The concept and application of antisense oligonucleotides

Study on the Role of ampG in the Regulation of Plasmid-Mediated ampC -Induced Expression in Klebsiella pneumoniae

Objective

In this study, we constructed ampG knock-out and knock-in strains from a clinically isolated Kp1strain carrying ampR-ampC in its plasmid and compared them with the Kp NTUH-K2044 strain to investigate the relationship between ampG and ampR-ampC-induced expression.

Methods

We created the ampG gene deletion mutant strains Kp1-ΔampG and Kp NTUH-K2044-ΔampG with pKO3-km plasmid using homologous recombination technology. We constructed the Kp NTUH-K2044-RC and Kp NTUH-K2044-ΔampG-RC drug resistance model strains with plasmid pACYC184. We constructed the ampG knock-in strains by introducing the ampG genes of Kp1, Enterobacter cloacae 029M, Pseudomonas aeruginosa PAO1, Escherichia coli ATCC25922, and Salmonella typhimurium LT2 into the ampG gene-deleted strains with carrier pet-30a. Real-time polymerase chain reaction (real-time PCR) was used to detect the relative expressions of ampC and ampG mRNAs.

Results

Compared with Kp1, the induction phenotype of the ampC of Kp1-ΔampG strain disappeared, the ampC expression was reduced, and the minimal inhibitory concentration (MIC) values of cefoxitin and ceftazidime significant decrease from 128 μg/mL to 1 μg/mL. Based on Kp1, five strain were successfully constructed to complement the ampG genes from five knock-in strain, and all of the above complemented strains showed inducible expression of ampC and restored the expression of ampG to varying degrees, as well as restored resistance to the antimicrobial drugs cefoxitin and ceftazidime (P < 0.05). The ampC and ampG genes were barely expressed in Kp NTUH-K2044-ΔampG-RC when compared with Kp NTUH-K2044-RC. The expressions of ampG and ampC in each knock-in strain were recovered, the induction phenotype of ampC was restored, and the MIC values of cefoxitin and ceftazidime were increased. (P < 0.05).

Conclusion

In this study, we found that ampG was an essential regulator for the plasmid-mediated ampC-induced expression in K. pneumoniae.

Antiadhesion molecule therapy in inflammatory bowel disease

Adhesion molecules regulate the influx of leukocytes in normal and inflamed gut. Some of these molecules such as MadCAM-1 are specific for the gastrointestinal endothelium, but in inflammatory bowel diseases most of the adhesion factors are up-regulated. Adhesion molecules also are involved in local lymphocyte stimulation and antigen presentation within the intestinal mucosa. Recently, therapeutic compounds directed against trafficking of lymphocytes toward the gut mucosa have been designed, and are being developed as a novel class of drugs in the treatment of Crohn's disease (CD) and ulcerative colitis. This review deals with the immunological aspects of leukocyte trafficking focused on gut homing of T cells. Secondly, the changes in adhesion molecules and T-cell trafficking during intestinal inflammation are discussed. Finally, we review the clinical data that have been gathered in trials of biological therapies directed against adhesion molecules. Both antiintercellular adhesion molecule-1 (ICAM-1) and anti-alpha4 integrin strategies are being developed. Trials with the anti-ICAM-1 antisense oligonucleotide, ISIS-2302, in steroid-refractory CD have provided conflicting efficacy data. The anti-alpha4 integrin antibodies natalizumab (Antegren) and LDP-02 are in phase III and phase II trials, respectively. In the near future, these novel biological agents may prove valuable therapeutic tools in the management of refractory IBD.

Advantages of antisense drugs for the treatment of oral diseases

For almost two decades, antisense oligonucleotides (AS-ON) have been used successfully to suppress and regulate gene expression in vitro and in vivo. They are, meanwhile, well established to serve as molecular tools for several biologic applications, from the study of single gene functions up to complex target gene validations. Based on an at least theoretically simple mode of action, the sequence-specific inhibition of mRNA functions after complex formation by Watson-Crick base pairing and presumably enzymatic degradation of the target mRNA, they obviously carry a high therapeutic potential for the treatment of human diseases. In recent years, a remarkable number of clinical trials have been initiated and performed to evaluate the therapeutic usefulness of antisense technology. However, after the successful development of the first antisense-based drug Vitravene (Isis Pharmaceutical Inc., Carlsbad, CA) in 1998, no second product has appeared on the market to date. Here, we describe substantial advantages for the development of antisense-based drugs against less severe oral diseases that represent novel but highly promising application fields of the technology.