Evaluation of glycyl-arginine and lysyl-aspartic acid dipeptides for their antimicrobial, antibiofilm, and anticancer potentials.

Antibacterial resistance and cancer are worldwide challenges and have been defined as major threats by international health organizations. Peptides are produced naturally by all organisms and have a variety of immunomodulatory, physiological, and wound-healing properties. They can also provide protection against microorganisms and tumor cells. Therefore, we aimed to determine the antimicrobial, antibiofilm, and anticancer potentials of Glycyl-Arginine and Lysyl-Aspartic acid dipeptides. The Broth Dilution and Crystal Violet Binding assays assessed the antimicrobial tests and biofilm inhibitory effects. The MTT assay was used to measure the cytotoxic effects of dipeptides on HeLa cell viability. According to our results, Candida tropicalis T26 and Proteus mirabilis U15 strains were determined as more resistant to Staphylococcus epidermidis W17 against Glycyl-Arginine and Lysyl-Aspartic acid dipeptides with MICs higher than 2 mM (1 mg/mL). Sub-MICs of Glycyl-Arginine caused inhibitions against biofilm formation of all the tested clinical isolates, with the highest inhibition observed against S. epidermidisW17. Lysyl-Aspartic acid exhibited zero to no effect against biofilm formation of P. mirabilisU15, and S. epidermidisW17, whereas it exhibited 52% inhibition of biofilm formation of C. tropicalisT26. Cell viability results revealed that HeLa cell viability decreases with increasing concentration of both dipeptides. Also, parallel to antimicrobial tests, Glycyl-Arginine has a greater cytotoxic effect compared to Lysyl-Aspartic acid. The findings from this study will contribute to the advancement of novel strategies involving dipeptide-based synthesizable molecules and drug development studies. However, it is essential to note that there are still challenges, including the need for extensive experimental and clinical trials.

Bone marrow derived mesenchymal stem cells ameliorate inflammatory response in an in vitro model of familial hemophagocytic lymphohistiocytosis 2.

BACKGROUND: Familial hemophagocytic lymphohistiocytosis 2 (FHL2) is the most common familial type of hemophagocytic lymphohistiocytosis with immune dysregulation. FHL2 patients have mutations in the perforin gene which cause overactivation and proliferation of cytotoxic T lymphocytes and natural killer cells. Perforin is the key component of the cytolytic granule response function of cytotoxic T lymphocytes and natural killer cells. Perforin dysfunction causes a cytotoxic immune deficiency with a clinical outcome of uncontrolled and continuous immune stimulation response. This excessive stimulation leads to continuous systemic inflammation and, ultimately, multiorgan failure. Radical therapy is hematopoietic stem cell transplantation which is limited by the availability of a donor. Exacerbations of inflammatory attacks require a palliative immunosuppressive regimen. There is a need for an alternative or adjuvant therapy to maintain these patients when immunosuppression is ineffective or a donor is not available. Beneficial actions of mesenchymal stem cells (MSCs) have been shown in autoimmune diseases in clinical trials and are attributed to their immune-modulatory properties. This study aimed to assess the immune-modulatory effect of MSCs in an in-vitro model of FHL2. METHODS: We generated a targeted mutation in the perforin gene of NK92 cells to create an in-vitro FLH2 model using Crispr/Cas technology. A coculture setup was employed to assess the immunomodulatory efficacy of MSCs. RESULTS: Engineered NK92 clones did not show PRF1 mRNA expression and failed to secrete perforin upon phorbol myristate acetate-ionomycin stimulation, providing evidence for a valid FHL2 model. Coculture media of the engineered cells were investigated for the abundance of several cytokines. Coculture with MSCs revealed a reduction in major proinflammatory cytokines and an induction in anti-inflammatory and immunomodulatory cytokines compared to the parental NK92 cells. CONCLUSIONS: This study shows the ameliorating effect of MSCs as an adjuvant immune modulator toward the therapy of FHL2 patients. MSCs are supportive therapy candidates for FHL2 patients under circumstances where prolonged immunosuppression is required to gain time before allogeneic hematopoietic stem cell transplantation.

Hyperoxic or hypoxic environment?

We read the article by Khan et al. (2017) in a recent issue of this journal with great interest. We would like to congratulate the authors for this report. In the article, the authors focused primarily on the characteristics of adiposederived mesenchymal stem cells (Ad-MSCs) by altering culture environment. The results of the study showed that culture medium containing 0.5% gelatin enhanced the proliferation rate, induced immunosuppression, and activated BMP-7 and the wnt/AXIN/ß-catenin pathway in Ad-MSCs. However, we believe there is a misunderstanding in the introduction section of the article. A review of the literature shows that certain characteristics of MSCs can be modified with altered culture environments or preconditioned incubation processes. Khan et al. also cited a review published by Song et al. in 2010, as mentioned in the Introduction. This study indicated that preconditioning MSCs under hypoxic conditions enhanced the activity of the MSCs, suggesting a new perspective for the cellular treatment of cardiac tissue damages. In this review, hypoxic conditions were shown to have cytoprotective effects for MSCs, regulated paracrine factors, and increased the VEGF secretion (Song et al., 2010). Likewise, several studies with different designs in the literature yielded similar results (Kadle et al., 2016; Ciria et al., 2017). Therefore, we believe that the term "hyperoxic conditions" mentioned in the introduction of Khan et al.'s article (in citation to the study of Song et al.) is confusing. We recommend that this erroneous term be corrected to prevent any misunderstanding for the readers. We believe that the authors of the article would regard our opinion as a contribution.

Effects of VEGF and MSCs on vascular regeneration in a trauma model in rats.

In the human body, vascular injuries that are caused by trauma, vessel lumen stenosis, and occlusions are often irreversible and can lead to sequelae formation as the vessels cannot reproduce fast enough. To solve this problem, the blood flow must be returned to the region as fast as possible. The adipose tissue contains progenitor cells with angiogenic potential and can be used to resolve the issue. In the present study, mesenchymal stem cells (MSCs) derived from rat adipose tissue, vascular endothelial growth factor (VEGF), and their mixture were applied on the dorsum of a rat, which was traumatized and its contribution to vascular regeneration was reviewed. No application was made to the control group. The results showed that the percentage of necrotic area was significantly lower in the MSC group than that of all the other groups. When the VEGF group was compared to the VEGF + MSCs, the percentage of necrotic area was observed to be similiar. However, VEGF showed effects only when a large quantites of VEGF was applied to the flap area. VEGF could not fully respond to the needs, whereas MSCs can produce VEGF according to the needs of tissue. This makes them superior to stem cells.

Polyethylene glycol-based cationically charged hydrogel beads as a new microcarrier for cell culture.

A new polyethylene glycol (PEG) based microcarrier was designed and examined by the attachment and growth of mouse fibroblast cells. In the design of microcarrier, a PEG-based macromonomer, polyethyleneglycol methacrylate (PEGMA), was selected as the main component of hydrogel beads since PEG is known as a nontoxic and biocompatible material. A relatively new cationic comonomer, N-[3-(dimethylamino)propyl]methacrylamide (DMAPM), with higher ionization ability with respect to the similar comonomers was used for providing cationic charge to the hydrogel structure. In the first part, a suspension copolymerization method was developed for the production of cationically charged hydrogel beads as a potential microcarrier for cell culturing. The suspension copolymerization by using ethylene dimethacrylate (EDM) as cross-linking agent and cyclohexanol as the diluent provided spherical, polydisperse poly(PEGMA-DMAPM-EDM) hydrogel beads with an average size of 121 microm. The hydrogel beads exhibited a pH-dependent swelling behavior. The L929 mouse fibroblast cells were cultured on poly(PEGMA-DMAPM-EDM) hydrogel beads with an initial concentration of 200,000 cells/mL. The cells were incubated in Dulbecco's modified Eagle's medium during 5 days and the cell proliferation was investigated at every 24 h. An effective cell attachment and growth up to 3.5 x 10(6) cells/mL were observed with the poly(PEGMA-DMAPM-EDM) hydrogel beads. The results indicated that the proposed microcarrier was a significant alternative to the hydrogel beads obtained by the copolymerization of 2-hydroxyethyl methacrylate and 2-dimethylaminoethylmethacrylate commonly used in microcarrier-facilitated cell culturing studies.

Effects of two multi-step self-etch primer/adhesives on apoptosis in human gingival fibroblasts in vitro.

Various in vitro studies have shown induction of apoptosis by monomers incorporated to dental restorative materials and adhesive resins, while information regarding the effect of monomer combinations as commercially available products on apoptosis is limited. The aim of this study was to investigate the effects of two multi-step self-etch primer/adhesive systems on apoptosis of cultured primary human gingival fibroblasts. Cells were treated up to 48 h with Clearfil SE Bond (Kuraray, Japan) and FL Bond (Shofu, Japan) at 1:1000 v:v ratio to determine cell proliferation, using 0.02 mM staurosporine as positive control. Apoptosis was assessed using propidium iodide/acridine orange (PI/AO) staining, compared to nontreated controls. When compared to FL Bond, exposure of gingival fibroblasts to Clearfil SE Primer and Clearfil SE Bond resulted in a higher degree of cell proliferation. PI/AO staining revealed typical morphological features of apoptosis in FL Bond and Staurosporine groups, while some cells cultured in the presence of primer and adhesive components of Clearfil SE Bond showed nuclear fragmentation, indicative of early apoptosis. Our results indicate that apoptotic potential of the multi-step self-etch adhesives were material-dependent within the 48 h test period.