The decreases of nephrin and nuclear WT1 in podocytes may cause albuminuria during the experimental sepsis in mice.

Sepsis is induced by infectious challenges, and septic organ failure often occurs under local and systemic inflammation. Albuminuria is also evident during sepsis, but little is known about the molecular basis of septic albuminuria. Using lipopolysaccharide (LPS)-treated mice as a sepsis model, we found that the loss of nephrin, a key component for maintaining podocyte slit diaphragm, became evident in accordance with the onset of albuminuria, especially 36 h post-LPS challenge (i.e., albumiuric stage). Likewise, nephrin mRNA levels were decreased to 13% of saline-treated mice. Such a transcriptional suppression of nephrin was associated with the loss of nucleus-localized Wilms tumor-1 (WT1), a transcriptional factor for up-regulating nephrin gene. Thereafter, urinary albumin levels were decreased in mice between 72 and 96 h post-LPS challenge (i.e., recovery-stage). Notably, nuclear localization of WT1 seemed to be normalized, and nephrin mRNA and protein levels returned near the basal level 72 h post-LPS challenge. During LPS-mediated sepsis, there was a transient increase in blood interleukin-1ß, a suppressor of nephrin production in podocytes. Therefore, down-regulation of nephrin by the loss in nuclear WT1, along with hyper-cytokinemia, may underlie the mechanisms by which albuminuria is induced by infectious stresses.

Type 2a sodium-phosphate co-transporter serves as a histological predictor of renal dysfunction and tubular apical damage in the kidneys of septic mice.

Acute renal failure (ARF) occurs in septic patients and is histologically characterized by tubular apical damages, including brush border breakdown. Nevertheless, little information is available to identify the apical injury at a molecular level. Type 2a Na-phosphate (Pi) co-transporter (NaPiT2a) is constitutively expressed by brush borders of proximal tubules under a healthy condition. Therefore, we investigated if NaPiT2a could be used as a negative marker to predict the renal dysfunction, using an animal model of septic ARF. After the treatment of lipopolysaccharide (LPS), mice manifested the tubular apical injury and renal dysfunction, as evidenced by the increase in blood urea nitrogen (BUN) levels. Immunohistochemical examination revealed that the expression of NaPiT2a by renal proximal tubules became faint, being reciprocal to the development of tubular hypoxia during sepsis. Inversely, the loss in apical NaPiT2a was restored in a regenerating stage, associated with the recovery from renal hypoxia. Overall, there was a negative correlation between the NaPiT2a expression and BUN levels or tubular injury scores in septic mice. Our data indicate that the loss of NaPiT2a is a reliable marker for predicting the progression of septic ARF, while local hypoxia might be involved in the decrease of NaPiT2a expression.

Reciprocal regulation of IL-6 and IL-10 balance by HGF via recruitment of heme oxygenase-1 in macrophages for attenuation of liver injury in a mouse model of endotoxemia.

Acute liver injury is a clinical hallmark of endotoxemia regarding the features of septic organ failure. In this process, interleukin (IL)-6 and IL-10 are key contributors for eliciting pro- and anti-inflammatory responses, respectively. In contrast, heme oxygenase-1 (HO-1) provides a defense mechanism against endotoxemia by controlling the IL-6/IL-10 balance, but how higher levels of HO-1 are sustained under pathological conditions remains unknown. Using a mouse model of endotoxemia, we provide evidence to show that hepatocyte growth factor (HGF) enhances HO-1 expression in macrophages, thereby up-regulating IL-10 and down-regulating IL-6 productions. Lipopolysaccharide (LPS)-treated mice manifested acute liver injury similar to that observed in septic patients, while administration of recombinant HGF enhanced expression of HO-1 by hepatic macrophages in vivo. As a result, HGF blocked the onset of hepatic injuries in LPS-treated mice. More importantly, when an HO-1 inhibitor (Sn-PP) was administered with HGF into LPS-treated mice, the protective effects of HGF against hepatic injury were attenuated. Furthermore, Sn-PP partially restored the HGF-mediated decrease in plasma IL-6 levels, while it inhibited the HGF-stimulated increase in plasma IL-10 levels. In the culture of macrophages (Raw264.7), HGF enhanced the LPS-mediated HO-1 induction, and this effect was abolished by cycloheximide, but not by actinomycin-D, thus suggesting that a post-transcriptional pathway is involved in HGF-mediated up-regulation of HO-1. Based on the current data, we conclude that up-regulation of HO-1 plays an important role in HGF-mediated hepatoprotection during endotoxemia, by favoring production of IL-10 over IL-6.

Hepatocyte growth factor prevents multiple organ injuries in endotoxemic mice through a heme oxygenase-1-dependent mechanism.

Acute renal failure (ARF) and acute respiratory distress syndrome (ARDS) are still lethal diseases during sepsis, whereas heme oxygenase-1 (HO-1) elicits a host defense response to sepsis. Herein, we provide evidence that hepatocyte growth factor (HGF) prevents ARF and ARDS via enhanced induction of HO-1. Lipopolysaccharide (LPS)-treated mice manifested renal and pulmonary injuries similar to those observed in septic patients, while HGF enhanced the HO-1 induction in renal tubular cells and in lung macrophages. As a result, onsets of ARF and ARDS were blocked by HGF in septic mice. Notably, an HO-1 inhibitor (SnPP) diminished the protective effects of HGF on LPS-induced organ injuries. Furthermore, the inhibitory effect of HGF on up-regulation of interleukin-1beta and interleukin-18 was largely restored by SnPP. This is the first report showing that "growth factor therapy" successfully inhibits both ARDS and ARF during endotoxemia, partially via HO-1-dependent suppression of hyper-cytokinemia.

Uptake ability of hepatic sinusoidal endothelial cells and enhancement by lipopolysaccharide.

The liver is one of the major organs that remove exogenous substances and waste products from the blood circulation. Hepatic macrophages (Kupffer cells) and sinusoidal endothelial cells are responsible for the scavenger function of the liver. The sinusoidal endothelial cells, called scavenger endothelial cells, are believed to take up only soluble substances and nanometer-sized particles under normal conditions, while Kupffer cells can ingest larger particles and whole cells. However, the sinusoidal endothelial cells may have the potential to take up considerably large particles under special conditions. In this morphological study, we compared the uptake ability between sinusoidal endothelial cells and Kupffer cells after intravenous injections of latex beads (20 nm, 100 nm and 500 nm in diameter), bovine serum albumin (BSA) and dextran. Under normal conditions, the sinusoidal endothelial cells vigorously took up 100-nm-sized latex beads as well as 20-nm latex beads. BSA and dextran were ingested by the endothelial cells but not the Kupffer cells. The administration of lipopolysaccharide (LPS), which mimics inflammation, stimulated the uptake by endothelial cells. The uptake of latex beads by Kupffer cells was also elevated under LPS-stimulated conditions, but the uptake of BSA and dextran by them was not. These findings suggest that the sinusoidal endothelial cells can ingest not only soluble substances but also larger particles than those expected, and their uptake ability is strengthened under inflammatory conditions.