Splenectomy exacerbates lung injury after ischemic acute kidney injury in mice

Patients with acute kidney injury (AKI) have increased serum proinflammatory cytokines and an increased occurrence of respiratory complications. The aim of the present study was to examine the effect of renal and extrarenal cytokine production on AKI-mediated lung injury in mice. C57Bl/6 mice underwent sham surgery, splenectomy, ischemic AKI, or ischemic AKI with splenectomy and kidney, spleen, and liver cytokine mRNA, serum cytokines, and lung injury were examined. The proinflammatory cytokines IL-6, CXCL1, IL-1β, and TNF-α were increased in the kidney, spleen, and liver within 6 h of ischemic AKI. Since splenic proinflammatory cytokines were increased, we hypothesized that splenectomy would protect against AKI-mediated lung injury. On the contrary, splenectomy with AKI resulted in increased serum IL-6 and worse lung injury as judged by increased lung capillary leak, higher lung myeloperoxidase activity, and higher lung CXCL1 vs. AKI alone. Splenectomy itself was not associated with increased serum IL-6 or lung injury vs. sham. To investigate the mechanism of the increased proinflammatory response, splenic production of the anti-inflammatory cytokine IL-10 was determined and was markedly upregulated. To confirm that splenic IL-10 downregulates the proinflammatory response of AKI, IL-10 was administered to splenectomized mice with AKI, which reduced serum IL-6 and improved lung injury. Our data demonstrate that AKI in the absence of a counter anti-inflammatory response by splenic IL-10 production results in an exuberant proinflammatory response and lung injury.     

Nitroxyl exacerbates ischemic cerebral injury and oxidative neurotoxicity

Nitroxyl (HNO) donor compounds function as potent vasorelaxants, improve myocardial contractility and reduce ischemia-reperfusion injury in the cardiovascular system. With respect to the nervous system, HNO donors have been shown to attenuate NMDA receptor activity and neuronal injury, suggesting that its production may be protective against cerebral ischemic damage. Hence, we studied the effect of the classical HNO-donor, Angeli's salt (AS), on a cerebral ischemia/reperfusion injury in a mouse model of experimental stroke and on related in vitro paradigms of neurotoxicity. I.p. injection of AS (40 μmol/kg) in mice prior to middle cerebral artery occlusion exacerbated cortical infarct size and worsened the persistent neurological deficit. AS not only decreased systolic blood pressure, but also induced systemic oxidative stress in vivo indicated by increased isoprostane levels in urine and serum. In vitro , neuronal damage induced by oxygen-glucose-deprivation of mature neuronal cultures was exacerbated by AS, although there was no direct effect on glutamate excitotoxicity. Finally, AS exacerbated oxidative glutamate toxicity – that is, cell death propagated via oxidative stress in immature neurons devoid of ionotropic glutamate receptors. Taken together, our data indicate that HNO might worsen cerebral ischemia-reperfusion injury by increasing oxidative stress and decreasing brain perfusion at concentrations shown to be cardioprotective in vivo .     

Chronic prenatal nicotine exposure sensitizes rat brain to acute postnatal nicotine challenge as assessed with ornithine decarboxylase

Prenatal exposure to nicotine has been shown to produce postnatal up-regulation of central nervous system nicotinic receptors and to alter subsequent differentiation of neural tissues. In the current study, pregnant rats received nicotine infusions of 6 mg/kg/day throughout gestation, administered by osmotic minipump implants; the postnatal development of cholinergic receptor reactivity was examined through measurements of the ability of acute nicotine administration to stimulate midbrain + brainstem ornithine decarboxylase (ODC) activity, a key regulatory enzyme in neural cell differentiation and growth. In control rats, the ODC response to nicotine was absent at birth and developed during the second postnatal week in parallel with the known ontogenetic rise of nicotinic receptors. Offspring of the nicotine-infused dams exhibited hyper-reactivity of ODC to postnatal acute nicotine challenge: the response developed earlier than in controls and subsequently the magnitude of the effect was 2-3 times greater. Since the development of cholinergic transmission influences differentiation of target cells, alterations in cholinergic nicotinic receptor mediated responses likely explain the delayed appearance of abnormal cell differentiation associated with prenatal nicotine.     

Biglycan-triggered TLR-2- and TLR-4-signaling exacerbates the pathophysiology of ischemic acute kidney injury

Exacerbated inflammation in renal ischemia–reperfusion injury, the major cause of intrinsic acute renal failure, is a key trigger of kidney damage. During disease endogenous danger signals stimulate innate immune cells via Toll-like receptors (TLR)-2 and -4 and accelerate inflammatory responses. Here we show that production of soluble biglycan, a small leucine-rich proteoglycan, is induced during reperfusion and that it functions as endogenous agonist of TLR-2/4. Biglycan-mediated activation of TLR-2/4 initiates an inflammatory response in native kidneys, which is marked by the release of cytokines and chemokines and recruitment of inflammatory cells. Overexpression of soluble circulating biglycan before ischemic reperfusion enhanced plasma and renal levels of TNF-α, CXCL1, CCL2 and CCL5, caused influx of neutrophils, macrophages and T cells and overall worsened renal function in wild type mice. We provide robust genetic evidence for TLR-2/4 requirement insofar as biglycan biological effects were markedly dampened in mice deficient in both innate immune receptors, Tlr2^−/−;Tlr4^−/− mice. Thus, signaling of soluble biglycan via TLR-2/4 could represent a novel therapeutic target for the prevention and possible treatment of patients with acute renal ischemia–reperfusion injury.     

HMGB1 in renal ischemic injury

Factors that initiate cellular damage and trigger the inflammatory response cascade and renal injury are not completely understood after renal ischemia-reperfusion injury (IRI). High-mobility group box-1 protein (HMGB1) is a damage-associated molecular pattern molecule that binds to chromatin, but upon signaling undergoes nuclear-cytoplasmic translocation and release from cells. Immunohistochemical and Western blot analysis identified HMGB1 nuclear-cytoplasmic translocation and release from renal cells (particularly vascular and tubular cells) into the venous circulation after IRI. Time course analysis indicated HMGB1 release into the venous circulation progressively increased parallel to increased renal ischemic duration. Ethyl pyruvate (EP) treatment blocked H(2)O(2) (oxidative stress)-induced HMGB1 release from human umbilical vein endothelial cells in vitro, and in vivo resulted in nuclear retention and significant blunting of HMGB1 release into the circulation after IRI. EP treatment before IRI improved short-term serum creatinine and albuminuria, proinflammatory cyto-/chemokine release, and long-term albuminuria and fibrosis. The renoprotective effect of EP was abolished when exogenous HMGB1 was injected, suggesting EP's therapeutic efficacy is mediated by blocking HMGB1 translocation and release. To determine the independent effects of circulating HMGB1 after injury, exogenous HMGB1 was administered to healthy animals at pathophysiological dose. HMGB1 administration induced a rapid surge in systemic circulating cyto-/chemokines (including TNF-α, eotaxin, G-CSF, IFN-γ, IL-10, IL-1α, IL-6, IP-10, and KC) and led to mobilization of bone marrow CD34+Flk1+ cells into the circulation. Our results indicate that increased ischemic duration causes progressively enhanced HMGB1 release into the circulation triggering damage/repair signaling, an effect inhibited by EP because of its ability to block HMGB1 nuclear-cytoplasmic translocation.     

Chronic kidney disease with comorbid cardiac dysfunction exacerbates cardiac and renal damage

To address the pathophysiological mechanisms underlying chronic kidney disease with comorbid cardiac dysfunction, we investigated renal and cardiac, functional and structural damage when myocardial infarction (MI) was applied in the setting of kidney injury (induced by 5/6 nephrectomy—STNx). STNx or Sham surgery was induced in male Sprague–Dawley rats with MI or Sham surgery performed 4 weeks later. Rats were maintained for a further 8 weeks. Rats (n = 36) were randomized into four groups: Sham+Sham, Sham+MI, STNx+Sham and STNx+MI. Increased renal tubulointerstitial fibrosis (P < 0.01) and kidney injury molecule‐1 expression (P < 0.01) was observed in STNx+MI compared to STNx+Sham animals, while there were no further reductions in renal function. Heart weight was increased in STNx+MI compared to STNx+Sham or Sham+MI animals (P < 0.05), despite no difference in blood pressure. STNx+MI rats demonstrated greater cardiomyocyte cross‐sectional area and increased cardiac interstitial fibrosis compared to either STNx+Sham (P < 0.01) or Sham+MI (P < 0.01) animals which was accompanied by an increase in diastolic dysfunction. These changes were associated with increases in ANP, cTGF and collagen I gene expression and phospho‐p38 MAPK and phospho‐p44/42 MAPK protein expression in the left ventricle. Addition of MI accelerated STNx‐induced structural damage but failed to significantly exacerbate renal dysfunction. These findings highlight the bidirectional response in this model known to occur in cardiorenal syndrome (CRS) and provide a useful model for examining potential therapies for CRS.     

Functional coupling of TRPM2 and extrasynaptic NMDARs exacerbates excitotoxicity in ischemic brain injury

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Agonist-induced release of nitric oxide during acute exposure to nicotine

While we have shown that acute infusion of nicotine impairs agonist-induced dilatation of resistance arterioles (Am. J. Physiol. 272:H2337-H2342, 1997), no studies have examined the release of nitric oxide in response to these agonists before and during treatment with nicotine. Thus, the first goal of the present study was to examine agonist-induced release of nitric oxide by the hamster cheek pouch microcirculation under control conditions and during acute infusion of nicotine. We measured the release of nitric oxide (Sievers NO analyzer) in response to repeated topical application of acetylcholine (1.0 microM) and 5'-adenosine diphosphate (ADP; 1.0 microM) during infusion of vehicle and during infusion of nicotine (2.0 microg/kg/min i.v. for 30 minutes followed by a maintenance dose of 0.35 microg/kg/min). In hamsters treated with vehicle, topical application of acetylcholine and ADP elicited reproducible increases in nitric oxide release. In contrast, in hamsters treated with nicotine, there was a marked inhibition of nitric oxide release in response to acetylcholine and ADP. In a previous study (J. Appl. Physiol. 85:1292-1298, 1998) we found that treatment of the hamster cheek pouch microcirculation with superoxide dismutase restored impaired agonist-induced vasodilatation during acute infusion of nicotine. Thus, our second goal was to examine whether superoxide dismutase would restore agonist-induced release of nitric oxide during infusion of nicotine. We found that treatment of the hamster cheek pouch microcirculation with superoxide dismutase prior to infusion of nicotine prevented nicotine-induced impairment of nitric oxide release in response to acetylcholine and ADP. We suggest that nicotine alters dilatation of arterioles via an increased release of superoxide anion and subsequent inactivation of nitric oxide.     

Elevation of renal glutathione enhances ischemic injury.

In a previous study, we tested the hypothesis that an elevated level of renal glutathione (GSH) would protect the kidney from ischemic injury. However, prior elevation of GSH with GSH monoethylester enhanced then injury induced by 35 min of ischemia and blood reflow [Scaduto RC Jr, Gattone VH, Grotyohann LW, et al; Effect of an altered glutathione content on renal ischemic injury. Am J Physiol 1988;255:F911-F921]. Additionally, GSH monoethylester produced morphologic alterations in the absence of ischemia. Thus the greater ischemic injury observed after GSH ester pretreatment could have been due to a synergistic effect between the events caused by ischemia and the pretreatment. The present study was conducted to evaluate the utility of elevating renal GSH levels by administration of GSH. Administration of GSH (1 mmol/kg body weight) caused a 3-fold elevation of renal GSH levels and a 6-fold elevation of renal cysteine levels after 60 min without causing changes in renal morphology or GFR. After 35 min of renal artery occlusion and 90 min of blood reflow, animals pretreated with GSH had a much greater decline in GFR than untreated control animals. This enhancement of renal ischemic injury in GSH-treated animals was similar to that observed following administration of GSH monoethylester. We conclude that administration of GSH is the method of choice for elevation of renal GSH and that elevation of renal GSH leads to an enhanced ischemia-induced injury which is independent of the method employed to elevate renal GSH.     

Chronic steatosis aggravates cold-storage induced acute ischemic injury in rat donor livers through the perturbation of lipophagy

In this study, we explored the effects of cold ischemia on chronic steatosis and lipid signaling in vivo. Sprague Dawley (SD) rat models of chronic steatosis were established. Pathological observations and liver indices were assessed through hematoxylin-eosin (HE)- and Oil Red O staining. Autophagy and metabolism in adipose tissue were analyzed under post-ischemia and hypoxic conditions via western blotting and immunofluorescent analysis.We found that cold ischemia treatment exacerbated hepatic steatosis and reduced lipid phagocytosis. This manifested as a loss of Microtubule-associated protein 1A/1B-light chain 3 (LC3) and Perilipin 2 (PLIN2), and lower levels of autophagy. Cold ischemia also inhibited lipophagy in transplanted rat livers, most notably in moderate-to-severe steatosis models. Ischemia and hypoxia inhibited lipid phagocytosis and increased lipid accumulation.Collectively, these data show that chronic steatosis aggravates cold storage induced acute ischemic injury in rat donor livers through the inhibition of lipophagy. Moderate-to-severe steatosis therefore influences the postoperative recovery of liver transplant recipients, which should be immediately transplanted to reduce the risk of cold ischemia.     

Oxygenation inhibits the physiological tissue-protecting mechanism and thereby exacerbates acute inflammatory lung injury

Acute respiratory distress syndrome (ARDS) usually requires symptomatic supportive therapy by intubation and mechanical ventilation with the supplemental use of high oxygen concentrations. Although oxygen therapy represents a life-saving measure, the recent discovery of a critical tissue-protecting mechanism predicts that administration of oxygen to ARDS patients with uncontrolled pulmonary inflammation also may have dangerous side effects. Oxygenation may weaken the local tissue hypoxia-driven and adenosine A_2A receptor (A_2AR)-mediated anti-inflammatory mechanism and thereby further exacerbate lung injury. Here we report experiments with wild-type and adenosine A_2AR-deficient mice that confirm the predicted effects of oxygen. These results also suggest the possibility of iatrogenic exacerbation of acute lung injury upon oxygen administration due to the oxygenation-associated elimination of A_2AR-mediated lung tissue-protecting pathway. We show that this potential complication of clinically widely used oxygenation procedures could be completely prevented by intratracheal injection of a selective A_2AR agonist to compensate for the oxygenation-related loss of the lung tissue-protecting endogenous adenosine. The identification of a major iatrogenic complication of oxygen therapy in conditions of acute lung inflammation attracts attention to the need for clinical and epidemiological studies of ARDS patients who require oxygen therapy. It is proposed that oxygen therapy in patients with ARDS and other causes of lung inflammation should be combined with anti-inflammatory measures, e.g., with inhalative application of A_2AR agonists. The reported observations may also answer the long-standing question as to why the lungs are the most susceptible to inflammatory injury and why lung failure usually precedes multiple organ failure.     

Chronic nicotine exposure alters blood-brain barrier permeability and diminishes brain uptake of methyllycaconitine

Methyllycaconitine (MLA) is reported to be a selective antagonist for the nicotinic acetylcholine receptor alpha7 subtype and has been found in animal behavioral studies to reduce nicotine self-administration and attenuate nicotine withdrawal symptoms. While MLA crosses the blood-brain barrier (BBB), no studies have assessed brain uptake in animals subjected to chronic nicotine exposure. Given that chronic nicotine administration has been reported to alter BBB parameters that may affect the kinetic BBB passage of MLA, we evaluated MLA brain uptake in naive and S-(-)nicotine-exposed rats (4.5 mg/kg/day for 28 days; osmotic minipumps) using in situ rat brain perfusions. Our results demonstrate that in situ(3)H-MLA brain uptake rates in naive animals approximate to intravenous kinetic data (K(in), 3.24 +/- 0.71 x 10(-4) mL/s/g). However, 28-day nicotine exposure diminished (3)H-MLA brain uptake by approximately 60% (K(in), 1.29 +/- 0.4 x 10(-4) mL/s/g). This reduction was not related to nicotine-induced (3)H-MLA brain efflux or BBB transport alterations. Similar experiments also demonstrated that the passive permeation of (14)C-thiourea was diminished approximately 24% after chronic nicotine exposure. Therefore, it appears that chronic nicotine exposure diminishes the blood-brain passive diffusion of compounds with very low extraction rates (i.e. permeability-limited compounds). These findings imply that the pharmacokinetics of neuropharmaceutical agents that are permeability limited may need to be re-evaluated in individuals exposed to nicotine.     

A TLR5 agonist inhibits acute renal ischemic failure

Reperfusion of ischemic organs induces a potent inflammatory response initiated by the generation of reactive oxygen species that directly damage tissue and promote leukocyte infiltration and activation that also mediate tissue injury. We recently found that radiation-induced tissue injury, which is caused by radiation-induced reactive oxygen species, is attenuated by administration of CBLB502, a pharmacologically optimized derivative of the TLR5 agonist flagellin. Therefore, we tested the ability of CBLB502 to attenuate injury in a murine model of acute ischemic renal failure. CBLB502 given 30 min before imposition of bilateral renal pedicle occlusion provided marked protection against the renal dysfunction and inflammation that follows reperfusion of ischemic kidneys, including marked decreases in leukocyte infiltration, proinflammatory cytokine production, and tubular injury. Importantly, CBLB502 given within 30 min after ischemic kidney reperfusion reproduced the protective effects of pretreatment with the TLR5 agonist, indicating a window following reperfusion in which CBLB502 administration abrogates acute renal ischemic failure. Bone marrow-reconstituted chimeras were used to show that the protective effects of CBLB502 could be delivered by intact MyD88 signaling on renal parenchymal cells. Consistent with this, Ab staining of kidney sections indicated that cells lining the renal vasculature expressed TLR5. Overall, these results indicate the use of TLR5 agonists as mitigators and protectants of acute renal ischemic failure.     

Chronic exposure to nicotine alters endothelium-dependent arteriolar dilatation: effect of superoxide dismutase.

The first goal of this study was to determine whether chronic injection of nicotine alters endothelium-dependent arteriolar dilatation. We measured the diameter of cheek pouch resistance arterioles (approximately 50 microm in diameter) in response to endothelium-dependent (acetylcholine and ADP) and -independent (nitroglycerin) agonists in control hamsters and hamsters treated with nicotine (2 microg. kg-1. day-1 for 2-3 wk). In control hamsters, acetylcholine (0.1 and 1.0 microM) dilated arterioles by 13 +/- 2 and 31 +/- 3%, respectively, and ADP (1.0 and 10 microM) dilated arterioles by 18 +/- 1 and 30 +/- 1%, respectively. In contrast, acetylcholine (0.1 and 1.0 microM) dilated arterioles by only 5 +/- 2 and 12 +/- 3%, respectively, and ADP (1.0 and 10 microM) dilated arterioles by only 7 +/- 2 and 13 +/- 3%, respectively, in animals treated with nicotine (P < 0.05 vs. response in control hamsters). Nitroglycerin produced similar dose-related dilatation of cheek pouch arterioles in control and nicotine-treated hamsters. Our second goal was to examine a possible mechanism for impaired endothelium-dependent arteriolar dilatation during chronic treatment with nicotine. We found that superfusion of the cheek pouch microcirculation with superoxide dismutase (150 U/ml) restored impaired endothelium-dependent, but did not alter endothelium-independent, arteriolar dilatation in hamsters treated with nicotine. Superfusion with superoxide dismutase did not alter endothelium-dependent or -independent arteriolar dilatation in control hamsters. We suggest that chronic exposure to nicotine produces selective impairment of endothelium-dependent arteriolar dilatation via a mechanism related to the synthesis/release of oxygen-derived free radicals.     

Protection against ischemic acute renal failure by prostaglandin infusion

We have shown that intravenous infusion of epinephrine (4ug/kg/min for 6 hours) into mongrel dogs consistently produces renal hemodynamic and histopathologic characteristics of ischemic acute renal failure (ARF). This study describes renal responses that were modified by intravenous infusion of prostaglandin E (PGE₂)(10 ug/min) one hour before and during a 6 hour infusion of epinephrine (4 ug/kg/min). Two groups of animals were studied: Group I (epinephrine alone) and Group II (epinephrine + PGE₂). Urine volume, glomerular filtration rate, urinary sodium excretion rate, urine osmolality, and serum urea nitrogen were measured. Renal tissues were studied using light and electron microscopy. While urine volume or glomerular filtration rate decreased significantly in both groups, they were slightly but significantly better in Group II than Group I. Urine osmolality significantly decreased in Group I but significantly increased in Group II. Group I animals became azotemic (mean serum urea nitrogen, 27 ± 1 mg/dl), whereas Group II animals showed serum urea nitrogen at the upper limits of normal (mean 20 ± 2 mg/dl). The difference was significant (P <.01). Severe acute tubular lesions were a consistent feature in Group I. Tubular lesions were less severe and infrequent in Group II animals. While mitochondrial dark bodies (electron microscopy) characterized tubular lesions in Group I, fewer mitochondria contained dark bodies in Group II animals. These dark bodies appear to be calcium and constitute a definitive sign of ischemia. Therefore, this study indicates that PGE₂ attenuates epinephrine-induced tubular ischemia and injury and ARF which may be attributed to excessive solute excretion or to inhibition of calcium influx into tubular mitochondria.     

Complement C5a exacerbates acute lung injury induced through autophagy-mediated alveolar macrophage apoptosis

Intestinal ischemia has a high mortality and often causes acute lung injury (ALI), which is a serious complication, and is accompanied by high mortality up to 40%. An intense local and systemic inflammation occurs during intestinal ischemia/reperfusion (IR)-induced lung injury resulting from activation of immune responses. It has been reported that one component of complement, C5a, is indispensable for the full development of IR-induced lung injury, whereas the detailed molecular mechanism remains to be elucidated. In this study, we found that intestinal IR induced ALI-like symptoms, and C5a receptor (C5aR) expression was upregulated in alveolar macrophages, which are resident macrophages in lung tissue and are important in pulmonary homeostasis. C5a produced during lung injury binds to C5aR in alveolar macrophages, initiates downstream signaling that promotes autophagy, leading to apoptosis of alveolar macrophages. Using Mφ-ATG5^−/− mice, in which the atg5 is deficient specifically in macrophages and autophagy is inhibited, we confirmed that in vivo C5a interacting with C5aR induced autophagy in alveolar macrophages, which promoted alveolar macrophage apoptosis. Further study indicated that autophagy was induced through C5aR-mediated degradation of bcl-2. Taken together, our results demonstrated that C5aR-mediated autophagy induced apoptosis in alveolar macrophages, disrupting pulmonary homeostasis and contributing to the development of ALI. This novel mechanism suggests new therapeutic potential of autophagy regulation in ALI.During diverse clinical procedures, transient ischemia and reperfusion, known as ischemia/reperfusion (IR) clinically, are found in organs or tissues, and cause intense inflammation, both locally and systemically,^{1, 2} which in turn leads to various types of injury, even multiple organ failure, contributing to high mortality. Acute lung injury (ALI) is a common outcome of IR, and usually occurs in patients with intestinal ischemia, leading to high mortality of 60–80%.³ In addition, ALI is a life-threatening complication associated with sepsis, pneumonia, trauma, and many other clinical conditions. Despite improvements in the management of critically ill patients, ALI mortality is approximately 40%, and survivors often do not return to a normal life.⁴ During the IR process, ischemia initiates a local inflammatory response, by releasing pro-inflammatory factors and activating/attracting inflammatory cells, such as neutrophils, macrophages, and lymphocytes.⁵ Oxidative stress resulting from ischemia also contributes to IR injury. Owing to the unique anatomic and physiological features, the lung is susceptible to IR injury through pro-inflammatory cytokines storm.⁶ Only a few pharmacologic treatment options are available for IR-induced ALI, which work by inhibiting inflammation or anti-oxidative effects.⁷ Obviously, more effort is needed to clarify the underlying pathophysiological mechanisms of ALI and find more efficient therapeutic methods.Macrophages are believed to derive from hematopoietic stem cells and are distributed all over the body. Macrophages are of vital importance in immune homeostasis, tissue remodeling, and biological events. Alveolar macrophages are resident lung macrophages, and present the first line of encountering inhaled substances.⁸ Alveolar macrophages have essential roles in maintaining pulmonary homeostasis, without pro-inflammatory effects.⁹ More importantly, alveolar macrophages suppress excessive inflammation, putatively through the strong inhibition of local immune cells, such as T lymphocytes and DCs. For example, rodent alveolar macrophages render inhibition on T-cell activation in the presence of DCs in vitro, through multiple mechanisms, such as releasing the suppressive cytokines, transforming growth factor-β and interleukin-10 (IL-10).^{8, 9, 10, 11, 12} If alveolar macrophages are depleted, the animals display stronger inflammatory responses to otherwise innocuous inhaled antigens.¹³ During ALI, cytokines and chemokines produced by tissue macrophages recruit neutrophils to the injury sites,¹⁴ but the neutrophil recruitment also affects alveolar macrophage activity.^15,16 IL-10 production is induced by macrophages after phagocytosis of apoptotic neutrophils, which in turn suppresses additional cytokine production and inflammation, affecting both pro-inflammatory and anti-inflammatory cellular components of ALI.¹² For these reasons, alveolar macrophages have attracted interest in studies on the mechanisms of ALI.^{8, 9, 10, 11}Complements are key mediators of the first line in protecting hosts from pathogen invasions and have been shown to be involved in IR-induced inflammation. During the ignition and amplification stages, complement activation contributes to inflammation-mediated tissue injury,^{1, 2, 17} which would be significantly diminished if complement factors were depleted.^{18, 19} The complement activation product, C5a, is essential for the full development of injury. C5a has the ability of chemotaxis²⁰ and it can also directly activate neutrophils and macrophages for chemokine production.²¹ C5a receptor (C5aR) signaling is required for C5a to render its effects on the process, as blockade of C5aR signaling will have similar effects to depletion of C5a in the survival of animals with cecal ligation and puncture,²² suggesting that intercepting C5a or C5aR signaling may provide a potential target for therapeutic treatment in inflammatory diseases.²³Although significant effort has been aimed at determining the mechanism of macrophages in ALI, the activity of C5aR on macrophages is unclear. This study aimed to clarify the role of C5aR in macrophage biology during ALI development, and found that elevated C5a induced C5aR signaling in alveolar macrophages, and contributed to autophagy-mediated apoptosis, thus exacerbating the ALI symptoms. This novel mechanism provides a potential role for autophagy regulation in ALI therapeutic applications.     

Testosterone exacerbates obstructive renal injury by stimulating TNF-alpha production and increasing proapoptotic and profibrotic signaling

Upper urinary tract obstruction is a common cause of renal dysfunction in children and adults. While there is clinical evidence of an increased male incidence and mortality rate with acute renal failure, the effect of gender and testosterone on obstructive renal injury has not previously been evaluated. We hypothesized that testosterone exacerbates proinflammatory TNF-alpha production and proapoptotic and profibrotic signaling during renal obstruction, resulting in increased apoptotic cell death and tubulointerstitial fibrosis. To study this, male, female, castrated male, and testosterone-treated oophorectomized female rats were subjected to sham operation or 3 days of unilateral ureteral obstruction (UUO). Renal cortical tissue was then analyzed for TNF-alpha production; proapoptotic caspase-8, -9, and -3 activity; apoptotic cell death; profibrotic transforming growth factor-beta1 production; and alpha-smooth muscle actin expression. In a separate arm, glomerular filtration rate (inulin clearance) was measured in rats pre- and post-UUO. Male and testosterone-treated oophorectomized female rats demonstrated a significant increase in TNF-alpha production, caspase activity, apoptotic cell death, tubulointerstitial fibrosis, and renal dysfunction during UUO compared with castrated males and normal female rats subjected to the same time course of obstruction. These results demonstrate that endogenous testosterone production in normal male rats and testosterone exogenously administered to oophorectomized females significantly increases TNF production and proapoptotic and profibrotic signaling during renal obstruction, resulting in increased apoptotic cell death, tubulointerstitial fibrosis, and renal dysfunction.     

肾缺血预处理对心脏缺血／再灌注损伤的保护作用

目的：探讨肾缺血预处理对家兔心脏缺血／再灌注（I／R）损伤的影响及意义。方法：32只大耳白家兔随机分为假手术（SO）、心脏I／R、经典缺血预处理（CIPC）及肾缺血预处理（RIPC）4组。观察各组心肌梗塞面积、左室舒缩功能、心脏超微结构及心律失常发生率的变化。结果：CIPC、RIPC组,心肌梗塞面积、再灌性心律失常发生率较I／R组明显降低,左室舒缩功能明显恢复（P＜0.01）,心脏超微结构损伤明显减轻。结论：RIPC可诱导出与CIPC类似的心脏保护效应。