Biomedical subjects

Meijing Wang

Publications and source records attributed to Meijing Wang.

At least 37 records · Page 2Linked to original sources

PubMed2006

High passage number of stem cells adversely affects stem cell activation and myocardial protection.

Progenitor cell plasticity enhances positive remodeling of damaged tissue. We and others have previously shown that progenitor cells may limit apoptosis and modulate inflammation in part by the production of growth factors. However, recent studies suggest that progenitor cells senesce and lose their differentiation potential with increasing time in culture and passage. We hypothesize that murine bone marrow mesenchymal stem cells (MSCs) are cardioprotective against ischemia/reperfusion injury in the isolated perfused rat heart, and that passage number has an adverse effect on MSC activation and cardioprotection. Adult male and female Sprague-Dawley rat hearts were isolated, perfused via Langendorff model, and subjected to ischemia/reperfusion. Mouse MSCs were harvested, cultured, suspended in perfusate, and infused before global index ischemia. Hearts were assigned to controls or infusion with passage 3, 5, or 10 MSCs. In addition, MSCs in culture were stressed by hypoxia and increasing doses of endotoxin (lipopolysaccharide). Mesenchymal stem cell activation was determined by measuring vascular endothelial growth factor production with enzyme-linked immunosorbent assay. All data are reported as mean +/- SEM and were analyzed with 2-way analysis of variance. Differences are considered significant if P < 0.05. Passage 3 murine MSC infusion in hearts before ischemia reduced the depression of left ventricular developed pressure, attenuated the increase of end-diastolic pressure, and reduced the depression of +dP/dT and -dP/dT. However, the MSC protective effect disappeared in hearts infused with passage 5 and passage 10 MSCs. Although hypoxia and lipopolysaccharide resulted in significant activation of MSCs, passage 3 MSCs demonstrated significantly greater vascular endothelial growth factor release than passage 5 and 10 MSCs. Acute murine MSC infusion confers protection in isolated rat hearts. However, high passage number has an adverse effect on MSC activation and protection. This portends limited ex vivo expansion before possible therapeutic use.

Animals↗

PubMed2005

Does endogenous testosterone mediate the lower preconditioning threshold in males?

BACKGROUND: Preconditioning is injury-induced protection from subsequent insult. Recent data indicates that males have lower preconditioning thresholds compared to females. Therefore, we hypothesized that testosterone may mediate the lower preconditioning threshold observed in males. MATERIALS AND METHODS: Adult normal and castrated male Sprague-Dawley rats (n = 4-5) were given intraperitoneal (i.p.) injections of 125 or 500 microg/kg Salmonella typhimurium lipopolysaccharide (ETX) or 0.4 ml normal saline (NS). Another i.p. injection of 500 microg/kg ETX (injury dose) was given 24 h later. After 6 h, myocardial function was evaluated via the Langendorff perfusion model. Shams received only NS, while non-preconditioned rats (PC-) received NS followed by the 500 microg/kg ETX injury dose. Preconditioned rats received injections of 125 mug/kg ETX (PC +125) or 500 microg/kg ETX (PC +500), followed by the 500 microg/kg ETX injury dose. RESULTS: Normal PC +125 and PC +500 males were preconditioned and maintained cardiac function similar to shams (P > 0.05). Castrated PC +125 and PC +500 males were also preconditioned and maintained cardiac function similar to castrated shams (P > 0.05). Conversely, both normal and castrated PC-males showed significantly decreased cardiac function compared to shams (P < 0.05). CONCLUSIONS: Endogenous testosterone does not mediate the lower preconditioning threshold in males.

Animals↗

PubMed2005

Endogenous estrogen mediates a higher threshold for endotoxin-induced myocardial protection in females.

Myocardial endotoxin tolerance may be induced in both males and females; however, it remains unknown whether there are mechanistic and threshold differences between the sexes. We hypothesized that endogenous estrogen mediates a higher threshold for endotoxin (ETX)-induced protection in females. Adult proestrus and ovariectomized (OVX) female rats were preconditioned (PC) with intraperitoneal injections of 125 (PC+125) or 500 (PC+500) microg/kg Salmonella typhimurium LPS (ETX) or normal saline (PC-). Twenty-four hours later, injury dose ETX (500 microg/kg) was injected. After 6 h, myocardial function was measured via Langendorff. p38 MAPK and JNK activation and TNF-alpha, IL-1, and IL-6 expression were evaluated. ETX injury significantly decreased left ventricular developed pressure in PC- groups vs. controls. PC+500 regimen protected against ETX injury, resulting in normal cardiac function. PC+125 regimen protected OVX but not proestrus females, which had diminished myocardial function. Activated JNK and TNF-alpha increased in PC- but were diminished in PC+500 animals. Importantly, activated JNK and TNF increased in PC+125 proestrus females, whereas PC+125 OVX females displayed decreases in these molecules. There were no differences in p38 MAPK activation or expression of IL-1 or IL-6. These results demonstrate that proestrus females require a higher stimulus (PC+500) to achieve myocardial protection against ETX injury. Removal of endogenous estrogen (OVX) lowered the preconditioning threshold (PC+125), resulting in protection after lesser injury. Additionally, myocardial JNK and TNF expression was decreased in OVX PC+125 females, which correlated with myocardial function differences. Therefore, we conclude that endogenous estrogen mediates a higher threshold for ETX tolerance in female myocardium.

Animals↗

PubMed2005

Cellular and molecular mechanisms of sex differences in renal ischemia-reperfusion injury.

Renal ischemia-reperfusion (I/R) is an important etiopathological mechanism of acute renal failure (ARF). Despite improvements in the treatment of ARF, it is associated with significant morbidity and mortality. I/R injury also occurs during renal transplantation and leads to reduced allograft survival. Sex differences have been found in I/R injury in many different organs including the kidney. Women have half the mortality of men in ARF. In animal models also, females are protected against renal I/R injury. The mechanisms by which sex affects the outcome to renal I/R injury are being actively investigated. This review will examine the evidence for gender differences in renal I/R injury and discuss the probable mechanisms by which sex affects the renal response to I/R injury.

Acute Kidney Injury↗

PubMed2005

Stem cell transplantation as a therapeutic approach to organ failure.

BACKGROUND: Stem cell transplantation is one of the next great frontiers for surgery. Stem cells, which are undifferentiated and self-renewing, have shown the ability to differentiate into cardiomyocytes, as well as many other cell types for potential therapeutic use by surgeons. MATERIALS AND METHODS: As a result, stem cells have the potential to undo irreversible cellular damage, something traditional therapies could not cure. However, numerous issues must be resolved to permit safe and effective clinical application of stem cell therapy. These include the interpretation of cellular labeling, the origin of replicating myocytes, the homing mechanism of stem cells, and the differentiation process. RESULTS: Successful translational research will depend on precise delivery of these cells in real time to the area of interest, e.g., the spinal cord, liver, or heart. Surgeons will be better able to excise and replace/regrow, rather than excise alone. As such, a basic understanding of stem cell biology will benefit the surgeon scientist and clinical surgeon. CONCLUSIONS: The review: 1) discusses myocardial regeneration; 2) defines and categorizes stem cells; 3) presents evidence of stem cell transdifferentiation into cardiomyocytes; and, 4) delineates the therapeutic potential of stem cells in the treatment of ischemic heart disease.

Cardiomyopathies↗

PubMed2005

Preconditioning: gender effects.

Preconditioning is injury induced protection from subsequent injury. During preconditioning protective cellular responses to injury are up regulated resulting in acute and delayed defense against further damage. Several studies indicate that females experience a protective advantage after acute insult compared to males. Despite evidence of gender differences in acute injury, relatively few studies have evaluated whether there are sex differences in preconditioning. Variations in patients' pre-morbid preconditioning status may explain outcome variations that are not apparent in small animal studies. This review discusses the differences in response to acute injury experienced by males and females, the basic mechanisms of preconditioning, and the sex differences in the mechanisms of preconditioning.

Animals↗

PubMed2005

Is the preconditioning threshold different in females?

BACKGROUND: Preconditioning is injury induced protection against subsequent insult. Studies have shown that both males and females may be preconditioned. Females appear to have an innate cardioprotection, therefore, we hypothesized that the preconditioning threshold may differ between males and females. MATERIALS AND METHODS: Male and female rats were divided into five groups (n=4-9). Animals were given an intraperitoneal (i.p.) injection of 125, 250, or 500 micrograms/kilogram Salmonella typhimurium lipopolysaccharide (ETX) or 0.4-ml normal saline (NS). After 24-h incubation another i.p. injection of either 500 micrograms/kilogram ETX (injury dose) or NS was given and the animals incubated an additional 6 h. Shams received two injections of NS. Non-preconditioned rats (PC-) received NS followed by ETX. Preconditioned rats had i.p. injections of 125 mug/kg ETX (PC +125), 250 microg/kg ETX (PC +250), or 500 microg/kg ETX (PC +500) followed by the injury dose ETX. The rats were then anesthetized and myocardial function evaluated with the Langendorff perfusion model. RESULTS: PC +500 females were preconditioned and were able to maintain cardiac function similar to shams. Conversely, PC +125 females were not preconditioned with this stimulus and had a significant decrease in cardiac function similar to PC- rats. Male PC +500 and PC +125 rats, however, retained cardiac function comparable to shams, while PC- males showed a significant decrement. CONCLUSIONS: Males and females may each be preconditioned by endotoxin; however, the preconditioning threshold is higher in females than males.

Animals↗

PubMed2005

Intracellular signaling mechanisms of sex hormones in acute myocardial inflammation and injury.

Sex hormones are important modifiers of the acute inflammatory response to injury, an important aspect of myocardial depression and apoptosis following ischemia or endotoxemia. Hemorrhage, trauma, ischemia/reperfusion, burn and sepsis each lead to cardiac dysfunction. Gender has been shown to influence the inflammatory response as well as outcomes following acute injury. The mechanisms by which sex affects the inflammatory response and the outcome to acute injury are being actively investigated. It is now recognized that myocardial inflammation plays a crucial role in I/R-induced myocardial dysfunction. Inflammatory mediators, such as TNF-alpha are produced by cardiomyocytes and contribute to myocardial functional depression and apoptosis. Gender differences in the inflammatory response following burn injury have been demonstrated. However, gender differences in the setting of acute I/R-induced inflammation are unclear. In addition, a critical component of the signal transduction pathway leading to myocardial inflammation is the activation of p38 mitogen-activated protein kinase (MAPK). In other systems, it appears that gender differences exist in the p38 MAPK signaling pathway. The inflammatory response, including the p38 MAPK signaling cascade and expression of proinflammatory cytokines such as TNF-alpha and IL-1beta, may precipitate cardiomyocyte apoptosis following I/R injury. Apoptosis may be an essential component in the pathogenesis of heart failure, and there is evidence that myocyte apoptosis in the failing human heart is markedly lower in women than in men. The prevention of cell death attenuates I/R-induced injury on myocardial anatomy and performance. This review will: 1) examine evidence for gender differences in the outcome to acute injury; 2) explain the myocardial inflammatory response to acute injury; and 3) elucidate the various mechanisms by which gender and sex hormones affect the myocardial response to acute injury.

Acute Disease↗

PubMed2005

p38 mitogen activated protein kinase mediates both death signaling and functional depression in the heart.

BACKGROUND: Understanding the myocardial inflammatory response to ischemia is an important part of achieving the elusive clinical goal of long-enduring myocardial protection. p38 mitogen-activated protein kinase (MAPK) has been implicated in oxidant stress-induced myocardial tumor necrosis factor production. However, it is unknown whether p38 MAPK mediates the following important events in both myocardial apoptosis and functional depression: mitogen-activated protein kinase-activated protein kinase 2, caspase-1, caspase-3, and caspase-11 activation, and tumor necrosis factor, interleukin-1beta and interleukin-6 production. METHODS: Isolated rat hearts were perfused and subjected to an ischemia-reperfusion insult, with and without preischemic infusion of 20 microM SB203580 (p38 MAPK inhibitor). Myocardial functional measurements were continuously recorded throughout the experiments. Myocardial tissue was then assessed for products of p38 MAPK activation, expression of tumor necrosis factor, interleukin-1beta and interleukin-6, and activation of caspase-1, caspase-3 and caspase-11. RESULTS: Postischemic recovery of left ventricular developed pressure, +dP/dt and -dP/dt was significantly increased by p38 MAPK inhibition (MKI) (left ventricular developed pressure: 48.4 +/- 3.87 MKI versus 32.7 +/- 4.32 mm Hg; +dP/dt: 1392.0 +/- 141.7 MKI versus 896.7 +/- 128.5 mm Hg/s; -dP/dt: -889.9 +/- 97.63 MKI versus -548.9 +/- 71.29 mmHg/s). p38 MAPK inhibition also significantly reduced ischemia-reperfusion-induced elevation of left ventricular end-diastolic pressure (82.76 +/- 4.59 MKI vs 69.95 +/- 3.55 mm Hg). p38 MKI decreased myocardial tumor necrosis factor, interleukin-1beta and interleukin-6 protein levels, and reduced active myocardial caspase-1, caspase-3 and caspase-11. CONCLUSIONS: The p38 MAPK pathway indeed mediates the following important events in myocardial apoptosis and functional depression: mitogen-activated protein kinase-activated protein kinase 2, caspase-1, caspase-3 and caspase-11 activation, and tumor necrosis factor, interleukin-1beta, interleukin-6 production after myocardial ischemia. Single site (p38 MAPK) inhibition of these events may have important therapeutic implications in myocardial protection.

Animals↗

PubMed2005

Aprotinin improves kidney function and decreases tubular cell apoptosis and proapoptotic signaling after renal ischemia-reperfusion.

OBJECTIVE: The purpose of the study was to determine the effects of aprotinin on (1) renal function, (2) apoptosis and apoptotic signaling, and (3) the inflammatory response of the kidney after ischemia-reperfusion injury. METHODS: Male rats underwent a sham procedure or left renal ischemia for 1 hour. Rats were divided into three groups and received no reperfusion, reperfusion for 1 hour, or reperfusion for 24 hours. The animals undergoing ischemia received saline solution alone or aprotinin (60,000 kIU/kg). At the end of the experiment, a sample for serum creatinine was taken and the left kidney was harvested. The kidney was analyzed for expression of tumor necrosis factor alpha, interleukin 1beta, and interleukin 6 (enzyme-linked immunosorbent assay and reverse transcriptase-polymerase chain reaction) and activation of p38 mitogen-activated protein kinase, caspase 3, and caspase 8 (Western blot). The kidney was assessed for apoptosis with enzyme-linked immunosorbent assay and by terminal deoxynucleotidyl transferase biotin-deoxyuridine triphosphate nick-end labeling staining of tissue slides. RESULTS: Aprotinin significantly decreased the rise in serum creatinine and apoptosis caused by ischemia-reperfusion. Aprotinin significantly reduced interleukin 1 and 6 messenger RNA production and showed a trend toward reducing tumor necrosis factor messenger RNA production after ischemia. Aprotinin also significantly reduced caspase 8 activation and showed a trend toward decreasing p38 mitogen-activated protein kinase activation after 1 hour of reperfusion. CONCLUSION: These results suggest that aprotinin provides protection from renal ischemia-reperfusion injury. They also suggest that aprotinin may do so by affecting apoptotic signaling and inflammatory cytokine production. Aprotinin is a potential therapeutic measure in clinical situations where renal ischemia-reperfusion injury can be anticipated, provided adequate heparinization is possible.

Animals↗

PubMed2005

Endothelium-dependent pulmonary artery vasorelaxation is dysfunctional in males but not females after acute lung injury.

BACKGROUND: Mortality after acute respiratory distress syndrome is higher in males than in females. Gender differences in pulmonary vascular reactivity and local inflammatory response may explain this disparity. We hypothesized that endothelium-dependent pulmonary vasorelaxation is impaired in males and that this effect is related to differences in local inflammatory cytokine expression from the pulmonary vasculature. METHODS: Pulmonary artery (PA) rings (n = 12-16 per group) were isolated from adult male and female Sprague-Dawley rats treated with endotoxin (Salmonella typhimurium lipopolysaccharide, 20 mg/kg IP) or vehicle (0.9% normal saline), and connected to force transducers for measurement of isometric force displacement. Dose-response curves (0.01-10 micromol/L) to the endothelium-dependent vasodilator acetylcholine and the endothelium-independent vasodilator sodium nitroprusside were generated. PA rings were also evaluated for inducible nitric oxide synthase, tumor necrosis factor-alpha, and interleukin 1beta messenger RNA (mRNA) by reverse transcriptase-polymerase chain reaction. RESULTS: Endotoxin had no effect on the maximum PA contraction in males (564.4 +/- 37.37 mg vs 633.3 +/- 54.67 mg vehicle) or females (446.3 +/- 20.00 mg vs 444.2 +/- 33.02 mg vehicle), but endothelium-dependent vasodilation was significantly decreased in males (47.49 +/- 5.63% vs 77.61 +/- 9.41% vehicle). Endothelium-independent vasodilation remained intact during endotoxemia. Endotoxin increased the PA expression of inducible nitric oxide synthase mRNA, but there was no gender difference. There was no change in expression of PA tumor necrosis factor, whereas endotoxemic males, but not females, had increased interleukin 1beta mRNA, compared with vehicle. CONCLUSIONS: These results suggest that sepsis-induced vascular dysfunction differs between males and females, and, therefore, treatment of acute lung injury may require gender-specific therapies.

Animals↗

PubMed2005

Sexual dimorphism in myocardial tumor necrosis factor-alpha and cardiac function during endotoxin tolerance.

BACKGROUND: Preconditioning is injury-induced protection against subsequent injury and may be induced by a variety of stimuli. Both males and females may be preconditioned; however, if females are relatively protected against the initial insult, is their preconditioning threshold higher? We hypothesized that preconditioning injury threshold differences may exist between genders, which may be associated with differences in myocardial inflammatory monokine production. METHODS: Male and female Sprague-Dawley rats (n=3-5/group) were given intraperitoneal injections of 125 or 500 microg/kg Salmonella typhimurium lipopolysaccharide (ETX) or 0.4 mL normal saline (NS; 154 mmol/L NaCl). After 24 hours, another injection of 500 microg/kg ETX (injury dose) or NS was given, and the animals were incubated an additional 1 or 6 hours. The rats were anesthetized and myocardial function evaluated via the Langendorff perfusion model. Tumor necrosis factor-alpha (TNF-alpha), interleukin-(IL)-1beta, and IL-6 were measured in 1-hour animals via an enzyme-linked immunosorbent assay. Nonpreconditioned rats (PC-) received NS followed by ETX. Preconditioned rats received either 125 microg/kg ETX (PC+125) or 500 microg/kg ETX (PC+500) followed by injury dose ETX. RESULTS: PC+125 and PC+500 males, as well as PC+500 females, were preconditioned and retained cardiac function similar to shams. PC+125 females were not preconditioned with this stimulus and had a decrease in cardiac function similar to PC- rats. Furthermore, PC+125 and PC+500 males, and PC+500 females had decreased release of TNF-alpha after preconditioning, while PC- animals and PC+125 females did not. CONCLUSIONS: Males and females can be preconditioned by endotoxin; however the preconditioning threshold is higher in females than males.

Animals↗

PubMed2005

Sex differences in the myocardial inflammatory response to acute injury.

Hemorrhage, trauma, ischemia/reperfusion, burn, and sepsis each lead to cardiac dysfunction. These insults lead to an inflammatory cascade, which plays an important role in this process. Gender has been shown to influence the inflammatory response, as well as outcomes after acute injury. The mechanisms by which gender affects the inflammatory response to and the outcome of acute injury are being actively investigated. We searched PubMed for articles in the English language by using the search words sex, gender, estrogen, testosterone, inflammation, acute injury, ischemia reperfusion, sepsis, trauma, and burns. These were used in various combinations. We read the abstracts of the relevant titles to confirm their relevance, and the full articles were then extracted. References from extracted articles were checked for any additional relevant articles. This review will examine evidence for gender differences in the outcome to acute injury, explain the myocardial inflammatory response to acute injury, and elucidate the various mechanisms by which gender affects the myocardial response to acute injury.

Adenosine Triphosphate↗

PubMed2005

Zaprinast attenuates hypoxic pulmonary artery injury and causes less aortic relaxation than milrinone.

Hypoxic pulmonary vasoconstriction is a challenging clinical problem with limited therapeutic options. Milrinone, a phosphodiesterase (PDE)-3 inhibitor, is frequently used to treat perioperative pulmonary hypertension. However, recent evidence suggests that the PDE-5 isoform may be more specific for lung tissue. We hypothesized that the PDE-5 inhibitor zaprinast has greater efficacy for pulmonary vasorelaxation, attenuation of hypoxic pulmonary vasoconstriction, and inhibition of hypoxia-induced pulmonary artery cytokine expression when compared with milrinone. To study this, isolated rat pulmonary artery and thoracic aorta rings suspended in physiologic organ baths for measurement of isometric force transduction were treated with vehicle (dimethyl sulfoxide), milrinone, or zaprinast to assess pulmonary artery relaxation, thoracic aorta relaxation, inhibition of hypoxic (pO2 = 30-35 mmHg) pulmonary vasoconstriction, and hypoxia-induced pulmonary artery TNF-alpha and IL-1beta expression (reverse transcriptase-PCR). Milrinone and zaprinast resulted in dose-dependent pulmonary artery and aortic relaxation, but zaprinast caused significantly less aortic relaxation compared with milrinone (50.12% +/- 3.36% versus 91.03% +/- 2.97%, P < 0.001). Zaprinast, but not milrinone, significantly inhibited hypoxic pulmonary vasoconstriction (zaprinast, 58.42% +/- 5.37%; milrinone, 77.65% +/- 4.42% versus vehicle: 74.42% +/- 7.54%). Hypoxia-induced upregulation of TNF-alpha and IL-1beta mRNA in pulmonary artery was decreased by zaprinast, but not milrinone, pretreatment. These results suggest that zaprinast, but not milrinone, preferentially vasodilates pulmonary artery over aorta, attenuates hypoxic pulmonary vasoconstriction, and inhibits hypoxia-induced pulmonary artery TNF-alpha and IL-1beta expression. Therefore, PDE-5 inhibition may be advantageous in the treatment of pulmonary hypertension.

Animals↗

PubMed2004

Role of endogenous testosterone in myocardial proinflammatory and proapoptotic signaling after acute ischemia-reperfusion.

Myocardial ischemia is the leading cause of death in both men and women; however, very little information exists regarding the effect of testosterone on the response of myocardium to acute ischemic injury. We hypothesized that testosterone may exert deleterious effects on myocardial inflammatory cytokine production, p38 MAPK activation, apoptotic signaling, and myocardial functional recovery after acute ischemia-reperfusion (I/R). To study this, isolated, perfused rat hearts (Langendorff) from adult males, castrated males, and males treated with a testosterone receptor blocker (flutamide) were subjected to 25 min of ischemia followed by 40 min of reperfusion. Myocardial contractile function (left ventricular developed pressure, left ventricular end-diastolic pressure, positive and negative first derivative of pressure) was continuously recorded. After reperfusion, hearts were analyzed for expression of tissue TNF-alpha, IL-1beta, and IL-6 (ELISA) and activation of p38 MAPK, caspase-1, caspase-3, caspase-11, and Bcl-2 (Western blot). All indices of postischemic myocardial functional recovery were significantly higher in castrated males or flutamide-treated males compared with untreated males. After I/R, castrated male and flutamide-treated male hearts had decreased TNF-alpha, IL-1beta, and IL-6; decreased activated p38 MAPK; decreased caspase-1, caspase-3, and caspase-11; and increased Bcl-2 expression compared with untreated males. These results show that blocking the testosterone receptor (flutamide) or depleting testosterone (castration) in normal males improves myocardial function after I/R. These effects may be attributed to the proinflammatory and/or the proapoptotic properties of endogenous testosterone. Further understanding may allow therapeutic manipulation of sex hormone signaling mechanisms in the treatment of acute I/R.

Acute Disease↗

PubMed2004

Sex differences in the myocardial inflammatory response to ischemia-reperfusion injury.

The myocardium generates inflammatory mediators during ischemia-reperfusion (I/R), and these mediators contribute to cardiac functional depression and apoptosis. The great majority of these data have been derived from male animals and humans. Sex has a profound effect over many inflammatory responses; however, it is unknown whether sex affects the cardiac inflammatory response to acute myocardial I/R. We hypothesized the existence of inherent sex differences in myocardial function, expression of inflammatory cytokines, and activation of the p38 mitogen-activated protein kinase (MAPK) signaling pathway after I/R. Isolated rat hearts from age-matched adult males and females were perfused (Langendorff), and myocardial contractile function was continuously recorded. After I/R, myocardium was assessed for expression of TNF-alpha, IL-1beta, and IL-6 (RT-PCR, ELISA); IL-1alpha and IL-10 mRNA (RT-PCR); and activation of p38 MAPK (Western blot). All indexes of postischemic myocardial function [left ventricular developed pressure, left ventricular end-diastolic pressure, and maximal positive (+dP/dt) and negative (-dP/dt) values of the first derivative of pressure] were significantly improved in females compared with males. Compared with males, females had decreased myocardial TNF-alpha, IL-1beta, and IL-6 (mRNA, protein) and decreased activation of p38 MAPK pathway. These data demonstrate that hearts from age-matched adult females are relatively protected against I/R injury, possibly due to a diminished inflammatory response.

Animals↗

PubMed2004

Hypoxic pulmonary vasoconstriction and pulmonary artery tissue cytokine expression are mediated by protein kinase C.

Pulmonary arteries exhibit a marked vasoconstriction when exposed to hypoxic conditions. Although this may be an adaptive response to match lung ventilation with perfusion, the potential consequences of sustained pulmonary vasoconstriction include pulmonary hypertension and right heart failure. Concomitant production of proinflammatory mediators during hypoxia may exacerbate acute increases in pulmonary vascular resistance. We hypothesized that acute hypoxia causes pulmonary arterial contraction and increases the pulmonary artery tissue expression of proinflammatory cytokines via a protein kinase C (PKC)-mediated mechanism. To study this, isometric force displacement was measured in isolated rat pulmonary artery rings during hypoxia in the presence and absence of the PKC inhibitors calphostin C or chelerythrine. In separate experiments, pulmonary artery rings were treated with the PKC activator thymeleatoxin for 60 min. After hypoxia, with or without PKC inhibition, or PKC activation alone, pulmonary artery rings were subjected to mRNA analysis for TNF-alpha and IL-1beta via RT-PCR. Our results showed that, in isolated pulmonary arteries, hypoxia caused a biphasic contraction and increased expression of TNF-alpha and IL-1beta mRNA. Both effects were inhibited by PKC inhibition. PKC activation resulted in pulmonary artery contraction and increased the pulmonary artery expression of TNF-alpha and IL-1beta mRNA. These findings suggest that hypoxia induces the expression of inflammatory cytokines and causes vasoconstriction via a PKC-dependent mechanism. We conclude that PKC may have a central role in modulating hypoxic pulmonary vasoconstriction, and further elucidation of its involvement may lead to therapeutic application.

Alkaloids↗

PubMed2004

Syntaxin 1A regulation of weakly inactivating N-type Ca2+ channels.

N- and P/Q-type Ca2+ channels are abundant in nerve terminals where they interact with proteins of the release apparatus, including syntaxin 1A and SNAP-25. In previous studies on N- or P/Q-type Ca2+ channels, syntaxin 1A co-expression reduced current amplitudes, increased voltage-dependent inactivation and/or enhanced G-protein inhibition. However, these studies were conducted in Ca2+ channels that exhibited significant voltage-dependent inactivation. We previously reported that N-type current in bovine chromaffin cells exhibits very little voltage-dependent inactivation and we identified the Ca2+ channel subunits involved. This study was undertaken to determine the effect of syntaxin 1A on this weakly inactivating Ca2+ channel. Co-expression of syntaxin 1A with the weakly inactivating bovine N-type Ca2+ channels in Xenopus oocytes did not appear to alter inactivation but dramatically reduced current amplitudes, without changing cell surface expression. To further understand the mechanisms of syntaxin 1A regulation of this weakly inactivating channel, we examined mutants of the alpha1B subunit, beta2a subunit and syntaxin 1A. We determined that the synprint site of alpha1B and the C-terminal third of syntaxin 1A were necessary for the reduced current amplitude. In addition we show that enhanced G-protein-dependent modulation of the Ca2+ current by syntaxin 1A cannot explain the large suppression of Ca2+ current observed. Of most significance, syntaxin 1A increased voltage-dependent inactivation in channels containing mutant beta2a subunits that cannot be palmitoylated. Our data suggest that changes in inactivation can not explain the reduction in current amplitude produced by co-expressing syntaxin and a weakly inactivating Ca2+ channel.

Animals↗