatively stable even with fluctuations in AT mass. If adipocyte number is stable in adulthood, despite well-documented birth and death of adipocytes, then this would suggest that birth may be coupled to death in a regenerative cycle. To test this hypothesis, we examined the dynamics of birth of new fat cells in relationship to adipocyte death, using high fidelity stable isotope tracer methods in C57Bl6 mice. We discovered birth of new adipocytes at higher frequency in histological proximity to dead adipocytes. In diet-induced obesity, adipogenesis surged after an adipocyte death peak beyond 8 weeks of high fat feeding. Through transcriptional analyses of adipose tissue and fractionated adipocytes, we found that the dominant cell death signals were inflammasome-related. Pro-inflammatory signals were particularly evident in hypertrophied adipocytes or with deletion of a constitutive oxygen sensor and inhibitor of Hypoxia inducible factor (HIF), Egln1. We leveraged the potential role for the inflammasome in adipocyte death to test the adipocyte death-birth hypothesis, finding that Caspase 1 loss of function attenuated adipocyte death and birth in murine visceral adipose tissue. These data collectively point to a regenerative cycle of adipocyte death and birth as a driver of adipogenesis in adult murine adipose tissue.

Six new N-substituted quinazolinones were synthesized and evaluated for their adenosine antagonistic activity using allergic mice model where 1, 3-dibenzyl and 1, 3-dibutyl-quinazolindiones were found to be potent than 1, 3-dimethylanalogues. They were not significant in controlling the neutrophil and lymphocyte count but effective in controlling the eosinophil influx. In adenosine receptor binding studies, 1,3-dimethyl and 1,3-dibutyl derivatives were found to have significant adenosine A1 receptor binding efficiency with Ki values 9nM and 10nM, respectively, while 1,3- dibenzyl-quinazolinone was found to have significant binding to adenosine A2A receptor showing the influence of alkyl and aralkyl groups present in these compounds. Thus, the present work indicates the possibility to explore quinazolindiones as adenosine receptor ligands.

Background PEGylated L‐asparaginase (PEG‐ASNase) is an essential chemotherapeutic agent used in the treatment of pediatric acute lymphoblastic leukemia (ALL) that depletes L‐asparagine and leads to leukemic cell apoptosis. However, this agent is avoided in adult ALL protocols due to its high risk of liver toxicity. Clinical studies have implied that the mechanism of PEG‐ASNase‐induced liver toxicity is due to defect in hepatic β oxidation; however, no study has investigated the mechanism or the role of β oxidation in PEG‐ASNase‐induced hepatic toxicity. Our study aims to demonstrate that PEG‐ASNase‐induced liver toxicity is not due to hepatic defects in fatty acid oxidation, VLDL secretion, or fatty acid synthesis. Rather, our data suggest that the toxicity may be due to a novel mechanism of fatty liver involving drug‐induced adipose lipolysis. Methods 8‐week‐old male Balb/c mice received 1,500 IU/kg of PEG‐ASNase and were sacrifice at 1, 3, 5, or 7 days after drug administration. Blood, liver, and white adipose tissue (WAT) were harvested after sacrifice. Liver lipids were directly quantified and further assessed via Oil red O and H&E staining. Total and direct bilirubin, ALT, AST, and non‐esterified fatty acids (NEFA) were measure in plasma. The mRNA and protein levels of genes involved in hepatic fatty acid oxidation, lipid synthesis, and VLDL secretion were determined. To assess the effect of PEG‐ASNase on WAT lipolysis, the protein levels of Atgl, phosphorylated Hsl, and protein kinase A (PKA) were measured. Results PEG‐ASNase treatment in mice led to total body, liver, and WAT weight loss. Mice developed hepatic microvesicular steatosis after 3–7 days of drug administration. Plasma direct and total bilirubin levels were elevated 8‐fold relative to controls, whereas ALT, AST, and NEFA concentrations were elevated 2‐fold 3–7 days after PEG‐ASNase. Furthermore, we found, that the hepatic mRNA and protein levels of Srebp‐1c and Fas, which are involved in fatty acid synthesis, were downregulated suggesting a decrease in lipid synthesis after PEG‐ASNase. Furthermore, the hepatic gene and protein expression of Pparα, Lcad, and Mcad, which are involved in fatty acid oxidation, were upregulated after PEG‐ASNase. In vivo VLDL secretion was also increased 3 days after PEG‐ASNase administration. Taken together, our data indicate that other lipid sources are mediating the drug‐induced fatty liver. Among WAT, we found that PEG‐ASNase elevated ATGL, phosphorylated HSL, and PKA protein levels, consistent with the WAT weight loss and the increased plasma NEFA levels. Conclusion Our data suggest that PEG‐ASNase‐induced WAT lipolysis leads to the development of microvesicular hepatic steatosis and toxicity. Our future studies will determine whether PEG‐ASNase hepatic steatosis can be inhibited via the pharmacological or genetic inhibition of adipose lipolysis and identify the molecular mechanism leading to PKA activation and lipolysis. Support or Funding Information NIH Grants RO1 CA216815. University of Pittsburgh School of ...

Adipose tissue (AT) expands by a combination of two fundamental cellular mechanisms: hypertrophic growth of existing adipocytes or through generation of new adipocytes also known as hyperplastic growth. Multiple lines of evidence suggest a limited capacity for hyperplastic growth of adipose tissue in adulthood and that adipocyte number is relatively stable even with fluctuations in AT mass. If adipocyte number is stable in adulthood, despite well-documented birth and death of adipocytes, then this would suggest that birth may be coupled to death in a regenerative cycle. To test this hypothesis, we examined the dynamics of birth of new fat cells in relationship to adipocyte death, using high fidelity stable isotope tracer methods in C57Bl6 mice. We discovered birth of new adipocytes at higher frequency in histological proximity to dead adipocytes. In diet-induced obesity, adipogenesis surged after an adipocyte death peak beyond 8 weeks of high fat feeding. Through transcriptional analyses of adipose tissue and fractionated adipocytes, we found that the dominant cell death signals were inflammasome-related. Pro-inflammatory signals were particularly evident in hypertrophied adipocytes or with deletion of a constitutive oxygen sensor and inhibitor of Hypoxia inducible factor (HIF), Egln1. We leveraged the potential role for the inflammasome in adipocyte death to test the adipocyte death-birth hypothesis, finding that Caspase 1 loss of function attenuated adipocyte death and birth in murine visceral adipose tissue. These data collectively point to a regenerative cycle of adipocyte death and birth as a driver of adipogenesis in adult murine adipose tissue.