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ZDHHC13 is a member of DHHC-containing palmitoyl acyltransferases (PATs) family of enzymes. It functions by post-translationally adding 16-carbon palmitate to proteins through a thioester linkage. We have previously shown that mice carrying a recessive Zdhhc13 nonsense mutation causing a Zdhcc13 deficiency develop alopecia, amyloidosis and osteoporosis. Our goal was to investigate the pathogenic mechanism of osteoporosis in the context of this mutation in mice. Body size, skeletal structure and trabecular bone were similar in Zdhhc13 WT and mutant mice at birth. Growth retardation and delayed secondary ossification center formation were first observed at day 10 and at 4 weeks of age, disorganization in growth plate structure and osteoporosis became evident in mutant mice. Serial microCT from 4-20 week-olds revealed that Zdhhc13 mutant mice had reduced bone mineral density. Through co-immunoprecipitation and acyl-biotin exchange, MT1-MMP was identified as a direct substrate of ZDHHC13. In cells, reduction of MT1-MMP palmitoylation affected its subcellular distribution and was associated with decreased VEGF and osteocalcin expression in chondrocytes and osteoblasts. In Zdhhc13 mutant mice epiphysis where MT1-MMP was under palmitoylated, VEGF in hypertrophic chondrocytes and osteocalcin at the cartilage-bone interface were reduced based on immunohistochemical analyses. Our results suggest that Zdhhc13 is a novel regulator of postnatal skeletal development and bone mass acquisition. To our knowledge, these are the first data to suggest that ZDHHC13-mediated MT1-MMP palmitoylation is a key modulator of bone homeostasis. These data may provide novel insights into the role of palmitoylation in the pathogenesis of human osteoporosis. [ABSTRACT FROM AUTHOR]

Objective: This study investigated the 8003 base pair (bp) fragmentation damage of brain mitochondrial DNA in newborn piglets at different times after hypoxic-ischemic brain damage (HIBD) so as to explore the biomolecular foundation of neonatal neuronal metabolic disorders., Methods: Fifty 3-day-old piglets were randomly assigned into Control and HIBD groups. The HIBD group was subdivided into groups sacrificed at 0, 24, 48 and 72 hrs post-HIBD (n=10). HIBD was induced by left carotid ligation and exposure to 8% oxygen for 2 hours. The Control group was exposed to air and was sham-operated. The left hippocampal cortexes of all subjects were obtained to amplify the fragments of 200 bp and 8003 bp by the LX-PCR method. The PCR products were electrophoresed on agaros gels to obtain the integral optical density (IOD)., Results: The IOD of 8003 bp fragment was markedly reduced in the HIBD 0 hr group (22.616 +/- 2.276) when compared with that of the Control group (56.995 +/- 0.317) (P < 0.05). The IOD value remained lower at 24 hrs (27.719 +/- 0.309) and 48 hrs post-HIBD (49.491 +/- 3.233) (P < 0.05). Until 72 hrs post-HIBD, the IOD (55.972 +/- 2.236) restored to the control value., Conclusions: The brain mitochondrial DNA was fragmented in newborn piglets following brain hypoxia-ischemia. It did not recover to normal until 72 hrs post-HIBD. The fragmentation damage of mitochondrial DNA may be related to the depression of mitochondrial respiratory enzymes activity and neuron apoptosis.

Objective: To study the change of beta 1-integrin in neonatal rats with ischemic renal injury., Methods: Twenty-four neonatal rats weighing from 30 to 40 g were chosen. Anesthesia was carried out by peritoneal injection of nembutal-sodium solution (4 mg/100 g). Renal ischemic injury model was induced by clamping the left renal pedicle for different periods of time. The kidneys of normal neonatal rats were functioned as the control group. Immunofluorescence technique was used to detect the location of beta 1-integrin in kidney, especially in cortex., Results: In control group, beta 1-integrin subunit was found to be located mainly in the basal membrane of tubular epithelial cell. After 10 minutes of ischemia, immunostaining highlighted the broken basement membranes of the experiment groups. The longer the ischemia continued, the more the broken points we observed. There were significant differences between the experiment groups and the control group. Yet, no significant difference in the IOD value of beta 1-integrin was seen between the 10-min-ischemia and 30-min-ischemia groups., Conclusion: Under physiological condition, beta 1-integrin is distributed over the basal membrane of the tubular epithelial cell of neonatal rat. Ischemic injury can cause the changes of beta 1-integrin which may be the reason of exfoliation and depolarization of tubular epithelia cell.

Objective: By studying the distribution and expression of beta 1-integrin and its mRNA in renal tubular epithelial cell at different ischemia/reperfusion time phases we probe the role of beta 1-integrin in I/R injury of neonatal animals., Methods: The neonatal SD rat ischemia/reperfusion model was set up. Immunofluorescent staining and in situ hybridization (ISH) were used to show the distribution and expression of beta 1-integrin with its mRNA in renal tubular epithelial cells and the quantities of beta 1-integrin and its mRNA were counted by ImagePlus-Pro system., Results: 1. beta 1-integrin was located at the basal plasma membrane in normal renal tubular epithelial cells. After ischemia for 0.5 h, the redistribution was not significant. After reperfusing for 0.5 h, beta 1-integrin began to move onto the lateral and apex surfaces of cells. This kind of change was most apparent after reperfusion for 2 h and was accompanied with reduced expression and destruction of renal tubular. No positive dying was seen in the lumen. The regeneration started 24 hours post-ischemia. beta 1-integrin was redistributed onto the basal plasma membrane. After reperfusion for 120 hours, the regeneration ended, but the expression did not gain the normal level. 2. The mRNA of beta 1-integrin was mainly expressed in the cell plasma. Its expression was increased while reperfusion for 0.5 h to 2 h and was still above normal level after 24 h to 120 h of reperfusion., Conclusion: The distribution of beta 1-integrin was "depolarized" and its expression was reduced. But the level of mRNA was raised, which indicated that during ischemia/reperfusion injury, there were mechanisms that influenced the distribution and synthesis of beta 1-integrin at the same time.

Objective: To clarify the effect of hypoxia and ischemia on the concentration of Ca2+ in myocardial mitochondria, and on the activity of respiratory chain complex IV--cytochrome oxidase (CCO) in neonatal swines, and to find out the change of myocardial mitochondria during hypoxic-ischemic brain damage (HIBD)., Methods: The study was performed on neonatal swines. For establishment of HIBD model, the left carotid was ligated and the swine was placed under hypoxia for two hours. Then the concentration of Ca2+ and the activity of respiratory chain complex IV in myocardial cell mitochondria were measured at 0 hour and 24, 48, 72 hours after reoxygenation. The measured values from these 0-, 24-, 48-, 72-hour-HIBD-groups (n = 10 per group) and from the normal control group (n = 10) were statistically analyzed by means of ANOVA, Newman-Keuls test and linear correlation., Results: After the swines were placed under hypoxia-ischemia for two hours, 1. the concentration of Ca2+ in myocardial mitochondria increased, till 24 hours after re-oxygenation, and then it descended at 48 hours and 72 hours after reoxygenation; 2. the activity of myocardial mitochondrial respiratory chain complex IV descended, though activity recovery was seen at 48 and 72 hours, it did not come back to normal level at 72 hours after reoxygenation; 3. the concentration of Ca2+ in myocardial mitochondria was negatively correlated with the activity of respiratory chain complex IV., Conclusion: The results showed that in the neonatal swines with HIBD, the mitochondrial respiratory chain in myocardial cell was damaged by hypoxia-ischemia, yet it could be rehabilitated after reoxygenation. Calcium overload in myocardial mitochondria after hypoxia-ischemia might be one of the causes of the descending activity of respiratory chain complex IV.