Tyrphostin AG 556 improves survival and reduces multiorgan failure in canine Escherichia coli peritonitis

Implication of G i proteins and Src tyrosine kinases in endotoxin-induced signal transduction events and mediator production

Previous studies have suggested that heterotrimeric G proteins and tyrosine kinases may be involved in lipopolysaccharide (LPS) signaling events. Signal transduction pathways activated by LPS were examined in human promonocytic THP-1 cells. We hypothesized that Gi proteins and Src tyrosine kinase differentially affect mitogen-activated protein (MAP) kinases (MAPK) and nuclear factor kappa (NF- B) activation. Post-receptor coupling to G i proteins were examined using pertussis toxin (PTx), which inhibits G i receptor-coupling. The involvement of the Src family of tyrosine kinases was examined using the selective Src tyrosine kinase inhibitor pyrazolopyrimidine-2 (PP2). Pretreatment of THP-1 cells with PTx attenuated LPS-induced activation of c-Jun-N-terminal kinase (JNK) and p38 kinase, and production of tumor necrosis factor-alpha (TNF-) and thromboxane B2 (TxB2). Pretreatment with PP2 inhibited TNF- and TxB2 production, but had no effect on p38 kinase or JNK signaling. Therefore, the G i-coupled signaling pathways and Src tyrosine kinase-coupled signaling pathways are necessary for LPS-induced TNF- and TxB2 production, but differ in their effects on MAPK activation. Neither PTx nor PP2 inhibited LPS-induced activation of interleukin receptor activated kinase (IRAK) or inhibitedtranslocation of NF- B. However, PP2 inhibitedLPS-inducedNF-B transactivation of a luciferase reporter gene construct in a concentration-dependent manner. Thus, LPS induction of Src tyrosine kinases may be essential in downstream NF- B transactivation of genes following DNA binding. PTx had no effect on NF- B activation of the reporter construct. These data suggest upstream divergence in signaling through G i pathways leading to MAPK activation and other signaling events leading to I B degradation and NF- B DNA binding.

Tyrosine Kinase Inhibitor Tyrphostin AG490 Inhibits Osteoclast Differentiation in Collagenase-Induced Osteoarthritis

The janus kinase (JAK)-signal transducer and activator of transcription (STAT) cascade plays a principal role in the signaling of a vast array of cytokines and growth factors which stimulates diverse cellular functions and immune responses. Osteoarthritis (OA) is the most common joint disease in the adult population. The present study was designed to evaluate the effects of tyrosine kinase inhibitor, tyrphostin AG490 in a mouse model of collagenase-induced osteoarthritis (CIOA). CIOA was provoked by two intraarticular (i.a.) injections of collagenase in mice and intraperitoneally (i.p.) treated with AG490 at a dose of 5 mg/kg at days 0, 5 and 10 and at a dose of 8 mg/kg at day 18. The administration of AG490 in CIOA mice inhibited osteoclast generation in bone and the loss of glycosaminoglycans and proteoglycans in cartilage. Tyrphostin decreased the levels of IFN-γ, IL1, IL-6 and IL-17 in the synovial fluid (SF) dependant on the time post AG490 administration. Limited numbers of CD11b positive Ly6G neutrophils in blood and SF along with a decrease of F4/80 positive cells in synovial fluid (SF) were observed in tyrphostin AG490-treated arthritic mice. AG490 inhibited M-CSF+RANKL-induced cytokine production by bone marrow (BM) cells and the differentiation of BM cells in vitro. Because of the findings presented, we argue that tyrphostin AG490 may hold promising therapeutic potential against important clinical conditions such as osteoarthritis (OA).

Investigation of tyrphostin AG 556 for testicular torsion-induced ischemia reperfusion injury in rat

OBJECTIVE

To investigate the effects of tyrphostin AG 556, a tyrosine kinase inhibitor (TKI) in an experimental model of testicular ischemia-reperfusion (I/R) injury.

MATERIAL AND METHODS

Twenty-four adult male rats were randomly divided into four groups (n = 6): sham, torsion/detorsion (T/D), T/D + dimethylsulfoxide (DMSO) (vehicle group), and T/D + DMSO + tyrphostin AG 556. Testicular torsion was achieved by rotating the left testis 720° clockwise for 4 h. Thirty minutes before detorsion, 3 mg/kg tyrphostin AG 556 was injected transperitoneally in the AG 556 group and DMSO was injected transperitoneally in the DMSO group. After 2 h of reperfusion arterial blood samples were collected for biochemical analysis for malondialdehyde (MDA), ischemia modified albumin (IMA), SCUBE1 (signal peptide-CUB [complement C1r/C1s, Uegf, and Bmp1] and EGF [epidermal growth factor] like domain-containing protein 1), total oxidant status (TOS), total antioxidant status (TAS), and oxidative stress index (OSI) parameters, and ipsilateral orchiectomies were performed for histopathological examination based on the semi-quantitative Johnsen's mean testicular biopsy score (MTBS) in all groups.

RESULTS

Tyrphostin AG 556 exhibited a protective effect against I/R injury in testicular torsion. Of the biochemical parameters evaluated as a result of testicular I/R, IMA, MDA, and TOS levels were significantly elevated. There was no significant difference in terms of these biochemical parameters between the sham and AG 556 groups. Significant histopathological injury was determined by comparing the T/D and sham groups. According to histopathological injury scores, significant differences were determined between T/D and AG 556 groups and between AG 556 and sham groups. AG 556 had a superior improving effect on Johnsen's scores than DMSO.

CONCLUSIONS

Our results suggest that the use of tyrphostin AG 556 prior to testicular reperfusion has a protective effect against testicular I/R injury.

Toll-like receptor-4 antagonist eritoran tetrasodium for severe sepsis

The human innate immune system initiates inflammation in response to bacterial molecules, particularly Gram-negative bacterial endotoxin. The steps by which endotoxin exposure leads to systemic inflammation include binding to Toll-like receptor-4 that specifically recognizes endotoxin and subsequently triggers cellular and molecular inflammatory responses. Severe sepsis is a systemic inflammatory response to infection that induces organ dysfunction and threatens a person's survival. Severe sepsis is frequently associated with increased blood levels of endotoxin. It is a significant medical problem that effects approximately 700,000 patients every year in the USA, resulting in 250,000 deaths. Eritoran tetrasodium is a nonpathogenic analog of bacterial endotoxin that antagonizes inflammatory signaling by the immune receptor Toll-like receptor-4. Eritoran is being evaluated for the treatment of patients with severe sepsis.

Animal models of sepsis and sepsis-induced kidney injury

Sepsis is characterized by a severe inflammatory response to infection, and its complications, including acute kidney injury, can be fatal. Animal models that correctly mimic human disease are extremely valuable because they hasten the development of clinically useful therapeutics. Too often, however, animal models do not properly mimic human disease. In this Review, we outline a bedside-to-bench-to-bedside approach that has resulted in improved animal models for the study of sepsis - a complex disease for which preventive and therapeutic strategies are unfortunately lacking. We also highlight a few of the promising avenues for therapeutic advances and biomarkers for sepsis and sepsis-induced acute kidney injury. Finally, we review how the study of drug targets and biomarkers are affected by and in turn have influenced these evolving animal models.

A canine model of septic shock: balancing animal welfare and scientific relevance

A shock canine pneumonia model that permitted relief of discomfort with the use of objective criteria was developed and validated. After intrabronchial Staphylococcus aureus challenge, mechanical ventilation, antibiotics, fluids, vasopressors, sedatives, and analgesics were titrated based on algorithms for 96 h. Increasing S. aureus (1 to 8 x 10(9) colony-forming units/kg) produced decreasing survival rates (P = 0.04). From 4 to 96 h, changes in arterial-alveolar oxygen gradients, mean pulmonary artery pressure, IL-1, serum sodium levels, mechanical ventilation, and vasopressor support were ordered based on survival time [acute nonsurvivors (< or =24 h until death, n = 8) > or = subacute nonsurvivors (>24 to 96 h until death, n = 8) > or = survivors (> or =96 h until death, n = 22) (all P < 0.05)]. In the first 12 h, increases in lactate and renal abnormalities were greatest in acute nonsurvivors (all P < 0.05). Compared with survivors, subacute nonsurvivors had greater rises in cytokines and liver enzymes and greater falls in platelets, white cell counts, pH, and urine output from 24 to 96 h (all P < 0.05). Importantly, these changes were not attributable to dosages of sedation, which decreased in nonsurvivors [survivors vs. nonsurvivors: 5.0 +/- 1.0 vs. 3.8 +/- 0.7 ml x h(-1) x (fentanyl/midazolam/ medetomidine)(-1); P = 0.02]. In this model, the pain control regimen did not mask changes in metabolic function and lung injury or the need for more hemodynamic and pulmonary support related to increasing severity of sepsis. The integration into this model of both specific and supportive titrated therapies routinely used in septic patients may provide a more realistic setting to evaluate therapies for sepsis.

Statins and sepsis: multiple modifications at multiple levels

Sepsis, an infection-induced inflammatory syndrome, is a leading and increasing cause of mortality worldwide. Animal and human observational studies suggest statins may prevent the morbidity and mortality associated with the sepsis syndrome. In this Review, we describe the demonstrated mechanisms through which statins modulate the inflammatory response associated with sepsis. These mechanisms include effects on cell signalling with consequent changes at the transcriptional level, the induction of haem oxygenase, the direct alteration of leucocyte-endothelial cell interaction, and the reduced expression of MHC II. Since statins do not target individual inflammatory mediators, but possibly reduce the overall magnitude of the systemic response, this effect could prove an important distinguishing feature modulating the host response to septic insults. This work establishes the biological plausibility needed for future trials of statins in critical illness.

Statins: panacea for sepsis?

Sepsis occurs when the immune system responds to a localised infection at a systemic level, thereby causing tissue damage and organ dysfunction. Statins have proven health benefits in many diseases involving vascular inflammation and injury. Recent animal data suggest that the administration of a statin before a sepsis-inducing insult reduces morbidity and improves survival. The immunomodulatory and anti-inflammatory effects of statins, collectively referred to as pleiotropic effects, lend biological plausibility to such findings. Limited human data hint at reduced mortality rates in bacteraemic patients, and a reduced risk of sepsis in patients with bacterial infections concurrently taking statins. These lines of evidence point to a potential new treatment and prevention modality for sepsis. The stage is set for randomised controlled clinical trials that will determine whether statins represent a safe and beneficial treatment in critically ill, septic patients and whether statins are effective at preventing sepsis in high-risk clinical settings.

Tyrphostin AG 126 reduces intestinal ischemia-reperfusion injury in the rat

In this study, we evaluated the effect of tyrphostin AG126, a tyrosine kinase inhibitor, in the splanchnic artery occlusion (SAO) shock mediated injury. SAO shock was induced in rats by clamping both the superior mesenteric artery and the celiac trunk for 45 min. After 1 h of reperfusion, SAO shocked rats developed a significant fall in mean arterial blood pressure. Ileum analysis revealed that SAO shock is characterized by a significant (P<0.01) induction in TNF-alpha and IL-1 ileum levels, while immunohistochemistry examination of necrotic ileum demonstrated a marked increase in the immunoreactivity in intracellular adhesion molecule (ICAM-1) and nitrotyrosine formation. A significant increase in myeloperoxidase activity (P<0.01) was also observed in rats subjected to ischemia-reperfusion injury. Tyrphostin AG126, given intraperitoneally 30 min before ischemia at the dose of 5 mg/kg, significantly improved mean arterial blood pressure, markedly reduced TNF-alpha and IL-1beta levels and the positive staining of ICAM-1 into the reperfused ileum. Tyrphostin AG126 significantly improved the histological status of the reperfused tissue. In conclusion, this study demonstrates that tyrphostin AG126 exerts multiple protective effects in splanchnic artery occlusion/reperfusion shock and suggests that this tyrosine kinase inhibitor may be a candidate for consideration as a therapeutic intervention for ischemia-reperfusion injury.

The effect of tyrphostin AG-556 on intimal thickening in a mouse model of arterial injury

BACKGROUND

Inflammation has been shown to play an important role in promoting the response to arterial injury and proinflammatory cytokines, such as tumor necrosis factor (TNF) alpha, are candidate mediators. AG-556 is a tyrosine kinase inhibitor proven to be effective in a model of multiple sclerosis-like syndrome in mice due to its immunomodulating effect. In the current study, we investigated the effect of the tyrphostin AG-556 on neointimal thickening and cytokine profile in a model of arterial injury in the mouse.

METHODS

Injury was induced by external cuff placement on the left femoral artery of wild-type C57BL/6 mice. AG-556 dissolved in DMSO was injected intraperitoneally daily to the injured mice in a dosage of 2 mg/mouse. Control mice received DMSO injections. Histological analysis was carried out to assess neointimal formation. Splenocytes were cultured in the absence and presence of a mitogen for evaluation of thymidine incorporation and cytokine production.

RESULTS

AG-556 treatment significantly attenuated intimal thickening (43,000+/-17,000 microm2; n=11) when compared to DMSO administration (286,000+/-127,000 microm2; n=10; P<0.05). Basal interferon-gamma production by splenocytes from AG-556-treated mice was increased by approximately 20-fold in comparison with levels in DMSO-treated animals, whereas Con-A induced secretion of the cytokine was similar between both groups. Levels of TNF-alpha, IL-4 and IL-10 in the culture supernatant from treated and non-treated animals did not differ significantly.

CONCLUSION

The tyrosine kinase inhibitor AG-556 may have a role in the reduction of intimal thickening. The effect could be mediated via an immune modulating effect involving a significant increase in the smooth muscle cell inhibitory cytokine IFN-gamma.

Tyrosine kinase inhibition reduces inflammation in the acute stage of experimental pneumococcal meningitis

Bacterial meningitis is an acute inflammatory disease of the central nervous system with a mortality rate of up to 30%. Excessive stimulation of the host immune system by bacterial surface components contributes to this devastating outcome. In vitro studies have shown that protein tyrosine kinase inhibitors are highly effective in preventing the release of proinflammatory cytokines induced by pneumococcal cell walls in microglia. In a well-established rat model, intracisternal injection of purified pneumococcal cell walls induced meningitis characterized by increases in the regional cerebral blood flow and intracranial pressure, an influx of leukocytes, and high concentrations of tumor necrosis factor alpha (TNF-alpha) in the cerebrospinal fluid. Compared with the values at the beginning of the experiment, intraperitoneal injection of tyrphostin AG 126 reduced the increases in regional cerebral blood flow (at 6 h, 127% +/- 14% versus 222% +/- 51% of the baseline value; P < 0.05) and intracranial pressure (at 6 h, 0.8 +/- 2.4 versus 5.4 +/- 2.0 mm of Hg; P < 0.05), the influx of leukocytes (at 6 h, 1,336 +/- 737 versus 4,350 +/- 2,182 leukocytes/microl; P < 0.05), and the TNF-alpha concentration (at 6 h, 261 +/- 188 versus 873 +/- 135 pg/microl; P < 0.05). These results demonstrate that inhibition of AG 126-sensitive tyrosine kinase pathways may provide new approaches for preventing excessive inflammation and reducing the increases in blood flow and intracranial pressure in the acute phase of bacterial meningitis.

The effect of early and late treatment with the tyrphostin AG-556 on the progression of experimental autoimmune myocarditis

Experimental autoimmune myocarditis (EAM) in rats is a T-cell-mediated disorder; the involvement of TNF-alpha in this disorder has been demonstrated. EAM represents a model for human autoimmune myocarditis, a condition for which no optimal treatment is currently available. Tyrphostins AG-126 and AG-556 were previously shown to reduce TNF-alpha production and its end-organ cytotoxicity, thus proving beneficial in animal models of septic shock and experimental autoimmune encephalomyelitis. To study the effects of AG-126 and AG-556 on EAM, we induced the disorder in male Lewis rats through immunization against myosin and subsequently treated the rats with both agents or the control DMSO both before and after the appearance of myocardial inflammation. AG-556 administered daily for 21 days from the day of EAM induction, significantly reduced the severity of myocarditis. Similarly, AG-556 administered for an additional 10 days after myosin immunization (when signs of inflammation are already present) attenuated the progression of myocarditis, though AG-126 did not. TNF-alpha and IFN-gamma production by in vitro sensitized splenocytes from AG-556-treated rats was significantly diminished as compared with control cells from EAM animals. Thus, AG-556 may represent a novel strategy of ameliorating the progression of myocarditis without non-selectively compromising the immune system.

The effects of tyrphostine Ag 556 on experimental spinal cord ischemia reperfusion injury

BACKGROUND

To investigate the effects of Tyrphostin Ag 556 on spinal cord ischemia reperfusion injury.

METHODS

The inhibition of tyrosine kinase may represent a novel approach in the treatment of spinal cord ischemia reperfusion injury. Recently, a family of tyrosine kinase inhibitors, the tyrphostins, has been successfully used in models of endotoxemia, peritonitis, and hypovolemic shock.

MATERIALS AND METHODS

Twenty-four Wistar rats were used in the study. Rats were divided into 4 groups of 6 animals. The groups were named as sham operated group, injury group, vehicle group, and treatment group. Clamping of the abdominal aorta was performed for 45 minutes with all of the groups except sham-operated group. All of the rats were sacrificed 24 hours after the operation for biochemical and ultrastructural studies.

RESULTS

Tyrphostin Ag 556 treatment was found effective on experimental spinal cord ischemia reperfusion injury. The Malondialdehyde (MDA) values of the treatment group were statistically significant lower then the other reperfusion injury groups. The histologic examination showed better cellular structure in the treatment group than the other reperfusion injury groups. The neurologic scores of the treatment group also improved after treatment.

CONCLUSIONS

Tyrphostin Ag 556 alters spinal cord ischemia reperfusion injury by inhibiting protein kinases. Further investigations will be required to determine the long-term effects of this drug.

The tyrosine kinase inhibitor tyrphostin AG126 reduces renal ischemia/reperfusion injury in the rat

BACKGROUND

We investigate the effects of tyrphostin AG126, an inhibitor of tyrosine kinase activity, on the renal dysfunction and injury caused by ischemia/reperfusion (I/R) of the kidney.

METHODS

Tyrphostin AG126 (5 mg/kg intraperitoneally) was administered to male Wistar rats 30 minutes prior to bilateral renal ischemia for 45 minutes followed by reperfusion for up to 48 hours. Biochemical markers of renal dysfunction and injury were measured and renal sections assessed for renal injury. Expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) and formation of nitrotyrosine and poly (ADP) ribose (PAR) were assessed using immunohistochemistry. Rat proximal tubular cells (PTCs) were incubated with interferon-gamma (100 IU/mL), bacterial lipopolysaccharide (10 microg/mL), and with increasing concentrations of tyrphostin AG126 (0.0001-1 mmol/L) for 24 hours. Nitric oxide production was measured in both plasma from rats subjected to I/R and in incubation medium from PTCs.

RESULTS

After 6 hours of reperfusion, tyrphostin AG126 significantly reduced the increase in serum and urinary indicators of renal dysfunction and injury caused by I/R and reduced histologic evidence of renal injury. Tyrphostin AG126 also improved renal function (after 24 and 48 hours of reperfusion) and reduced the histologic signs of renal injury (after 48 hours of reperfusion). Tyrphostin AG126 reduced the expression of iNOS and nitric oxide levels in both rat plasma and in PTC cultures, as well as expression of COX-2. Tyrphostin AG126 also reduced nitrotyrosine and PAR formation, suggesting reduction of nitrosative stress and poly (ADP-ribose) polymerase (PARP) activation, respectively.

CONCLUSION

Taken together, these results show that tyrphostin AG126 significantly reduces the renal dysfunction and injury caused by I/R of the kidney. We propose that inhibition of tyrosine kinase activity may be useful against renal I/R injury.

Tyrphostin reduces the organ injury in haemorrhagic shock: role of inducible nitric oxide synthase

We investigate the effects of the tyrosine kinase inhibitor, tyrphostin AG126 on the organ injury and dysfunction (kidney, liver, pancreas, muscle and or brain) associated with haemorrhagic shock in the anaesthetised rat. Haemorrhage (sufficient to lower mean arterial blood pressure to 45 mmHg for 90 min) and subsequent resuscitation with the shed blood resulted (within 4 h after resuscitation) in expression of inducible nitric oxide synthase inhibitor (iNOS), positive staining for nitrotyrosine (liver), renal, liver and pancreatic injury, and injury to the muscle and brain. Pre-treatment (30 min prior to the onset of haemorrhage) with the tyrosine kinase inhibitor tyrphostin AG126 reduced the iNOS expression, nitrotyrosine formation, hepatic, brain or muscular injury, and to a lesser extent, the renal injury caused by haemorrhage and resuscitation. Selective inhibition of iNOS activity with N-(3-(aminomethyl)benzyl) acetamidine (1400 W, 10 mg kg(-1) i.v., 5 min prior to the onset of resuscitation), also attenuated nitrotyrosine formation, renal dysfunction, liver injury and brain or muscular injury associated with haemorrhagic shock. The expression of iNOS protein was unaffected by 1400 W. We propose that the activation of tyrosine kinases and the induction of iNOS contribute to the multiple organ injury caused by severe haemorrhage and resuscitation.

beta-Lapachone reduces endotoxin-induced macrophage activation and lung edema and mortality

beta-Lapachone, a 1,2-naphthoquinone, is a novel chemotherapeutic agent. It has been shown to be capable of suppressing inducible nitric oxide synthase expression and function in rat alveolar macrophages. The authors further performed experiments to examine the molecular mechanism of beta-lapachone on LPS-induced responses in rat alveolar macrophages and to evaluate its in vivo antiinflammatory effect. A significant increase in nitrite production and inducible nitric oxide synthase expression was elicited in macrophages treated with LPS that was inhibited by coincubation with beta-lapachone. beta-Lapachone could also inhibit the production of tumor necrosis factor-alpha induced by LPS. LPS induces protein tyrosine phosphorylation and nuclear factor-kappaB binding activity by gel mobility shift assay in macrophages. These events were significantly inhibited by beta-lapachone. Furthermore, beta-lapachone in vivo protected against the induction of lung edema, lung-inducible nitric oxide synthase protein expression and nuclear factor-kappaB activation, lethality, and increased plasma nitrite and serum tumor necrosis factor-alpha levels induced by LPS. These results indicate that beta-lapachone suppresses inducible nitric oxide synthase induction and tumor necrosis factor-alpha production mediated by the inhibition of protein tyrosine phosphorylation and nuclear factor-kappaB activation caused by LPS. This results in a beneficial effect in an animal model of sepsis.

Tyrphostin AG-556 reduces myocardial infarct size and improves cardiac performance in the rat

TNF-alpha is a proinflammatory cytokine, abundantly expressed after myocardial infarction. It has been suggested that it exhibits myocardial suppressive and cytotoxic effects. AG-556 is a tyrosine kinase inhibitor synthesized based on its ability to reduce TNF-alpha production and cell toxicity, and to improve experimental models mediated by TNF-alpha (i.e., peritontitis and experimental autoimmune encephalomyelitis). Daily, for 7 days, rats were injected ip with either AG-556 dissolved in DMSO or with the control vehicle. Infarct size was determined in the hearts as well as in fibrous scar formation. Cardiac TNF-alpha expression was evaluated by ELISA and immunohistochemistry. Functional hemodynamic parameters were evaluated employing echocardiography prior to sacrifice. AG-556 treatment reduced MI size at 7 days with a parallel effect on fibrous tissue formation. TNF-alpha production by splenocytes was reduced upon AG-556 treatment, whereas no differences were evident between the groups with regard to myocardial cytokine expression. AG-556 attenuated the decrease in fractional shortening at the expense of preserving end systolic diameter. AG-556 has proven beneficial in reducing myocardial infarct size and attenuated consequent hemodynamic deterioration in the rat model. If reconfirmed, AG-556 may be of potential clinical use in post-MI patients.

Protein kinase inhibitors as a therapeutic modality

Most of the signal transduction pathways are mediated by protein kinases regulating every aspect of cell function. Mutations which deregulate their expression or their function or both result in cancers. Therefore, protein kinase inhibitors has become the focus of development of new therapies for cancer. Almost all 120 protein tyrosine kinases are involved in signaling, whereas only a handful of Ser/Thr kinases are involved. Thus, most of the effort is directed toward the development of tyrosine phosphorylation inhibitors. The success of Gleevec in the treatment of chronic myeloid leukemia and of Iressa for lung cancer validates the approach.

Endotoxin as a drug target

OBJECTIVE

To review the preclinical and clinical evidence that antiendotoxin therapeutic strategies are potentially useful in the prevention and treatment of septic shock.

STUDY DESIGN

A critical review of the literature over the past 30 yrs relating basic and clinical research on the therapeutic value of endotoxin as a target for the prevention and treatment of severe sepsis and septic shock.

MAIN RESULTS

Bacterial endotoxin is a potent and predominant microbial mediator that induces an intense inflammatory and procoagulant response by elements of the innate immune response. This macromolecule is capable of inducing lethal septic shock in experimental animals, and a large number of preclinical studies consistently demonstrate the survival advantage of endotoxin inhibition in experimental models of sepsis. Clinical studies indicate that endotoxin may be found in the systemic circulation in the majority of humans with septic shock. Endotoxemia is largely independent of the nature of the infecting microorganism despite the fact that this molecule is specifically found in the outer membrane of Gram-negative bacteria only. Antiendotoxin strategies studied thus far have not provided reproducible survival benefits in clinical trials in septic patients.

CONCLUSIONS

Despite compelling evidence of the critical importance of endotoxin in the pathogenesis of Gram-negative bacterial sepsis in preclinical investigations and numerous clinical interventional trials, the utility of antiendotoxin approaches to significantly reduce the mortality rate in human septic shock remains unproven. Ongoing clinical trials with specific endotoxin inhibitors should determine the potential value of this therapeutic approach to the management of septic shock.

Lyn- and ERK-mediated vs. Ca2+ -mediated neutrophil O responses with thermal injury

We evaluated the dependency of neutrophil O production on PTK-Lyn and MAPK-ERK1/2 in rats after thermal injury. Activation of PTK-Lyn was assessed by immunoprecipitation. Phosphorylation of ERK1/2 was assessed by Western blot analysis. O production was measured by isoluminol-enhanced luminometry. Imaging technique was employed to measure neutrophil [Ca2+](i) in individual cells. Thermal injury caused marked upregulation of Lyn and ERK1/2 accompanying enhanced neutrophil O production. Treatment of rats with PTK blocker (AG556) or MAPK blocker (AG1478) before burn injury caused complete inhibition of the respective kinase activation. Both AG556 and AG1478 produced an ~66% inhibition in O production. Treatment with diltiazem (DZ) produced an ~37% inhibition of O production without affecting Lyn or ERK1/2 activation with burn injury. Ca2+ mobilization was upregulated with burn injury but not affected by treatment of burn rats with AG556. Unlike the partial inhibition of burn-induced O production by AG556, AG1478, or DZ, platelet-activating factor antagonist (PAFa) treatment of burn rats produced near complete inhibition of O production. PAFa treatment also blocked activation of Lyn. The findings suggest that the near complete inhibition of O production by PAFa was a result of blockade of PTK as well as Ca2+ signaling. Overall, our studies show that enhanced neutrophil O production after thermal injury is a result of potentiation of Ca2+ -linked and -independent signaling triggered by inflammatory agents such as PAF.

Risk and the efficacy of antiinflammatory agents: retrospective and confirmatory studies of sepsis

We investigated whether a relationship between risk of death and treatment effect could explain the disparate results between the preclinical and clinical sepsis trials of antiinflammatory agents over the last decade. A metaregression analysis of cited preclinical studies showed that the treatment effects of these agents were highly dependent on risk of death (p = 0.0001) and that animals were studied at significantly higher control mortality rates than humans (median [25th-75th quartile], 88% [79-96%] versus 39% [32-42%], p = 0.0001). An analysis of the clinical trials showed that antiinflammatory agents were also significantly more efficacious in septic patients with higher risk of death (p = 0.002) and were harmful in those with low risk. To test this relationship prospectively, we studied antiinflammatory agents in models employing differing doses of bacterial challenge to produce the full range of risk of death. We found that the efficacy of these agents, although very beneficial at high control mortality rates, was much reduced (p = 0.0001) and similar to those in human trials at moderate control mortality rates (i.e., 30 to 40%). The efficacy of antiinflammatory agents during sepsis is dependent on the risk of death, an observation that explains the apparent contradiction between preclinical and clinical trial results. Accounting for this relationship may be necessary for the safe and effective development of antiinflammatory therapies for sepsis.

Tumor necrosis factor-alpha impairs endothelium-dependent relaxation of rat renal arteries, independent of tyrosine kinase

We hypothesized that tumor necrosis factor-alpha (TNF-alpha) mimics endotoxin in attenuating endothelium-dependent vasodilation and smooth muscle constriction of rat renal arteries, and that tyrosine kinase is involved. Isolated rat renal arteries (n =6 per group), pretreated for 2 h by genistein (4',5,7-trihydroxyisoflavone, 10 microg/mL, a tyrosine kinase inhibitor) or vehicle, were exposed for 2 h to recombinant human (rh) TNF-alpha (100 ng/mL) or vehicle. rhTNF-alpha attenuated (P < 0.05) the constriction response to depolarizing 125 mM KCl (952.6+/-125.3 mg/mm vs. 1191.4+/-136.8 mg/mm in rhTNF-alpha-exposed and control segments, respectively), but did not affect the constriction response to norepinephrine (NE, 0.01-10 microM). Genistein did not affect the constriction response to KCl. The concentration-response relation to NE in genistein-pretreated control segments showed (P < 0.05) a rightward shift, while the maximum constriction was not affected. Genistein did not prevent a reduction (P < 0.05) by rhTNF-alpha in the maximum response to NE (721.7+/-42.4 mg/mm vs. 999.8+/-84.4 mg/mm in controls). The endothelium-dependent relaxation induced by (acetyl choline) ACh (0.001-1.0 microM) was attenuated (P < 0.05) by rhTNF-alpha (39.4%+/-6.7% and 77.4%+/-10.0% in rhTNF-alpha-exposed and control segments, respectively). The reduction (P < 0.05) in maximum ACh-induced relaxation after exposure to rhTNF-alpha was not affected by genistein (44.6%+/-3.4% and 70.8% x 2.2% in genistein-pretreated rhTNF-alpha-exposed and control segments, respectively). Hence, the attenuated endothelium-dependent relaxation and smooth muscle constriction of rat renal arteries following short-term rhTNF-alpha exposure, mimicking the effect of endotoxin, does not involve the activity of tyrosine kinase. The latter may be involved in pharmacomechanical coupling, by increasing Ca2+ sensitivity, but less in the electromechanical coupling of smooth muscle constriction.

Mitogen-activated protein kinases mediate activator protein-1-dependent human inducible nitric-oxide synthase promoter activation

Inducible nitric-oxide synthase (iNOS) is an important signaling protein involved in the regulation of biological processes (e.g. vasodilation, inflammation) and is subject to transcriptional regulation by cytokines and lipopolysaccharide (LPS). Full activation of the human iNOS (hiNOS) promoter by cytokines (i.e., tumor necrosis factor-alpha, interleukin-1beta, interferon-gamma (IFN-gamma)) required downstream and upstream nuclear factor-kappaB (-115, -8283) and activator protein-1 (AP-1) (-5115, -5301) transcription factor binding sites. Human lung epithelial (A549) cells were transiently transfected with luciferase reporter plasmids containing an 8.3-kilobase human iNOS promoter to examine the molecular signaling events necessary for hiNOS transcriptional activation. The combination of LPS and IFN-gamma, but neither alone, increased hiNOS promoter activity 28-fold, in a reaction requiring two critical AP-1 (JunD-Fra-2) promoter binding sites. Mitogen-activated protein kinases (MAPKs) were assessed as potential activators of AP-1 and the hiNOS promoter. Both pharmacological and molecular inhibitors of the extracellular signal-related kinase (ERK) and p38 pathways reduced cytokine mixture (CM)- and LPS/IFN-gamma-induced promoter activation. By gel retardation analysis, the addition of MAP/ERK kinase-1 and p38 inhibitors significantly diminished AP-1 binding in both CM- and LPS/IFN-gamma-stimulated cells. Thus, p38- and ERK-dependent pathways, through effects on the AP-1 complex, activate the hiNOS promoter in cells stimulated with CM or LPS/IFN-gamma.

Inhibition of tyrosine kinase signaling after trauma-hemorrhage: a novel approach for improving organ function and decreasing susceptibility to subsequent sepsis

OBJECTIVE

To determine whether administration of a tyrosine kinase inhibitor after trauma-hemorrhage has any beneficial effects on cardiovascular parameters and hepatocellular function and on survival rate after subsequent sepsis.

BACKGROUND

Increased inflammatory cytokine release and concomitant activation of intracellular signaling pathways contributes to multiple organ dysfunction and increased susceptibility to subsequent sepsis after severe hemorrhagic shock.

METHODS

Male Sprague-Dawley rats underwent a midline laparotomy (i.e., soft-tissue trauma induced) and were then bled to and maintained at a mean arterial pressure of 40 mmHg until 40% of the maximal shed blood volume was returned in the form of Ringer's lactate. The rats were then resuscitated with four times the shed blood volume in the form of Ringer's lactate during a 60-minute period. A tyrosine kinase inhibitor, AG 556 (7.5 mg/kg), or vehicle was administered intraperitoneally at the middle of resuscitation. At 24 hours after resuscitation, various in vivo parameters such as heart performance, cardiac index, and hepatocellular function (i.e., the maximum velocity and the overall efficiency of indocyanine green clearance) were determined. Phosphorylation state of the mitogen-activated protein kinases p44/42 and p38 in the liver was assessed by Western blot analysis. In additional groups of rats, sepsis was induced by cecal ligation and puncture at 20 hours after hemorrhage. The necrotic cecum was excised 10 hours thereafter, and the survival rate was monitored for a period of 10 days.

RESULTS

AG 556 treatment restored the depressed cardiovascular and hepatocellular functions after trauma-hemorrhage and resuscitation, which was associated with reduced phosphorylation of mitogen-activated protein kinases p44/42 and p38. Moreover, treatment with AG 556 significantly increased the survival rate of rats after trauma-hemorrhage and induction of subsequent sepsis compared with vehicle-treated rats.

CONCLUSION

Inhibition of tyrosine kinase signaling after trauma-hemorrhage may represent a novel therapeutic approach for improving organ functions and decreasing the death rate from subsequent sepsis under such conditions.

Multi-drug strategies are necessary to inhibit the synergistic mechanism causing tissue damage and organ failure in post infectious sequelae

The paper discusses the principal evidence that supports the concept that cell and tissue injury in infectious and post-infectious and inflammatory sequelae might involve a deleterious synergistic interaction among microbial- and host-derived pro-inflammatory agonists. Experimental models had proposed that a rapid cell and tissue injury might be induced by combinations among subtoxic amounts of three major groups of agonists generated both by microorganisms and by the host's own defense systems. These include: (1) oxidants: Superoxide, H(2)O(2), OH', oxidants generated by xanthine-xanthine-oxidase, ROO; HOC1, NO, OONO'-, (2) the membrane-injuring and perforating agents, microbial hemolysins, phospholipases A(2) and C, lysophosphatides, bactericidal cationic proteins, fatty acids, bile salts and the attack complex of complement a, certain xenobics and (3) the highly cationic proteinases, elastase and cathepsin G, as well as collagenase, plasmin, trypsin and a variety of microbial proteinases. Cell killing by combinations among the various agonists also results in the release of membrane-associated arachidonate and metabolites. Cell damage might be further enhanced by certain cytokines either acting directly on targets or through their capacity to prime phagocytes to generate excessive amounts of oxidants. The microbial cell wall components, lipoteichoic acid (LTA), lipopolysaccharides (LPS) and peptidoglycan (PPG), released following bacteriolysis, induced either by cationic proteins from neutrophils and eosinophils or by beta lactam antibiotics, are potent activators of macrophages which can release oxidants, cytolytic cytokines and NO. The microbial cell wall components can also activate the cascades of coagulation, complement and fibrinolysis. All these cascades might further synergize with microbial toxins and metabolites and with phagocyte-derived agonsits to amplify tissue damage and to induce septic shock, multiple organ failure, 'flesh-eating' syndromes, etc. The long persistence of non-biodegradable bacterial cell wall components within activated macrophages in granulomatous inflammation might be the result of the inactivation by oxidants and proteinases of bacterial autolytic wall enzymes (muramidases). The unsuccessful attempts in recent clinical trials to prevent septic shock by the administration of single antagonists is disconcerting. It does suggest however that, since tissue damage in post-infectious syndromes is most probably the end result of synergistic interactions among a multiplicity of agents, only agents which might depress bacteriolysis in vivo and 'cocktails' of appropriate antagonists, but not single antagonists, if administered at the early phases of infection especially to patients at high risk, might help to control the development of post-infectious syndromes. However, the use of adequate predictive markers for sepsis and other post-infectious complications is highly desirable. Although it is conceivable that anti-inflammatory strategies might also be counter-productive as they might act as 'double-edge swords', intensive investigations to devise combination therapies are warranted. The present review also lists the major anti-inflammatory agents and strategies and combinations among them which have been proposed in the last few years for clinical treatments of sepsis and other post-infectious complications.

Can we learn from the pathogenetic strategies of group A hemolytic streptococci how tissues are injured and organs fail in post-infectious and inflammatory sequelae?

The purpose of this review-hypothesis is to discuss the literature which had proposed the concept that the mechanisms by which infectious and inflammatory processes induce cell and tissue injury, in vivo, might paradoxically involve a deleterious synergistic 'cross-talk', among microbial- and host-derived pro-inflammatory agonists. This argument is based on studies of the mechanisms of tissue damage caused by catalase-negative group A hemolytic streptococci and also on a large body of evidence describing synergistic interactions among a multiplicity of agonists leading to cell and tissue damage in inflammatory and infectious processes. A very rapid cell damage (necrosis), accompanied by the release of large amounts of arachidonic acid and metabolites, could be induced when subtoxic amounts of oxidants (superoxide, oxidants generated by xanthine-xanthine oxidase, HOCl, NO), synergized with subtoxic amounts of a large series of membrane-perforating agents (streptococcal and other bacterial-derived hemolysins, phospholipases A2 and C, lysophosphatides, cationic proteins, fatty acids, xenobiotics, the attack complex of complement and certain cytokines). Subtoxic amounts of proteinases (elastase, cathepsin G, plasmin, trypsin) very dramatically further enhanced cell damage induced by combinations between oxidants and the membrane perforators. Thus, irrespective of the source of agonists, whether derived from microorganisms or from the hosts, a triad comprised of an oxidant, a membrane perforator, and a proteinase constitutes a potent cytolytic cocktail the activity of which may be further enhanced by certain cytokines. The role played by non-biodegradable microbial cell wall components (lipopolysaccharide, lipoteichoic acid, peptidoglycan) released following polycation- and antibiotic-induced bacteriolysis in the activation of macrophages to release oxidants, cytolytic cytokines and NO is also discussed in relation to the pathophysiology of granulomatous inflammation and sepsis. The recent failures to prevent septic shock by the administration of only single antagonists is disconcerting. It suggests, however, that since tissue damage in post-infectious syndromes is caused by synergistic interactions among a multiplicity of agents, only cocktails of appropriate antagonists, if administered at the early phase of infection and to patients at high risk, might prevent the development of post-infectious syndromes.

Procalcitonin expression in human peripheral blood mononuclear cells and its modulation by lipopolysaccharides and sepsis-related cytokines in vitro

Procalcitonin (PCT), the precursor of calcitonin, was recently put forward as a diagnostic marker of systemic bacterial infection and sepsis. The major PCT production site in sepsis still remains unclear. Because of a certain association between increased levels of PCT and leukocyte-derived cytokines during sepsis, we assessed the possible expression of PCT in human peripheral blood mononuclear cells (PBMCs) and the modulation of PCT by lipopolysaccharides (LPS) and various sepsis-related cytokines by reverse transcriptase-polymerase chain reaction (RT-PCR) by using a novel primer set and flow cytometric analysis with intracellular staining with antibodies to the PCT components calcitonin and katacalcin. RT-PCR and flow cytometric analysis demonstrated that PBMCs express PCT both on mRNA and on protein levels. LPS and various proinflammatory cytokines (interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor-alpha (TNF-alpha), IL-2) had pronounced stimulatory effects on the expression of PCT mRNA. Under identical experimental conditions the anti-inflammatory cytokine IL-10 had no effect on the expression of mRNA for PCT. Flow cytometric analysis demonstrated increased intracellular amounts of PCT components after LPS stimulation. Thus we demonstrate for the first time that PCT is expressed in PBMCs. This expression is modulated by bacterial LPS and sepsis-related cytokines. Therefore PBMCs may be among the sources of elevated PCT levels in patients with sepsis.

Protein tyrosine kinase inhibitors as novel therapeutic agents

Protein tyrosine kinases (PTKs) play a key role in normal cell and tissue development. Enhanced PTK activity is intimately correlated with proliferative diseases, such as cancers, leukemias, psoriasis, and restenosis. This realization prompted us to systematically synthesize tyrosine phosphorylation inhibitors (tyrphostins) as potential drugs. Over the years, we have demonstrated the ability to synthesize selective tyrphostins aimed at different receptor, as well as at nonreceptor, tyrosine kinases. Some of these tyrphostins have shown efficacy in vivo as antileukemic agents and antirestenosis agents. AG 490, a Jak-2 inhibitor, is potent against recurrent pre-B acute lymphoblastic leukemia. AG 1295, a selective platelet-derived growth factor receptor kinase inhibitor, inhibits 50% of balloon injury-induced stenosis in the phemoral arteries of pigs. AG 1517 (SU 5271), a potent epiderminal growth factor receptor kinase inhibitor, is currently in clinical trials for psoriasis. Similarly, SU 5416, a potent kinase inhibitor of the vascular endothelial growth factor receptor/kinase domain receptor/Flk-1, is currently in clinical trials as an anticancer agent by virtue of its strong anti-angiogenic activity. These findings demonstrate that the identification of PTKs that play a key role in a defined disease state can lead to a selective drug. Tyrphostins also show efficacy in vivo in inflammatory diseases such as sepsis, cirrhosis, and experimental autoimmune encephalitis.

Variables affecting outcome in critically ill patients

Critical care medicine has evolved as a field of science and clinical care. Despite important contributions to our understanding of the molecular basis of critical illness, we still remain troubled by our lack of insight into why some patients have favorable outcomes from critical illness and others do not. This article explores the hypothesis that at least five important variables may alter the outcome of patients suffering from a variety of critical illnesses. These variables include the premorbid immune or genetic status of the patient, the patient's gender, the circulating cholesterol concentration, the patient's age, and various iatrogenic and nosocomial events. Insights into the importance of these five variables may provide opportunities for physicians and scientists to improve outcome in patients suffering from critical illness. Clearly, altering iatrogenic and nosocomial events is already within the realm of opportunity.

Suppression of experimental autoimmune encephalomyelitis by tyrphostin AG-556

Tyrosine kinase blockers from the AG 126/AG-556 tyrphostin family are shown to inhibit the lipopolysaccharide (LPS)-induced production of tumor necrosis factor alpha (TNFalpha), nitric oxide (NO), and prostaglandin E2 (PGE2) in primary rat astrocytes cultures. The tyrphostin AG-556 which was previously shown to be effective against sepsis in mice and dogs also show excellent efficacy in inhibiting experimental autoimmune encephalomyelitis (EAE) in mice. AG-556 does not block the activation of JNK/SAPK and of p38/HOG and therefore seems to act at a target down stream to these kinases which is activated in stress or at a target on an obligatory parallel pathway. These findings together with previous results showing inhibition of sepsis in mice and dogs suggest that protein tyrosine kinase (PTK) blockers of the AG-556 family may be considered in the management of human autoimmune disorders such as multiple sclerosis (MS).

Murine hepatitis virus strain 3 induces the macrophage prothrombinase fgl-2 through p38 mitogen-activated protein kinase activation

The clinical syndrome of acute liver failure produced by fulminant viral hepatitis can be reproduced in mice by infection with murine hepatitis virus strain 3 (MHV-3). Although it is clear that MHV-3-induced hepatitis depends upon macrophage activation and the expression of a specific prothrombinase, fgl-2, the signaling pathways involved in virally stimulated cell activation are unclear. Since we had previously found that MHV-3 induces the tyrosine phosphorylation of cellular proteins, we investigated the roles of the mitogen-activated protein kinase (MAPK) proteins. In a series of Western blots, immunoprecipitation and in vitro kinase assay studies, we found that both the extracellular signal-related kinase (ERK) and p38 MAPK proteins are tyrosine-phosphorylated and activated following exposure of murine peritoneal exudative macrophages (PEM) to MHV-3. Although p38 phosphorylation and activity are induced soon after MHV-3 exposure, peaking by 1-5 min, ERK phosphorylation and activity increase more gradually, peaking at 20-30 min and gradually fading thereafter. Interestingly, whereas selective p38 inhibition with SB203580 (1-20 microM) abolished the virally stimulated induction of fgl-2 mRNA, protein, and functional activity, selective ERK inhibition with PD98059 (1-50 microM) limited fgl-2 functional activity but had little to no effect on fgl-2 mRNA or protein levels. Moreover, whereas inhibition of ERK had no effect on p38 activity, p38 inhibition consistently increased MHV-3-induced ERK activity. To ensure that these pathways were relevant in vivo, MHV-3 was injected intraperitoneally, and peritoneal exudative macrophages were collected. Again, MHV-3 exposure led to increased p38 and ERK tyrosine phosphorylation. These data argue that MHV-3 induces tightly interconnected ERK and p38 MAPK cascades in the macrophage both in vitro and in vivo. Although the ERK and p38 MAPK proteins have discordant effects at the level of fgl-2 expression, both converge at the level of its activity, suggesting that targeted MAPK inhibition may ultimately be useful in the modulation of viral hepatitis.

Antiendotoxin strategies for the prevention and treatment of septic shock. New approaches and future directions

Therapy for Gram-negative sepsis remains unsatisfactory despite a concerted effort to develop new treatments for this common, life-threatening syndrome. Current research continues on several fronts to improve the treatment options available to clinicians in the management of these critically ill patients. Recently, a greater understanding of the complex molecular basis of endotoxin-mediated pathophysiological effects in humans has generated a number of novel therapeutic agents for sepsis. Several of these treatment strategies have already entered clinical trials and it is hoped that some of these therapies will become widely available in the near future. In this review, the current status of the most promising new antiendotoxin agents is summarised, and the major obstacles to the successful clinical development of these therapies are described. New antiendotoxin therapies include those which interrupt the synthesis of endotoxin, bind and neutralise its activity, prevent endotoxin interactions with host effector cells and interfere with endotoxin-mediated signal transduction pathways. Potential therapeutic strategies involving these agents consist of endotoxin analogues, antibodies, subunit vaccines, binding columns, recombinant human proteins and small molecule inhibitors of endotoxin synthesis and intracellular signalling. The pitfalls of previous antiendotoxin clinical investigations and the perils of future clinical trial designs are discussed in the context of unmet needs and realistic expectations for success. While considerable progress has been made, effective and new treatments for Gram-negative bacterial sepsis continues to elude us at the present time. This has been to the detriment of patients, investigators and pharmaceutical companies alike. It will require focused efforts by basic scientists, continued support by industry and enlightened study designs by clinical investigators to successfully develop antiendotoxin in therapies for use in septic patients in the future.

Protein tyrosine phosphorylation mediates TNF-induced endothelial-neutrophil adhesion in vitro

Proinflammatory cytokines initiate the vascular inflammatory response via the upregulation of adhesion molecules on the luminal endothelial surface. We investigated directly the role of protein tyrosine phosphorylation in the upregulation of the endothelial adhesion molecules, intercellular adhesion molecule 1 (ICAM-1) and E-selectin, and the consequent adhesion of neutrophils, after tumor necrosis factor (TNF)-alpha-stimulation of human aortic endothelial cells in vitro. Time- and dose-dependent TNF-alpha-stimulated ICAM-1 and E-selectin upregulation and neutrophil adhesion each were suppressed by tyrosine kinase inhibitors, including genistein (200 microM), but not genistein, its isoflavone analog without tyrosine kinase inhibitory activity. Tyrphostin AG 126, a synthetic selective tyrosine kinase inhibitor, also suppressed ICAM-1 and E-selectin upregulation and neutrophil adhesion, each in a dose-dependent manner, whereas tyrphostin AG 1288 had no effect. Tyrosine phosphorylation of two proteins (85 and 145 kDa in the cytoskeleton fraction) found minutes after TNF-alpha-stimulation was also inhibited by genistein. These findings suggest that, in endothelial cells, TNF-alpha upregulates ICAM-1 and E-selectin expression and consequent neutrophil adhesion via protein tyrosine phosphorylation.