Possible Impact of Impaired Double-stranded RNA Degradation and Nitrosative Stress on Immuno-inflammatory Cascade in Type 2 Diabetes

Abstract

The immune response can be triggered by molecules derived from microorganisms (PAMP) or from molecules derived from damaged or dead host cells, known as the damage-associated molecular-pattern molecules (DAMP). Their immune effects are accompanied by altered redox environment. The level of stable end products of nitric oxide (NO)- plasma nitrate and nitrite (NOx), carbonyl groups (PCO) and nitrotyrosine (NTY), in relation to the metabolism of dsRNAs (poly I:C and poly A:U) and xanthine oxidase (XO activity), in plasma of type2 diabetic patients was determined. Thirty-six patients with type 2 diabetes (age group 34-66 years, 19 male and 17 female) were allocated to the study. Diabetic patients had a significantly higher level of plasma NOx products, NTY and PCO, fructosamine (FA) and XO activity indicating about altered redox environment. The concentration of circulating ribonucleic acids (CNAs) was significantly higher in type 2 diabetic patients, which was accompanied by a significantly decreased activity of RNase against double stranded RNA forms (poly I:C and poly A:U), compared to control samples. To determine whether CNAs, as possible DAMP molecules, are capable of exerting effect on inflammatory and host antiviral response, the effect of isolated CNAs on NF-kappaB, Bcl-2, Bax, MDA-5 and IRF-3 regulation was evaluated in culture of fresh isolated thymocytes. Circulating nucleic acids isolated from type 2 diabetic patients were able to upregulate NF-kappaB more than control RNA samples. In the same experimental conditions the mild Bcl-2 upregulation, followed by the marked Bax upregulation, was demonstrated. Since the Bcl-2/Bax ratio was lower in type 2 diabetic samples, obtained results may implicate that CNAs may exert proapoptotic response in type 2 diabetes. The CNAs isolated from diabetic patients were able to downregulate MDA-5 and IRF-3, very important subjects of the surveillance and cellular anti-viral response. The major findings of the present study are that impaired dsRNA metabolism may lead to increased level of different sized RNAs in type 2 diabetic patients. Acting as possible DAMP molecules, they may contribute to higher susceptibility of immune cells to inflammatory cascade via NF-kappaB activation, and possible MDA-5/IRF-3 axis downregulation, what may have an influence on further ineffective response against different pathogens.

Circulating nucleic acids as possible damage-associated molecular patterns in different stages of renal failure

“…Purified RNAs and related oligonucleotides were used for spectrophotometric scan analysis, explained in our previous report. 17 The UV spectra obtained in our study are in a close agreement with recent revised UV extinction coefficients of RNA and related nucleotides.…”

“…Similar results were documented in our report, concerning the level of circulating nucleic acids in diabetic patients. 17 In our further research, residential macrophages were exposed to media supplemented with physiological saline or with nucleic acids isolated from control healthy subjects or patients with renal diseases. The level of NF-kB, p38, MDA-5, IRF-3, and IRF-7 was determinate in cells.…”

“…12,15,16 Decreased activity of extracellular RNases was documented in some chronic or autoimmune diseases in our recent reports. 16,17 We hypothesized that the available circulating nucleic acids, acting as DAMPs, may be a possible pathogenetic mechanism capable of modulating immunoinflammatory reaction in patients with CRF.…”

Circulating Ribonucleic Acids and Metabolic Stress Parameters May Reflect Progression of Autoimmune or Inflammatory Conditions in Juvenile Type 1 Diabetes

“…This test was the most efficient for isolation of short RNA fragments, giving the best recovery results. Plasma RNA isolation was performed according to the manufacturer"s instructions and data were compared according to the published results [22,23,24]. Plasma concentrations were calculated by employing the corresponding standard [27].…”

“…Our present research is driven by our previous clinical and experimental results, where it was noted that: (1) the level of circulating RNA species and oligonucleotides is higher in diabetes, especially in the juvenile type [21,22,23]; (2) the activity of extracellular RNases toward the ssRNAs and dsRNAs is significantly decreased in diabetes mellitus, presumably because of their time-and dose-dependent glycation [22]; (3) circulating oligonucleotides exerted a peak of maximal absorbance at 270 nm by the spectroscopic scan analysis, equal to cytosine-rich polynucleotide (polyC), compared to different standards [22]; (4) circulating RNAs, isolated from type 2 adult diabetic patients, are able to induce an inflammatory response in isolated thymocytes via NF-κB activation, yet they decreased the antiviral response [24]. It is very intriguing that the macrophage scavenger receptors are unable to recognize polyC [25].…”