Shunhua Hu

Glucosamine improves cardiac function following trauma-hemorrhage by increased protein O-GlcNAcylation and attenuation of NF-κB signaling

We have previously demonstrated that in a rat model of trauma-hemorrhage (T-H), glucosamine administration during resuscitation improved cardiac function, reduced circulating levels of inflammatory cytokines, and increased tissue levels of O-linked N-acetylglucosamine (O-GlcNAc) on proteins. The mechanism(s) by which glucosamine mediated its protective effect were not determined; therefore, the goal of this study was to test the hypothesis that glucosamine treatment attenuated the activation of the nuclear factor-kappaB (NF-kappaB) signaling pathway in the heart via an increase in protein O-GlcNAc levels. Fasted male rats were subjected to T-H by bleeding to a mean arterial blood pressure of 40 mmHg for 90 min followed by resuscitation. Glucosamine treatment during resuscitation significantly attenuated the T-H-induced increase in cardiac levels of TNF-alpha and IL-6 mRNA, IkappaB-alpha phosphorylation, NF-kappaB, NF-kappaB DNA binding activity, ICAM-1, and MPO activity. LPS (2 microg/ml) increased the levels of IkappaB-alpha phosphorylation, TNF-alpha, ICAM-1, and NF-kappaB in primary cultured cardiomyocytes, which was significantly attenuated by glucosamine treatment and overexpression of O-GlcNAc transferase; both interventions also significantly increased O-GlcNAc levels. In contrast, the transfection of neonatal rat ventricular myocytes with OGT small-interfering RNA decreased O-GlcNAc transferase and O-GlcNAc levels and enhanced the LPS-induced increase in IkappaB-alpha phosphorylation. Glucosamine treatment of macrophage cell line RAW 264.7 also increased O-GlcNAc levels and attenuated the LPS-induced activation of NF-kappaB. These results demonstrate that the modulation of O-GlcNAc levels alters the response of cardiomyocytes to the activation of the NF-kappaB pathway, which may contribute to the glucosamine-mediated improvement in cardiac function following hemorrhagic shock.

The protective effects of PUGNAc on cardiac function after trauma-hemorrhage are mediated via increased protein O-GlcNAc levels.

We have previously shown that administration of glucosamine after trauma-hemorrhage (TH) improved cardiac output and organ perfusion, and this was associated with increased levels of O-linked N-acetylglucosamine (O-GlcNAc) on proteins in the heart and brain. An alternative means of increasing O-GlcNAc levels is by inhibition of O-linked N-acetylglucosaminidase, which catalyzes the removal of N-acetylglucosamine from proteins, with O-(2-acetamido-2-deoxy-d-glucopyranosylidene) amino-N-phenylcarbamate (PUGNAc). The goal of this study, therefore, was to determine whether PUGNAc administration after TH also improves recovery of organ perfusion and function. Fasted male rats were bled to and maintained at a mean arterial blood pressure of 40 mmHg for 90 min, followed by fluid resuscitation. Intravenous administration of PUGNAc (200 &mgr;mol/kg body weight) 30 min after the onset of resuscitation significantly improved cardiac output compared with the vehicle controls (12.3 ± 1.3 mL/min per 100 g body weight vs. 25.5 ± 2.0 mL/min per 100 g body weight; P < 0.05), decreased total peripheral resistance (6.6 ± 0.8 mmHg/mL per minute per 100 g body weight vs. 3.7 ± 0.3 mmHg/mL per minute per 100 g body weight; P < 0.05), and increased perfusion of critical organ systems, including the kidney and liver, determined at 2 h after the end of resuscitation. Treatment with PUGNAc also attenuated the TH-induced increase in plasma IL-6 levels (864 ± 112 pg/mL vs. 392 ± 188 pg/mL; P < 0.05) and TNF-&agr; levels (216 ± 21 pg/mL vs. 94 ± 11 pg/mL; P < 0.05) and significantly increased O-GlcNAc levels in the heart, liver, and kidney. Thus, PUGNAc, like glucosamine, improves cardiac function and organ perfusion and reduced the level of circulating IL-6 and TNF-&agr; after TH. The similar effects of glucosamine and PUGNAc support the notion that the protection associated with both interventions is mediated via increased protein O-GlcNAc levels.

Estrogen prevents intestinal inflammation after trauma-hemorrhage via downregulation of angiotensin II and angiotensin II subtype I receptor

Although angiotensin II (Ang II) plays a key role in development of organ ischemia-reperfusion injury, it remains unclear whether it is involved in development of intestinal injury following trauma-hemorrhage (T-H). Studies have shown that 17beta-estradiol (E2) administration following T-H improves small intestinal blood flow; however, it is unclear whether Ang II plays a role in this E2-mediated salutary effect. Male Sprague-Dawley rats underwent laparotomy and hemorrhagic shock (removal of 60% total blood volume, fluid resuscitation after 90 min). At onset of resuscitation, rats were treated with vehicle, E2, or E2 and estrogen receptor antagonist ICI 182,780 (ICI). A separate group of rats was treated with Ang II subtype I receptor (AT1R) antagonist losartan. At 24 h after T-H, plasma Ang II, IL-6, TNF-alpha, intercellular adhesion molecule (ICAM)-1, cytokine-induced neutrophil chemoattractant (CINC)-1 and CINC-3 levels, myeloperoxidase (MPO) activity, and AT1R expression were determined. T-H significantly increased plasma and intestinal Ang II, IL-6, TNF-alpha levels, intestinal ICAM-1, CINC-1, CINC-3 levels, MPO activity, and AT1R protein compared with shams. E2 treatment following T-H attenuated increased intestinal MPO activity, Ang II level, and AT1R protein expression. ICI administration abolished the salutary effects of E2. In contrast, losartan administration attenuated increased MPO activity without affecting Ang II and AT1R levels. Thus Ang II plays a role in producing small intestine inflammation following T-H, and the salutary effects of E2 on intestinal inflammation are mediated in part by Ang II and AT1R downregulation.

Mechanism of salutary effects of finasteride on post-traumatic immune/inflammatory response: upregulation of estradiol synthesis.

Objective:The aim of this study was to evaluate whether pretreatment with finasteride, a 5α-reductase inhibitor, improves immune functions after trauma-hemorrhage. Summary Background Data:A number of studies have provided evidence for a gender dimorphism in host defense after trauma. Under stress conditions, such as trauma-hemorrhage, androgenic hormones have immunosuppressive effects, leading to increased susceptibility to sepsis, morbidity, and mortality. Testosterone is converted by 5α-reductase to 5α-dihydrotestosterone (DHT), a more potent androgen. Methods:Male C3H/HeN mice (8–10 weeks) were randomly assigned to receive finasteride or vehicle for 2 days and were then subjected to trauma-hemorrhage or sham operation. Trauma-hemorrhage was induced by a midline laparotomy and approximately 90 minutes of hemorrhagic shock (blood pressure, 35 mm Hg), followed by fluid resuscitation. Animals were killed 2 hours after resuscitation or sham procedure. Plasma levels and Kupffer cell production of cytokines (TNF-α, IL-6, IL-10, MCP-1, KC, and MIP-1α), lung neutrophil infiltration, and edema were evaluated. Results:Finasteride administration prevented the increase in cytokine plasma levels, decreased DHT, and increased 17β-estradiol plasma concentrations. In addition, neutrophil infiltration and edema formation in the lung were reduced by finasteride. The salutary effects of finasteride were abrogated after coadministration with an estrogen receptor inhibitor (ICI 182,780). Increased Kupffer cell cytokine production normally observed after trauma-hemorrhage was prevented by treatment with finasteride. Conclusion:These results suggest that inhibition of 5α-reductase leads to the conversion of testosterone to 17β-estradiol, which produces salutary effects on the post-traumatic immune response.

Mechanism of hepatoprotection in proestrus female rats following trauma-hemorrhage: heme oxygenase-1-derived normalization of hepatic inflammatory responses

Hepatic damage occurs in males and ovariectomized (OVX), not in proestrus (PE), females following trauma‐hemorrhage (T‐H). The mechanism responsible for hepatoprotection remains unknown. We hypothesized protection in PE is a result of enhanced heme oxygenase‐1 (HO‐1)‐derived down‐regulation of liver inflammatory responses. PE and OVX rats underwent T‐H (midline laparotomy, 60% blood loss). PE rats received vehicle (Veh; saline), HO‐1 inhibitor chromium mesoporphyrin IX chloride (CrMP; 2.5 mg/kg), zinc protoporphyrin IX (ZnPP; 25 mg/kg), or Akt/PI‐3K inhibitor Wortmannin (Wort; 1 mg/kg) 30 min prior to resuscitation or sham operation i.p. OVX rats received Veh or 17β‐estradiol (E2; 1 mg/kg) 30 min before hemorrhage. Rats were killed 2 h thereafter. Following T‐H, left ventricular performance was maintained in PE and E2 OVX rats but was depressed in OVX and CrMP‐, ZnPP‐, and Wort‐treated PE rats; liver damage was not evident in PE rats, and CrMP, ZnPP, and Wort abrogated protection; liver HO‐1, p38 MAPK, Akt/PI3K, and Bcl‐2 expression increased in PE and E2 OVX rats, which was abrogated by CrMP, ZnPP, and Wort, and liver ICAM‐1, caspase‐3, phospho‐IκB‐α, and NF‐κB expression increased in OVX and CrMP‐, ZnPP‐, and Wort‐PE rats; liver myeloperoxidase, NF‐κB DNA‐binding activity, TNF‐α, IL‐6, plasma proinflammatory cytokines, and cytokine‐induced neutrophil chemoattractants increased in OVX and CrMP‐, ZnPP‐, and Wort‐PE rats; and plasma estradiol levels and hepatic estrogen receptor‐α and ‐β expression decreased in OVX but were unaltered by CrMP, ZnPP, and Wort. Thus, enhanced HO‐1 in PE and E2 OVX females modulates inflammatory responses and protects liver following T‐H.