Mitochondrial Lon regulates apoptosis through the association with Hsp60-mtHsp70 complex.

Human Lon protease is a mitochondrial matrix protein with several functions, including protein degradation, mitochondrial DNA (mtDNA) binding, and chaperone activity. Lon is currently emerging as an important regulator of mitochondria-contributed tumorigenesis due to its overexpression in cancer cells. To understand the mechanism of increased Lon in tumor cells, we studied the interactome to identify the chaperone Lon-associated proteins by proteomics approaches using the cells overexpressing Lon. In the present study, we designed a method connecting co-immunoprecipitation (Co-IP) to in-solution digestion for the shotgun mass spectrometry. We identified 76 proteins that were putative Lon-associated proteins that participated in mitochondrial chaperone system, cellular metabolism and energy, cell death and survival, and mtDNA stability. The association between Lon and NDUFS8 or Hsp60-mtHsp70 complex was confirmed by Co-IP and immunofluorescence co-localization assay. We then found that the protein stability/level of Hsp60-mtHsp70 complex depends on the level of Lon under oxidative stress. Most importantly, the ability of increased Lon-inhibited apoptosis is dependent on Hsp60 that binds p53 to inhibit apoptosis. These results suggest that the mechanism underlying cell survival regulated by Lon is mediated by the maintenance of the protein stability of Hsp60-mtHsp70 complex. This new knowledge of chaperone Lon interactome will allow us to better understand the cellular mechanism of Lon in mitochondrial function and of its overexpression in enhancing cell survival and tumorigenesis.

Overexpression of Lon contributes to survival and aggressive phenotype of cancer cells through mitochondrial complex I-mediated generation of reactive oxygen species.

Lon protease is a multifunction protein and operates in protein quality control and stress response pathways in mitochondria. Human Lon is upregulated under oxidative and hypoxic stresses that represent the stress phenotypes of cancer. However, little literature undertakes comprehensive and detailed investigations on the tumorigenic role of Lon. Overexpression of Lon promotes cell proliferation, apoptotic resistance to stresses, and transformation. Furthermore, Lon overexpression induces the production of mitochondrial reactive oxygen species (ROS) that result from Lon-mediated upregulation of NDUFS8, a mitochondrial Fe-S protein in complex I of electron transport chain. Increased level of mitochondrial ROS promotes cell proliferation, cell survival, cell migration, and epithelial-mesenchymal transition through mitogen-activated protein kinase (MAPK) and Ras-ERK activation. Overall, the present report for the first time demonstrates the role of Lon overexpression in tumorigenesis. Lon overexpression gives an apoptotic resistance to stresses and induces mitochondrial ROS production through Complex I as signaling molecules to activate Ras and MAPK signaling, giving the survival advantages and adaptation to cancer cells. Finally, in silico and immunohistochemistry analysis showed that Lon is overexpressed specifically in various types of cancer tissue including oral cancer.

Acceptance of an ABO-incompatible mismatched (AB(+) to O(+)) liver allograft with the use of daclizumab and mycophenolate mofetil.

Liver allograft survival rates of 50% to 60% are reported in blood group A, group B, group O (ABO)-incompatible mismatched grafts even when aggressive immunosuppressive protocols, including plasmapheresis, OKT(3), cyclophosphamide, cyclosporine, prostaglandin E(1), and steroids, are used. A 59-year-old woman, blood type O(+), required emergency retransplantation posttransplantation day 2 because of primary nonfunction of the liver allograft. A blood type AB(+) allograft was used. Induction immunosuppressive therapy included tacrolimus, mycophenolate mofetil, OKT(3) (muromonab-CD(3)), steroids, and prostaglandin E(1). In addition, plasmapheresis was performed daily for 9 days. OKT(3) and prostaglandin E(1) were also discontinued postoperative day 9. Biopsy-proven acute cellular rejection was diagnosed postoperative day 12 and was treated with double-dose OKT(3) (10 mg) for another 6 days. On the day OKT(3) was discontinued, daclizumab, 60 mg, was administered intravenously. This dose was repeated every 2 weeks for a total of 5 doses. At 1-year follow-up, the patient is doing very well with normal liver function. We are unaware of previous reports of the use of daclizumab and mycophenolate mofetil as part of an immunosuppressive protocol aimed to induce acceptance of ABO-incompatible mismatched liver allografts. Based on our experience with this case, it seems that mycophenolate mofetil is an adequate replacement for cyclophosphamide. We also believe daclizumab provided adequate protection at a critical time. Further experience with both these drugs is required to establish their role in ABO-incompatible mismatched liver allografts.

Impact of retrograde cerebral perfusion on aortic arch aneurysm repair.

OBJECTIVE: Protection of the brain is a primary concern in aortic arch surgery. Retrograde cerebral perfusion is a relatively new technique used for cerebral protection during profound hypothermic circulatory arrest. This study was designed to compare, retrospectively, the outcome of 109 patients undergoing aortic arch operation with and without the use of retrograde cerebral perfusion. METHODS: Fifty-five patients had profound hypothermic circulatory arrest alone, and 54 patients had supplemental cerebral protection with retrograde cerebral perfusion. Mean age was 61 +/- 13 years and 58 +/- 14 years, respectively (mean +/- standard deviation). Twenty-two preoperative and intraoperative characteristics, including age, sex, acuity, presence of aortic dissection, and aneurysm rupture, were similar in the 2 groups (P >.05). RESULTS: Mean circulatory arrest times (in minutes) were 30 +/- 19 in the group without retrograde cerebral perfusion and 33 +/- 19 in the group with retrograde cerebral perfusion, respectively. chi(2) Analysis revealed that patients operated on with the use of retrograde cerebral perfusion had significantly lower hospital mortality (15% vs 31%; P =.04) and in-hospital permanent neurologic complications (9% vs 27%; P =.01). Retrograde cerebral perfusion failed to reduce the prevalence of temporary neurologic dysfunction (17% vs 18%; P =.9). Stepwise multiple logistic regression revealed that extracorporeal circulation time, age, and lack of retrograde cerebral perfusion were statistically significant independent risk factors for hospital mortality. The same analysis revealed that lack of retrograde cerebral perfusion was the only significant independent risk factor for permanent neurologic dysfunction. CONCLUSION: Retrograde cerebral perfusion decreased the prevalence of permanent neurologic complications and the hospital mortality in patients undergoing aortic arch operations.

Memantine for prevention of spinal cord injury in a rabbit model.

BACKGROUND: This study was conducted to investigate the effect of memantine, a noncompetitive N-methyl-d-aspartate receptor antagonist, on the neurologic outcome of spinal cord ischemia after aortic occlusion. MATERIALS AND METHODS: New Zealand White rabbits were anesthetized and spinal cord ischemia was induced for 40 minutes by infrarenal aortic occlusion. Animals were randomly allocated to 3 groups. Group 1 (n = 8, control) received no pharmacologic intervention, group 2 (n = 8) received intra-aortic memantine infusion (20 mg/kg) after aortic crossclamping, and group 3 (n = 8) was treated with systemic memantine infusion (20 mg/kg) 45 minutes before aortic occlusion. Neurologic status was scored by the Tarlov system (in which 4 is normal and 0 is paraplegia) at 12, 24, 36, and 48 hours after the operation. Lumbar spinal root stimulation potentials and motor evoked potentials from lower limb muscles were monitored before, during, and after the operation. After the animals were killed, the spinal cords were studied histopathologically. RESULTS: All potentials disappeared shortly after aortic crossclamping. They returned earlier in both memantine-treated groups than in the placebo group. Histologic examination of spinal cords revealed a few abnormal motor neurons in memantine-treated rabbits but found extensive injury in the control group. At 12 hours the median Tarlov scores were 0 in the control group (group 1), 2 in the intra-aortic memantine group (group 2, P =.001 versus control), and 3 in the systemic group (group 3, P =.0002 versus control). At 24 hours median Tarlov scores were 0, 2.5 (P =.0002), and 4 (P =. 0002), respectively. Finally, at both 36 and 48 hours median Tarlov scores were 0, 3 (P =.0006), and 4 (P =.0002), respectively. CONCLUSION: Memantine significantly reduced neurologic injury related to spinal cord ischemia and reperfusion after aortic occlusion.

Perioperative risk factors for mortality in patients with acute type A aortic dissection.

BACKGROUND: Patients with acute type A aortic dissection are associated with a high mortality rate and postoperative complications. This study was designed to explore perioperative risk factors for death in patients with acute type A aortic dissection. METHODS AND RESULTS: One hundred nine consecutive surgical patients with acute type A aortic dissection were included in the present study. Thirty-five perioperative risk factors were used in the statistical analysis for mortality prediction. The 30-day mortality rate for all patients was 30% (33 of 109). Univariate analysis revealed 5 preoperative and intraoperative risk factors that were found to be statistically significant predictors for death: older age, renal failure, preoperative hemodynamic instability, preoperative cardiopulmonary resuscitation, and lack of retrograde cerebral perfusion (P < 0.05). Rupture of aneurysm, hypothermic circulatory arrest time, and operation date were not found to be risk factors for death. Stepwise multiple logistic regression confirmed that older age and lack of retrograde cerebral perfusion were statistically significant independent risk factors for death (P < 0.05). Four postoperative complications were found to be statistically significant prognostic indicators for death: liver failure, stroke, sepsis, and reoperation after the initial surgery (P < 0.05). CONCLUSIONS: Perioperative risk factors for death after the operation for acute type A aortic dissection were identified. This will allow physicians and surgeons to better assess the patient's risk, which will lead to better outcome.

Impact of minimum hematocrit during cardiopulmonary bypass on mortality in patients undergoing coronary artery surgery.

BACKGROUND: The hematocrit on cardiopulmonary bypass (CPB) frequently falls to a low level during many cardiac surgical procedures. This study was designed to explore the impact on mortality of minimum hematocrit level achieved during the CPB after coronary artery surgery. METHODS AND RESULTS: Two thousand seven hundred thirty-eight sequential isolated coronary artery surgery patients during a 42-month period at a tertiary academic center were included in this study. Thirty-one standardized preoperative risk factors used in a multiple logistic regression revealed eight statistically significant independent predictors for postoperative mortality. Minimum hematocrit level during CPB was then added to the regression model and was found to be an independent risk factor for mortality. The entire patient population was divided into dichotomous groups using different minimum hematocrit levels on CPB for the determination of cutoff points by multiple logistic regression. After adjusting for other risk factors, the minimum hematocrit level of 14% was found to be a statistically significant cutoff point. Patients with minimum hematocrit levels < or =14% were found to have an increased probability of risk-adjusted mortality (odds ratio, 2.70; P=.002). A subgroup analysis revealed that high-risk patients with minimum hematocrit levels < or =17% were found to have a significantly increased probability of postoperative mortality (odds ratio, 2.20; P=.017). CONCLUSIONS: Minimum hematocrit level during CPB is an independent risk factor for mortality after coronary artery surgery. There is a significantly increased risk of mortality for hematocrit levels < or =14%. For high-risk patients, there is a significantly increased risk of mortality for hematocrit levels < or =17%.

VLSI neuroprocessors for video motion detection.

The system design of a locally connected competitive neural network for video motion detection is presented. The motion information from a sequence of image data can be determined through a two-dimensional multiprocessor array in which each processing element consists of an analog neuroprocessor. Massively parallel neurocomputing is done by compact and efficient neuroprocessors. Local data transfer between the neuroprocessors is performed by using an analog point-to-point interconnection scheme. To maintain strong signal strength over the whole system, global data communication between the host computer and neuroprocessors is carried out in a digital common bus. A mixed-signal very large scale integration (VLSI) neural chip that includes multiple neuroprocessors for fast video motion detection has been developed. Measured results of the programmable synapse, and winner-takes-all circuitry are presented. Based on the measurement data, system-level analysis on a sequence of real-world images was conducted.

A VLSI neural processor for image data compression using self-organization networks.

An adaptive electronic neural network processor has been developed for high-speed image compression based on a frequency-sensitive self-organization algorithm. The performance of this self-organization network and that of a conventional algorithm for vector quantization are compared. The proposed method is quite efficient and can achieve near-optimal results. The neural network processor includes a pipelined codebook generator and a paralleled vector quantizer, which obtains a time complexity O(1) for each quantization vector. A mixed-signal design technique with analog circuitry to perform neural computation and digital circuitry to process multiple-bit address information are used. A prototype chip for a 25-D adaptive vector quantizer of 64 code words was designed, fabricated, and tested. It occupies a silicon area of 4.6 mmx6.8 mm in a 2.0 mum scalable CMOS technology and provides a computing capability as high as 3.2 billion connections/s. The experimental results for the chip and the winner-take-all circuit test structure are presented.