Radioprotection of craniofacial bone growth

In this review, the potential of pharmacologic therapy for prevention of radiation-induced bone growth inhibition is discussed. Significant radioprotection using the radioprotector Amifostine has been achieved in animal models of radiation-induced retardation of long and craniofacial bone growth. Moreover, radioprotection in vitro has been achieved in a number of cell lines, including osteoblast-like, endothelial, and fibroblastic. This evidence may support future clinical investigations of radioprotector Amifostine or similar substances for radioprotection of the growing craniofacial skeleton.     

An in vitro model of radiation-induced craniofacial bone growth inhibition

Radiation-induced craniofacial bone growth inhibition is a consequence of therapeutic radiation in the survivors of pediatric head and neck cancer. Previously, the infant rabbit orbitozygomatic complex (OZC) was established as a reliable animal model. The purpose of this study was to develop a cell culture model from the rabbit OZC to study the effects of radiation in the craniofacial skeleton.Infant (7-week-old) New Zealand white rabbits were used in this study. Periostea from both OZC were harvested in sterile conditions, introduced into cell culture by way of sequential digestion, and subcultured at confluence. Cultures were analyzed for cellular proliferation (methylthiazoletetrazolium assay), alkaline phosphatase activity, collagen type I expression, and mineralization. Electron microscopy was performed to reveal the in vitro ultrastructure. Subsequently, rabbits were irradiated with sham or 15 Gy radiation, and cell cultures were developed and analyzed for cell numbers.Cell cultures, grown from OZC periostea, expressed osteoblast-like phenotype, with high alkaline phosphatase activity, collagen type 1 expression, and mineralization in an osteogenic environment. Electron microscopy confirmed the characteristic ultrastructural features of osteogenesis in vitro. Finally, significantly (P < 0.01) fewer cells were obtained from animals treated with 15 Gy radiation compared with those from control animals.A primary cell culture with osteoblast-like cellular phenotype was developed from infant rabbit OZC periosteum. This cell culture system responded to in vivo administered radiation by a significant decrease in cell numbers. This in vitro model will be subsequently used to study the cellular mechanisms of radiation and radioprotection in craniofacial osteoblast-like cells.     

Synthesis and Pharmacological Activity of N-[β-(<Emphasis Type="Italic">para</Emphasis>-substituted benzoyl)ethyl]isoleucine and -Methionine

A series of N-[β-(p-substituted benzoyl)ethyl]-isoleucine and -methionine derivatives have been synthesized via the alkylation of amino acids with p-substituted β-diethylaminopropiophenone hydrochlorides. Some of the synthesized compounds possess significant antiinflammatory activity. __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 39, No. 7, pp. 26 – 27, July, 2005.     

Multiphoton Imaging of the Glomerular Permeability of Angiotensinogen

Patients and animals with renal injury exhibit increased urinary excretion of angiotensinogen. Although increased tubular synthesis of angiotensinogen contributes to the increased excretion, we do not know to what degree glomerular filtration of systemic angiotensinogen, especially through an abnormal glomerular filtration barrier, contributes to the increase in urinary levels. Here, we used multiphoton microscopy to visualize and quantify the glomerular permeability of angiotensinogen in the intact mouse and rat kidney. In healthy mice and Munich-Wistar-Frömter rats at the early stage of glomerulosclerosis, the glomerular sieving coefficient of systemically infused Atto565-labeled human angiotensinogen (Atto565-hAGT), which rodent renin cannot cleave, was only 25% of the glomerular sieving coefficient of albumin, and its urinary excretion was undetectable. In a more advanced phase of kidney disease, the glomerular permeability of Atto565-hAGT was slightly higher but still very low. Furthermore, unlike urinary albumin, the significantly higher urinary excretion of endogenous rat angiotensinogen did not correlate with either the Atto565-hAGT or Atto565-albumin glomerular sieving coefficients. These results strongly suggest that the vast majority of urinary angiotensinogen originates from the tubules rather than glomerular filtration.The renin–angiotensin system (RAS) is one of the most important regulatory mechanisms of body fluid, electrolyte homeostasis, and BP.^1–4 RAS in the kidney is independently regulated from RAS in the systemic circulation, and it has been implicated in the development of hypertension and kidney diseases. For example, renal epithelial cell-specific overexpression of human angiotensinogen (AGT) in human renin transgenic mice resulted in increased renal angiotensin II, hypertension, and renal fibrosis without any changes in circulating angiotensin II.⁵ Also, Dahl salt-sensitive rats, which show low plasma renin activity under high salt feeding, had higher renal angiotensin II content in the kidney compared with normal salt-fed control animals.⁶ Although all components that are necessary for angiotensin II production are expressed in the kidney,³ AGT is, currently, the only component that is noninvasively measurable in the urine of patients. The level of urinary AGT reflects the activity of the intrarenal RAS, and it is associated with pathologic states in several experimental^7,8 and clinical studies.^9,10 Although the major source of the circulating AGT is the liver, we and others have previously shown that AGT is produced in the proximal tubules through a de novo pathway.^3,11 Intravenously injected human recombinant AGT (hAGT), which has little affinity for enzymatic cleavage by rodent renin because of high species specificity,^12,13 was undetectable in the urine of angiotensin II-induced hypertensive rats,⁸ suggesting that the increase in urinary AGT is likely of tubular rather than glomerular (plasma) origin. However, the plasma level of AGT is much greater than the plasma level of urinary AGT, and therefore, the increase in urinary AGT in a kidney injury model could result from the damage of the glomerular filtration barrier (GFB) and AGT leakage into the urine.Therefore, the present study was conducted to measure exactly how much AGT is filtered through the GFB and ultimately, excreted through the urine in normal circumstances and the glomerulosclerosis model of Munich-Wistar-Frömter (MWF) rats that shows significant GFB damage. We compared the glomerular permeability of AGT with the glomerular permeability of albumin, because albumin (66 kD) has a molecular mass similar to AGT (∼60 kD); also, the increase in its urinary excretion closely reflects the decline of renal function. Indirectly, these studies also addressed the currently highly debated issue of the glomerular filtration of albumin.^14–19 To compare the glomerular processing of these two proteins, we employed intravital multiphoton fluorescence microscopy, which has been used by our laboratory^15,20,21 and the laboratories of others,^16–19 to directly and quantitatively visualize the glomerular permeability of macromolecules.