TLR9 stimulation of B-cells induces transcription of p53 and prevents spontaneous and irradiation-induced cell death independent of DNA damage responses. Implications for Common variable immunodeficiency

Abstract

In the present study, we address the important issue of whether B-cells protected from irradiation-induced cell death, may survive with elevated levels of DNA damage. If so, such cells would be at higher risk of gaining mutations and undergoing malignant transformation. We show that stimulation of B-cells with the TLR9 ligands CpG-oligodeoxynucleotides (CpG-ODN) prevents spontaneous and irradiation-induced death of normal peripheral blood B-cells, and of B-cells from patients diagnosed with Common variable immunodeficiency (CVID). The TLR9-mediated survival is enhanced by the vitamin A metabolite retinoic acid (RA). Importantly, neither stimulation of B-cells via TLR9 alone or with RA increases irradiation-induced DNA strand breaks and DNA damage responses such as activation of ATM and DNA-PKcs. We prove that elevated levels of γH2AX imposed by irradiation of stimulated B-cells is not due to induction of DNA double strand breaks, but merely reflects increased levels of total H2AX upon stimulation. Interestingly however, we unexpectedly find that TLR9 stimulation of B-cells induces low amounts of inactive p53, explained by transcriptional induction of TP53. Taken together, we show that enhanced survival of irradiated B-cells is not accompanied by elevated levels of DNA damage. Our results imply that TLR9-mediated activation of B-cells not only promotes cell survival, but may via p53 provide cells with a barrier against harmful consequences of enhanced activation and proliferation. As CVID-derived B-cells are more radiosensitive and prone to undergo apoptosis than normal B-cells, our data support treatment of CVID patients with CpG-ODN and RA.

Triptolide sensitizes breast cancer cells to Doxorubicin through the DNA damage response inhibition

“…ATM alteration or insufficient expression is thought to be an important factor for cancer initiation and development. On the other hand, studies show that inhibition of ATM activity could be favorable for DNA‐damage based treatment including chemotherapy and radiotherapy . Moreover, higher ATM expression level in cancer cells is associated with drug resistance …”

TLR9 Polymorphisms Might Contribute to the Ethnicity Bias for EBV-Infected Nasopharyngeal Carcinoma

“…Therefore the genes involved in lipid metabolism and TLR9 regulation mentioned earlier, and the NF-kb-mediated signals, might play the contributing role in NPC occurrence. With regard to cell survival, TLR9 helps p53 expression; therefore lack of TLR9 function might result in lack of p53 and thus lack of apoptosis in cancers (Holm et al, 2017). These findings indicate a possible role of TLR9 in controlling susceptibility toward EBV for the mongoloid populations, who show higher occurrence of NPC.…”

Heat-killed Salmonella Typhimurium protects mice against carbon ion radiation

“… 16 , 18 TLR stimulation has been demonstrated to minimize injuries induced by photon-based ionizing radiation. 12 – 14 However, the radioprotective effects of TLRs against heavy ion radiation have not been investigated. To the best of our knowledge, HKST is the first TLR co-agonist reported to protect organisms against heavy ion radiation.…”

“…Since the first report that activation of TLR5 protected mice and monkeys against radiation injury, 11 stimulation of other TLRs (such as TLR2/6, TLR4 and TLR9) has been demonstrated to minimize radiation-induced damage. 12 – 14 Salmonella Typhimurium was reported to be recognized by multiple TLRs, including TLR2 and TLR4, thereby stimulating the immune system. 15 , 16 Previous studies have shown that pretreatment with attenuated Salmonella Typhimurium may induce protective cell-mediated immunity and facilitate the conversion of immunosuppressive myeloid-derived suppressor cells into tumor necrosis factor-α-secreting neutrophil-like myeloid cells, thereby protecting mice against malaria or tumor growth.…”