Collagen-stimulating factor from embryonic brain has ascorbate-like activity and stimulates prolyl hydroxylation in cultured muscle cells

Hyaluronic Acid: The Reason for Its Variety of Physiological and Biochemical Functional Properties

Introduction:

Many physicians may be unfamiliar with the importance of hyaluronic acid (HA) and its physiological and biochemical functions at cellular level. Despite the vast number of published studies using HA in medical treatments, it is still difficult for the reader to clearly distinguish the different types of HA employed in different medical applications. In addition, published studies do not mention the exact type of HA used or its biochemical properties. Usually, a study mentions only its molecular weight and concentration, which are insufficient to know its exact designed properties or to make a comparison with other types of HA.

Methodology:

This article is intended to summarise the information about native and modified HAs with a focus on explaining their different physiological and biochemical functions in the human body, their different commercially available types, and how they affect the associated medical applications. The goal is to provide a basis to researchers and physicians for distinguishing different types of HA and their properties in order to enhance physicians’ clinical practice in terms of application of different types of HA to treatments and to help the international research community to change the reporting of HA characteristics in published papers. This is necessary to enhance future acquisition of data, with the ability to create an HA data bank for further research and as a reference for different HA types and their medical applications.

Conclusion:

These developments should enhance the scientific and clinical knowledge about HA. Furthermore, the overall approach in this paper can be applied to other similar substances.

Antioxidant perturbations in the olfactory mucosa of alachlor-treated rats

The chloracetanilide herbicide alachlor (2-chloro-2',6'-diethyl-N-(methoxymethyl)acetanilide) induces olfactory mucosal tumors in rats following chronic dietary exposure. Previous reports demonstrated that alachlor exposure was associated with depletion of glutathione (GSH) in liver in vivo and in vitro, but did not address this issue in the target tissue for the carcinogenic response. In this study we investigated a potential oxidative stress pathway in olfactory tissue by examining perturbations in olfactory mucosal antioxidants. Male Long-Evans rats were fed alachlor for up to 10 days (10-126 mg/kg per day), and intracellular reduced GSH and ascorbate levels were measured in olfactory mucosa. Both GSH and ascorbate rapidly decreased in olfactory mucosa following alachlor exposure, with a subsequent increase in both antioxidants to approximately 160% of control levels in the high dose group, and recovery of GSH to control levels in all groups by 10 days. Using Western blot analysis, we found that the modifier subunit of the rate-limiting enzyme in GSH synthesis, glutamate-cysteine ligase, increased in olfactory mucosa and remained elevated (126 mg/kg per day group). Two ascorbate transporters were detected by RT-PCR in olfactory mucosa, but neither appeared to be upregulated by alachlor exposure, and ascorbate synthesis was not stimulated in olfactory mucosa by alachlor treatment. Dietary exposure to alachlor depletes olfactory mucosa antioxidants, which may contribute to DNA damage and tissue-specific tumor formation.

Congruity of acetylcholine receptor, acetylcholinesterase, and Dolichos biflorus lectin binding glycoprotein in postsynaptic-like sarcolemmal specializations in noninnervated regenerating rat muscles

Noninnervated regenerating muscles are able to form focal postsynaptic-like sarcolemmal specializations either in places of the former motor endplates ("junctional" specializations) or elsewhere along the muscle fibers (extrajunctional specializations). The triple labeling histochemical method was introduced to analyse the congruity of focalization in such specializations of 3 synaptic components: acetylcholinesterase (AChE), acetylcholine receptor (AChR), and a specific synaptic glycoprotein which binds Dolichos biflorus lectin (DBAR). Noninnervated regenerating soleus and extensor digitorum longus (EDL) muscles of the rat were examined and compared with denervated muscles of neonatal and adult rats. All junctional sarcolemmal specializations in noninnervated regenerating muscles accumulated AChE and AChR. Localization of the 2 components was identical within the limits of resolution of the method. DBAR could not be demonstrated in junctional specializations in 17-day-old regenerating muscles. It seems that an agrin-like inducing substance in the former junctional basal lamina invariably triggers the accumulation of both AChE and AChR in the underlying sarcolemma of the regenerating muscle fiber. However, accumulation of DBAR would probably require the presence of the motor nerve. In most of the extrajunctional sarcolemmal specializations in 8-day-old regenerating soleus and EDL muscles, both AChE and AChR accumulated. However, about 10 percent of AChE accumulations lacked AChR and about 35% of AChR accumulations lacked AChE. Even greater variability was observed in 17-day-old regenerating muscles. The presence of DBAR in the extrajunctional postsynaptic-like sarcolemmal specializations could not be demonstrated. Similar extrajunctional sarcolemmal specializations were observed in denervated postnatal rat muscles. About 70% contained both AChE and AChR, and 30% contained only AChR, but none contained DBAR. In denervated mature muscles, sparse extrajunctional AChR accumulations did not contain detectable amounts of AChE. The ability to form complex postsynaptic-like sarcolemmal specializations in the absence of nerve, which is probably inherent to noninnervated immature muscle fibers, may be reduced with muscle maturation. Variable accumulation of individual components in the postsynaptic-like specializations indicates that different triggering factors may be involved in their accumulation or, at least, the mechanisms of their accumulation can function relatively independently.

Stimulation of collagen production in vitro by ascorbic acid released from explants of migrating avian neural crest

Embryonic neuronal tissues contain a collagen-stimulating factor, shown to enhance the hydroxylation and secretion of proline-containing macromolecules by cultured muscle cells. Here we report on a similar activity found during avian embryonic development in explants of migrating mesencephalic neural crest. The degree of proline hydroxylation of proteins secreted into the medium was stimulated 2.5-6-fold in neural crest-muscle and neural crest-somite cocultures, as compared with control cultures devoid of crest explants. No such stimulation occurred when cocultures were treated with the enzyme ascorbate oxidase (EC 1.10.3.3), suggesting that the active factor in neural crest explants was ascorbic acid or an ascorbate-like molecule. Further characterization of this molecule was performed in crest explants and other embryonic tissues by using HPLC with amperometric detection: this study revealed that migrating cephalic neural crest contains 1.5 micrograms ascorbic acid per mg protein. Our results suggest that ascorbic acid and/or related molecule(s) could act during development of the nervous system as a trigger for collagen production and subsequent assembly of an extracellular matrix.

Ciliary ganglia and spinal cord explants release an ascorbate-like compound which stimulates proline hydroxylation and collagen formation in muscle cultures

A low-molecular-weight factor from embryonic rat brain stimulates collagen production in rat muscle cultures. This effect is associated with increased hydroxylation of proline residues in collagenous proteins produced by the cells. Here, we show that increased hydroxylation (22-and 7.5-fold) was also observed with extracts of rat embryonic spinal cord and extracts of the rat pheochromocytoma cell line PC12. A 5-25-fold stimulation in proline hydroxylation was obtained when muscle cells were cocultured with chick ciliary ganglia or with embryonic rat spinal cord explants. Medium conditioned by rat spinal cord explants also increased prolyl hydroxylation. Incubation of the muscle-nerve cocultures with ascorbate oxidase markedly reduced the observed increase in proline hydroxylation. These results show that the cultured explants release a factor which promotes proline hydroxylation and collagen production by muscle. This factor seems to be ascorbic acid or an ascorbate-like compound.