Despite significant advances in intensive care therapy and antibiotics, severe sepsis accounts for 9% of all deaths in the United States annually. The pathological sequelae of sepsis are characterized by a systemic inflammatory response, but experimental therapeutics that target specific early inflammatory mediators [tumor necrosis factor (TNF) and IL-1␤] have not proven efficacious in the clinic. We recently identified high mobility group box 1 (HMGB1) as a late mediator of endotoxin-induced lethality that exhibits significantly delayed kinetics relative to TNF and IL-1␤. Here, we report that serum HMGB1 levels are increased significantly in a standardized model of murine sepsis, beginning 18 h after surgical induction of peritonitis. Specific inhibition of HMGB1 activity [with either anti-HMGB1 antibody (600 g per mouse) or the DNAbinding A box (600 g per mouse)] beginning as late as 24 h after surgical induction of peritonitis significantly increased survival (nonimmune IgG-treated controls ‫؍‬ 28% vs. anti-HMGB1 antibody group ‫؍‬ 72%, P < 0.03; GST control protein ‫؍‬ 28% vs. A box ‫؍‬ 68%, P < 0.03). Animals treated with either HMGB1 antagonist were protected against the development of organ injury, as evidenced by improved levels of serum creatinine and blood urea nitrogen. These observations demonstrate that specific inhibition of endogenous HMGB1 therapeutically reverses lethality of established sepsis indicating that HMGB1 inhibitors can be administered in a clinically relevant time frame.

The inflammasome regulates release of caspase activation-dependent cytokines, including IL-1β, IL-18, and high-mobility group box 1 (HMGB1)1-5. During the course of studying HMGB1 release mechanisms, we discovered an important role of double-stranded RNA dependent protein kinase (PKR) in inflammasome activation. Exposure of macrophages to inflammasome agonists induced PKR autophosphorylation. PKR inactivation by genetic deletion or pharmacological inhibition severely impaired inflammasome activation in response to double-stranded RNA, ATP, monosodium urate, adjuvant aluminum, rotenone, live E. coli, anthrax lethal toxin, DNA transfection, and S. Typhimurium infection. PKR deficiency significantly inhibited the secretion of IL-1beta, IL-18 and HMGB1 in E. coli-induced peritonitis. PKR physically interacts with multiple inflammasome components, including NLR family pyrin domain-containing 3 (NLRP3), NLR family pyrin domain-containing 1 (NLRP1), NLR family CARD domain-containing protein 4 (NLRC4), Absent in melanoma 2 (AIM2), and broadly regulates inflammasome activation. PKR autophosphorylation in a cell free system with recombinant NLRP3, ASC and pro-casapse-1 reconstitutes inflammasome activity. These results reveal a critical role of PKR in inflammasome activation, and indicate that it should be possible to pharmacologically target this molecule to treat inflammation.

The dihydrochalcone phlorizin is a natural product and dietary constituent found in a number of fruit trees. It has been used as a pharmaceutical and tool for physiology research for over 150 years. Phlorizin's principal pharmacological action is to produce renal glycosuria and block intestinal glucose absorption through inhibition of the sodium-glucose symporters located in the proximal renal tubule and mucosa of the small intestine. This review covers the role phlorizin has played in the history of diabetes mellitus and its use as an agent to understand fundamental concepts in renal physiology as well as summarizes the physiology of cellular glucose transport and the pathophysiology of renal glycosuria. It reviews the biology and pathobiology of glucose transporters and discusses the medical botany of phlorizin and the potential effects of plant flavonoids, such as phlorizin, on human metabolism. Lastly, it describes the clinical pharmacology and toxicology of phlorizin, including investigational uses of phlorizin and phlorizin analogs in the treatment of diabetes, obesity, and stress hyperglycemia.